Effect of Feeding Protein-Protected Lipid upon Growth and Reproductive Development of Yearling Heifers2,3

An experiment was designed to determine the effects of dietary monensin on age and weight at puberty in Bos taurus crossbred beef heifers. One hundred and forty heifers were allotted to two weight classes: heavy (H) and light (L) groups, consisting of heifers above and below the average weaning weight, respectively. Heifers within each weight class were assigned to one of three diets during a 203-d winter feeding period: (1) R, 80% roughage: 20% concentrate; (2) M1, R diet plus monensin (200 mg/head daily) with feed intake restricted to produce average daily gains (ADG) similar to R and (3) M2, R diet plus monensin (200 mg/head daily). ADG was higher (P less than .001) for M2 heifers than for R and M1 heifers, which performed similarly. Age and weight at puberty were similar across treatments in L heifers. However, in the H group, HM1 and HM2 heifers were younger (P less than .07) at puberty than HR heifers and this difference was not removed by covariate adjustment of either ADG or body weight. Weigh at puberty was greater (P less than .01) for HM2 heifers than for HM1 or HR heifers; however, this difference was removed by covariate adjustment of either ADG or body weight. Ninety-one percent of LM2 heifers and 100% of all other groups had reached puberty before the breeding season. Pregnancy rates did not differ significantly between treatment groups. Supplementation of a high roughage diet with monensin decreased age at puberty of heifers in the heavy weight class and this decrease was not due to increased body weight or ADG. Perhaps heifers with above average weaning weight possess a greater inherent growth potential than heifers below the average weaning weight and hence are more capable of utilizing monensin to an advantage.

Section: Nttoductionmentioning

confidence: 87%

Relationship of Growth and Puberty in Beef Heifers Fed Monensin

Moseley

Dunn

Kaltenbach

et al. 1982

“…Results from our study and several others (Short and Bellows, 1971;Brooks et al, 1985;Yelich et al, 1992;Hopper et al, 1993) do not support the critical body composition hypothesis in beef heifers. In addition, increasing the rate of fat deposition through nutrition (Rhodes et al, 1978;Hopper et al, 1993) or breeding (Bergfeld et al, 1993) has not necessarily reduced age at puberty. These experiments reinforce the assertions of Bronson and Manning (1991) that body composition has little direct physiological or biological relationship to the onset of estrous cycles.…”

Section: Discussionmentioning

confidence: 99%

Body composition and metabolic profiles associated with puberty in beef heifers1

Hall

Staigmiller

Bellows

et al. 1995

Rapid growth large frame (RL, n = 61) or average growth medium frame (AM, n = 71) biotype heifers fed to achieve either moderate (MOD, .6 kg/d) or high ADG (HI, 1.0 kg/d) were used to determine whether puberty occurs at similar body composition or metabolic status. A heifer was considered pubertal after being detected in estrus and then forming a functional corpus luteum. Live animal estimates of body composition and blood samples for assessment of metabolic status were taken at 13 +/- .2 d after estrus for all heifers. Body composition and metabolic status were assessed every 56 d from 7 mo of age until puberty in a subset of 80 heifers representing all biotype-diet combinations. At puberty, 32 of these 80 heifers were slaughtered and physical and chemical composition of the empty body were determined. High-gain diet heifers were younger, heavier, taller, and more muscular (all P < .01) at puberty than MOD heifers. Slaughter measurements paralleled live animal estimates; bodies of HI and RL heifers contained more (P < .01) carcass and noncarcass components than those of MOD and AM heifers, respectively. Carcasses of RL and HI heifers were more (P < .05) muscular and fatter than AM and MOD heifers. At puberty, HI heifers had a greater (P < .01) mass of moisture, fat, and fat-free organic matter (FFOM) than MOD, whereas RL heifers had more moisture, ash, and FFOM than AM. Percentage of fat was greater (22.1 +/- 1.0 vs 1.0 vs 19.1 +/- 1.0; P < .05) and percentage of moisture was less (55.4 +/- .6 vs 58.1 +/- .6; P < .01) in bodies of HI than in those of MOD heifers. Concentrations of blood urea nitrogen and insulin were greater (P < .05) in HI than in MOD heifers. Diet did not influence concentration of IGF-I or glucose, and metabolic markers were unaffected by biotype. No dramatic changes in body composition or metabolic signals were detected before puberty. Puberty did not occur at similar body composition or metabolic status in all heifers.

“…Hip height was higher ( P < .05) with than without concentrate supplements and was similar among supplement treatments (Table 2). Conversely, Rhodes et al (1978) noted decreased skeletal development by heifers fed a protected tallow product. Backfat thickness at slaughter was increased similarly by all concentrate supplements ( P < .05).…”

Section: Methodsmentioning

confidence: 95%

Effects of supplementing growing steers with high levels of partially hydrogenated tallow on feed intake, digestibility, live weight gain, and carcass characteristics

et al. 1993

Effects of supplementing growing steers consuming forage-based diets with high levels of partially hydrogenated tallow on feed intake, digestibility, live weight gain, and carcass characteristics were determined in this study. In Exp. 1, Holstein steer calves were fed bermudagrass hay alone (Control) and with a ground corn-based concentrate at .95% BW (DM basis) plus partially hydrogenated tallow at 0 (Basal), .33 (low fat; LF), or .67% BW (high fat; HF) in a Latin square. Total DMI was increased by concentrate supplementation and was lower for HF than for LF (P < .05; 3.18, 3.83, 4.25, and 3.17 kg/d for Control, Basal, LF, and HF, respectively). In Exp. 2, grazing Angus x Hereford steers (270 kg +/- .4 initial shrunk BW) were fed the same supplements as in Exp. 1 for 84 or 98 d and slaughtered. Live weight gain was increased (P < .05) by concentrate supplementation (1.01, 1.34, 1.41, and 1.30 kg/d for Control, Basal, Low, and High, respectively). The concentration of total lipids in longissimus muscle was 2.51, 2.53, 3.05, and 3.03% of wet tissue for Control, Basal, LF, and HF, respectively (Basal > the mean of LF and HF; P < .07); the proportion of palmitic acid in total fatty acids was similar among treatments. Fat supplementation did not markedly affect sensory, taste, or tenderness characteristics of longissimus muscle. In conclusion, supplementing grazing beef steers with high levels of partially hydrogenated tallow, with slaughter at approximately 400-kg shrunk BW, tended to increase fat in longissimus muscle without altering the palmitic acid level in fatty acids, although sensory, taste, and tenderness characteristics were not modified.