Effect Of Dietary Supplementing Ruminally-protected Lysine And Methionine During Transition On The Performance Of Cows And Calves

The objectives of this study were to assess the effects of dietary supplementation of ruminally-protected lysine(RPL),or ruminally-protected methionine(RPM),and the combination(RPML)during the periparturient period(from 3 wk pre-calving until 3 wk post-calving)on the performance of transition dairy cows and passive immunity transfer of their'neonatal calves.Besides,to evaluate the effect of a continual supply of a combination of RPL and RPM during the high milking period(from 3 wk to 150 d post-calving)on the efficiency of production and fertility and nitrogen use.Chapter 1 provides a comprehensive literature review of RPL and RPM and the supplementation strategies to improve the performance of transition cows and their calves.In the 1^st experiment(transition cows experiment;Chapter 2).120 prepartum multiparous Holstein cows were used and divided into 4 groups:(1)the basal diets CON,n=30);(2)supplemental methionine(RPM,pre-calving at a rate of 0.16%of DM and post-calving at 0.12%DM,n=30);(3)supplemental lysine(RPL,pre-calving at 0.33%DM and post-calving at 0.24%DM,n=30);(4)the combination(RPML,pre-calving at 0.16%RPM+0.33%RPL DM and post-calving at 0.12%RPM+0.24%RPL of DM,n=30).Ruminally-protected amino acids were mixed with the premix and added to the total mixed ration(TMR).Colostrum samples were taken on the parturition day and analyzed.Milk yield and dry matter intake(DMI)were measured daily;milk samples were taken on the d 7,14,and 21 days relative to calving(DRC).Tail vessel samples were collected on d-21,-14,-7 before expected calving and d 0,7,14,and21 DRC.The CON cows always had lower DMI than other treatments.Providing RPAA to transition cows improved colostrum quality(Brix),energy-corrected milk(ECM),milk fat,total protein,and lactose percentages were greater(P<0.001),and decreased milk urea nitrogen and?-hydroxybutyrate concentrations(P?0.01).In the 2^nd experiment(calves experiment;Chapter 3).Eighty heifer calves born to the experimental cows were assigned into four treatments based on their dam'diets(n=20 calves per group).Keep the grouping of experiment 1.Calves were fed colostrum from their dams within 2 h of birth.Calves were then fed milk only(d 2 to 22),then a combination of milk and milk replacer(d 23 to 25),and fed a milk replacer only(d 25 to 60.Blood samples were taken immediately after calving and 12,24,and 48 hours and 5 and 7 days after birth.Serum total protein concentrations were higher in calves born from supplemented cows than those from unsupplemented cows(P<0.01).Treatments groups had higher plasma immunoglobulin G(Ig G)concentrations and passive immunity transfer percentage than those in the CON group(P<0.05).The daily gain was higher for calves born to cows fed amino acids than others(P<0.001).Birth body weight did not differ between the treatments(P=0.97).Weaning weight was higher in the RPML group than in the other groups(P<0.001).In the 3^rd experiment[(high milking period experiment(from 22 to 150 days in milk,DIM);Chapter4],to follow up on the performance of dairy cows during the subsequent lactation and the extent to which they are affected by feeding during the transition period.All experimental cows were fed a mixture of RPM and RPL(RPML,0.17%RPM,and 0.41%RPL of DM;n=25 cows in each treatment;1.80 Mcal/kg of DM)and kept the same grouping as experiment 1.Milk production,DMI,nitrogen utilization and fertility efficiency were measured.Milk and blood samples were taken on 21,30,60,90,120,and 150DIM.Perinatal cows that consumed amino acid had a higher milk production and milk protein yield and a greater peak milk yield and quickly reached the peak of milk(P<0.05).Nitrogen efficiency has improved in response to the continual supply of a combination of Lys and Met(P=0.04),but not during the transition period.A higher pregnancy rate was observed for cows that fed RPML?RPML diet compared to other cows(P<0.05).These results demonstrate that the continual dietary supply of ruminally-protected lysine and methionine during the periparturient period and afterward could be used as a nutritional strategy to improve dry matter intake,milk production,nitrogen utilization,and reduce consumption the incidence rate of metabolic disorder throughout the transition period and subsequent lactation.The benefit includes the enhancement of income over feed cost during both fresh and high milking periods and increased fertility efficiency.In addition to the improvement in the production efficiency of cows,the growth rate and immunity of neonatal calves have improved.This thesis summarizes the key findings and limitations of our research and suggestions for future studies.