Effect of grain type and processing index on growth performance, carcass quality, feeding behavior, and stress response of feedlot steers.
Moya, D., He, M.L., Jin, L., Wang, Y., Penner, G.B., Schwartzkopf-Genswein, K.S.G., and McAllister, T.A. (2015). "Effect of grain type and processing index on growth performance, carcass quality, feeding behavior, and stress response of feedlot steers.", Journal of Animal Science, 93(6), pp. 3091-3100. doi : 10.2527/jas.2014-8680 Access to full text
One hundred sixty crossbred steers (538 ± 36 kg BW) were used in an 84-d experiment with a randomized block design to study the effects of wheat or barley grain processed to 2 different indices on growth performance, feeding behavior, carcass characteristics, stress, and temperament of finishing beef cattle. Treatments were a wheat-based diet (88.4% of diet DM; WH) and a barley-based diet (89% of diet DM; BA), processed to an index of either 75% (HI) or 85% (LO) of their original volume weight. Cattle were allocated to 16 feedlot pens (10 animals per pen, 4 pens per treatment), 8 of which were equipped with the GrowSafe system for monitoring feeding behavior. Flight speed, hair, and saliva samples were collected on d 1, 28, 56, and 84 to determine temperament, acute, and chronic stress. All steers were slaughtered at the end of the experiment, and carcass quality was evaluated. Cattle fed WH had a lower (P < 0.05) meal length and frequency of visits per meal and tended (P = 0.10) to have a lower DMI, meal size, and feeding time than those fed BA. The LO processing index increased (P = 0.05) DMI and reduced (P < 0.05) the G:F and the percentage of saleable meat of the carcass compared to HI. There was a trend (P = 0.09) for a grain × processing index interaction, where cattle fed BA-LO had a lower incidence of severe liver abscesses compared with cattle fed other treatments. Cattle fed WH had greater hair cortisol concentrations (P = 0.01) and flight speed (P < 0.01) than those fed BA. There was a trend (P = 0.07) for a grain × processing index interaction, where heifers fed WH-LO had a lower salivary cortisol than those fed other treatments. Results suggest that a LO processing index had a negative effect on feed efficiency and carcass performance and that the WH diet caused a range of effects on feed intake and behavior indicative of steers with greater excitability and chronic stress.
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