| Autor: |
N H, Ciccioli, S L, Charles-Edwards, C, Floyd, R P, Wettemann, H T, Purvis, K S, Lusby, G W, Horn, D L, Lalman |
| Rok vydání: |
2005 |
| Předmět: |
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| Zdroj: |
Journal of animal science. 83(11) |
| ISSN: |
1525-3163 |
| Popis: |
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 (P0.05) than control and HS-30 heifers at the beginning of the breeding season. Thirty-one, 25, and 26% more HS-60 heifers were pubertal (P0.05) on May 1 compared with LS-30, HS-30, and control heifers, respectively. At puberty, HS-60 heifers were 24 and 22 d younger (P0.05) than LS-30 and control heifers, and 31 kg lighter (P0.01) 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 (P0.03) than control heifers at puberty. During a 60-d breeding period, the incidence of puberty was greater (P0.05) for HS and LS heifers than for control heifers and was greater (P0.05) 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. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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