beef heifers, puberty, progesterone, gnrh, fertility
A study using 143 replacement beef heifers was conducted over a 3-year period to determine the effects that progesterone or progesterone and gonadotropin releasing hormone (GnRH) would have on age at puberty in beef heifers. Progesterone treated heifers were 21.8 and 38.9 days younger (P<.05) at puberty than control heifers in the first 2 years of the study, while progesterone plus GnRH treated heifers were 35.4 days (P<.01) and 31.2 days (P<.05) younger than controls. No difference (P>.05) in age at puberty was detected between groups in the third year. While progesterone and progesterone plus GnRH treated heifers had a higher conception rate (P<.01) to Al than controls in the first year of the study, calving records showed they experienced a higher rate of embryonic loss. However, calving rate still remained higher than in the control group. These differences were not observed in the second year and calving data for the final year of the study is currently not available.
Number of Pages
South Dakota State University
Copyright © 1993 South Dakota State University.
Larson, C. L.; Miller, H. L.; Marshall, D. M.; and Long, M. B., "Effects of Administering Progesterone or Progesterone and GnRH on Age at Pubery in Crossbred Beef Heifers" (1993). South Dakota Beef Report, 1993. 11.