| Environmental pollution and shortage of protein feed is the main factor that restricts the sustainable development of animal husbandry in our country,improve the utilization rate of feed is an important means of saving feed resources to reduce waste emissions.The purpose of this study was to study the effects of dietary supplementing with active dry yeast(ADY)on growth performance,apparent digestibility of nutrients,serum biochemical indicators,slaughter performance and rumen microflora in beef cattle,investigating the difference in production performance between ADY supplemented with low nutrient levels and beef fed high-nutrient diets,which provided theoretical basis for production practice of active dry yeast.In this experiment,32 fattening beef cattle(simmental crossbred cattle × cattle-yaks),with an average body weight of 110 ± 12.85 kg were selected as subjects,and randomly divided into four treatment groups,detailed grouping are as follows: the low nutrition level group(control group),low nutrition level group + ADY 2 g/d·head(ADY2 group),low nutrition level group + ADY 4 g/d·head(ADY4 group)and high plane of nutrition group(HPN group).The formula design refers to the Chinese beef cattle breeding standard(NY/T 815-2004),in which the low nutrient level diet is designed according to the weight of 150 kg and the daily weight gain of 1.1 kg,and the high nutrient level diet is designed according to the daily weight gain of 1.2 kg.The formal test lasted 110 days.The results are as follows:(1)Dietary supplementing with ADY could improve production performance of beef cattle.Dietary supplementing with ADY has no significant effect on the final weight of beef cattle(P>0.05),the final weight of HPN group was significantly higher than that of control group(P<0.05),but there was no significant difference with ADY2 and ADY4 group(P>0.05).Dietary supplementing with ADY could improve ADG of beef cattle,the ADG of ADY2 and ADY4 group were significantly higher than that of control group(P<0.05),and the ADG of HPN group was significantly higher than that of control group and ADY2 group(P<0.05),but there was no significant difference with ADY4 group(P>0.05).The DMI of HPN group was significantly higher than that of control group and ADY2 group(P<0.05),but there was no significant difference with ADY4 group(P>0.05).There was no significant difference in FCR between the yeast-added group,the HPN group and the control group(P>0.05).(2)There was no significant difference in serum urea content of ADY2,ADY4 and control group(P>0.05),the serum urea content in the high nutrition diet group was significantly higher than that in the ADY4 group(P<0.05).The serum LDL content in ADY4 group was significantly higher than that in HPN group(P<0.05),but there was no significant difference in other two groups(P>0.05).The serum ALT content of in control group and ADY4 group were significantly higher than that in HPN group(P<0.05),but there was no significant difference between yeast addition group and control group(P>0.05).(3)The pre-slaughter live weight of the HPN group was significantly higher than that of the control group(P<0.05),but there was no significant difference between the pre-slaughter live weight of the ADY2 and ADY4 groups(P>0.05).The carcass weight in HPN group was significantly higher than that in control group and ADY2 group(P<0.05),but there was no significant difference between ADY4 group(P>0.05).The net meat weight of the HPN group was significantly higher than the other three groups(P<0.05).The dietary ADY had no significant effect on beef cattle net meat weight,slaughter rate and net meat rate(P>0.05).(4)Adding ADY or high nutrition diet had no significant effect on Moisture,CP,EE and Ash of beef(P>0.05).(5)The CP digestibility of ADY2 group and ADY4 group was not significantly different from that of the control group(P>0.05),the digestibility of CP in HPN group was significantly higher than that in control group and ADY2 group(P<0.05),but there was no significant difference with ADY4 group(P>0.05).The digestibility of ADF and NDF in ADY2 group and ADY4 group were not significantly different from that in the control group(P>0.05),while the NDF and ADF digestibility in HPN group was significantly higher than that in control group(P>0.05),the difference in NDF and ADF digestibility between HPN group and ADY2 and ADY4 group were not significant(P>0.05).(6)Dietary supplementation with ADY improved rumen fermentation.The rumen ammonium nitrogen content in the control group was significantly higher than that in the ADY2 group and ADY4 group(P<0.05),which was no significant difference with HPN group(P>0.05).The rumen VFA concentration and acetic acid concentration in the HPN group were significantly higher than those in the ADY4 group(P<0.05),which was not significantly different from the other two groups(P>0.05).The propionic acid concentrations in the ADY2,ADY4,and HPN group were significantly higher than those in the control group(P<0.05).Dietary supplementation with ADY or high-nutrient diet had no significant effect on rumen pH,MCP,butyric acid concentration and acetic acid/propionic acid in beef cattle(P>0.05).(7)Dietary supplementation of ADY has a significant effect on the rumen microflora of beef cattle,Simpson index and Shannon index in control group and HPN group were significantly higher than those of ADY4 group(P<0.05),but were not significantly compared with ADY2 group.At the phylum level,the relative abundance of Firmicutes in the HPN group was significantly higher than that in the ADY4 group(P<0.05),which was not significantly different from the other two groups(P>0.05).At the genus level,the relative abundance of Ruminococcaceae UCG-002 in ADY4 group was significantly higher than that in control group and HPN group(P<0.05),and there was no significant difference with ADY2 group(P>0.05).In conclusion,the diet supplementing with active dry yeast can improve the production performance of beef cattle,increase the benefit of breeding,but no significant effect on the chemical composition index(Moisture,CP,EE and Ash)of beef.Adding ADY in diet can improve apparent digestibility of nutrients and the utilization of nitrogen of beef cattle,increased rumen propionic acid production,increased energy efficiency in diets.Meanwhile,it reduced rumen microbial diversity and increased of the relative abundance of Ruminococcaceae UCG-002.Under the conditions of this experiment,the production performance of beef cattle fed with low nutrition level diet(NEmf: 5.11 MJ/kg,CP: 12 %)supplemented with 4 g/d ADY was similar to that of high plane of nutrition diet(NEmf: 5.87 MJ/kg,CP:13.05 %). |
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