Many advances in genetic selection, nutrition, housing and disease control have been incorporated into modern pork production since the 1950s resulting in highly prolific females and practices and technologies, which ...Many advances in genetic selection, nutrition, housing and disease control have been incorporated into modern pork production since the 1950s resulting in highly prolific females and practices and technologies, which significantly increased efficiency of reproduction in the breeding herd. The objective of this manuscript is to review the literature and current industry practices employed for reproductive management. In particular the authors focus on assisted reproduction technologies and their application for enhanced productivity. Modern maternal line genotypes have lower appetites and exceptional lean growth potential compared to females of 20 yr ago. Thus, nutrient requirements and management techniques and technologies, which affect gilt development and sow longevity, require continuous updating. Failure to detect estrus accurately has the greatest impact on farrowing rate and litter size. Yet, even accurate estrus detection will not compensate for the variability in the interval between onset of estrus and actual time of ovulation. However, administration of GnRH analogs in weaned sows and in gilts after withdrawal of altrenogest do overcome this variability and thereby synchronize ovulation, which makes fixed-time AI practical. Seasonal infertility, mediated by temperature and photoperiod, is a persistent problem. Training workers in the art of stockmanship is of increasing importance as consumers become more interested in humane animal care. Altrenogest, is used to synchronize the estrous cycle of gilts, to prolong gestation for 2-3 d to synchronize farrowing and to postpone post-weaning estrus. P.G. 600~ is used for induction of estrus in pre-pubertal gilts and as a treatment to overcome seasonal anestrous. Sperm cell numbers/dose of semen is significantly less for post cervical AI than for cervical AI. Real-time ultrasonography is used to determine pregnancy during wk 3-5. PGF2a effectively induces farrowing when administered within two d of normal gestation length. Ovulation synchronization, single fixed-time AI and induced parturition may lead to farrowing synchronization, which facilitates supervision and reduces stillbirths and piglet mortality. Attendance and assistance at farrowing is important especially to ensure adequate colostrum consumption by piglets immediately after birth. New performance terminologies are presented.展开更多
Background:Mammary gland development during late gestation in gilts is a major factor that alters the composition of colostrum and growth performance of piglets.Plasma valine is taken up and metabolized extensively by...Background:Mammary gland development during late gestation in gilts is a major factor that alters the composition of colostrum and growth performance of piglets.Plasma valine is taken up and metabolized extensively by the mammary gland;however,the effects of valine on mammary gland development during late gestation are still unclear.Thirty primiparous gilts were divided into three treatment groups(n=10)and received one of the three diets starting on day 75 of gestation until the day of farrowing.The total dietary valine to lysine ratio of the three diets was 0.63(LV),0.73(MV),and 0.93(HV),respectively.Results:Dietary valine supplementation during late gestation did not affect(P>0.05)the litter size and weight at farrowing;however,the piglet weight and average daily gain at weaning were linearly increased(P<0.05)as the dietary valine increased.The highest piglet weight at weaning was observed when the gilts were provided the HV diet.Dietary valine supplementation linearly elevated(P<0.05)protein,fat and solids-not-fat and some free amino acids content in colostrum.The concentration of prolactin in plasma of gilts was linearly increased in response to valine supplementation at days 1 and 10 of lactation(P<0.05).Furthermore,with increasing dietary valine allowance,a linear increase(P<0.05)was observed in the area of the lumen of alveolus and the content of DNA,RNA,and total protein in the mammary tissues at day 1 of lactation.Moreover,the protein expression of cyclin D1,p-mTOR,p-S6,and p-4EBP1 was also linearly increased(P<0.05)in the mammary tissue at day 1 of lactation.However,no difference(P>0.05)was observed in the indices related to mammary development and the mTOR signaling pathway at day 21 of lactation.Conclusion:The results revealed that increasing the total dietary valine to lysine ratio to 0.93 during late gestation significantly enhances the piglet weight and average daily gain at weaning probably due to improved development of mammary gland.展开更多
Background:The hyper-prolificacy Meishan gilts achieved a superior endometrial gland development(EGD)than white crossbred gilts during the ovary-independent period(before 60 d of age).Then,the EGD continues under the ...Background:The hyper-prolificacy Meishan gilts achieved a superior endometrial gland development(EGD)than white crossbred gilts during the ovary-independent period(before 60 d of age).Then,the EGD continues under the management of ovary-derived steroid hormones that regulated by gut microbiota(after 60 d of age).However,whether Meishan gilts’superiority in EGD lasting to the ovary-dependent period(after 60 d of age)and the role of gut microbiota in this period both remain unclear.Methods:Meishan gilts and Landrace x Yorkshire(LxY)gilts were raised under the same housing and feeding conditions until sexual maturity and then we compared their EGD and gut microbiota.Meanwhile,we transplanted fecal microbiota from Meishan gilts to L×Y gilts to explore the role of gut microbiota in EGD.We sampled plasma every 3 weeks and collected the uterus,ovary,liver,and rectal feces after the sacrifice.We then determined the hormone concentrations and expressions of the EGD-related genes.We also profiled the gut microbiota using 16S rDNA sequencing and metabolites of plasma and liver tissue using untargeted metabolomics.Finally,the correlation analysis and significant test was conducted between FMT-shifted gut microbes and EGD-related indices.Results:Meishan gilts have larger endometrial gland area(P<0.001),longer uterine horn length(P<0.01)but lighter uterine horn weight(P<0.05),a distinctive gut microbiota compared with L×Y gilts.Fecal microbiota transplantation(FMT)increased endometrial gland area(P<0.01).FMT markedly shifted the metabolite profiles of both liver and plasma,and these differential metabolites enriched in steroid hormone biosynthesis pathway.FMT increased estradiol and insulin-like growth factor 1 but decreased progesterone dynamically.FMT also increased the expression of the EGD-related genes estrogen receptor 1 gene,epithelial cadherin,and forkhead box protein A2.There is a significant correlation between FMT-shifted gut microbes and EGD-related indices.Conclusion:Sexually matured Meishan gilts achieved a superior EGD than LxY gilts.Meanwhile,gut microbiota contribute to the EGD potentially via regulating of steroid hormones during the ovary-dependent period.展开更多
