EFFECT OF RETINOL PALMITATE ON OVULATION RATE AND EMBRYO QUALITY IN SUPEROVULATED CATTLE

We evaluated the influence of administration of retinol palmitate (Vit amin A) on ovulation rate and embryo quality in 48 beef cows superovul ated with 2 different doses of FSH. Synchronization of estrus was acco mplished by giving 2 injections of prostaglandin F-2 alpha (PGF) 11 d apart. Multiple ovulation was induced by giving a total of either 32.5 mg or 27 mg of FSH over 4 d beginning on the 8th to 10th d post estru s. Within FSH dose, cows received either I million IU of Vitamin A (im ) in corn oil or an equivalent volume of corn oil alone on the Ist d o f FSH injections. Embryos were recovered nonsurgically and evaluated 7 d post estrus. Ovulation rate was estimated on the day of embryo reco very by use of transrectal ultrasonography and actual counts of corpor a lutea were made on ovaries taken at slaughter following embryo recov ery. The FSH response rate (percentage of cows with multiple ovulation s) for all cows was 65.9% and was not affected by FSH dose or Vitamin A. Cows with less than 20 ovulations had a higher percentage of total embryos recovered (59.6 vs 35.8%; P = 0.002), and more of those embryo s were transferable (36.2 vs 14.3%; P = 0.005) compared to cows with m ore than 20 ovulations. The dose of FSH did not affect embryo quality or the total number of embryos recovered, but the lower dosage resulte d in more ovulations per cow (26.7 vs 18.0; P = 0.03). Vitamin A did n ot affect ovulation rate or total embryos recovered, but it increased the mean number of high quality (Grades 1 and 2; 4.25 vs 1.86; P = 0.0 1) and total transferable embryos (Grades 1, 2 and 3; 5.87 vs 3.13; P = 0.04). The mean number of blastocysts was greater for Vitamin A-trea ted cows (2.25 vs .73; P = 0.02). Means for nontransferable embryos we re not different between FSK dose or Vitamin A treatment groups. These findings suggest that 1) ovulation rates above 20 per cow do not yiel d gains in total or transferable embryos, and 2) Vitamin A may improve embryo quality without affecting ovulation rate in superovulated catt le.