Heifer development systems: Dry-lot feeding compared with grazing dormant winter forage1

Abstract

Two hundred ninety-nine Angusbased, nulliparous heifers (253 ± 2 kg initial BW) from 3 production years were utilized to compare traditional postweaning dry lot (DL) development with a more extensive winter grazing system utilizing a combination of corn residue and winter range (EXT). Heifers developed in the DL were offered a common diet after the weaning period for 208 d in yr 1, 194 d in yr 2, and 150 d in yr 3 until breeding. Heifers developed in EXT grazed corn residue for 135 d in yr 1, 106 d in yr 2, and 91 d in yr 3, and then fed in the DL until breeding (yr 1) or grazed dormant winter grass for approximately 60 d before being fed in the DL (yr 2 and 3). All 3 years, heifers were estrus synchronized, with timed AI performed in yr 1. In yr 2 and 3, estrus was detected and those detected in estrus were artificially inseminated approximately 12 h later. Heifers were exposed to bulls 10 d after the last AI for 60 d while grazing summer pasture. During the winter grazing period, EXT heifers gained less (P = 0.01) BW than DL heifers and EXT heifers had lighter (P = 0.02) BW at breeding. Fewer (P < 0.01) EXT heifers reached puberty before breeding. Conception to AI was not different (P = 0.23); however, AI pregnancy rate tended (P = 0.08) to be less in EXT heifers. Final pregnancy rates were not different (P = 0.38) between treatment groups. Although EXT heifers had lighter (P = 0.02) BW at pregnancy diagnosis; however, they did compensate with greater (P = 0.05) ADG after breeding, resulting in similar (P = 0.22) precalving BW. Winter development system did not influence (P > 0.10) percentage of calving in the first 21 d, calf birth date, and calf birth BW, or dystocia score. Pregnancy rate after the second breeding season was not different (P = 0.56) between treatments. Heifer development using extended winter grazing reduced (P < 0.01) the cost of producing a pregnant heifer by $45 compared with DL.

Effect of development system on growth and reproductive performance of beef heifers1,2

“…Research reports published through the 1980s demonstrated a much greater negative effect of limited postweaning growth on age of puberty and subsequent pregnancy rate (Short and Bellows, 1971;Wiltbank et al, 1985;Patterson et al, 1989). More recent studies (Buskirk et al, 1995;Freetly and Cundiff, 1997;Lynch et al, 1997;Funston and Larson, 2011) suggest less of a negative impact of delayed puberty on pregnancy rates. Evidenced by the findings in the current study, decreased winter BW gain of MG heifers in the extensive BG system resulted in greater BW gain during the breeding season, which may explain overall pregnancy rates.…”

“…Developing heifers to attain a target BW of 55% of Roberts et al, 2007, Roberts et al, 2009Martin et al, 2008;Larson et al, 2011) that demonstrated that developing replacement heifers to lighter target BW ranging from 50 to 57% of mature BW before breeding reduced development costs, but had no negative effect on reproductive performance or subsequent calf performance. Funston and Larson (2011) reported that developing heifers on corn residue or winter range reduced development costs by $45/ pregnant heifer. The advantages of developing heifers in extensive winter grazing systems are decreased stored feed requirements, direct deposition of manure nutrients on the wintering site, and reduced yardage costs (Jungnitsch et al, 2011;Kelln et al, 2011).…”

Precocidade De Parto Na Estação De Parição Sobre a Eficiência Produtiva De Vacas Primíparas Aos 24 Meses De Idade

“…Porém, de nada vale esta prenhez precoce das novilhas se as mesmas não repetirem cria, sendo perdida toda a alimentação diferenciada para acelerar o processo de puberdade e acasalamento (27) , bem como sendo descartados por infertilidade animais geneticamente superiores em rebanhos que trabalham com melhoramento genético (29) . Isso é determinado, provavelmente, pelo maior tempo de recuperação das vacas, com maiores pesos, condições corporais e, consequentemente, melhor resposta reprodutiva (9) .…”

Growth and reproductive performance of 14- to 15-month-old Hereford heifers

“…The NRC (1996) recommends a target BW of 60% mature cow weight at the beginning of the breeding season to obtain high reproduction rates. However, studies carried out in the last decades comparing intensive with extensive systems found that lower target weights (50-57% of the mature weight) reduce production costs and do not negatively affect reproductive performance (Funston and Deutscher, 2004;Roberts et al, 2009;Funston and Larson, 2011;Mulliniks et al, 2013). Considering that the geographical region of the farm and the applied production system do not allow for heavy mature and weaning weights, heifers need to achieve a higher percentage of the mature weight of a cow to reach puberty.…”