This study was to evaluate how low phosphorus(P)diets affect growth performance and fecal P excretion in Xia-Nan cattle and to elucidate the underlying mechanisms.Thirty-two healthy Xia-Nan bulls with similar body wei...This study was to evaluate how low phosphorus(P)diets affect growth performance and fecal P excretion in Xia-Nan cattle and to elucidate the underlying mechanisms.Thirty-two healthy Xia-Nan bulls with similar body weights(BW;267.42±45.77 kg)were assigned to four groups with eight individual replicate pens per group in a completely randomized block design,stratified by initial BW and average dry matter intake(DMI).Cattle were fed total mixed rations(concentrate-to-forage ratio 40:60)with varying dietary P levels(DM basis):0.16%(XPA),0.19%(XPB),0.22%(XPC),and 0.25%(XPD;control)for 90 d.The first three groups were considered low-P treatments.Compared with the XPD group,XPA showed significantly lower average daily gain(ADG;P=0.018)and DMI(P=0.046),while XPB and XPC showed no differences(P>0.05).XPB group showed a significant lower feed conversion ratio(FCR)than XPA(P=0.049)and had the lowest FCR among all groups.Total-tract apparent digestibility of calcium(Ca;P=0.006)and P(P=0.006)decreased linearly with dietary P reduction.P intake(P<0.001)and fecal P content(P<0.001)were significantly lower in low-P groups than in the XPD group and decreased linearly with P reduction.Serum concentrations of parathormone hormone(PTH;P<0.001),1,25-dihydroxyvitamin D_(3)(1,25(OH)_(2)D_(3);P=0.005),Ca(P<0.001),and P(P<0.001)were positively correlated with decreasing dietary P levels,whereas calcitonin(CT;P=0.016)and alkaline phosphatase(ALP;P=0.006)were negatively correlated.XPB and XPD groups had higher molar proportions of propionate(P<0.001)and butyrate(P=0.006)but lower acetate molar proportion(P<0.001)and acetate-to-propionate ratio(P<0.001)than XPA.Fecal P excretion correlated positively with Ruminococcaceae_UCG-005,Saccharofermentans,and Butyrivibrio,and negatively with Rikenellaceae_RC9_gut_group and uncultured_bacteriumf_F082.These results suggest that reducing dietary P to 0.19%(XPB)maintained optimal growth performance while reducing environmental P pollution in XiaNan cattle.展开更多
基金supported by the Research and demonstration of key Technologies for low-cost,healthy and Efficient Beef Cattle breeding(Grant No.2024BBF01008)National Natural Science Foundation of China(Grant No.32302764)Hunan Provincial Natural Science Foundation(Grant No.2024JJ5179).
文摘This study was to evaluate how low phosphorus(P)diets affect growth performance and fecal P excretion in Xia-Nan cattle and to elucidate the underlying mechanisms.Thirty-two healthy Xia-Nan bulls with similar body weights(BW;267.42±45.77 kg)were assigned to four groups with eight individual replicate pens per group in a completely randomized block design,stratified by initial BW and average dry matter intake(DMI).Cattle were fed total mixed rations(concentrate-to-forage ratio 40:60)with varying dietary P levels(DM basis):0.16%(XPA),0.19%(XPB),0.22%(XPC),and 0.25%(XPD;control)for 90 d.The first three groups were considered low-P treatments.Compared with the XPD group,XPA showed significantly lower average daily gain(ADG;P=0.018)and DMI(P=0.046),while XPB and XPC showed no differences(P>0.05).XPB group showed a significant lower feed conversion ratio(FCR)than XPA(P=0.049)and had the lowest FCR among all groups.Total-tract apparent digestibility of calcium(Ca;P=0.006)and P(P=0.006)decreased linearly with dietary P reduction.P intake(P<0.001)and fecal P content(P<0.001)were significantly lower in low-P groups than in the XPD group and decreased linearly with P reduction.Serum concentrations of parathormone hormone(PTH;P<0.001),1,25-dihydroxyvitamin D_(3)(1,25(OH)_(2)D_(3);P=0.005),Ca(P<0.001),and P(P<0.001)were positively correlated with decreasing dietary P levels,whereas calcitonin(CT;P=0.016)and alkaline phosphatase(ALP;P=0.006)were negatively correlated.XPB and XPD groups had higher molar proportions of propionate(P<0.001)and butyrate(P=0.006)but lower acetate molar proportion(P<0.001)and acetate-to-propionate ratio(P<0.001)than XPA.Fecal P excretion correlated positively with Ruminococcaceae_UCG-005,Saccharofermentans,and Butyrivibrio,and negatively with Rikenellaceae_RC9_gut_group and uncultured_bacteriumf_F082.These results suggest that reducing dietary P to 0.19%(XPB)maintained optimal growth performance while reducing environmental P pollution in XiaNan cattle.
