Effect Of Diets With Low Energy And RPL Supplementation For Per-partum Cows On Colostrum Quality, Growth Performance Of Pre-Weaning Calves

The aim of this experiment is to provide a theoretical foundation and practical reference for the maternal effect of low-energy diet in the early perinatal period in China and rational utilization of additives though investigating the effects of low dietary energy level and rumen-protected lysine?RPL?for per-partum cows on colostrum quality of cows,growth performance,serum indexes and rumen fermentation of pre-weaning calve.The details are in the following three trials:Trial 1:Effect of diets with low energy and RPL supplementation for per-partum cows on cows.This experiment was used 2×2 factorial design,including net energy for lactating cow?NEL,6.40 and 5.73 MJ/kg DM?and RPL?0,40 g/d per head?.Fifty-two dry Holstein cows in 3 parities were blocked by body score and predicted calving date and randomly assigned to 1 of 4 treatments.Cows were fed in the four groups including a basal diet?B?,a low energy diet?L?,the basal diet supplemented with RPL?BL?and the low energy diet supplemented with RPL?LL?,respectively.The experiment was lasted from day 21 before expected date of calving of cows to calving.Calving difficulty was conducted when cows calved.The colostrum was collected during the first milking time after giving birth,and the contents of total solids,protein,fat and lactose,IgG,IgM and IgA were measured.The results were showed as follows:Transition diets with low energy level decreased total solid,lactose and IgM content in the colostrum?P?0.05?;RPL supplementation in transition maternal diets had no effect on calving difficulty and colostrum indexes?P>0.05?.No interaction was observed between transition dietary energy level and RPL supplementation on calving difficulty and colostrum quality of cows?P?0.05?.Trial 2:Effect of diets with low energy and RPL supplementation for per-partum cows on growth performance of pre-weaning calves.Calves from cows in trial 1 were taken as research objects.After delivery,calves of each group were selected to be tested from birth to weaning.Postpartum calves in each group were fed the same diet.Body weight and body side were measured on birth?0 d?,21 d,42 d,60 d.Feed intake and fecal status of each calf were recorded every day to calculate diarrhea frequency and fecal index.The results were showed as follows:1)Transition diets with low energy level decreased body weight at 42 and 60 days of age?P?0.05?,body height at21 and 60 days of age?P?0.05?,body length at 21 and 60 days of age?P?0.05?and chest girth of female calves at birth,21 and 60 days of age?P?0.05?,increased body length of male calves at 21 days of age?P?0.05?,increased body weight of male calves at 60 days of age?P?0.05?and chest girth of male calves at 21 days of age?P?0.05?.RPL supplementation in transition maternal diets increased body length of female calves at 21 days of age?P?0.05?,and had a decreasing trend on body weight of male calves at 42?P=0.0519?and 60?P=0.0730?days of age.2)Transition diets with low energy level reduced the ADG of female calves from 0 to 21 d,21 to 42 d and F/G from 0 to 60 d?P?0.05?,and the ADFI of female calves from 42 to 60 d and F/G of male calves from 0 to 60 d?P?0.05?.RPL supplementation in transition maternal diets had no significant effect on the ADG,ADFI and F/G of the female calves?P>0.05?.3)Diets with different energy level and RPL supplementation for per-partum cows had no significant effect on the diarrhea frequency and fecal index of calves before weaning?P>0.05?.4)No interaction was observed between transition dietary energy level and RPL supplementation on growth performance of pre-weaning calves?P?0.05?.Trial 3:Effect of diets with low energy and RPL supplementation for per-partum cows on serum indexes and rumen fermentation of pre-weaning calves.Trial design and trial calves are the same as trial 2.Blood samples were collected from calves at 0 d?before colostrum feeding?,1 d?after colostrum feeding?and 60 d?9:00?before morning feeding,and the contents of serum glucose?GLU?,total protein?TP?,albumin?ALB?and urea nitrogen?BUN?were measured.Rumen liquid was collected on 60 d to measure its pH,ammonia nitrogen?NH₃-N?and volatile fatty acid?VFA?concentrations.The results were showed as follows:1)Transition diets with low energy level reduced the contents of GLU at birth,TP at birth,ALB at birth,GLB at birth,BUN at birth of female calves,and decreased the contents of GLU at birth,TP at birth,ALB at birth and 1 day,GLB at birth,BUN at birth and 60 days of male calves?P?0.05?.RPL supplementation in transition maternal diets had no significant effect on the content of GLU,TP,ALB,GLB and BUN of female calves?P>0.05?,and decreased the content of GLU at 60 days of male calves?P?0.05?.2)TVFA,Acetic acid,Propionic acid,Isobutyric acid,butyric acid,Isovaleric acid and Valeric acid in the rumen liquid of calves of maternal diets with low energy level were lower?P?0.05?;RPL supplementation in transition cows'diets had no significant effects on rumen fermentation indexes of calves?P?0.05?.3)No interaction was observed between transition dietary energy level and RPL supplementation on serum indexes and rumen fermentation indexes of pre-weaning calves?P?0.05?.In sum up,transition diets with different energy levels can regulate the growth and health of the subgeneration,but the diets with low energy level is not conducive to the growth and development of calves.RPL supplementation in transition cows'diets is not affected to the preweaning calves.Therefore,diets with low energy and RPL supplementation for per-partum cows is not alternative to basal diets with normal standardized energy level.