PROGESTERONE AND LUTEINIZING HORMONE CONCENTRATION IN SERUM OF PREGNANT GILTS ON DIFFERENT LEVELS OF FEED CONSUMPTION

Abstract

Blood serum progesterone (P) and luteinizing hormone (LH) were determined in 31 Lacombe gilts at a 3- to 4-day interval from 10 to 56 days of pregnancy. They were fed 1.50 (L), 2.25 (M) or 3.00 (H) kg of a 16% protein diet/day and had average daily gains of 0.16 ± 0.02 (SE), 0.36 ± 0.02 and 0.60 ± 0.02 kg/day, respectively. All gilts were slaughtered between 59 and 61 days of pregnancy. The treatments had no effect on the number of corpora lutea (13.9 ± 0.4 CL), number of fetuses (10.8 ± 0.6), fetal survival (78.3 ± 3.7%) or mean fetal weight (122 ± 3 g). The gilts on the H level of feeding had heavier (P < 0.05) ovaries (18.4 ± 0.8 g) than those of the L (15.6 ± 0.7 g) or M (15.6 ± 0.8 g) treatment groups. Serum P concentration declined during the blood collection period (b = −0.12, −0.06 and −0.09 for the L, M and H groups, respectively). Serum P concentrations also were different (P < 0.01) for each treatment group (L, 16.7 ± 0.3; M, 13.8 ± 0.03; and H, 11.8 ± 0.3 ng/mL). The serum LH concentration was greater (P < 0.05) for the M gilts (0.63 ± 0.05 ng/mL) than for the L (0.37 ± 0.04 ng/mL) or H (0.47 ± 0.05 ng/mL) gilts. Significant correlations were observed among the number of fetuses, number of CL, ovarian weight and P for the L gilts, and the number of fetuses and CL for the M gilts. These results suggest that growth rate is a major contributor to differences in blood P and LH concentrations during pregnancy and that the animal adjusts its P and LH production to its specific requirements for the maintenance of pregnancy.