C.G. Farmer

Effect of a wide range in the ratio of supplemental rumen degradable protein to starch on utilization of low-quality, grass hay by beef steers

Hereford×Angus steers were used in a 14-treatment, 2-period, crossover design experiment to examine effects of a wide range in the ratio of supplemental starch to rumen degradable protein (RDP) on low-quality forage utilization and ruminal characteristics. Steers were given ad libitum access to grass hay (4.9% CP, 42.4% ruminally degradable) and supplemented in a 2×7 factorial arrangement of treatments. All supplements were administered directly into the rumen and delivered one of two levels of ruminally degradable starch (cornstarch grits; 0 and 0.3% of initial BW) and one of seven levels of RDP (sodium caseinate; 0, 0.015, 0.051, 0.087, 0.123, 0.159, and 0.195% of initial BW). Supplementation with RDP increased consumption of forage OM, total OM, NDF, and digestible OM in a quadratic (P<0.01) fashion (intake increased and then declined). Starch supplementation depressed (P<0.01) forage OM and NDF intakes. In general, RDP supplementation elicited a positive quadratic response on NDF digestion (P=0.02). However, an interaction between supplemental starch and RDP level was observed (P<0.01) for NDF digestion. At the four lowest levels of supplemental RDP, starch supplementation substantially reduced NDF digestion, although for steers receiving the three highest levels of supplemental RDP, starch supplementation had little effect on NDF digestion. In contrast, neither the starch×RDP interaction nor the starch main effect was significant for OM digestion, which increased linearly (P<0.01) with supplemental RDP. Supplementation with RDP altered passage rate of acid detergent insoluble ash in a quadratic (P=0.05) manner that paralleled the intake response. However, liquid passage rate was not affected significantly. A decline in ruminal pH was associated (P=0.02) with increasing supplemental RDP and tended (P=0.07) to be associated with increasing starch, but it was not requisite for starch-induced depressions in NDF digestion. Ruminal NH3 concentration increased in response to increasing RDP, although the increase when starch was supplemented was less than that observed without starch (P=0.03). Supplemental starch generally elicited negative effects on low-quality forage intake and fiber digestion, but the effects on fiber digestion were overridden by adequate supplemental RDP. Supplemental RDP exerted a highly positive effect on consumption and digestion of this low-quality forage.

Determining the influence of different levelsof urea supplementation when beef cows grazing winter pasture are supplemented at different frequencies during the prepartum period

One hundred sixty spring-calving Hereford × Angus cows grazing lowquality, tallgrass-prairie range during the winter of 2000-2001 were supplemented before calving either daily or three times weekly. The supplement contained 40% CP with 0, 15, 30, or 45% of the supplemental degradable intake protein from urea. Supplement was fed at 4 lbs/head daily to cows receiving supplement daily. Cows receiving supplement three times weekly were fed the same amount of weekly supplement, but split equally among their supplementation events. After calving, all cows received a supplement without urea on a daily basis. In general, prepartum supplements that contained more urea prompted greater body weight loss; however, the effect of increasing urea was most noticeable when supplements were fed only three times weekly. When averaged across supplementation frequencies, increasing the level of supplemental urea tended (P=0.15) to decrease pregnancy rate in beef cows that had received urea supplementation before calving.

Relative value of ruminally degradable and undegradable protein on the utilization of low-quality prairie hay by steers

An experiment was performed to investigate the impact of providing six levels of ruminally degradable protein (RDP; protein that is available to ruminal microbes) in combination with two levels of ruminally undegradable protein (RUP; protein that is not available to the ruminal microbes, but can be digested directly by cattle) on the intake and digestion of low-quality prairie hay. Twelve steers were provided unlimited access to low-quality prairie hay (5.3% crude protein and 71.7% neutral detergent fiber) throughout the trial. To simulate dietary RUP, casein was infused abomasally once daily at either 0 or 0.087% of body weight. To simulate dietary RDP, casein was infused ruminally once daily at 0, 0.029, 0.058, 0.087, 0.116, or 0.145% of body weight. As provision of RDP increased, forage intake and fiber digestion increased. Supplementing with RUP alone increased forage intake but not fiber digestion, although the intake response was not as large as providing the same amount of RDP. In conclusion, RUP is less efficient than RDP in stimulating forage intake and digestion.

