introduction:

Probiotics have received extensive attention as a new type of safe, efficient and non-polluting feed additive. Probiotics mainly include yeast preparations, lactic acid bacteria preparations, Bacillus preparations and mixed bacteria preparations. Saccharomyces cerevisiae (Saccha romyces cerevisiae) is the most widely used yeast, which is mainly divided into two types: active yeast preparations and yeast culture preparations. Saccharomyces cerevisiae is widely used in the production of dairy cows, and there are many studies on the health status and milk production performance of dairy cows. Yeast-fermented feed can improve the rumen fermentation function and improve feed utilization (Ouellet, 2016), and at the same time, it can protect the body’s health, reduce the occurrence of diseases, and increase economic benefits (Wu Xiaoyan, 2014). The effect of active yeast and its fermented feed on rumen fermentation parameters was evaluated in vitro, and it was found that active yeast significantly increased the content of bacterial protein in the in vitro fermentation broth, and the effect was better than that of fermented feed (Zhang Zheng, 2017). Yeast culture is also widely used in dairy cow production. It can be added to dairy cow feed as an additive to improve the negative energy balance of dairy cows during the perinatal period (YE Gengping, 2014). The research on the effect of adding active yeast or yeast culture alone on milk production and performance of dairy cows is common, but adding active yeast and its culture on milk production performance, feed intake, blood biochemical indicators and immune Few studies have been reported on the impact of force. The experiment was conducted by adding a certain dose of active yeast and yeast culture to the dairy cow's diet to explore its effects on milk production performance, feed intake, blood biochemical indexes and immunity of dairy cows in different lactation periods.

Test design:

According to a two-factor completely randomized block design, 48 lactating Holstein dairy cows with the same parity and similar body weight [(534±20) kg] were selected. 24 animals were selected in each period and randomly divided into 4 groups with 6 animals in each group. The experimental treatments of each group were as follows: the control group (CG group) was fed the basal diet; the other three experimental groups were supplemented with 0.075% yeast (LY group) and 0.100% selenium-enriched yeast (SY group) on the basis of the control group. And 0.075% yeast and 0.100% selenium-enriched yeast mixture (LY+SY group). The total period of the experiment was 45d, including 10d pre-feeding period and 35d formal period.

experiment material:

Yeast and selenium-enriched yeast products are purchased from the market. The viable count of yeast is 1.5×10 10 cfu/g; the content of selenium in yeast is 0.200%, and the moisture content is less than 6%.

result:

1 Dry matter intake and lactation efficiency of dairy cows

It can be seen from Table 1 that different treatments had no significant effect on the dry matter intake of dairy cows (P>0.05), but in the middle lactation period, the dry matter intake of dairy cows in the SY group was higher than that in the CG, LY, and LY+SY groups, respectively. At the early stage of lactation, the feed utilization rate of the SY group was significantly lower than that of the LY and LY+SY groups (P0.05).


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2 Milk production and milk quality of dairy cows

It can be seen from Table 2: in the early stage of lactation, the milk production of different treatment groups was significantly different, and the milk production of the CG and SY groups was significantly higher than that of the LY group (P0.05).


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3 Dairy cow blood biochemical indicators

It can be seen from Table 3 that in the early stage of lactation, the content of AMY in the blood of dairy cows was the highest in the CG group, which was not significantly different from the other three treatment groups. In mid-lactation, the AMY content in the blood of cows in the LY+SY group was significantly higher than that in the other three treatment groups (P0.05). The content of the group was the highest, which was significantly higher than that of the CG and SY groups (P