Effect of dietary protein and exogenous gonadotropin-releasing hormone on circulating progesterone concentrations and performance of Holstein cows.
Sixty-three Holstein cows were used in a 2 x 2 factorial arrangement of treatments to determine the effects of dietary protein and exogenous gonadotropin-releasing hormone on performance postpartum and on circulating concentrations of progesterone. The experimental diets, 14 or 20% CP (dry basis), were fed from parturition to 14 wk postpartum. Blood serum urea N was elevated in the cows fed the 20% versus 14% CP diet. Feed intake was increased, but yield and composition of milk were not affected by the higher protein diet. Circulating concentrations of progesterone were lower in cows fed 20% than 14% protein on d 12 of both the synchronized and subsequent estrous cycles. Exogenous gonadotropin-releasing hormone administered on d 12 of the preceding estrous cycle did not increase the concentration of progesterone on d 12 of the subsequent estrous cycle. Luteal phase concentrations of progesterone were reduced by high dietary protein, but were not affected by gonadotropin-releasing hormone given on d 12 of the preceding cycle.
Sonderman
J P
JP
Department of Animal Science, University of Nebraska, Lincoln 68583-0908.
Larson
L L
LL
D000818:Animals; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D004044:Dietary Proteins / Q000494:pharmacology*; D004435:Eating / Q000187:drug effects; D005260:Female; D007774:Lactation / Q000187:drug effects*; D016014:Linear Models; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D049590:Postpartum Period / Q000378:metabolism / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D011897:Random Allocation
D004044:Dietary Proteins; D010906:Pituitary Hormone-Releasing Hormones; D011374:Progesterone