Background： The current study was carried out to determine effects of dietary protein source and crude protein（CP）level on carcass characteristics, meat quality, and muscle amino acid（AA） profile in finishing gil...Background： The current study was carried out to determine effects of dietary protein source and crude protein（CP）level on carcass characteristics, meat quality, and muscle amino acid（AA） profile in finishing gilts. The experiment was designed as a 2 × 2 factorial arrangement with two sources of dietary proteins（cottonseed meal, CSM vs. soybean meal, SBM） and two levels of CP（12 % vs. 14 %, as-fed basis）. Seventy-two crossbred gilts（89.5 ± 0.9 kg） were allotted to one of four dietary treatments in a randomized complete block design for a period of 28 d. All diets were formulated to be isoenergetic and similar concentrations of standardized ileal digestible essential AA covering the nutrient requirements of pigs.Results： Growth, carcass characteristics and meat quality were not affected by dietary protein source nor crude protein level（P ＆gt; 0.10） except that average daily feed intake was increased by CSM diets（P = 0.03）. Gilts offered reduced protein diets had lower muscle p H45min（P 〈 0.05）. Neither dietary protein source nor crude protein level influenced N deposition. However, reduced protein diets decreased N intake, N excretion, and serum urea nitrogen content, whilst improved N efficiency（P 〈 0.01）. CSM diets increased N intake（P = 0.04）,but did not depress N efficiency. The concentrations of phenylalanine, tryptophan, cysteine and tyrosine（P 〈 0.05） of the longissimus muscle were decreased when gilts offered CSM diets, while muscle intracellular free valine concentration was increased（P = 0.03）. The gilts offered reduced protein diets had greater intracellular concentrations of free methionine, lysine, and total AA in muscle（P 〈 0.05）.Conclusion： These results suggest that CSM could replace SBM as a primary protein source in finishing pig diets in terms of performance, N efficiency, carcass characteristics, and meat quality, but decrease the concentrations of muscle specific AA. Furthermore, the reduced protein diet played an important role in increasing muscle intracellular concentrations of specific free amino acids（FAA）, and in reducing the relative ratios of specific FAA to lysine in longissimus dorsi muscle of pig, whose biological meaning needs further studies.展开更多
Background:Replacement gilts are typically fed ad libitum,whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits.The objective of this study was to...Background:Replacement gilts are typically fed ad libitum,whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits.The objective of this study was to investigate the effect of meal frequency on the metabolic status and ovarian follicular development in gilts.Methods:A total of 36 gilts(Landrace×Yorkshire)with an age of 150±3 d and a body weight of 77.6±3.8 kg were randomly allocated into one of three groups(n=12 in each group),and based on the group allocation,the gilts were fed at a frequency of one meal(T1),two meals(T2),or six meals per day(T6)for 14 consecutive weeks.The effects of the meal frequency on growth preference,nutrient utilization,short-chain fatty acid production by gut microbial,the post-meal dynamics in the metabolic status,reproductive hormone secretions,and ovarian follicular development in the gilts were measured.Results:The gilts in the T1 group presented a higher average daily gain(+48 g/d,P<0.05)and a higher body weight(+4.9 kg,P<0.05)than those in the T6 group.The meal frequency had no effect on the apparent digestibility of dry matter,crude protein,ether extract,ash,and gross energy,with the exception that the T1 gilts exhibited a greater NDF digestibility than the T6 gilts(P<0.05).The nitrogen balance analysis revealed that the T1 gilts presented decreased urine excretion of nitrogen(−8.17 g/d,P<0.05)and higher nitrogen retention(+9.81 g/d,P<0.05),and thus exhibited higher nitrogen utilization than the T6 gilts.The time-course dynamics of glucose,α-amino nitrogen,urea,lactate,and insulin levels in serum revealed that the T1 group exhibited higher utilization of nutrients after a meal than the T2 or T6 gilts.The T1 gilts also had a higher acetate content and SCFAs in feces than the T6 gilts(P<0.05).The age,body weight and backfat thickness of the gilts at first estrous expression were not affected by the meal frequency,but the gilts in the T1 group had higher levels of serum luteinizing hormone on the 18th day of the 3rd estrus cycle and 17β-estradiol,a larger number of growing follicles and corpora lutea,and higher mRNA expression levels of genes related to follicular development on the 19th day of the 3rd estrus cycle.Conclusions:The current findings revealed the benefits of a lower meal frequency equal feed intake on nutrient utilization and reproductive function in replacement gilts,and thus provide new insights into the nutritional strategy for replacement gilts,and the dietary pattern for other mammals,such as humans.展开更多
Orexin has several biological functions, including the regulation of reproductive endocrine signaling, which has received much attention. However, little is known about the mechanism through which orexin regulates the...Orexin has several biological functions, including the regulation of reproductive endocrine signaling, which has received much attention. However, little is known about the mechanism through which orexin regulates the levels of neuroendocrine hormones and peptides. We injected orexin A or physiological saline into the lateral ventricle of 10 ovariectomized （OVX） gilts, and determined the subsequent changes in serum luteinizing hormone （LH） concentration by using radioimmunoassay （RIA）. We also examined the expression of GnRH, NPY, and POMC mRNAs in the hypothalamus and that of LH, folliclestimulating hormone （FSH）, POMC, and ghrelin mRNAs in the pituitary by using semi-quantitative reverse transcription polymerase chain reaction. We found the following results： （1） Orexin A transiently promoted LH secretion; serum LH concentration started to increase at 10 min after the orexin injection, peaked at 30 min, and returned to its initial level at 1.5 h; （2） orexin A upregulated GnRH mRNA expression and downregulated NPY and POMC mRNAs expression in the hypothalamus; （3） orexin A upregulated LH and FSH mRNAs expression （FSH, P〉 0.05）, but downregulated ghrelin mRNA expression in the pituitary. No significant effects were observed on the pituitary expression of FSH and POMC mRNAs. Our data suggest that orexin A regulates reproductive function by stimulating GnRH and LH release directly and indirectly via its effects on NPY, POMC and ghrelin expression.展开更多
