Influence of timing of gain on growth and reproductive performance of beef replacement heifers.

Abstract

Our objective was to determine whether beef heifers could be developed by delaying the majority of weight gain until the last third of the developmental period before the onset of the breeding season. Spring-born Angus x Hereford heifers were used in each of two consecutive years and were allotted at weaning to gain either .45 kg/d for the entire developmental period (yr 1 = 159 d, n = 40; yr 2 = 168 d, n = 40; EVENGAIN) or to gain .11 kg/d from d 0 to 112, followed by .91 kg/d from d 112 to 159 (yr 1, n = 40) or d 168 (yr 2, n = 40; LATEGAIN). Body weights and condition scores were determined at d 0, 112, and 159 (yr 1) or d 0, 112, and 168 (yr 2). Heifers were subjected to a 60-d breeding season. Frame scores and pelvic areas were determined at the conclusion of the breeding season. Actual daily gains for EVENGAIN heifers for yr 1 and yr 2 were .60 and .51 kg/d, respectively. LATEGAIN heifers gained .25 and .05 kg/d during the restricted phases from d 0 to 112, followed by 1.14 and 1.32 kg/d during the accelerated growth phases for yr 1 and 2, respectively. Body weight at the onset of the breeding season and weight at puberty were not different between treatments in either year. Age at puberty did not differ in yr 1, but, age at puberty in yr 2 was delayed (P < .01) in LATEGAIN (406.9 d) compared to EVENGAIN (386.3 d) heifers. The LATEGAIN and EVENGAIN heifers had similar pelvic areas, frame scores, and body condition scores in each year. First-service conception rates of both groups were similar in yr 1 (55.5 vs 55.3%). In yr 2, LATEGAIN heifers tended (P = .18) to have an increase in first-service conception rate compared to EVENGAIN heifers (71.1 vs 56.4%). No treatment differences occurred in either average age of conception or overall pregnancy rates at the conclusion of the breeding season for either year. The LATEGAIN heifers were developed to a similar BW on 12 (P < .01) and 2.5% (not statistically significant) less feed for yr 1 and 2, respectively, compared to EVENGAIN heifers. We interpret these data to indicate that delaying the majority of weight gain until late in heifer development may decrease costs without detrimental effects on reproductive performance.

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

“…The decreased percentage of EXT heifers being pubertal was likely the result of several factors including growth rate, winter diet, possibly monensin supplementation, which was a function of diet quality, and other behavioral and environmental factors differing in each development system. These data agree with recent literature indicating reduced postweaning ADG resulting from lower diet quality, with or without moderate realimentation before breeding, reduces the percentage of heifers attaining puberty (Granger et al, 1990;Lalman et al, 1993;Buskirk et al, 1995Buskirk et al, , 1996Marston et al, 1995;Lynch et al, 1997;Ciccioli et al, 2005;Gasser et al, 2006). Martin et al (2008) indicated reducing the percentage of mature BW at breeding by approximately 6% resulted in a nonsignificant, 17% decrease in percentage of pubertal heifers at breeding.…”

“…Genetics may have adapted to minimize the negative effect of delayed puberty on firstservice conception. Previous research indicates no effect of moderate nutrient restriction leading to reduced ADG during postweaning development, regardless of pubertal effects, on first service conception or percentage of heifers calving to the first conception (Lalman et al, 1993;Buskirk et al, 1995;Lynch et al, 1997;Funston and Deutscher, 2004;Martin et al, 2008). Similarly, in the present study, grazing heifers on CR or winter grass for a portion of postweaning development did not affect (P = 0.23) AI conception rate compared with heifers developed in a DL.…”

“…However, final pregnancy rate was not different (P = 0.38) between EXT and DL Nontraditional heifer development heifers. Nearly all previous research indicates postweaning BW gain restriction resulted in similar final pregnancy rates (Granger et al, 1990;Lalman et al, 1993;Buskirk et al, 1995;1996;Lynch et al, 1997;Funston and Deutscher, 2004;Ciccioli et al, 2005;Gasser et al, 2006;Martin et al, 2008). The percentage of heifers calving in the first 21 d was similar (P = 0.30; Table 7) between treatments and greater than 70% for the entire group, indicating heifers not becoming pregnant to AI became pregnant at the subsequent estrus.…”

Recría de terneras parda de montaña: alimentación y desarrollo productivo

“…Se podrían utilizar niveles bajos de alimentación durante los primeros meses del periodo de recría y suplementar a los animales para alcanzar un plano alto de alimentación con la antelación suficiente para utilizar la habilidad de los animales de razas cárnicas para aprovechar el crecimiento compensatorio y ganar peso rápida y eficientemente, sin afectar a la respuesta reproductiva (Lynch et al, 1997).…”

Argentine rangeland quality influences reproduction of yearling pregnant heifers?

“…Consequently, the availability of seeded and fertilized improved pastures, in most situations, is an important factor for successful management of pregnant beef heifers. Cultivated pastures would then be needed to grow the female calves of approximately 160 kg at weaning to reach to 60-65% of adult weight, close to 260-280 kg head -1 in November at the onset of breeding (Lynch et al 1997). However, cultivated pastures are also frequently used to feed pregnant heifers during winter months.…”