Abstract:

We investigated the effects on the blood biochemical indexes， antioxidant indexes， rumen fermentation indexes， and rumen bacteria of two different ratios of mulberry silage as a replacement for soybean meal in the diet of Xiangdong black goats. Forty-five healthy Xiangdong black goat rams aged 5-6 months with similar body weight （18.2±1.6 kg） were randomly divided into three groups： a control group （group CK）， a 50% replacement group （group S₁） and a 100% replacement group （group S₂）. The pre-test period was 7 days， and the formal experimental period was 55 days. The remaining feed from the previous day was weighed every morning before feeding and the goats were weighed every 2 weeks. On the morning of the 54^th day of the formal test period， blood samples were collected from the jugular vein of each goat. Rumen fluid was collected orally 3 hours after morning feeding on the 54^th day and before morning feeding on the 55^th day of the formal experimental period for the determination of blood indexes， rumen fermentation indexes， and rumen microbial composition. The results showed that the final body weight， average daily gain， and dry matter intake were significantly higher in the S₁ and S₂ groups than in the CK group （P<0.05）. The serum low density lipoprotein cholesterol concentration was significantly lower in group S₂ than in the CK group and group S₁ （P<0.05）， and serum albumin and cholinesterase concentrations were significantly higher in group S₂ than in the CK group （P<0.05）. The total antioxidant capacity was significantly higher in groups S₁ and S₂ than in the CK group （P<0.05）， but the malondialdehyde content was significantly higher in group S₂ than in the CK group （P<0.05）. As the amount of mulberry protein in the diet increased， the molar ratio of acetic acid to isovaleric acid decreased significantly （P<0.05）， and the molar ratio of propionic acid to valeric acid increased. The replacement of soybean meal in the diet with mulberry silage did not affect the alpha diversity of rumen microorganisms （P>0.05）. The dominant taxa in the three groups were Bacteroidota and Bacillota. With increasing amounts of mulberry silage in the diet， the abundance of Bacillotaincreased significantly （P<0.05）， and the abundance of Bacteroidota decreased significantly （P<0.05）. The dominant bacteriain the threegroups were Xylanibacter， Butyrivibrio， Segatella，Succiniclasticum， Fibrobacter， and Olivibacter. The abundance of Butyrivibrio was significantly higher in group S₂ than in the CK group and group S₁ （P<0.05）， and that of Olivibacter was significantly lower in group S₂ than in the CK group and group S₁ （P<0.05）. These results show that replacing soybean meal with mulberry silage in the diet of goats improved their metabolism and increased their antioxidant capacity without affecting the alpha diversity of their rumen microorganisms. Therefore， this resource has promising applications in ruminant breeding.

Key words: silage mulberry, soybean protein, blood biochemistry, rumen microorganism, goat