SIRE BREED OF CALF INFLUENCES PERIPARTUM ENDOCRINE PROFILES AND POSTPARTUM ANESTRUS IN BRAHMAN COWS

The literature indicates that sire breed of calf influences beef calf performance. However, there is little information concerning sire bree d of calf effects on reproduction in beef cows. in this experiment, An gus (A), Brahman (B), or Tuli (T) bulls were bred to 136 Brahman (B) c ows to examine sire breed of calf influence on peripartum hormone prof iles and the length of postpartum anestrus. Cows were bled from 7 d pr epartum to 28 d postpartum to determine peripartum hormone concentrati ons. Cows carrying AB calves had greater (P < 0.05) prepartum estradio l-17 beta concentrations than did cows carrying BE and TB calves. Prep artum and postpartum progesterone concentrations did not differ betwee n cows with AB, BE, and TB calves. Cows with TB calves had lower (P < 0.01) 13,14-dihydro-15-keto-prostaglandin F-2 alpha (PGFM) concentrati ons than did cows with AB and BE calves during the early postpartum pe riod. Adjusting for birth weight removed the sire breed of calf effect on postpartum PGFM concentrations, but not prepartum estradiol-17 bet a. Postpartum anestrus was shorter (P < 0.05) for cows nursing BE calv es (84 +/- 6 d) than for cows nursing AB (101 +/- 6 d) or TB calves (1 10 +/- 7 d). Adjustment for estradiol or PGFM concentrations did not r educe sire breed of calf effects on the length of postpartum anestrus. Further work is needed to determine how calf genotype may modulate th e postpartum reproductive function of the dam. (C) Elsevier Science In c. 1996