Incidence of puberty in beef heifers fed high- or low-starch diets for different periods before breeding1

Abstract

Spring-born Hereford x Angus heifers (n = 206) were used to determine effects of energy supplementation programs and amount of starch in the diet on incidence of puberty. In Exp. 1, heifers (205 +/- 5 kg; n = 68) grazing dormant native pasture were fed 0.9 kg/d (as-fed basis) of a 42% CP supplement from November until February 14. Heifers were stratified by weaning weight and allotted randomly to treatment before breeding (May to July). Treatments were 1) 0.9 kg (as-fed basis) of a 42% CP supplement/d and pasture (control); 2) a high-starch (HS) diet (73% corn; 53% starch) fed in a drylot for 60 d (HS-60); 3) a HS diet fed in drylot for 30 d (HS-30); or 4) a low-starch (LS) diet (49% corn; 37% starch) self-fed on pasture for 30 d (LS-30). The HS-60 and HS-30 heifers were limited-fed to gain 0.9 kg/d, and the LS-30 heifers had ad libitum access to the diet. High-starch-60 and LS-30 heifers were heavier (P < 0.05) than control and HS-30 heifers at the beginning of the breeding season. Thirty-one, 25, and 26% more HS-60 heifers were pubertal (P < 0.05) on May 1 compared with LS-30, HS-30, and control heifers, respectively. At puberty, HS-60 heifers were 24 and 22 d younger (P < 0.05) than LS-30 and control heifers, and 31 kg lighter (P < 0.01) than LS-30 heifers. In Exp. 2, heifers grazed dormant pasture and were fed 0.9 kg (as-fed basis) of a 42% CP supplement/d from weaning in October to late February; then heifers were assigned randomly to treatments for 60 d before the breeding season. In two years, control heifers (n = 46) grazed pasture and received 0.9 kg of SBM supplement/d; LS (n = 46) heifers were self-fed a distiller's grain and soybean hull-based diet in drylot; and HS heifers (n = 46) were limited-fed a corn-based diet in drylot. During treatment, HS and LS heifers had greater weight gains than control heifers. Pubertal BW (313 +/- 6 kg) was not influenced by treatment, but HS and LS heifers were younger (P < 0.03) than control heifers at puberty. During a 60-d breeding period, the incidence of puberty was greater (P < 0.05) for HS and LS heifers than for control heifers and was greater (P < 0.05) in HS than in LS heifers in Year 1. Feeding a LS or a HS diet for 30 d before breeding may be inadequate to stimulate puberty in beef heifers, but feeding a diet with a greater amount of starch for 60 d before breeding may increase the incidence of puberty during breeding of heifers that have inadequate yearling weight.

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.…”

“…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.…”

Reproductive responses and progesterone levels of postpartum oestrus synchronization in goats with different body reserves

“…Llewelyn et al (1992) studied indigenous African goats and observed that the return of ovarian activity after parturition occurred prior to improvement in body condition and weight. Furthermore, Ciccioli et al (2005) found in beef heifers that the response to oestrus synchronization in the first oestrus cycle in the postpartum period is not influenced by body Silva et al condition at parturition. In general, the CIDR-PGF2α hormone protocol is a highly efficient treatment in synchronizing oestrus in goats (Oliveira et al, 2001) and in postpartum cows (Lucy et al, 2001;Flores et al, 2006), demonstrating better efficiency in simulating corpus luteum function.…”

Metabolizable protein supply while grazing dormant winter forage during heifer development alters pregnancy and subsequent in-herd retention rate

“…Heifers developed on pasture (36RUP and 50RUP) had greater (P < 0.01) ADG from the time of breeding to pregnancy diagnosis. Heifers developed on low-quality winter range may compensate for the minimal prebreeding ADG and gain more BW during the breeding season than heifers fed in a drylot due to decreased maintenance requirements and the ability to respond to a seasonal improvement in forage quality (Marston et al, 1995;Ciccioli et al, 2005).…”