The objective of the study was to investigate the effects of dietary energy levels and sources on the blood metabolites,hormone secretion and the composition of follicular fluid in gilts.Fifty-four gilts with initial ...The objective of the study was to investigate the effects of dietary energy levels and sources on the blood metabolites,hormone secretion and the composition of follicular fluid in gilts.Fifty-four gilts with initial body weight of(59±4.2) kg were randomly allotted to six treatments.Treatments were low, normal,and high energy feeding levels,which were 87.5%,100%and 112.5%of recommendatory energy requirements by NRC(1998),respectively,and dietary energy sources(starch or fat).Blood samples and follicular fluids were collected on D18 and D19 of the second estrous cycle.The results showed that plasma concentrations of triglycerides and total cholesterol were higher in the fat group than that in the starch group(P【0.05),but those of glucose were similar between the two energy sources(P】0.05);dietary energy level exerted no effect on blood metabolites concentration(P】0.05).Gilts fed the high energy diet had a higher area under curve of plasma insulin(Insulin AUC),insulin-like growth factor-Ⅰ(IGF-Ⅰ) and leptin than did gilts fed the lower energy diet(P【0.05),but there was no significant difference between fat versus starch(P】0.05).Luteinizing hormone(LH) pulses were higher in gilts fed high energy rather than that in low energy diets(P】0.05),plasma concentration of estradiol(E<sub>2</sub>) was higher in the fat group than that in the starch group(P【0.05).The number of large follicles(diameter≥4 mm) and concentrations of IGF-Ⅰand E<sub>2</sub> in follicular fluid were increasing significant as the level of energy increased(P【0.05),but the numbers of large follicles and follicular fluid composition were not affected by the source of dietary energy(P】0.05).The results indicate that gilts fed high energy diets had elevated plasma concentrations of metabolic hormones,IGF-Ⅰand LH secretion,and increased follicular fluid concentrations of IGF-Ⅰ,E<sub>2</sub> and numbers of large follicles;gilts fed the dietary fat had a higher plasma concentration of cholesterol and E<sub>2</sub>.展开更多
Administration of genistein to barrows increased anterior pituitary (AP) concentrations of IGF-I and LH and increased expression of AP IGF receptor. Whether similar changes occur in gilts remains to be determined. The...Administration of genistein to barrows increased anterior pituitary (AP) concentrations of IGF-I and LH and increased expression of AP IGF receptor. Whether similar changes occur in gilts remains to be determined. The objective of this experiment was to determine if short term administration of genistein increased expression of components of the AP IGF system and hypothalamic hormones and receptors involved in gonadotropin synthesis and/or release in the gilt. Sixteen crossbred gilts of similar weight (97.7 kg) were ovariectomized and assigned to either control (C;n = 8) or genistein (G;n = 8) groups. Genistein pigs received 800 mg of genistein in DMSO while C pigs received an equal volume of DMSO i.m. on day 0, 1, 2, and 3. Blood samples were obtained on day 0, 1, 2, and 3. Pigs were slaughtered on d 4 when blood, AP, and medial basal hypothalami (MBH) were collected. No difference was detected (P > 0.05) in AP concentrations of IGF-I or serum concentrations of IGF-I in C and G pigs. Anterior pituitary concentrations of LH were greater (P 0.05) in C and G pigs. Relative expression of AP IGFBP-5 and GnRHR was increased (P < 0.05) in G pigs compared with C pigs. Relative expression of AP LHβ did not differ between C and G pigs. Relative expression of MBH kisspeptin was greater (P < 0.01) in G pigs than C pigs. These data provided evidence that short term administration of genistein increased expression of hypothalamic and hypophyseal hormones in gilts which could influence subsequent reproduction.展开更多
<span style="font-family:Verdana;">Kisspeptin has been demonstrated to affect reproductive cyclicity and the attainment of puberty in multiple species, presumably through its actions on gonadotropin re...<span style="font-family:Verdana;">Kisspeptin has been demonstrated to affect reproductive cyclicity and the attainment of puberty in multiple species, presumably through its actions on gonadotropin releasing hormone and luteinizing hormone. Kisspeptin administration causes increased plasma concentrations of LH in pigs, sheep, and rats. The objective of this experiment was to evaluate changes in the hypothalamic kisspeptin system throughout the estrous cycle in gilts. Estrus was synchronized in forty crossbred gilts (191 d, 121 kg) and estrus detection was performed by exposing gilts to a mature boar. The first day gilts stood immobile was denoted d 1 of the estrous cycle. Blood samples were collected via jugular venipuncture on d 1, 4, 7, 9, 14, 16, and 19 of the estrous cycle. Ten animals were slaughtered on d 1, 9, 14, and 21 of the estrous cycle when medial basal hypothalami, anterior pituitary glands, and blood were collected. Relative expression of hypothalamic kisspeptin (KISS1), kisspeptin receptor (KISS1R), estrogen receptors-a, anterior pituitary gland GnRH receptor, </span><i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-actin</span><span style="font-family:Verdana;" "="">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> and GAPDH was determined using real-time reverse transcriptase PCR. Fold changes in relative expression were determined using the Relative Expression Software Tool. Relative expression of KISS1 was increased (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.006) 3.2 fold on d 1 versus d 21 and 2.3 fold (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.003) on d 9 versus d 21 of the estrous cycle, but was not different (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> > 0.05) among the remaining days of the estrous cycle. Relative expression of estrogen receptor-b was decreased (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.05) 0.8 fold on d 9 versus d 21 and (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.005) 0.7 fold on d 14 versus d 21, but was not different (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> > 0.05) among the remaining days. Relative expression of anterior pituitary gland GnRH receptor was increased (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> < 0.01) on d 1 and 21 versus d 9 and 14. These data support the notion that medial basal hypothalamic expression of KISS1 changes throughout the estrous cycle and may influence reproductive cyclicity in the gilt.</span></span>展开更多
