Supplementation based on protein or energy ingredients to beef cattle consuming low-quality cool-season forages: II. Performance, reproductive, and metabolic responses of replacement heifers.
This experiment evaluated the influence of supplement composition on performance, reproductive, and metabolic responses of Angus × Hereford heifers consuming a low-quality cool-season forage (8.7% CP and 57% TDN). Sixty heifers (initial age = 226 ± 3 d) were allocated into 15 drylot pens (4 heifers/pen and 5 pens/treatment) and assigned to 1) supplementation with soybean meal (PROT), 2) supplementation with a mixture of cracked corn, soybean meal, and urea (68:22:10 ratio, DM basis; ENER), or 3) no supplementation (CON). Heifers were offered meadow foxtail (Alopecurus pratensis L.) hay for ad libitum consumption during the experiment (d -10 to 160). Beginning on d 0, PROT and ENER were provided daily at a rate of 1.30 and 1.40 kg of DM/heifer to ensure that PROT and ENER intakes were isocaloric and isonitrogenous. Hay and total DMI were recorded for 5 consecutive days during each month of the experiment. Blood was collected every 10 d for analysis of plasma progesterone to evaluate puberty attainment. Blood samples collected on d -10, 60, 120, and 150 were also analyzed for plasma concentrations of plasma urea N (PUN), glucose, insulin, IGF-I, NEFA, and leptin. Liver samples were collected on d 100 from 2 heifers/pen and analyzed for mRNA expression of genes associated with nutritional metabolism. No treatment effect was detected (P = 0.33) on forage DMI. Total DMI, ADG, and mean concentrations of glucose, insulin, and IGF-I as well as hepatic mRNA expression of IGF-I and IGFBP-3 were greater (P ≤ 0.02) for PROT and ENER compared with CON and similar between PROT and ENER (P ≥ 0.13). Mean PUN concentrations were also greater (P < 0.01) for PROT and ENER compared with CON, whereas PROT heifers had greater (P < 0.01) PUN compared with ENER. Plasma leptin concentrations were similar between ENER and PROT (P ≥ 0.19) and greater (P ≤ 0.03) for ENER and PROT compared with CON on d 120 and 150 (treatment × day interaction, P = 0.03). Hepatic mRNA expression of mitochondrial phosphoenolpyruvate carboxykinase was greater (P = 0.05) in PROT compared with CON and ENER and similar between CON and ENER (P = 0.98). The proportion of heifers pubertal on d 160 was greater (P < 0.01) in ENER compared with PROT and CON and similar between PROT and CON (P = 0.38). In conclusion, beef heifers consuming a low-quality cool-season forage had a similar increase in DMI, growth, and overall metabolic status if offered supplements based on soybean meal or corn at 0.5% of BW.
Eastern Oregon Agricultural Research Center, Oregon State University, Burns 97720.
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Cappellozza
Eastern Oregon Agricultural Research Center, Oregon State University, Burns 97720 reinaldo.cooke@oregonstate.edu.
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Cooke
Eastern Oregon Agricultural Research Center, Oregon State University, Burns 97720.
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MM
Reis
Mountain Research Station, North Carolina State University, Waynesville 28786.
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P
Moriel
Division of Animal Sciences, University of Missouri, Columbia 65211.
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Keisler
Eastern Oregon Agricultural Research Center, Oregon State University, Burns 97720.
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Bohnert
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000502:physiology*; D019587:Dietary Supplements; D005260:Female; D007328:Insulin / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin / Q000097:blood; D008099:Liver / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism; D006109:Poaceae; D011374:Progesterone / Q000097:blood; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D012741:Sexual Maturation / Q000502:physiology*; D013025:Glycine max; D003313:Zea mays
D001786:Blood Glucose; D007328:Insulin; D018972:Insulin-Like Growth Factor Binding Protein 3; D020738:Leptin; D011374:Progesterone; D007334:Insulin-Like Growth Factor I; D019764:Phosphoenolpyruvate Carboxykinase (ATP)
beef heifers; gene expression; low-quality cool-season forage; metabolism; performance; supplementation