摘要
A total of 480 nursery pigs （Duroc x Landrace x Large White） were utilized in two experiments conducted to determine the effects of different ratios of standardized ileal digestible lysine （SID- Lys） to metabolizable energy （ME） ratio on the performance, nutrient digestibility, plasma urea nitrogen （PUN） ,and plasma free amino acids of 10 to 28 kg pigs. In Exp. 1, 192 pigs （ 10.58 kg） were assigned to one of four treatments. The treatments consisted of diets with a ME content of 3.2, 3.25, 3.3, or 3.35 Mcal/kg with a constant SID-Lys：ME ratio of 3.7 g/Mcal. The experiment lasted 28 days. Pigs which were fed the diets containing 3.3 and 3.35 Mcal/kg ME had lower feed intakes （ P 〈 0.05）than those fed 3.2 Mcal/kg. Feed efficiency was linearly improved with increasing dietary ME （ P 〈0.05）. Increasing the dietary ME level also increased （P 〈0.05 ） dry matter and energy digestibility. Therefore,3.3 Mcal/kg ME was selected for Exp. 2 in which 288 pigs （ 10.60 kg） were assigned to one of six treatments. Treatments consisted of SID-Lys： ME ratios of 3.1,3.3,3.5,3.7,3.9, or 4.1 g/Mcal with all diets providing 3.3 Mcal of ME/kg. Weight gain and feed efficiency were increased （P 〈0.05 ） as the SID-Lys：ME ratio in diet increased. Based on a straight broken-line model ,the estimated SID-Lys：ME ratio to maximize weight gain was 3.74.
A total of 480 nursery pigs （Duroc x Landrace x Large White） were utilized in two experiments conducted to determine the effects of different ratios of standardized ileal digestible lysine （SID- Lys） to metabolizable energy （ME） ratio on the performance, nutrient digestibility, plasma urea nitrogen （PUN） ,and plasma free amino acids of 10 to 28 kg pigs. In Exp. 1, 192 pigs （ 10.58 kg） were assigned to one of four treatments. The treatments consisted of diets with a ME content of 3.2, 3.25, 3.3, or 3.35 Mcal/kg with a constant SID-Lys：ME ratio of 3.7 g/Mcal. The experiment lasted 28 days. Pigs which were fed the diets containing 3.3 and 3.35 Mcal/kg ME had lower feed intakes （ P 〈 0.05）than those fed 3.2 Mcal/kg. Feed efficiency was linearly improved with increasing dietary ME （ P 〈0.05）. Increasing the dietary ME level also increased （P 〈0.05 ） dry matter and energy digestibility. Therefore,3.3 Mcal/kg ME was selected for Exp. 2 in which 288 pigs （ 10.60 kg） were assigned to one of six treatments. Treatments consisted of SID-Lys： ME ratios of 3.1,3.3,3.5,3.7,3.9, or 4.1 g/Mcal with all diets providing 3.3 Mcal of ME/kg. Weight gain and feed efficiency were increased （P 〈0.05 ） as the SID-Lys：ME ratio in diet increased. Based on a straight broken-line model ,the estimated SID-Lys：ME ratio to maximize weight gain was 3.74.
基金
support received from the State Key Laboratory of Animal Nutrition of China ( No .2004DA125184-0810)
National Natural Science Foundation of China(No .31072040)
Guangdong Cooperation Project be-tween Industry-Academia-Research of China ( No .2009B090300110)
the Ministry of Science and Technology of the People’s Republic of China ( No .2006BAD12B05-10and No . Nyhyzx07-34)