This experiment was aimed to investigate some changes of ovarian structure in order to confirm the onset of puberty in Thai indigenous gilts. Fifty female animals collected from the North-Eastern area of Thailand were...This experiment was aimed to investigate some changes of ovarian structure in order to confirm the onset of puberty in Thai indigenous gilts. Fifty female animals collected from the North-Eastern area of Thailand were slaughtered in the different age groups as 0, 1, 2, 3, 3.5, 4, 4.5, 5, 5.5 and 6 months of age, respectively （each group = 5 pigs）, for monitoring corpus luteum （CL） occurrence on ovarian surface and some changes of reproductive structure. CL was clearly found for the first time in the 4.5 months age group （P 〈 0.05） which was defined as the first ovulation; nevertheless, group of follicles with 〉 2.0 mm in diameter appeared for the first time in the 3.5 month age group （P 〈 0.05）. For other conformations, size of uterine horns, oviducts or ovaries, including weight of ovaries or whole reproductive tracts, were significantly developed （P 〈 0.05） that was initially taken place in the 3.5 months age group onwards. Thus, it was summarized that the onset of puberty in Thai indigenous gilts, affirmed by CL appearance at the first time, should be happened between 4.0 and 4.5 months of age; however, the development of reproductive structure and follicles to prepare in approaching puberty should be started before 3.5 months of age.展开更多
Maternal proline(Pro)supplementation enhances fetal survival and placental development in mice.However,the effect of Pro on fetal and placental development in gilts remains to be investigated,particularly in the conte...Maternal proline(Pro)supplementation enhances fetal survival and placental development in mice.However,the effect of Pro on fetal and placental development in gilts remains to be investigated,particularly in the context of obesity-induced impaired pregnancy.Here,we investigated the effect of dietary Pro on fetal and placental development in obese gilts.Exp.1:On day 60 of gestation,48 gilts with similar delivery times were selected and followed up until delivery to determine the relationship between maternal obesity,litter performance,and Pro abundance in term placentae.The results showed that impaired reproductive performance was associated with body condition parameters and inadequate placental Pro availability of gilts.Exp.2:A total of 114 gilts were then used in a 2×3 factorial design to investigate the interaction between body condition(factor I:normal or obese gilts)and dietary Pro levels(factor II:low[0.89%,L-Pro],medium[1.39%,M-Pro],and high[1.89%,H-Pro])on farrowing performance and placental angiogenesis.This resulted in six treatment combinations:normal-L-Pro,obese-L-Pro,normal-M-Pro,obese-M-Pro,normal-H-Pro,and obese-H-Pro.The effective number of replicates per group was 17,21,19,21,18,and 18,respectively(1 gilt per replicate).The results showed that increasing Pro intake increased piglet birth weight(P=0.001),litter weight(P<0.001),placental efficiency(P=0.036)and placental vascular density(P<0.001),and decreased the number of mummified fetuses(P=0.001),the rate of low-birth-weight piglets(P=0.005),and the rate of invalid piglets(P=0.029).Interaction effects were observed between body condition and dietary Pro levels on piglet birth weight(P=0.046),within-litter birth weight variation(P=0.012),and placental vascular density(P=0.007).Moreover,the beneficial effect of Pro on farrowing performance may be related to the improvement of sirtuin 1-superoxide dismutase 2-mitochondrial reactive oxygen species axis homeostasis and angiogenesis in the placenta.Our results suggest that gestation diets need to provide adequate Pro to meet the needs of fetal and placental development,particularly in obese gilts.展开更多
The present study was aimed at investigating the adverse effects of dietary zearalenone(ZEA) on the lymphocyte proliferation rate(LPR), interleukin-2(IL-2), mRNA expressions of pro-inflammatory cytokines, and histopat...The present study was aimed at investigating the adverse effects of dietary zearalenone(ZEA) on the lymphocyte proliferation rate(LPR), interleukin-2(IL-2), mRNA expressions of pro-inflammatory cytokines, and histopathologic changes of spleen in post-weanling gilts. A total of 20 crossbred piglets(Yorkshire × Landrace × Duroc) with an initial BW of 10.36 ± 1.21 kg(21 d of age) were used in the study.Piglets were fed a basal diet with an addition of 0.1.1,2.0, or 3.2 mg/kg purified ZEA for 18 d ad libitum.The results showed that LPR and IL-2 production of spleen decreased linearly(P < 0.05) as dietary ZEA increased. Splenic mRNA expressions of interleukin-1β(IL-1β) and interleukin-6(IL-6) were linearly upregulated(P < 0.05) as dietary ZEA increased. On the contrary, linear down-regulation(P<0.05) of mRNA expression of interferon-γ(IFN-γ) was observed as dietary ZEA increased. Swelling splenocyte in1.1 mg/kg ZEA treatments, atrophy of white pulp and swelling of red pulp in 2.0 and 3.2 mg/kg ZEA treatments were observed. The cytoplasmic edema in 1.1 mg/kg ZEA treatments, significant chromatin deformation in 2.0 mg/kg ZEA treatment and phagocytosis in 3.2 mg/kg ZEA treatment were observed.Results suggested that dietary ZEA at 1.1 to 3.2 mg/kg can induce splenic damages and negatively affect immune function of spleen in post-weanling gilts.展开更多
The effects of age,body weight(BW),and backfat thickness(BF)of replacement gilts at first estrus and first mating on their subsequent reproductive performance and retention of their first 2 parities as sows was evalua...The effects of age,body weight(BW),and backfat thickness(BF)of replacement gilts at first estrus and first mating on their subsequent reproductive performance and retention of their first 2 parities as sows was evaluated.A total of 3,025 Danish replacement gilts were categorized by farm(allocated to 4 farms),cross combination,age,BW and BF at first estrus and first mating,estrous cycle number at first mating,and flush feeding before first mating.The result shows that all the factors mentioned above were significantly associated with reproductive performance and retention rates of the first 2 parities.Farm 3 had more piglets born alive per litter(BA)(P<0.05).Farms 3 and 4 had more healthy piglets per litter(HP)(P<0.05).Farm 4 had the most piglets weaned per litter(PW)(P<0.05).Landrace×Landrace×Yorkshire(L×L×Y)replacement gilts had the most total piglets born per litter(TB),BA,HP,PW and a higher retention rate of the 2 parities than Landrace×Yorkshire(L×Y)replacement gilts(P<0.05).In addition,flush feeding before first mating had the most TB,BA,HP,PW,and a higher retention rate of the 2 parities than no flush feeding(P<0.05).Because the effects of replacement gilts rearing parameters on reproductive performance traits differed,we used 100 replacement gilts as a unit and the total number of weaned piglets from the first 2 parities as a new index.Replacement gilts undergoing their first estrus between 180 and 210 d of age at 115 to 124.9 kg BW and 14 to 15 mm BF had significantly higher reproductive indexes for their first 2 parities per 100 replacement gilts.Replacement gilts that mated between 210 and 230 d of age at 140 to 149.9 kg BW and 15 to 16 mm BF had optimal reproductive indexes.These results provide a new insight into the complex relationships among these reproductive performance traits and may help guide successful management of replacement gilts as a pivotal starting point for future fertility and longevity of rearing herds.展开更多
