| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
ANIMAL GROWTH, PHYSIOLOGY, AND REPRODUCTION |
Department of Animal Sciences, The Ohio State University, Columbus 43210
3 Corresponding author: day.5{at}osu.edu
In beef heifers weaned between 3 and 4 mo of age and fed a high-concentrate diet, approximately 50% reach puberty before 300 d of age (precocious puberty). The objectives of this experiment were 1) to determine whether precocious puberty could be induced experimentally by weaning heifers early and feeding a high-concentrate diet, and 2) to determine the dynamics of secretion of LH associated with precocious puberty. Crossbred Angus and Simmental heifer calves were weaned at 73 ± 3 d of age and 115 ± 3 kg of BW and fed a high-concentrate (60% corn; HI, n = 9) or control diet (30% corn; CONT, n = 9). Heifers were fed individually, and target BW gains were 1.50 and 0.75 kg/d for the HI and CONT treatments, respectively. Heifers were weighed every 2 wk. Blood samples were collected weekly and assayed for progesterone concentration to determine age at puberty. Serial blood samples were collected at 20-min intervals for 24 h at mean ages of 102, 130, 158, 172, 190, 203, 217, 231, and 259 d and assayed for LH concentration to evaluate the dynamics of secretion of LH. Heifers fed the HI diet exhibited greater BW gain (P < 0.01) than CONT heifers (1.27 ± 0.05 vs. 0.85 ± 0.05 kg/d, respectively). As a result, BW in the HI treatment was greater (P < 0.01) than in the CONT treatment by 188 d of age and remained different through the end of the experiment. Precocious puberty occurred in 8 of 9 heifers fed the HI diet and 0 of 9 heifers fed the CONT diet. Age at puberty was reduced in the HI (P < 0.01) compared with the CONT heifers (262 ± 10 vs. 368 ± 10 d of age, respectively). Body weight at puberty was also reduced in the HI (P < 0.05) compared with the CONT treatment (327 ± 17 vs. 403 ± 23 kg, respectively). Heifers attaining puberty during the experiment continued with subsequent luteal phases as evidenced by cyclic patterns of progesterone concentrations. Frequency of pulses of LH (pulses/24 h) increased with age (P < 0.01) for both treatments. Heifers in the HI treatment exhibited a greater number of pulses of LH (P < 0.01) than those in the CONT treatment by 190 d of age and in all subsequent collection periods (treatment x age, P < 0.05). Mean LH concentrations also increased with age (P < 0.01) for both treatments but did not differ between treatments. In conclusion, precocious puberty induced by early weaning and feeding of a high-concentrate diet is preceded by increasing frequency of pulses of LH.
Key Words: early weaning • heifer • luteinizing hormone • puberty
This article has been cited by other articles:
|
|
 |
|
  C. L. Gasser, E. J. Behlke, D. E. Grum, and M. L. Day Effect of timing of feeding a high-concentrate diet on growth and attainment of puberty in early-weaned heifers J Anim Sci, November 1, 2006; 84(11): 3118 - 3122. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. L. Gasser, C. R. Burke, M. L. Mussard, E. J. Behlke, D. E. Grum, J. E. Kinder, and M. L. Day Induction of precocious puberty in heifers II: Advanced ovarian follicular development J Anim Sci, August 1, 2006; 84(8): 2042 - 2049. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. L. Gasser, G. A. Bridges, M. L. Mussard, D. E. Grum, J. E. Kinder, and M. L. Day Induction of precocious puberty in heifers III: Hastened reduction of estradiol negative feedback on secretion of luteinizing hormone J Anim Sci, August 1, 2006; 84(8): 2050 - 2056. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
