Forty-eight Holstein lactating cows with similar body condition, parity, lactation period, and milk production were selected and randomly divided into control group (blank) and AMPs group (50 g/head/day). The number of somatic cells, milk fat rate, milk protein rate in milk were recorded during the experiment. The results show that, addition of AMPs in the diet significantly reduced the number of milk somatic cells by 75.86% (P<0.01) and increase the milk fat rate (P<0.05), but it has no effect on the milk protein rate. (P>0.05).
Keywords: lactating dairy cows; antimicrobial peptides; milk protein; milk fat rate; somatic cell count
The number of somatic cells in milk is an important reference indicator to measure the health of the milk cow’s mammary glands. Dairy farms generally use the number of somatic cells in the DHI data to predict recessive mastitis in dairy cows. An excessively high number of somatic cells indicates to the cow’s health is recessive. The tendency of mastitis is mainly manifested in the decrease in milk production, the sharp increase in the number of somatic cells in the milk, the increase in the activity of the enzymes in the milk and the changes in the milk composition, which affect the milk quality.
Mastitis is one of the most common diseases in the production process of dairy cows. The incidence rate during production is as high as 40%. It is one of the important diseases that seriously affect economic benefits. According to several reports, recessive mastitis can reduce milk production by 10%~ 15%. Recessive mastitis is an inflammatory disease caused by the stimulation of the breast tissue by pathogenic bacteria and chemical and physical factors. The main pathogenic bacteria are Staphylococcus, Streptococcus, Escherichia coli, and Pseudomonas [1, 2]. The research and application of antimicrobial peptides (AMPs) is new ideas for solving latent mastitis in dairy cows. AMPs is not only had the function of broad-spectrum against pathogenic microorganisms [3-5], but It has antibacterial effects on Streptococcus agalactiae and Staphylococcus aureus that cause mastitis , and it can improve animal resistance and immune response , improve the health of mammary gland, reduce the number of somatic cells in the milk, improve the quality of milk, and improve the intake of dairy cow concentrates. Volume and milk production. It has antibacterial effects on Streptococcus agalactiae and Staphylococcus aureus that cause mastitis , and it can improve animal resistance and immune response , improve the health of the mammary glands, reduce the number of somatic cells in the milk, improve the quality of milk, and at the same time increase the feed intake and milk production.
The purpose of this experiment was to study the supplementation of antimicrobial peptides to milk cow feed on milk somatic cell count, and to provide a new idea for solving cow's recessive mastitis and improving milk quality.
Materials and Methods
1.1 Experimental design and feeding management
48 Holstein cows with similar body condition, parity and milk yield were randomly divided into control group and experimental group, with 4 replicates in each group and 6 cows in each replicate (Table 1). The basic diet of dairy farm was used as the control group, and the experimental group was added with antimicrobial peptides (Tideasy C) 50 g /day/head on the basis of the basic diet. The whole experimental period was 35 days, and the first 5 days was the pre-feeding period. The feeding conditions of the experimental cows were similar to those of the cattle farm. The experimental dairy diet was composed of forage and concentrate. The forage included alfalfa, Leymus chinensis, apple meal, betaine and corn silage. The cows were fed and collected milk three times a day. The test site was in Shanghai Guangming Yuejin 2 farm.
Table 1 Basic information of experimental cows
1.2 Milk sample collection and processing
Milk samples were collected from the experiment cows before the start of the experiment (September, 20) and at the end of the experiment (October, 25). Milk sample of each cow was collected and placed in a milk sample tube (100 mL) during milking on the sampling day and mixed the milk samples in the proportion of 4:3:3 for milk in the morning, noon and evening. The milk samples were sent to Shanghai dairy Testing Center for determination milk somatic cell number, milk fat percentage and milk protein content were analyzed.
1.3 Data analysis
The data were analyzed by ANOVA in SAS.
Results and Discussion
The effects of antimicrobial peptides on somatic cell count and other milk components are shown in Table 2. It can be seen from the data in Table 2 that there was no significant difference in the number of milk somatic cells between the two groups at the beginning of the experiment, but after the experiment, the number of milk somatic cells in the experimental group (Tideasy C) decreased from 14.44x104 cells/mlL to 5.57x104 cells/mL (decreased by 61.43%), and the difference was extremely significant (P<0.01), while the control group increased by 57.69%. The data showed that the antimicrobial peptides (TIdeasy C) could significantly reduce the number of milk somatic cells. Moreover, antimicrobial peptides can effectively inhibit the growth of pathogens causing mastitis, such as Staphylococcus, Streptococcus, Escherichia coli and pyogenic bacteria. At the same time, Tideasy C can stimulate the immune response ability and immune level of dairy cows and improve the resistance of dairy cows to diseases. It can improve the health of mammary gland of lactating cows, reduce the content of milk somatic cells, and prevent the occult mastitis to a certain extent.
In addition, according to the milk protein data in Table 2, the milk protein of both the control group and the experimental group was improved, and the difference of eachgroup was significant (P<0.01), but the difference between the two groups was not significant (P>0.05). This may be because during the experiment, the formula adjustment improved the synthesis of rumen protein or rumen microbial protein in concentrate supplement, which increased the available protein in small intestine and led to the increase of milk protein rate.
For the milk fat rate, it can be seen that the milk fat rate of the control group and the experimental group was low before the experiment, which may be due to the low ratio of feed. But the milk fat rate of the two groups was improved after the experiment, and the results between the control group and the experimental group was similar. but the milk fat rate of the experimental group was lower at the end of the experiment. The experiment group increased by 19.67% while control group 3.94%, and the difference was significant (P<0.05). This indicated that antimicrobial peptides may improve the rumen fermentation mode, stimulate the formation of acetic acid, thus increasing the milk fat rate, but it has no effect on milk protein.
The results showed that the addition of antimicrobial peptides in concentrate feed could significantly reduce the number of milk somatic cells and prevent the occurrence of subclinical mastitis to a certain extent. Antimicrobial peptides are believed to be an ideal health care product for dairy farms in the future because of its safety, green, non-toxic side effects and no residue.
Table 2. Effect of Antimicrobial peptides on the improvement of milk quality in dairy cow
Note: different letters on the shoulder of the same row indicate significant difference (P<0.01),
different letters on the subscript of the same column indicate significant difference (P<0.05),
and no letters on the same row or the same column indicate no significant difference (P>0.05).
1. Antimicrobial peptides can significantly reduce the number of milk somatic cells, reduce the occurrence of cow recessive mastitis. Moreover, antimicrobial peptides effectively inhibit the growth of Staphylococcus, Streptococcus, Escherichia coli and pyogenic bacteria causing mastitis. In addition, antimicrobial peptides can stimulate the immune response ability and immune level of dairy cows, and improve the resistance of dairy cows to diseases.
2. Antimicrobial peptide improve rumen fermentation mode, stimulate acetic acid formation and increase milk fat rate, but it has no effect on milk protein.