文摘Many advances in genetic selection, nutrition, housing and disease control have been incorporated into modern pork production since the 1950s resulting in highly prolific females and practices and technologies, which significantly increased efficiency of reproduction in the breeding herd. The objective of this manuscript is to review the literature and current industry practices employed for reproductive management. In particular the authors focus on assisted reproduction technologies and their application for enhanced productivity. Modern maternal line genotypes have lower appetites and exceptional lean growth potential compared to females of 20 yr ago. Thus, nutrient requirements and management techniques and technologies, which affect gilt development and sow longevity, require continuous updating. Failure to detect estrus accurately has the greatest impact on farrowing rate and litter size. Yet, even accurate estrus detection will not compensate for the variability in the interval between onset of estrus and actual time of ovulation. However, administration of GnRH analogs in weaned sows and in gilts after withdrawal of altrenogest do overcome this variability and thereby synchronize ovulation, which makes fixed-time AI practical. Seasonal infertility, mediated by temperature and photoperiod, is a persistent problem. Training workers in the art of stockmanship is of increasing importance as consumers become more interested in humane animal care. Altrenogest, is used to synchronize the estrous cycle of gilts, to prolong gestation for 2-3 d to synchronize farrowing and to postpone post-weaning estrus. P.G. 600~ is used for induction of estrus in pre-pubertal gilts and as a treatment to overcome seasonal anestrous. Sperm cell numbers/dose of semen is significantly less for post cervical AI than for cervical AI. Real-time ultrasonography is used to determine pregnancy during wk 3-5. PGF2a effectively induces farrowing when administered within two d of normal gestation length. Ovulation synchronization, single fixed-time AI and induced parturition may lead to farrowing synchronization, which facilitates supervision and reduces stillbirths and piglet mortality. Attendance and assistance at farrowing is important especially to ensure adequate colostrum consumption by piglets immediately after birth. New performance terminologies are presented.
基金supported by The National Key Research and Development Program of China(2018YFD0501003)The Outstanding Talents Training Program of Guangdong Academy of Agricultural Sciences,China Agriculture Research System(CARS-35)Supporting Program for Guangdong Agricultural Research&Development Center of Livestock and Poultry Healthy Breeding.Operating Funds for Guangdong Provincial Key Laboratory of Animal Breeding and Nutrition(2014B030301054).
文摘Background:Mammary gland development during late gestation in gilts is a major factor that alters the composition of colostrum and growth performance of piglets.Plasma valine is taken up and metabolized extensively by the mammary gland;however,the effects of valine on mammary gland development during late gestation are still unclear.Thirty primiparous gilts were divided into three treatment groups(n=10)and received one of the three diets starting on day 75 of gestation until the day of farrowing.The total dietary valine to lysine ratio of the three diets was 0.63(LV),0.73(MV),and 0.93(HV),respectively.Results:Dietary valine supplementation during late gestation did not affect(P>0.05)the litter size and weight at farrowing;however,the piglet weight and average daily gain at weaning were linearly increased(P<0.05)as the dietary valine increased.The highest piglet weight at weaning was observed when the gilts were provided the HV diet.Dietary valine supplementation linearly elevated(P<0.05)protein,fat and solids-not-fat and some free amino acids content in colostrum.The concentration of prolactin in plasma of gilts was linearly increased in response to valine supplementation at days 1 and 10 of lactation(P<0.05).Furthermore,with increasing dietary valine allowance,a linear increase(P<0.05)was observed in the area of the lumen of alveolus and the content of DNA,RNA,and total protein in the mammary tissues at day 1 of lactation.Moreover,the protein expression of cyclin D1,p-mTOR,p-S6,and p-4EBP1 was also linearly increased(P<0.05)in the mammary tissue at day 1 of lactation.However,no difference(P>0.05)was observed in the indices related to mammary development and the mTOR signaling pathway at day 21 of lactation.Conclusion:The results revealed that increasing the total dietary valine to lysine ratio to 0.93 during late gestation significantly enhances the piglet weight and average daily gain at weaning probably due to improved development of mammary gland.
基金supported by the Natural Science Foundation of China(31730090 and 31925037)Hubei Provincial Natural Science Foundation of China(2018CFA020).
文摘Background:The hyper-prolificacy Meishan gilts achieved a superior endometrial gland development(EGD)than white crossbred gilts during the ovary-independent period(before 60 d of age).Then,the EGD continues under the management of ovary-derived steroid hormones that regulated by gut microbiota(after 60 d of age).However,whether Meishan gilts’superiority in EGD lasting to the ovary-dependent period(after 60 d of age)and the role of gut microbiota in this period both remain unclear.Methods:Meishan gilts and Landrace x Yorkshire(LxY)gilts were raised under the same housing and feeding conditions until sexual maturity and then we compared their EGD and gut microbiota.Meanwhile,we transplanted fecal microbiota from Meishan gilts to L×Y gilts to explore the role of gut microbiota in EGD.We sampled plasma every 3 weeks and collected the uterus,ovary,liver,and rectal feces after the sacrifice.We then determined the hormone concentrations and expressions of the EGD-related genes.We also profiled the gut microbiota using 16S rDNA sequencing and metabolites of plasma and liver tissue using untargeted metabolomics.Finally,the correlation analysis and significant test was conducted between FMT-shifted gut microbes and EGD-related indices.Results:Meishan gilts have larger endometrial gland area(P<0.001),longer uterine horn length(P<0.01)but lighter uterine horn weight(P<0.05),a distinctive gut microbiota compared with L×Y gilts.Fecal microbiota transplantation(FMT)increased endometrial gland area(P<0.01).FMT markedly shifted the metabolite profiles of both liver and plasma,and these differential metabolites enriched in steroid hormone biosynthesis pathway.FMT increased estradiol and insulin-like growth factor 1 but decreased progesterone dynamically.FMT also increased the expression of the EGD-related genes estrogen receptor 1 gene,epithelial cadherin,and forkhead box protein A2.There is a significant correlation between FMT-shifted gut microbes and EGD-related indices.Conclusion:Sexually matured Meishan gilts achieved a superior EGD than LxY gilts.Meanwhile,gut microbiota contribute to the EGD potentially via regulating of steroid hormones during the ovary-dependent period.
