Effect Of Rumen-Undegraded Fat On Milking Performance And Reproductivity And Resistance To Diseases In Post-Parturient Dairy Cows

Metabolic changes in post-parturient dairy cows are typically characterized by negative energy balance (NEB),which results in not only reduced milk yield,but also reduced reproductivity,shortened service period and,increased susceptibility to metabolic disorders and infectious disease.Supplemental fat,an energy substance, has been demonstrated to prevent negative energy balance in lactating dairy cow in many researches oversea.However,up to date,there are limited reports focused on this event in China. Accordingly,the present study was conducted to examine the effect of supplemental rumen-protected fat on production and plasma metabolite in dairy cow with high milk yield after calving, so as to provide a basis for generalization of this kind of products.Study 1 Prevalence trend of diseases in lactating cows in a dairy herd located in Shanghai areaThe present survey was focused on the milk yield, reproductivity, and incidence of infectious diseases in lactating dairy cow from 2000 to 2004.It was found that the milk yield was increased and peaked at 8000kg in 2003. With the increasing of milk yield, the incidence of the mastitis and endometritis don't tend to increase correlatively, and the conception rate of oestrus and reproduction rate were interrelated to reduce.It was demonstrated that the decreased reproductivity is associated with intense negative energy balance resulting from increased milk yield in high yield cows. Study 2 Effect of rumen-undegraded fat on milk yield,body condition scoring and milk composition in post-parturient dairy cowsForty multiparous Holstein dairy cows with similar parity and milk yielding of the last year were allocated equally into a control and an experimental group according to matched-pair grouping design.Beginning at the day of parturition until 90 days after parturition,cows in the experimental group were fed basic diet supplemented with 400 g rumen-undegraded fat. It was found that rumen-undegraded fat did not alter dry matter intake (DIM) (P>0.05).However,it increased milk yielding (P<0.05).Milk fat percentage tended to be increased by supplemental fat,although the differences between the two groups were not pronounced (P>0.05).There were no differences in milk protein percentage between the two groups (P>0.05).However,it tended to reduce somatic cell counts (SCC) in milk ( P>0.05).Body Condition Scoring (BCS) in two groups' showed significantly change.It was concluded that supplemental fat increased milk performance.Study 3 Effect of rumen-undegraded fat on clinical hematology in post.parturient dairy cowsForty multiparous Holstein dairy cows with similar parity and milk yielding of the last year were allocated equally into a control and an experimental group according to matched-pair grouping design. Beginning at the day of parturition until 90 days after parturition,cows in the experimental group were fed basic diet supplemented with 400 g rumen-undegraded fat.It was found that rumen-undegraded fat did not significantly alter RBC,PCV and MCV,MCH,MCHC (P>0.05).Supplemental fat had minor effect on the total number of peripheral leukocytes and the number of lymphocyte (P>0.05).It was concluded that supplemental fat improved immune function to a certain extent.Study 4 Effect of rumen-undegraded fat on plasma metabolites in post-parturient dairy cowsForty Holstein dairy cows were allocated equally into a control and an experimental group according to matched-pair grouping design. Beginning at the day of parturition until 90 days after parturition,cows in the experimental group were fed basic diet supplemented with 400 g rumen-undegraded fat.Blood samples were collected from vena caudalis for detection of plasma total protein,albumin,globin,glucose,urea nitrogen and nonesterified fatty acids (NEFA) on days 0,15,30,45,60,75 and 90 after parturition,respectively.It was found that rumen-undegraded fat did not alter the concentration of plasma total protein,albumin,globin or glucose.They were no significantly difference in serum calcium,tfiglycefide,cholesterol concentration in different groups.However,supplemental fat significantly increased plasma NEFA concentration during the first 30 days after parturition.In conclusion,supplemental fat enhanced lipolysis in a short term;however,it had no adverse effect on plasma protein and glucose metabolite.Study 5 The effect of rumen-undegraded fat on productivity and reproductivity in a dairy herdCows with similar years of age, parities,onset of lactating and previous 305-day milk yield were divided into a control group (308 cows) and a treated group (379 cows) at random. Starting at days 8 after parturition, supplemental rumen-undegraded fat was increasingly added to the basal diets of the treated group until every cow received 100 g on days 14 after parturition.Thereafter, 100 g rumen-undegraded fat was increased by degrees at an interval of 6 days until 400 g were added on day 26 after parturition,and then remained constant until days 100 after parturition.Beginning at days 101 after parturition, rumen-undegraded fat was decreased progressively at a rate of 100 g every 6 days until supplementation of fat was canceled on days 119 after parturition. It was found that supplemental rumen-undegraded fat increased the milk yield, milk fat percentage and body condition score (BCS).Cows in rumen passed fat-treated group had shortened interval of calving, increased concept rate of oestrus, breeding coefficient per year and percentage of oestrus both in primiparous and multimiparous cows within 80 days after calving.Incidences of placenta retention and metritis were deceased by supplemental rumen-undegraded fat.It was demonstrated that rumen-undegraded fat improved both the productivity and reproductivity in dairy cows.It demonstrated that:1.The increased incidence of infectious diseases and decreased reproductivity is associated with intense negative energy balance resulting from increased milk yield in high yield cows2.Supplementation of rumen-undegraded fat to the diet of postpartum cows had no effects on blood cell status, plasma protein,glucose and calcium.However,it significantly increased milk yield, and tended to elevate milk fat percentage and to reduce SCC in milk.3.Supplemental rumen-undegraded fat was also shown to improve reproductivity inpostpartum cows in a dairy herd.Based on those findings,it is suggested that rumen-undegraded fat can be generalized for practice.