Effect Of Selenium Source And Supplement Levels In The Ration On Composition And Selenium Deposition In The Milk Of Dairy Cows

The aim of this study is to use the way of food chain, two kinds of different levels of selenium source were added into the ration of dairy cows, through absorption, transformation and excretion of the dairy cows, the high-selenium milk can be produced. And it is important to be able to develop feeding systems that produce high-selenium milk and the products can consistently meet specifications. It provides an important reference for the application of selenium in dairy-farming industry.35 health Holstein cows were selected, and the parity, milk yield, lactation days were similar. They were divided into 7 groups.3 groups were fed with sodium selenite,4 groups were fed with selenium yeast. The group of sodium selenite levels was 5mg/d,10mg/d,15mg/d respectively. The group of selenium yeast levels was 5mg/d, 10mg/d, 15mg/d,20mg/d respectively.Test one The influence results selenium source and supplement levels in the ration on production and composition of dairy cows show that:(1) The effect on milk production, lacto protein rate, milk fat rate, solid of non-fat content is not obvious, the difference between the treatment group is not significant(P>0.05) when supplement different levels of sodium selenite and selenium yeast in the ration; Lactose content shows ascendant as test days increase, but when trial end, lactose content decrease, selenium diet is to the influence mechanism of lactose content come from selenium diet should have further research.(2)The milk somatic cell count reduced after supplememnt selenium in the ration, the largest percentage decline is 15mg/d yeast selenium, and it reduced 42.22% than Od.(3) After supplement different levels of two kinds of selenium source, urea nitrogen content in milk declined compared with that before experiment, which 15mg/d selenium yeast reduced 3.33%, the effect was the best. Somatic cell count and fertility rate have a significantly negative correlation, adding selenium in the ration can improve the fertility rate in practical production.Test two The influence results selenium source and supplement levels in the ration, on milk selenium deposition of dairy cows as follows:(1)After the cows were fed the ration which adds selenium, the milk selenium level had significantly improved (P<0.01), the milk selenium content improve as concentration of selenium yeast increase. The selenium yeast group 15mg/d and 20mg/d had better effect than the other groups, respectively improved 2.77 times and 3.4 times.(2)After the diet added the two kinds of selenium, milk selenium content is up to peak rapidly in sodium selenite group, it keeps a stable level after 5th d; the milk selenium is up to the plateau period until 36th d of yeast selenium group. After the end of experiment, the milk selenium levels fell rapidly, the content of milk selenium in sodium selenite group reduced to the level that before experiment in 7th d, but the selenium yeast group was still higher than the level that before experiment after ending the experiment one week, we can get 43.32μg/L and 44.78μg/L milk Se in 15mg/d group and 20mg/d group.The experiment results approve that:the influence on milk composition is not significant when adding different levels of sodium selenite and yeast selenium.The selenium content of sodium selenite group does not change significantly, but in selenium yeast group, milk selenium content improved as the amount of selenium yeast increased, adding 15mg/d and 20mg/d selenium yeast had the best performance. This was probably because selenium yeast had solved the oxidation of the sodium selenite in the rumen and reduced its biological efficiency. If the experimental results applied in practical production, not only the dairy farms bring good economic benefit, but also can enhance the national constitution, promote economic development.