基金financially supported by the National Key Basic Research Program of China (2012CB124702, 2013CB127302)National Natural Science Foundation of China (31272452)the National Key Technology R&D Program of China (2011BAD26B01)
文摘Background： The current study was carried out to determine effects of dietary protein source and crude protein（CP）level on carcass characteristics, meat quality, and muscle amino acid（AA） profile in finishing gilts. The experiment was designed as a 2 × 2 factorial arrangement with two sources of dietary proteins（cottonseed meal, CSM vs. soybean meal, SBM） and two levels of CP（12 % vs. 14 %, as-fed basis）. Seventy-two crossbred gilts（89.5 ± 0.9 kg） were allotted to one of four dietary treatments in a randomized complete block design for a period of 28 d. All diets were formulated to be isoenergetic and similar concentrations of standardized ileal digestible essential AA covering the nutrient requirements of pigs.Results： Growth, carcass characteristics and meat quality were not affected by dietary protein source nor crude protein level（P ＆gt; 0.10） except that average daily feed intake was increased by CSM diets（P = 0.03）. Gilts offered reduced protein diets had lower muscle p H45min（P 〈 0.05）. Neither dietary protein source nor crude protein level influenced N deposition. However, reduced protein diets decreased N intake, N excretion, and serum urea nitrogen content, whilst improved N efficiency（P 〈 0.01）. CSM diets increased N intake（P = 0.04）,but did not depress N efficiency. The concentrations of phenylalanine, tryptophan, cysteine and tyrosine（P 〈 0.05） of the longissimus muscle were decreased when gilts offered CSM diets, while muscle intracellular free valine concentration was increased（P = 0.03）. The gilts offered reduced protein diets had greater intracellular concentrations of free methionine, lysine, and total AA in muscle（P 〈 0.05）.Conclusion： These results suggest that CSM could replace SBM as a primary protein source in finishing pig diets in terms of performance, N efficiency, carcass characteristics, and meat quality, but decrease the concentrations of muscle specific AA. Furthermore, the reduced protein diet played an important role in increasing muscle intracellular concentrations of specific free amino acids（FAA）, and in reducing the relative ratios of specific FAA to lysine in longissimus dorsi muscle of pig, whose biological meaning needs further studies.
基金This study was supported by National Key R&D Program of China(2018YFD0501005)National Natural Science Foundation of China,PR China(31772616).
文摘Background:Replacement gilts are typically fed ad libitum,whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits.The objective of this study was to investigate the effect of meal frequency on the metabolic status and ovarian follicular development in gilts.Methods:A total of 36 gilts(Landrace×Yorkshire)with an age of 150±3 d and a body weight of 77.6±3.8 kg were randomly allocated into one of three groups(n=12 in each group),and based on the group allocation,the gilts were fed at a frequency of one meal(T1),two meals(T2),or six meals per day(T6)for 14 consecutive weeks.The effects of the meal frequency on growth preference,nutrient utilization,short-chain fatty acid production by gut microbial,the post-meal dynamics in the metabolic status,reproductive hormone secretions,and ovarian follicular development in the gilts were measured.Results:The gilts in the T1 group presented a higher average daily gain(+48 g/d,P<0.05)and a higher body weight(+4.9 kg,P<0.05)than those in the T6 group.The meal frequency had no effect on the apparent digestibility of dry matter,crude protein,ether extract,ash,and gross energy,with the exception that the T1 gilts exhibited a greater NDF digestibility than the T6 gilts(P<0.05).The nitrogen balance analysis revealed that the T1 gilts presented decreased urine excretion of nitrogen(−8.17 g/d,P<0.05)and higher nitrogen retention(+9.81 g/d,P<0.05),and thus exhibited higher nitrogen utilization than the T6 gilts.The time-course dynamics of glucose,α-amino nitrogen,urea,lactate,and insulin levels in serum revealed that the T1 group exhibited higher utilization of nutrients after a meal than the T2 or T6 gilts.The T1 gilts also had a higher acetate content and SCFAs in feces than the T6 gilts(P<0.05).The age,body weight and backfat thickness of the gilts at first estrous expression were not affected by the meal frequency,but the gilts in the T1 group had higher levels of serum luteinizing hormone on the 18th day of the 3rd estrus cycle and 17β-estradiol,a larger number of growing follicles and corpora lutea,and higher mRNA expression levels of genes related to follicular development on the 19th day of the 3rd estrus cycle.Conclusions:The current findings revealed the benefits of a lower meal frequency equal feed intake on nutrient utilization and reproductive function in replacement gilts,and thus provide new insights into the nutritional strategy for replacement gilts,and the dietary pattern for other mammals,such as humans.
基金sponsored by the National Natural Sci-ence Foundation of China (30471248)
文摘Orexin has several biological functions, including the regulation of reproductive endocrine signaling, which has received much attention. However, little is known about the mechanism through which orexin regulates the levels of neuroendocrine hormones and peptides. We injected orexin A or physiological saline into the lateral ventricle of 10 ovariectomized （OVX） gilts, and determined the subsequent changes in serum luteinizing hormone （LH） concentration by using radioimmunoassay （RIA）. We also examined the expression of GnRH, NPY, and POMC mRNAs in the hypothalamus and that of LH, folliclestimulating hormone （FSH）, POMC, and ghrelin mRNAs in the pituitary by using semi-quantitative reverse transcription polymerase chain reaction. We found the following results： （1） Orexin A transiently promoted LH secretion; serum LH concentration started to increase at 10 min after the orexin injection, peaked at 30 min, and returned to its initial level at 1.5 h; （2） orexin A upregulated GnRH mRNA expression and downregulated NPY and POMC mRNAs expression in the hypothalamus; （3） orexin A upregulated LH and FSH mRNAs expression （FSH, P〉 0.05）, but downregulated ghrelin mRNA expression in the pituitary. No significant effects were observed on the pituitary expression of FSH and POMC mRNAs. Our data suggest that orexin A regulates reproductive function by stimulating GnRH and LH release directly and indirectly via its effects on NPY, POMC and ghrelin expression.
