| Three different experiments were conducted to investigate the effects of cysteamine (CS) and yeast culture(YC) on the on nutrient apparent digestibility, ruminal microbial protein production, milk performance, nitrogen excretion and blood biochemical parameters, determine the suitable supplemental of cysteamine, yeast culture, combination supplemental of cysteamine and yeast culturein in dairy cow.1. Effects of supplemental levels of cysteamine on apparent digestibility, ruminal microbial protein production, milk performance, nitrogen excretion and blood biochemical parameters of dairy cowsThis experiment was conducted to determine the suitable supplemental of cysteamine in dairy cow.A total of 40 Holstein lactating cows with similar age, body weight, milk yield and lactation stage (135±15 day in milk) were divided into 4 groups, and each group had 10 replicates with 1 cow per replicate. The supplement level of CS in control and test groups 1,2 and 3 was 0,15,20 and 25 g/(d·head), respectively. The pretest lasted for 15 days, and the test lasted for 60 days.The results showed that the different CS supplementation in dietary had no significant effect on main nutrient intake(p>0.05), increased the apparent digestibility of crude protein(P<0.05). From the perspective of microbial protein, the supplementation of 20 g/(d·head) CS was extremely significant than the control group(P<0.01). CS could significantly increase milk yields, milk fat percentage and milk protein concentration (P<0.05 or P<0.01), but significantly reduced milk somatic cell count (P<0.05). Compared with control group, total nitrogen excretion in test groups was significantly reduced (P<0.01), especially the supplementation of 20 g/(d·head) of CS. Dietary supplementation with CS significantly effects the levels of total protein, globulin, urea nitrogen, growth hormone in the serum(P<0.05), but the serum glucose, albumin, alanine transferase, creatinine, insulin had no significant effect(P>0.05).Based on the data of pparent digestibility, ruminal microbial protein production, milk performance, nitrogen excretion and blood biochemical parameters, it can be concluded that the suitable supplemental level of CS is 20 g/(d·head) in dairy cows under the condition in the present study.2. Effects of supplemental levels of yeast culture on apparent digestibility, ruminal microbial protein production, milk performance, nitrogen excretion and blood biochemical parameters of dairy cowsThis experiment was conducted to determine the suitable supplemental of yeast culture in dairy cow. A total of 40 Holstein lactating cows with similar age, body weight, milk yield and lactation stage (135±15 day in milk) were divided into 4 groups, and each group had 6 replicates with 1 cow per replicate. The supplement level of YC in control and test groups 1,2 and 3 was 0,80,100 and 110 g/(d·head), respectively. The pretest lasted for 15 days, and the test lasted for 60 days.The results showed that the different YC supplementation in dietary had significant increased on DM intake(P<0.05), increased the apparent digestibility of DM, CP, Ca, P(P<0.05). The supplementation of 100 g/(d-head) YC was significantly increased by 18.5% compared ruminal microbial protein production than control group(P<0.01),10.05% greater daily yields of milk than control group(P<0.01) and reduced nitrogen excretion by 12.01% compared to control group (P<0.01). YC could increase milk fat percentage and milk protein concentration (P<0.05), significantly reduced milk somatic cell count (P<0.05), effects the levels of glucose, globulin, urea nitrogen, insulin in the serum(P<0.05).Based on the data of pparent digestibility, ruminal microbial protein production, milk performance, nitrogen excretion and blood biochemical parameters, it can be concluded that the suitable supplemental level of YC is 100 g/(d·head) in dairy cows under the condition in the present study.3. Effects of combination supplemental levels of cysteamine and yeast culture on apparent digestibility, ruminal microbial protein production, milk performance, nitrogen excretion and blood biochemical parameters of dairy cowsThis experiment was conducted to determine the combination supplemental of cysteamine and yeast culture in dairy cow. A total of 40 Holstein lactating cows with similar age, body weight, milk yield and lactation stage (135±15 day in milk) were divided into 10 groups, group C was fed a basal diet, experimental groups were jointly supplemented with CS and YC at different levels. The supplemental levels of CS were designed as 17.5 (L),20 (M),22.5 g/(d·head) (H). The supplemental levels of YC were designed as 90 (L),100 (M),110 g/(d·head) (H). The experimental groups were LL, ML, HL, LM, MM, HM, LH, MH and HH groups, and each group had 4 replicates with 1 cow per replicate. The pretest lasted for 15 days, and the test lasted for 60 days.The results showed that supplementation of CS and YC in dairy cow diets could increased on DM intake(P<0.05), increased the apparent digestibility of DM, CP, Ca, P(P<0.05). The combination supplementation levels of CS and YC are 22.5 and 100 g/(d·head) was significantly increased by 26.53% compared ruminal microbial protein production than control group(P<0.01),25.33% greater daily yields of milk than control group(P<0.01) and reduced nitrogen excretion by 27.25% compared to control group (P<0.01). Supplementation CS and YC could increase milk fat percentage and milk protein concentration (P<0.05), significantly reduced milk somatic cell count (P<0.05), especially the treatment group HM. Supplementation CS and YC could effects the levels of glucose, globulin, urea nitrogen, insulin, growth hormone in the serum (P<0.05).Based on the data of pparent digestibility, ruminal microbial protein production, milk performance, nitrogen excretion and blood biochemical parameters, it can be concluded that the optimal combination supplemental levels of CS and YC are 22.5 and 100 g/(d·head) under the condition in the present study. |
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