Effects Of Laminaria Japonica Hydrolysate On Performance,Serum Indices And Rumen Environment Of Lactating Dairy Cows

Previous studies have shown that kelp has beneficial effects on improving performance,antioxidant and immunity of livestock and poultry.The purpose of this study was to observe the effects of Laminaria japonica hydrolysate（LPH）supplementation on lactating dairy cows.Ninety healthy lactating Holstein cows with parities 2.6±1.6,average milk yield of 41.2±6.57 kg/d and lactation days of 125±16 days were randomly divided into three groups with 30 cows in each group.The experiment lasted for 60 days.The experimental treatments were fed 0（control group）,15（low dose group）or 30 g/d（high dose group）LPH,respectively.The experimental results were as follows:Supplementation with LPH significantly reduced dry matter intake in high dose group（P<0.01）,but there was no significant difference between low dose group and control group（P>0.05）.The experimental treatments had no significant effect on milk yield of dairy cows（P>0.05）.Affected by lactation stage,milk yield in the three groups gradually decreased during the experiment period,but the low dose group had a tendency to delay the decline（P=0.09）.LPH supplementation could significantly increase milk protein content（P<0.05）,and the somatic cell count tended to decrease in low dose group（P=0.07）.Results of serum biochemical indexes showed that supplementation with LPH could significantly reduce the total cholesterol content in serum（P<0.05）,and significantly increase the serum glucose and high density lipoprotein cholesterol content in high dose group（P<0.01）.The low-dose group had a tendency to increase total protein content（P=0.06）,and the high-dose group had a tendency to decrease low-density lipoprotein cholesterol content（P=0.09）.The results of serum antioxidant and inmmune indexes showed that the experimental treatments significantly increased serum total antioxidant capacity（P<0.01）and super oxide dismutase content（P=0.01）,and significantly decreased serum malondialdehyde content（P<0.01）.Supplementation with LPH significantly increased the contents of Immunoglobulin A（P<0.01）and Immunoglobulin G（P<0.01）in serum,and the contents of Immunoglobulin M in low dose group were also significantly increased（P<0.05）.LPH supplementation had a tendency to decrease isobutyric acid（P=0.09）,but had no significant effects on rumen fluid pH value,acetic acid,propionic acid,butyric acid,isovalerate acid,valerate acid and caproic acid（P>0.05）.The results of rumen microflora showed that at the level of phylum,Spirochaetota abundance was decreased（P<0.05）,and the abundance of Campylobacterota was significantly decreased in low dose group（P<0.05）.At the genus level,The abundance of Schwartzia,Ruminobacter,Lachnospiraceae UCG-001 and Flavifiactor in low dose group was significantly decreased（P<0.05）.In the high-dose group,the abundance of unclassified Prevotellaceae,Sharpea,Ruminiclostridium,unclassified Bacteroidetes bd2-2 and SN8 was significantly increased（P<0.05）.The experimental treatments were significantly increased the abundance of Roseburia and Pseudoramibacter（P<0.05）,and that of Paraprevotella was significantly decreased（P<0.05）.In conclusion,supplementation with LPH can significantly enhance antioxidant capacity and immunity of dairy cows;Improve serum index,regulate blood lipid level.Supplementation with low dose（15 g/d）LPH can delay the decrease of milk yield and somatic cell number.In this study,the supplements of LPH had little effect on the performance of mid-lactation cows,but according to the antioxidant and other properties of LPH,it has the potential to be applied in the perinatal period,especially in the late perinatal period,and further research is needed.