EVALUATION OF CRUDE PROTEIN SUPPLEMENTATION TO BEEF CATTLE GRAZING LATE GROWING SEASON NATIVE RANGE

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2016-09-13

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Abstract

Two experiments evaluated the effects of altering dietary protein on beef cattle performance and nutrient excretion. In the first study, concurrent experiments were conducted to evaluate the effect of protein supplementation to beef cattle grazing warm-season shortgrass forage during the late growing season. For all Exp., treatments consisted of a supplemented group (1.32 kg of a 39% CP fed 3 times a week) and a non-supplemented control group. In Exp. 1, cow final BW (P = 0.24) and ADG (P = 0.38) were not affected by treatment. There was no difference (P = 0.97) in cow final BCS regardless of treatment. Calf ADG (P = 0.54) and weaning weight (P = 0.45) were not affected by treatment. In Exp. 2, cow final BW (P = 0.39) and final BCS (P = 0.81) did not differ between treatments. Cow ADG (P = 0.07) tended to be greater when supplemented with 0.22 kg CP per day. Calf ADG (P = 0.50) and weaning weight (P = 0.11) did not differ between treatments. In Exp. 3, heifer final BW (P = 0.17) was not different between treatments. Heifer ADG (P = 0.02) was greater for supplemented heifers. Supplementing protein to cattle grazing late season medium quality forage is advantageous for increasing ADG in replacement heifers and potentially beneficial to improve condition in lactating primiparous cows. In a separate study, a commercially available condensed tannin (CT) extract (ByPro; Silva Team, Ontario, CA) was included in a cereal grain-based diet at 3 levels (0, 1, or 2% of diet, DM basis). No group by treatment interactions was detected (P ≥ 0.18) among the response variables. Provision of CT did not affect (P ≥ 0.64) DM intake or apparent total-tract DM digestion. Nitrogen intake was not affected (P = 0.58) by inclusion of CT in the diet, but fecal N output increased (P = 0.04) at 2% CT inclusion compared with control. However, there was no difference (P = 0.36) in urine N output among treatments. Nitrogen retention was less than (P = 0.03) with 2% CT than 0 or 1% CT. Proportion of total N excreted in urine decreased (P = 0.03) with CT supplementation at 1 or 2% in the diet. Similarly the proportion of total N excreted in feces increased (P = 0.03) with 1 or 2% CT inclusion. Site of N excretion was shifted away from urine and toward feces when CT was included in a complete diet fed to beef cattle

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Keywords

Crude protein, forage, supplementation, cow-calf pairs

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