HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Byerley, D. J. Articles by Short, R. E. Search for Related Content PubMed PubMed Citation Articles by Byerley, D. J. Articles by Short, R. E.

Pregnancy Rates of Beef Heifers Bred Either on Puberal or Third Estrus^1,2,

Montana State University, Bozeman 59717 U.S. Department of Agriculture and Montanta Agricultural Experiment Station, Miles City 59301

Abstract

The objective of this study was to determine if pregnancy rates (PR) differed between beef heifers bred to fertile bulls on either their puberal (E1, n = 89) or third (E3, n = 67) estrus. Heifers were obtained from two lactations (Manhattan, L1; and Miles City, L2), and the experiment was conducted at Miles City. Heifers were assigned randomly within location to either E1 or E3. Heifers were fed to gain .56 kg·head^–1 ·d^'1 and observed twice daily for estrus. After exhibiting first estrus (puberty) and breeding, each heifer in E1 was palpated rectally on d 6, 9 and 12 ± 1 d (estrus = d 0) for the presence of a corpus luteum, and a venous blood sample was collected for assay of progesterone by radioimmunoassay. Heifers in E3 were palpated and bled on the same schedule as heifers in E1 after first estrus and after being bred to a fertile bull at third estrus. Pregnancy rates were determined by rectal palpation at approximately 38 d post-breeding. Location of origin did not affect (P>.10) weight at puberty or weight at breeding; however, heifers from L1 were younger (P<.05) than heifers from L2 at puberty and breeding. Pregnancy rates were 57 and 78% for heifers in E1 and E3, respectively (P<.05). Weight at breeding did not influence (P>.10) pregnancy rates. The probability of heifers in E1 becoming pregnant increased (P<.05) with increasing age, while age was not a factor (P>.10) for heifers in E3. These results indicated that fertility of puberal estrus in beef heifers is lower than third estrus. Higher fertility of third estrus may be related to maturational changes associated with cycling activity.

¹ Published with the approval of the Director of the Montana Agric. Exp. Sta. as Journal Series Paper No. J-1922. The authors express their appreciation to Ann Darling, Dave Phelps and the Physiology Crew at Miles City and Joanne Jensen for their excellent technical assistance, and to Dr. Richard Lund and Steve Kachman for their statistical expertise.

² This study was a contribution to the Western Regional Project, W-112; Reproductive Performance in Domestic Ruminants and was presented in part at the 78th Annu. Meet. of the Am. Soc. Anim. Sci., Manhattan, KS, Abstr. 549.

³ Anim. and Range Sci. Dept., Montana State Address reprint requests to James G. Berardinelli.

⁴ Fort Keogh Livestock and Range Res. Lab., USDA-ARS, Miles City, MT.

This article has been cited by other articles:

				J. L. Martin, K. W. Creighton, J. A. Musgrave, T. J. Klopfenstein, R. T. Clark, D. C. Adams, and R. N. Funston Effect of prebreeding body weight or progestin exposure before breeding on beef heifer performance through the second breeding season J Anim Sci, February 1, 2008; 86(2): 451 - 459. [Abstract] [Full Text] [PDF]

				K. A. Macdonald, L. R. McNaughton, G. A. Verkerk, J. W. Penno, L. J. Burton, D. P. Berry, P. J. S. Gore, J. A. S. Lancaster, and C. W. Holmes A Comparison of Three Strains of Holstein-Friesian Cows Grazed on Pasture: Growth, Development, and Puberty J Dairy Sci, August 1, 2007; 90(8): 3993 - 4003. [Abstract] [Full Text] [PDF]

				G. A. Perry, M. F. Smith, A. J. Roberts, M. D. MacNeil, and T. W. Geary Relationship between size of the ovulatory follicle and pregnancy success in beef heifers J Anim Sci, March 1, 2007; 85(3): 684 - 689. [Abstract] [Full Text] [PDF]

				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, D. E. Grum, M. L. Mussard, F. L. Fluharty, J. E. Kinder, and M. L. Day Induction of precocious puberty in heifers I: Enhanced secretion of luteinizing hormone J Anim Sci, August 1, 2006; 84(8): 2035 - 2041. [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]