Reproductive efficiency of range beef cows fed different quantities of ruminally undegradable protein before breeding1,2

Abstract

Two studies, using 128 crossbred, multiparous beef cows grazing native winter and spring rangeland, were conducted to determine effects of protein supplementation on nutrient status and subsequent calf and reproductive performance. Postparturient cows (body condition score [BC] = 3.9) were fed 1.82 kg of one of two supplements (54% CP at 490 g of CP/d) per cow on alternate days. Supplements were formulated to contain 50% (245/490 g of CP) ruminally undegradable (UD) CP (RU50) or 25% (119/490 g of CP) UD CP (RU25) and were fed until breeding (BC = 4.2). Late-calving cows (Study 1) were individually fed supplement while grazing native range. Early-calving cows (Study 2) were group-fed supplement on alternate days while grazing native range and were daily fed approximately 5.4 kg of medium-quality grass hay (10.5% CP). Late-calving cows had similar (P > .22) BW losses postpartum, whereas early-calving cows fed RU50 lost 39 kg less (P < .01) BW than did cows fed RU25. Cows that received RU25 returned to estrus sooner (P < .02), in the late-calving study, than cows fed RU50 (47 vs 56 d, respectively). The percentage of cows serviced in the first 21 d of breeding (96 and 100% for late- and early-calving studies, respectively) and pregnancy rates (88 and 86% for late- and early-calving studies, respectively) did not differ regardless of postpartum protein supplement. When adequate CP was provided in the diet for optimum function of the rumen, addition of ruminally undegraded CP decreased weight loss of mature, postpartum beef cows grazing native range.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of post-calving supplemental protein on calf performance and reproductive efficiency for beef cows fed silage

“…In their study, cows grazing smooth brome (Bromus inermis) were supplemented with a highly undegradable protein supplement based on CGM and blood meal. Other research has observed a positive relationship between level of UIP and cow weight gain (Wiley et al 1991;Dhuyvetter et al 1993;Rusche et al 1993). However, in those studies energy intake of cows was restricted, either by limit feeding or by forage quality.…”

Effects of Nutrition on Reproductive Performance of Beef Cattle

“…4 Supplementation with 50% rumen-undegradable or bypass protein after calving did not alter pregnancy rates in cows, compared with pregnancy rates in cows fed 25% bypass protein (88% and 86%, respectively). 27 Supplementation with 250 g of bypass protein (blood meal, corn gluten meal, and soybean meal) after calving increased the percentage of first-calf heifers that conceived during the first estrous cycle compared with heifers supplemented with 250 g of degradable protein (wheat mill run, soybean meal, and urea). Supplementation with bypass protein, however, did not affect the pregnancy rate for the breeding season.…”

The partial replacement of silage with straw, with or without barley or soybean meal, in rations for winter calving beef cows

“…Others have concluded that feeding protein to cows does not affect calf performance (Wiley et al 1991). Thus it would appear that a response to protein supplementation can be modified by the energy status of the cow, as well as the degradability and intake of the protein (Rusche et al 1992;Dhuyvetter et al 1993;Triplett et al 1995;Charmley et al 1999). …”

“…However, in contrast to energy, beef cows often exhibit a response in milk production and calf performance when diets are supplemented with protein. This is most apparent in low protein diets (de Garcia and Ward 1991;Wiley et al 1991;Dhuyvetter et al 1993), but has also been observed in diets of higher protein concentration, where the protein is highly degradable in the rumen (Rusche et al 1993;Charmley et al 1999;Charmley and Duynisveld 2004).…”