基金supported by Program for Changjiang Scholars and Innovative Research Team in University (IRT0555)National Natural Science Foundation (30471257) of China
文摘The objective of the study was to investigate the effects of dietary energy levels and sources on the blood metabolites,hormone secretion and the composition of follicular fluid in gilts.Fifty-four gilts with initial body weight of(59±4.2) kg were randomly allotted to six treatments.Treatments were low, normal,and high energy feeding levels,which were 87.5%,100%and 112.5%of recommendatory energy requirements by NRC(1998),respectively,and dietary energy sources(starch or fat).Blood samples and follicular fluids were collected on D18 and D19 of the second estrous cycle.The results showed that plasma concentrations of triglycerides and total cholesterol were higher in the fat group than that in the starch group(P【0.05),but those of glucose were similar between the two energy sources(P】0.05);dietary energy level exerted no effect on blood metabolites concentration(P】0.05).Gilts fed the high energy diet had a higher area under curve of plasma insulin(Insulin AUC),insulin-like growth factor-Ⅰ(IGF-Ⅰ) and leptin than did gilts fed the lower energy diet(P【0.05),but there was no significant difference between fat versus starch(P】0.05).Luteinizing hormone(LH) pulses were higher in gilts fed high energy rather than that in low energy diets(P】0.05),plasma concentration of estradiol(E<sub>2</sub>) was higher in the fat group than that in the starch group(P【0.05).The number of large follicles(diameter≥4 mm) and concentrations of IGF-Ⅰand E<sub>2</sub> in follicular fluid were increasing significant as the level of energy increased(P【0.05),but the numbers of large follicles and follicular fluid composition were not affected by the source of dietary energy(P】0.05).The results indicate that gilts fed high energy diets had elevated plasma concentrations of metabolic hormones,IGF-Ⅰand LH secretion,and increased follicular fluid concentrations of IGF-Ⅰ,E<sub>2</sub> and numbers of large follicles;gilts fed the dietary fat had a higher plasma concentration of cholesterol and E<sub>2</sub>.
文摘Administration of genistein to barrows increased anterior pituitary (AP) concentrations of IGF-I and LH and increased expression of AP IGF receptor. Whether similar changes occur in gilts remains to be determined. The objective of this experiment was to determine if short term administration of genistein increased expression of components of the AP IGF system and hypothalamic hormones and receptors involved in gonadotropin synthesis and/or release in the gilt. Sixteen crossbred gilts of similar weight (97.7 kg) were ovariectomized and assigned to either control (C;n = 8) or genistein (G;n = 8) groups. Genistein pigs received 800 mg of genistein in DMSO while C pigs received an equal volume of DMSO i.m. on day 0, 1, 2, and 3. Blood samples were obtained on day 0, 1, 2, and 3. Pigs were slaughtered on d 4 when blood, AP, and medial basal hypothalami (MBH) were collected. No difference was detected (P > 0.05) in AP concentrations of IGF-I or serum concentrations of IGF-I in C and G pigs. Anterior pituitary concentrations of LH were greater (P 0.05) in C and G pigs. Relative expression of AP IGFBP-5 and GnRHR was increased (P < 0.05) in G pigs compared with C pigs. Relative expression of AP LHβ did not differ between C and G pigs. Relative expression of MBH kisspeptin was greater (P < 0.01) in G pigs than C pigs. These data provided evidence that short term administration of genistein increased expression of hypothalamic and hypophyseal hormones in gilts which could influence subsequent reproduction.
文摘<span style="font-family:Verdana;">Kisspeptin has been demonstrated to affect reproductive cyclicity and the attainment of puberty in multiple species, presumably through its actions on gonadotropin releasing hormone and luteinizing hormone. Kisspeptin administration causes increased plasma concentrations of LH in pigs, sheep, and rats. The objective of this experiment was to evaluate changes in the hypothalamic kisspeptin system throughout the estrous cycle in gilts. Estrus was synchronized in forty crossbred gilts (191 d, 121 kg) and estrus detection was performed by exposing gilts to a mature boar. The first day gilts stood immobile was denoted d 1 of the estrous cycle. Blood samples were collected via jugular venipuncture on d 1, 4, 7, 9, 14, 16, and 19 of the estrous cycle. Ten animals were slaughtered on d 1, 9, 14, and 21 of the estrous cycle when medial basal hypothalami, anterior pituitary glands, and blood were collected. Relative expression of hypothalamic kisspeptin (KISS1), kisspeptin receptor (KISS1R), estrogen receptors-a, anterior pituitary gland GnRH receptor, </span><i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-actin</span><span style="font-family:Verdana;" "="">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> and GAPDH was determined using real-time reverse transcriptase PCR. Fold changes in relative expression were determined using the Relative Expression Software Tool. Relative expression of KISS1 was increased (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.006) 3.2 fold on d 1 versus d 21 and 2.3 fold (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.003) on d 9 versus d 21 of the estrous cycle, but was not different (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> > 0.05) among the remaining days of the estrous cycle. Relative expression of estrogen receptor-b was decreased (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.05) 0.8 fold on d 9 versus d 21 and (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> = 0.005) 0.7 fold on d 14 versus d 21, but was not different (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> > 0.05) among the remaining days. Relative expression of anterior pituitary gland GnRH receptor was increased (</span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> < 0.01) on d 1 and 21 versus d 9 and 14. These data support the notion that medial basal hypothalamic expression of KISS1 changes throughout the estrous cycle and may influence reproductive cyclicity in the gilt.</span></span>
文摘This experiment was aimed to investigate some changes of ovarian structure in order to confirm the onset of puberty in Thai indigenous gilts. Fifty female animals collected from the North-Eastern area of Thailand were slaughtered in the different age groups as 0, 1, 2, 3, 3.5, 4, 4.5, 5, 5.5 and 6 months of age, respectively （each group = 5 pigs）, for monitoring corpus luteum （CL） occurrence on ovarian surface and some changes of reproductive structure. CL was clearly found for the first time in the 4.5 months age group （P 〈 0.05） which was defined as the first ovulation; nevertheless, group of follicles with 〉 2.0 mm in diameter appeared for the first time in the 3.5 month age group （P 〈 0.05）. For other conformations, size of uterine horns, oviducts or ovaries, including weight of ovaries or whole reproductive tracts, were significantly developed （P 〈 0.05） that was initially taken place in the 3.5 months age group onwards. Thus, it was summarized that the onset of puberty in Thai indigenous gilts, affirmed by CL appearance at the first time, should be happened between 4.0 and 4.5 months of age; however, the development of reproductive structure and follicles to prepare in approaching puberty should be started before 3.5 months of age.
