Effects Of Rumen-protected Lysine On Production Performance And Blood Indicators Of Dairy Cows

The rumen-protection technology has largely solved the problem of low amino acid utilization in ruminants.Lysine is one of the most important limiting amino acids for ruminants.The addition of rumen-protected lysine in rations can help to regulate the protein level of rations,improve the conversion efficiency of nitrogen,and thus improve the productivity and immune function of ruminants,and to a certain extent,solve the problem of shortage of protein feed resources in China.The aim of this trial was to investigate the effect of rumen-protected lysine on the productive performance and blood parameters of dairy cows.Three hundred Holstein cows of similar pre-lactation(70±15 d),litter size(2-3)and milk yield were selected for this trial.The control group was fed the basal diet and the experimental group was supplemented with 30 g/(head-d)of rumen-protected lysine in the basal diet.The results showed that:Test one:Effect of rumen-protected lysine on the productive performance and farming benefits of dairy cows.(1)Effect on milk production efficiency:the cows’ feed intake was significantly increased on days 61-75(P<0.05),and the cows’ feed intake was significantly higher than that of the control group on days 46-60 and 76-90(P<0.01),and the difference in average dry matter intake between the two groups was highly significant(P<0.01);the cows’ milk production was significantly higher than that of the control group on days 16-60、76-90(P<0.01),and the milk yield of cows on days 61-75 was significantly increased compared to the control group(P<0.05),and the difference in milk production between the two groups was highly significant throughout the trial period(P<0.01);The feed conversion rate of cows in the test group was highly significantly higher than that of the control group on days 31-45(P<0.01),and significantly higher than that of the control group on days 16-30 and 46-60(P<0.05);the urea nitrogen content in milk of cows on days 15,30 and 60 was significantly lower than that of the control group(P<0.05),the lactose rate of cows on day 45 was significantly higher than that of the control group(P<0.05),the milk fat rate of cows on days 45 and 60 was significantly higher than that of the control group(P<0.05),the milk protein rate and milk cell count of cows in the two groups were not significantly different(P>0.05);the milk production efficiency of the test group was significantly higher than that of the control group on days 16-30 and 46-75(P<0.05),and the farming benefit was 7.1%higher than the control group.(2)Effect on apparent digestibility of feed nutrients:the apparent digestibility of EE in the diet was significantly higher than that of the control group on day 60(P<0.05),the apparent digestibility of DM was significantly higher than that of the control group on day 90(P<0.05),and there was no significant difference in the apparent digestibility of CP,NDF and ADF(P>0.05).(3)Effect on the content of harmful gases in the barn:the content of NH3 in the barn was significantly lower than that in the control group(P<0.05),and the difference in the content of H2S and CO2 gases in the barn between the two groups was not significant(P>0.05).(4)Effect on heat stress in cows:the difference between the temperature and humidity indices in the two groups of enclosures was not significant(P>0.05),the rectal temperature of cows was significantly reduced on day 90(P<0.05),and there was no significant difference between the respiratory rate and the temperature and humidity indices of enclosures in the two groups(P>0.05).There were no significant differences in the other periods for each index(P>0.05).Test two:Effect of rumen-protected lysine on blood indices of cows.The addition of rumen-protected lysine to the diet resulted in significantly lower serum BUN levels on day 30(P<0.05),and significantly higher TP levels on days 30 and 90 than in the control group(P<0.05),serum levels of ALB,ALT,AST,GLU and TG in dairy cows were not significantly different compared to the control group(P>0.05);Serum IgG levels were significantly increased(P<0.05),and serum IL-2 levels were significantly decreased on day 30 of the trial(P<0.05),while serum IgA,IgM,NEFA,TNF-α,IL-1βand IL-6 levels in cows were not significantly different from those in the control group(P>0.05).The differences in the other periods of the indicators were not significant(P>0.05).In summary,under the conditions of this trial,supplementation with rumen-protected lysine improved lactation performance and milk production efficiency;increased apparent digestibility of key nutrients;reduced harmful gas concentrations in the pen;alleviated heat stress in cows to some extent;improved some blood index levels in cows and improved body immunity and production performance,thus improving farming efficiency.