Effects Of Feeding Yeasts On Growth Performance,Rumen Fermentation And Blood Indices In Young Dairy Goats

Microecological preparation is a kind of high quality antibiotic substitutes under the background of total prohibition against antibiotics,which can effectively participate in the balance of gastrointestinal microecology,regulate microflora,promote digestion and absorption and other physiological functions,and have the advantages of no residue and no toxic side effects.Saccharomyces cerevisiae is a commonly used microecological preparation for ruminants,which can consume rumen oxygen,facilitate the proliferation of beneficial bacteria such as fiber degrading bacteria and protein degrading bacteria,improve nutrient digestibility,body health,and thus enhance animal growth and production performance.There are many researches about the effects of yeast on ruminants,but few researches on the feeding methods of yeast.In addition,most of the studies only observed the effects of yeast in the experimental period,without considering its long-term effects.It is assumed that the colonization of yeast in rumen is continuous,and the intermittent addition of Saccharomyces cerevisiae can reduce usage without changing the effect,so as to reduce the cost,and the effect of yeast is long-term effective.In this research,Saccharomyces cerevisiae were added to the diet in different ways to study the effects and mechanism of continuous and intermittent addition on young dairy goats,so as to provide a theoretical basis for improving the growth performance and reducing the raising cost of dairy goats.Sixty 4-month-old female Guanzhong dairy goats were randomly divided into three groups according to weight（19.65±0.41 kg）,which were control group,continuous addition group and intermittent addition group.The three groups was fed the following diets:（1）basal diet（control group）;（2）basal diet+3 g/d Saccharomyces cerevisiae per goat,continuously added daily（continuous addition group）;（3）Basal diet+4.5 g/d Saccharomyces cerevisiae per goat,every 5 d interval 5 d（intermittent addition group）.The experiment lasted for 67 days,including 7 days of pre-feeding period and 60 days of formal experimental period.At the end of the trial period,all the goats（6 months old）were returned to the large group for unified feeding.After 6 months（12 months old）,the weight and lambing of the goats were recorded and the long-term effect of Saccharomyces cerevisiae was observed.Body weight and body size of dairy goats were measured before morning feeding on d6 and 7 of pre-feeding period and d 29,30,59 and 60 of the formal trial period.Diet and leftovers samples were collected on d 1,30 and 60 of the formal trial period for determination of nutrient composition.Feces,rumen fluid and blood samples were collected to measure various indicators from 10 goats in each group at random on d 15,30,45 and 60of the trial period.Fecal samples were collected through the rectum 3 times a day for the determination of nutrients;rumen fluid samples were collected 2 h after morning feeding using an oral cannula to determine p H,NH₃-N,VFA and cellulase activity;blood samples were collected from the jugular vein at the same time for determination of serum biochemical and immune indicators.The test results are as follows:1.Compared with the control group and intermittent addition group,continuous addition of Saccharomyces cerevisiae tended to increase DMI（P=0.081）,significantly improve the apparent digestibility of NDF and ADF（P<0.001）,and improve ADG（P=0.044）,but had no significant effect on body size indexes（P>0.05）;follow up results showed that continuous addition of Saccharomyces cerevisiae could significantly increase body weight at 12 months（P=0.001）,weight gain at 6-12 months（P=0.027）and the birth weight of lambs（P=0.015）.There was no significant difference in growth performance between control group and intermittent addition group（P>0.05）.2.Continuous and intermittent addition of Saccharomyces cerevisiae significantly decreased the ammonia-nitrogen concentration of rumen fluid（P=0.046）and increased the isobutyric acid concentration（P=0.011）.The continuous addition group tended to increase the acetylesterase activity（P=0.074）,and there were no significant differences in rumen fluid p H value,VFA（except isobutyric acid）concentration and proportion among the three groups（P>0.05）.3.Continuous and intermittent addition of Saccharomyces cerevisiae could significantly reduce serum urea nitrogen concentration（P<0.001）,and the continuous addition group could also significantly reduce the serum globulin content（P=0.006）and increase the albumin-globulin ratio（P=0.022）,but had no significant effect on albumin concentration（P=0.442）.There were no significant differences in glucose and triglyceride concentrations among the three groups（P>0.05）.This experiment showed that the continuous addition of Saccharomyces cerevisiae can improve the utilization efficiency of feed protein and the growth performance of young dairy goats,and has a long-term effect,while the intermittent addition has no significant effect.