2942 Use of a stair-step compensatory gain nutritional regimen to program the onset of puberty in beef heifers 1 R. C. Cardoso,*† B. R. C. Alves,† L. D. Prezotto,*† J. F. Thorson,*† L. O. Tedeschi,† D. H. Keisler,‡ C. S. Park,§ M. Amstalden,† G. L. Williams,*† 2 *Animal Reproduction Laboratory, Texas A&M AgriLife Research, Beeville 78102; †Department of Animal Science, Texas A&M University, College Station 77843; ‡Division of Animal Sciences, University of Missouri, Columbia 65211; and §Department of Animal Sciences, North Dakota State University, Fargo 58108 ABSTRACT. It was hypothesized that metabolic pro- gramming of processes underlying puberty can be shifted temporally through the use of a stair-step compensatory growth model such that puberty is optimally timed to occur at 11 to 12 mo of age. Forty crossbred beef heifers were weaned at approximately 3.5 mo of age and, after a 2-wk acclimation period, were assigned randomly to 1 of 4 nutritional groups: 1) low control (LC), restricted feed intake of a forage-based diet to promote BW gain of 0.5 kg/d until 14 mo of age, 2) high control (HC), controlled feed intake of a high-concentrate diet to pro- mote BW gain of 1 kg/d until 14 mo of age, 3) stair-step 1 (SS-1), ad libitum feed intake of a high-concentrate diet until 6.5 mo of age followed by restricted access to a high-forage diet to promote BW gain of 0.35 kg/d until 9 mo of age, ad libitum feed intake of a high-concentrate diet until 11.5 mo of age, and restricted intake of a high- forage diet to promote BW gain of 0.35 kg/d until 14 mo of age, and 4) stair-step 2 (SS-2), reverse sequence of SS-1, beginning with restricted access to a high-forage diet. Body weight (every 2 wk) and circulating concen- trations of leptin (monthly) were determined throughout the experiment. Concentrations of progesterone in blood samples collected twice weekly beginning at 8 mo of age were used to determine pubertal status. Body weight gain followed a pattern similar to that proposed in our experimental design. Circulating concentrations of leptin increased following distinct elevations in BW but decreased abruptly after feed intake restriction. Survival analysis indicated that the percentage of pubertal heif- ers in the LC group was lower (P < 0.05) than all other groups throughout the experiment. Although heifers in SS-1 were nutritionally restricted between 6.5 and 9 mo of age, the proportion pubertal by 12 mo of age did not differ (P = 0.36) from that of the HC group, with 80% and 70% pubertal in SS-1 and HC, respectively. In con- trast, the proportion of heifers pubertal by 12 mo of age in the SS-2 group (40%) was lower (P < 0.05) than both HC and SS-1. However, by 14 mo of age, 90% of heifers in the SS-2 group had also attained puberty compared to only 40% of the LC group. In summary, these data provide evidence that changes in the nutritional and metabolic status during the early juvenile period can program the onset of puberty that occurs months later, allowing optimal timing of sexual maturation in replace- ment beef heifers. Key words: beef heifers, compensatory gain, leptin, nutritional programming, puberty © 2014 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2014.92:2942–2949 doi:10.2527/jas2014-7713 INTRODUCTION Developing managerial strategies that optimize the timing of sexual maturation of heifers to allow maxi- mum lifetime productivity remains a major goal of the beef industry. Because multiple estrous cycles before first breeding are often required to achieve optimal fer- tility (Byerley et al., 1987), assuring that puberty is at- tained in advance of 14 mo of age is critical for heifers to calve as 2-yr-olds (Lesmeister et al., 1973). 1 This project was supported by Agriculture and Food Research Initiative Competitive Grant 2009-65203-05678 from the USDA National Institute of Food and Agriculture. Appreciation is expressed to Thomas Moczygemba, Ethan Stevenson, Katie Owens, Kerry Dean, and Kenton Kruger for the assistance with animal care and to Sarah Sharpton for laboratory support. 2 Corresponding author: glwilliams@tamu.edu Received February 7, 2014. Accepted April 27, 2014. at ProQuest on July 21, 2014 www.journalofanimalscience.org Downloaded from