Failure of precalving supplementation of vitamin E and dietary fat to alter reproductive performance of first lactation cows or the health of their calves

A study was conducted to determine the effect of precalving supplementation with vitamin E and fat on the reproductive performance of first lactation cows and the health of their calves. Approximately 50 days before the first expected calving, 48 crossbred heifers were allotted to four treatments: 1) basal diet that consisted of 13 lb of prairie hay, 7.3 lb of milo, and 1 lb of supplement per heifer per day; 2) basal diet+supplement bringing the diet to 4% fat; 3) basal diet+supplement providing 1000 IU supplemental vitamin E/day; and 4) basal diet plus both fat and vitamin E. Supplementation of vitamin E and(or) fat had no effect on any reproductive trait in the cows or any immunological measurement in the calves.


Introduction
Previous research has shown vitamin E suppl ementatio n (500 to 1000 IU per cow per day) before calving t o improve the reproductive performanc e of dairy cows and reduce the incidence of conditions such as mastitis and udder edema.T his benefit is apparently related to vitam in E's function as an antioxidant and its ability to prevent lipid peroxidation of membranes.Information is l imited on the precalving use of vitamin E supplementation in beef cattle.An Alberta researcher reported a significant reduction in the incidence of calf scours in heifers receiving 100 0 IU of vitamin E per day for 60 to 100 days prior to calving.
The objective of our experiment was to examin e the effect of precalving supplementation of vitamin E with or without 4% total dietary fat on reproductive traits of first-lactation beef cows and immunological measurements on their calves.

Experimental Procedures
Approximatel y 50 days before the first expecte d calving, 48 crossbred beef heifers were allotte d randomly to four treatments: 1) a basal diet consisting of 13 lb of prairie hay and 7.3 lb of grain sorghum, plus 1 lb of a basic supplement per day ( control); 2) basal diet+1 lb of a supplement to bring the diet to 4% fat; 3) basal diet+ 1 lb of a supplement providing 1000 IU of supplemental vitamin E; and 4) basal diet+both fat and vitamin E. The basic supplement (c ontrol) consisted of 72% soybean meal, 27% gr ain sorghum, and 1% trace mineral premix.In the suppleme nt containing the fat, grain sorghu m was reduced to accommodate 24% added fat.In the supplemen t containing vitamin E, the grain sorghum was r educed to accommodate 3.6% of a vitamin E supplement.The fat was Fat Plus® (100% dry animal fat product; Farmland Industries, Inc.).
Within each treatment, pregnant heifers were allotted to replicates based on weight and expected calving date, resulting in heavy, average, and light weight replicates (n=4) .Heifers were maintained as replicates until approximately 14 to 16 days before their expected calving date, when they were transferred to a calving unit and continuously maintained on their respective dietary regimen until 48 h after calving.Heifers were weighed at the onset of dietary treatments, precalving, and 36 to 40 hours after calving.Body co n dition scores were assessed at the beginning of the trial and just before calving.
To determine plasma concentrations of vitam in E and selenium in the dams and their calves, blood was collected at the beginning of the trial, precalving, and 36 to 40 hours after calving.Colostrum samples were collected from each dam at 36 to 40 hours postcalving, and colostral concentration of immunoglobulin (IgG) was determined by t he use of single radial immunodiffusio n plates c ontaining monospecifi c antisera in buffere d agarose.To deter mine the calf IgG status, blood was collected from the calves at calving, before suckling, and 36 to 40 hours later.
Beginnin g 44 days after the first calving, weekly blood samples wer e collected from the cows and later analyzed for progesterone to determine first occurren ce of postpartum ovulation and luteal function.When serum progesterone exceeded 1 ng/ml in two consecutive samples, onset o f estrous was presumed.Cows were exposed to a bull for nat u ral mating during a 60-d breeding season.

Results and Discussion
Supplemental vitamin E and(or) fat had no effect on body weights, body condition score, rate of fetal membrane expulsion, interval to first ovulation, or pregnancy rates at the end of the breeding season (Table 2).

Table 1 . Nutrient Content of Basal Diet a
a Prairie hay and sorghum fed at the rate of 13 lb and 7.3 lb per heifer per day, respectively.b h

Table 2 . Effect of Maternal Treatment on Dam and Calf Weigh ts, Reproductive Traits, Colostral Vitamin E, and Immune Status of the Neonatal Calves
a