Effects Of Different Energy Sources Of Corn-based Diets On Production Performance Of Beefs At Different Stages Under Cold Stress

In this experiment,corn straw silage,corn stalk and concentrate supplements were used as raw materials,and Simmentals in similar health and physical condition were used as the research object to explore the effects of dietary energy composition on the production performance of beefs at different stages under cold stress.In the corn-derived diet design,and under the same nutritional levels,the diet of group A was supplemented with dry matter 2% palm fat powder as energy supply,while that of group B was added corn completely to increase the energy supply of starch.Then the effects of energy composition on the performance of heifers and breeding beef cattles were studied.The pre-test period was 15 days and the test period was 90 days.During the test period,beefs had free access to food and water.Experiment 1:The effects of corn-derived diet energy composition on the performance of heifers was studied.In this experiment,10 healthy Simmental heifers with good physical condition,similar month age and weight were selected and divided into two groups,each with 5 replicates.The results showed that the average daily weight gain of the added starch diet was significantly higher than that of the supplemental fat diet(P<0.05)under cold stress conditions.The feed pay was higher than the supplemental fat diet group by 10.5%.The digestibility of crude protein(CP),ether extracts(EE),acid detergent fiber(ADF),and neutral detergent fiber(NDF)in the added starch diet was significantly higher than those in the supplemental fat(P <0.05),and the digestibility of crude fiber(CF)in the added starch diet was not significant higher than that in the supplemental fat(P>0.05).As for the blood biochemical indicators,urea nitrogen,high-density lipoprotein cholesterol and total cholesterol were significantly lower than those in the supplemental fat.(P<0.05).From the description of cold stress conditions,the use of corn-derived diets for heifers,adding starch as energy composition is more effective than supplementing fat.Experiment 2: The effects of corn-derived diet energy composition on the performance of breeding beef cattles were studied.Eighteen healthy adult Simmental beef cattle aged 30 months were divided into two groups with 9 replicates in each group.There were 5 pregnant days(240 ± 20 days)in each group.The study showed that the digestibility of CP,EE,ADF,NDF and crude fiber in the supplemental fat was higher than that in the added starch diet,but the difference was not significant(P>0.05),especially the digestibility of the EE in the supplemental fat was significantly higher than that of the added starch diet(P<0.05).In terms of the blood biochemical indicators,the estradiol(E2)and TCHE in the supplemental fat were significantly higher than those in the added starch diet(P<0.05),which was helpful for the development of reproductive organs and promoted estrus;Data of the initial matching days indicated that the estrus time of the supplemental fat was 24 d earlier than that of the added starch diet;The calf’s birth weight in the supplemental fat was higher than that in the added starch diet.Under the condition of cold stress,supplemental fat diet has significant effect on breeding beef cattles to increase yak birth weight and promote postpartum estrus.