Effect of progesterone supplementation in repeat-breeder cattle on conception and plasma progesterone.
Reposital-type progesterone (75 mg/d for cows, 40 mg/d for heifers) or saline were administered to 24 Holstein cattle to assess the effects of exogenous progesterone (P) on fertility in repeat-breeders. Treatments were administered daily from day 6 to 10 after fourth, fifth and sixth insemination. Cumulative conception rate (57.1%) for the fourth through sixth insemination was affected by lactation number, service number, plasma P (4.67 ng/ml for pregnant cows vs 4.06 ng/ml for nonpregnant cows) and corpus luteum size on days 5 and 15. Plasma P concentrations were affected by day of cycle and size of corpus luteum on both ovaries on day 15. A treatment by day interaction accounted for higher plasma P in P-treated cattle than saline-treated cattle from day 5 through 15. Administration of exogenous P during early life of the corpus luteum in the repeat-breeder increased plasma P. Higher plasma P was associated with insemination success.
Thuemmel
A E
AE
Department of Dairy Science College of Agriculture and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315.
Gwazdauskas
F C
FC
Whittier
W D
WD
McGilliard
M L
ML
D000818:Animals; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000187:drug effects; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D009929:Organ Size / Q000187:drug effects; D010053:Ovary / Q000187:drug effects; D011247:Pregnancy; D011374:Progesterone / Q000097:blood / Q000494:pharmacology*
D011374:Progesterone