Effect of calf removal on serum luteinizing hormone and cortisol concentrations in postpartum beef cows

• Published in: Theriogenology Vol. 24; no. 1; pp. 119 - 129
• Main Authors: Whisnant, C.S., Kiser, T.E., Thompson, F.N.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.1985
• Subjects: BEEF CATTLE; beef cows; BLOOD COMPOSITION; BOVIN DE BOUCHERIE; calf removal; COMPOSICION DE LA SANGRE; COMPOSITION DU SANG; cortisol; COWS; GANADO DE CARNE; GLUCOCORTICOIDE; GLUCOCORTICOIDES; GLUCOCORTICOIDS; luteinizing hormone; PARTO; PARTURITION; postpartum; VACA; VACHE; calf removal; cortisol; postpartum; beef cows; luteinizing hormone
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/0093-691X(85)90217-1

Serum luteinizing hormone (LH) and cortisol concentrations were measured in ten fall calving, Angus cows averaging 38 ± 8 days postpartum. Calves from five cows were weaned at the beginning of the study. Blood samples were collected at 20 min. intervals for 48 h after weaning and for 8 h on day 4 and day 6 postweaning. Mean serum LH concentrations increased (P<0.01) in weaned cows (W) from 0.55 ± 0.01 ng/ml at time of calf removal to 1.3 ± 0.04 ng/ml 48 h afterwards. Comparable LH concentrations for suckled cows (S) were 0.65 ± 0.08 ng/ml and 0.62 ± 0.03 ng/ml respectively. Average serum LH concentrations at 48 h after weaning were greater (P<0.01) for W cows than S cows and a treatment by time interaction occurred (P<0.01) with serum LH concentrations increasing (P<0.01) from time of calf removal to 48 h after calf removal in W cows. Frequency of LH peaks increased (P<0.01) in W cows and by 48 h after weaning was greater (P<0.01) in W cows than in S cows. Magnitude of LH peaks did not differ between the two groups. Serum cortisol concentrations were not different between W and S cows except for a transient elevation (P<0.01) in W cows from 7.6 ± 0.9 ng/ml to 11.9 ± 1.0 ng/ml 9 to 12 h after calf removal. Since serum LH concentrations were increased in W cows but not in S cows at 48 h and serum cortisol concentrations increased transiently in W cows we suggest that circulating cortisol levels may not be a physiological inhibitor of LH secretion in the suckled postpartum beef cow.