Effects of frequency of supplementation on performance of beef cows grazing winter pasture

One hundred twenty spring-calving Hereford x Angus cows grazing low-quality tallgrass-prairie forage during the winter of 1998 were fed a 43% crude protein supplement 2, 3, 5, or 7 days a week. Supplement was fed at 4 lb/head daily to cows supplemented daily. The other cows still received 28 lb per week but divided equally among feedings. Cumulative performance (measured by changes in body condition score and body weight) was slightly better with increased supplementation frequency. However, the magnitude of differences in body condition and body weight changes, even for the most extreme treatment comparisons, were relatively small.

Effects of frequency of supplementation on the intake and digestion of low-quality forage by beef steers

A 43% CP (dry basis) supplement was fed to 16 ruminally fistulated steers on 2, 3, 5, or 7 days a week. Supplement was offered at .36% BW (dry basis) daily for steers that received supplement every day. For other treatments, the same amount of supplement was split equally among supplementation events. Forage intake and digestibility increased with increasing supplementation frequency. However, the difference in forage intake tended (cubic, P=.07) to be most prominent for the two extremes; the 3and 5-days-a-week treatments tended to be similar. Forage intake for steers supplemented on 2 days a week decreased on the days when they were supplemented. Although forage utilization may improve with increasing frequency of supplementation, the impact on performance is likely to be small unless differences in frequency of supplementation are extreme.

Effect of ruminal versus postruminal administration of degradable protein on utilization of low-quality forage by beef steers

Twelve ruminally fistulated steers were used to evaluate the effects of supplying a highly degradable protein source (casein) both ruminally and postruminally on intake and digestibility of low-quality native hay. Both protein supplementations substantially increased voluntary intake, organic matter digestion, rate of passage, ruminal ammonia, and blood urea concentrations, but intakes were considerably greater when protein was given ruminally as opposed to postruminally.

Wheat bran and second clears as supplemental energy sources for beef cows grazing winter pasture

Ninety spring-calving Hereford × Angus cows grazing low-quality, tallgrass-prairie forage during the winter were fed 5 lb/day of a supplement containing combinations of wheat bran (high in digestible fiber) and second clears (high in starch). The by-product combinations accounted for 47 to 49% of each supplement, as follows: 1) 100% wheat bran; 2) 67% wheat bran, 33% second clears; and 3) 33% wheat bran, 67% second clears. Cow performance was measured by changes in body weight and body condition score. The combinations of wheat bran and second clears had no significant effects on cow performance, calf birth weights, calf performance, or cow pregnancy rates.

Effect of supplemental carbohydrate source on the utilization of low-quality tallgrass-prairie hay by beef steers

Twenty ruminally fistulated steers were used in starch and various sugars, when fed with different two experiments to evaluate the effects of suppleamounts of DIP, on intake and digestion of lowmental carbohydrate source (starch, glucose, quality tallgrass-prairie hay. fructose, or sucrose) fed at .3% BW/day on the utilization of low-quality tallgrass-prairie hay. In Experiment 1, all supplemental carbohydrates were fed with a low level of supplemental degradable Twenty Hereford × Angus steers with ruminal intake protein. In Experiment 2, the level of fistulas were housed in individual tie stalls and used supplemental degradable intake protein was high. in two experiments. In both experiments, steers Intake of the tallgrass-prairie hay was not affected had free-choice access to low-quality tallgrasssignificantly by supplementation in either experiprairie hay (5.2% CP and 72.7% NDF in Exp. 1 ment, but as a result of the added carbohydrate, and 5.2% CP and 76.0% NDF in Exp. 2). Steers total intake was increased. When supplemental were randomly assigned to treatments at the beginprotein intake was inadequate, supplemental ning of each experiment. Treatments were either carbohydrates depressed digestion, but when no-supplement negative control (NC) or supplesupplemental protein was higher, fiber digestion mental starch, glucose (supplied as dextrose), was not depressed. Because of increased total fructose, or sucrose fed at .30% BW/daily. Suintake (forage plus supplement) and increased crose is a disaccharide composed of two digestion in Experiment 2, total digestible organic monosaccharides, glucose and fructose. We were matter intake was greater in the supplemented interested in sugars because of their presence in animals, with little difference among carbohydrate molasses-based liquid supplements and blocks. sources. Supplemented steers also received degradable