Supplementation based on protein or energy ingredients to beef cattle consuming low-quality cool-season forages: I. Forage disappearance parameters in rumen-fistulated steers and physiological responses in pregnant heifers.
Two experiments evaluated the influence of supplement composition on ruminal forage disappearance, performance, and physiological responses of Angus × Hereford cattle consuming a low-quality cool-season forage (8.7% CP and 57% TDN). In Exp. 1, 6 rumen-fistulated steers housed in individual pens were assigned to an incomplete 3 × 2 Latin square design containing 2 periods of 11 d each and the following treatments: 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). Steers were offered meadow foxtail (Alopecurus pratensis L.) hay for ad libitum consumption. Treatments were provided daily at 0.50 and 0.54% of shrunk BW/steer for PROT and ENER, respectively, to ensure that PROT and ENER intakes were isocaloric and isonitrogenous. No treatment effects were detected on rumen disappearance parameters of forage DM (P ≥ 0.33) and NDF (P ≥ 0.66). In Exp. 2, 35 pregnant heifers were ranked by initial BW on d -7 of the study, allocated into 12 feedlot pens (4 pens/treatment), and assigned to the same treatments and forage intake regimen as in Exp. 1 for 19 d. Treatments were fed once daily at 1.77 and 1.92 kg of DM/heifer for PROT and ENER, respectively, to achieve the same treatment intake as percent of initial BW used in Exp. 1 (0.50 and 0.54% for PROT and ENER, respectively). No treatment effects (P = 0.17) were detected on forage DMI. Total DMI was greater (P < 0.01) for PROT and ENER compared with CON and similar between PROT and ENER (P = 0.36). Accordingly, ADG was greater (P = 0.01) for PROT compared with CON, tended to be greater for ENER compared with CON (P = 0.08), and was similar between ENER and PROT (P = 0.28). Heifers receiving PROT and ENER had greater mean concentrations of plasma glucose (P = 0.03), insulin (P ≤ 0.09), IGF-I (P ≤ 0.04), and progesterone (P = 0.01) compared to CON, whereas ENER and PROT had similar concentrations of these variables (P ≥ 0.15). A treatment × hour interaction was detected (P < 0.01) for plasma urea N (PUN), given that PUN concentrations increased after supplementation for ENER and PROT (time effect, P < 0.01) but did not change for CON (time effect, P = 0.62). In conclusion, beef cattle consuming low-quality cool-season forages had similar ruminal forage disappearance and intake, performance, and physiological status if offered supplements based on soybean meal or corn at 0.5% of BW.
Oregon State University - Eastern Oregon Agricultural Research Center, Burns, 97720.
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Cappellozza
Oregon State University - Eastern Oregon Agricultural Research Center, Burns, 97720 reinaldo.cooke@oregonstate.edu.
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Cooke
Oregon State University - Eastern Oregon Agricultural Research Center, Burns, 97720 Faculdade de Medicina Veterinária e Zootecnia, UNESP - Univ. Estadual Paulista, Programa de Pós-Graduação em Zootecnia, Botucatu, SP, Brazil, 18618-970.
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Guarnieri Filho
Oregon State University - Eastern Oregon Agricultural Research Center, Burns, 97720.
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Bohnert
D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001806:Blood Urea Nitrogen; D001835:Body Weight / Q000502:physiology; D002417:Cattle / Q000502:physiology*; D019587:Dietary Supplements; D004435:Eating / Q000502:physiology; D005260:Female; D005747:Gastric Fistula / Q000662:veterinary; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D006109:Poaceae; D011247:Pregnancy; D012417:Rumen / Q000378:metabolism*; D012621:Seasons; D013025:Glycine max; D003313:Zea mays
D001786:Blood Glucose; D007328:Insulin; D007334:Insulin-Like Growth Factor I
beef cattle; low-quality forage; performance; physiology; ruminal forage disappearance; supplementation