基金funded by the National Natural Science Foundation of China (32272895 and 32172744)
文摘Maternal proline(Pro)supplementation enhances fetal survival and placental development in mice.However,the effect of Pro on fetal and placental development in gilts remains to be investigated,particularly in the context of obesity-induced impaired pregnancy.Here,we investigated the effect of dietary Pro on fetal and placental development in obese gilts.Exp.1:On day 60 of gestation,48 gilts with similar delivery times were selected and followed up until delivery to determine the relationship between maternal obesity,litter performance,and Pro abundance in term placentae.The results showed that impaired reproductive performance was associated with body condition parameters and inadequate placental Pro availability of gilts.Exp.2:A total of 114 gilts were then used in a 2×3 factorial design to investigate the interaction between body condition(factor I:normal or obese gilts)and dietary Pro levels(factor II:low[0.89%,L-Pro],medium[1.39%,M-Pro],and high[1.89%,H-Pro])on farrowing performance and placental angiogenesis.This resulted in six treatment combinations:normal-L-Pro,obese-L-Pro,normal-M-Pro,obese-M-Pro,normal-H-Pro,and obese-H-Pro.The effective number of replicates per group was 17,21,19,21,18,and 18,respectively(1 gilt per replicate).The results showed that increasing Pro intake increased piglet birth weight(P=0.001),litter weight(P<0.001),placental efficiency(P=0.036)and placental vascular density(P<0.001),and decreased the number of mummified fetuses(P=0.001),the rate of low-birth-weight piglets(P=0.005),and the rate of invalid piglets(P=0.029).Interaction effects were observed between body condition and dietary Pro levels on piglet birth weight(P=0.046),within-litter birth weight variation(P=0.012),and placental vascular density(P=0.007).Moreover,the beneficial effect of Pro on farrowing performance may be related to the improvement of sirtuin 1-superoxide dismutase 2-mitochondrial reactive oxygen species axis homeostasis and angiogenesis in the placenta.Our results suggest that gestation diets need to provide adequate Pro to meet the needs of fetal and placental development,particularly in obese gilts.
基金financed by National Nature Science Foundation of China (Project No. 31572441)special funds of modernagricultural industry technology system of pig industry of the Shandong Province (SDAIT-08-04)
文摘The present study was aimed at investigating the adverse effects of dietary zearalenone(ZEA) on the lymphocyte proliferation rate(LPR), interleukin-2(IL-2), mRNA expressions of pro-inflammatory cytokines, and histopathologic changes of spleen in post-weanling gilts. A total of 20 crossbred piglets(Yorkshire × Landrace × Duroc) with an initial BW of 10.36 ± 1.21 kg(21 d of age) were used in the study.Piglets were fed a basal diet with an addition of 0.1.1,2.0, or 3.2 mg/kg purified ZEA for 18 d ad libitum.The results showed that LPR and IL-2 production of spleen decreased linearly(P < 0.05) as dietary ZEA increased. Splenic mRNA expressions of interleukin-1β(IL-1β) and interleukin-6(IL-6) were linearly upregulated(P < 0.05) as dietary ZEA increased. On the contrary, linear down-regulation(P<0.05) of mRNA expression of interferon-γ(IFN-γ) was observed as dietary ZEA increased. Swelling splenocyte in1.1 mg/kg ZEA treatments, atrophy of white pulp and swelling of red pulp in 2.0 and 3.2 mg/kg ZEA treatments were observed. The cytoplasmic edema in 1.1 mg/kg ZEA treatments, significant chromatin deformation in 2.0 mg/kg ZEA treatment and phagocytosis in 3.2 mg/kg ZEA treatment were observed.Results suggested that dietary ZEA at 1.1 to 3.2 mg/kg can induce splenic damages and negatively affect immune function of spleen in post-weanling gilts.
基金This research was funded by the National Key Research and Development Project of China(NO.2021YFD1300401)the China Agriculture Research System(No.CARS-36).
文摘The effects of age,body weight(BW),and backfat thickness(BF)of replacement gilts at first estrus and first mating on their subsequent reproductive performance and retention of their first 2 parities as sows was evaluated.A total of 3,025 Danish replacement gilts were categorized by farm(allocated to 4 farms),cross combination,age,BW and BF at first estrus and first mating,estrous cycle number at first mating,and flush feeding before first mating.The result shows that all the factors mentioned above were significantly associated with reproductive performance and retention rates of the first 2 parities.Farm 3 had more piglets born alive per litter(BA)(P<0.05).Farms 3 and 4 had more healthy piglets per litter(HP)(P<0.05).Farm 4 had the most piglets weaned per litter(PW)(P<0.05).Landrace×Landrace×Yorkshire(L×L×Y)replacement gilts had the most total piglets born per litter(TB),BA,HP,PW and a higher retention rate of the 2 parities than Landrace×Yorkshire(L×Y)replacement gilts(P<0.05).In addition,flush feeding before first mating had the most TB,BA,HP,PW,and a higher retention rate of the 2 parities than no flush feeding(P<0.05).Because the effects of replacement gilts rearing parameters on reproductive performance traits differed,we used 100 replacement gilts as a unit and the total number of weaned piglets from the first 2 parities as a new index.Replacement gilts undergoing their first estrus between 180 and 210 d of age at 115 to 124.9 kg BW and 14 to 15 mm BF had significantly higher reproductive indexes for their first 2 parities per 100 replacement gilts.Replacement gilts that mated between 210 and 230 d of age at 140 to 149.9 kg BW and 15 to 16 mm BF had optimal reproductive indexes.These results provide a new insight into the complex relationships among these reproductive performance traits and may help guide successful management of replacement gilts as a pivotal starting point for future fertility and longevity of rearing herds.
