Effect of frequency of supplementation and protein concentration in supplements on performance and digestion characteristics of beef cattle consuming low-quality forages

Abstract

Three experiments evaluated whether effects of altered frequency of supplementation on forage use and cow performance depended on supplement CP concentration and (or) grain type when fed to cattle eating low-quality forages. All experiments included supplementation frequency (daily = 7x; three times weekly = 3x) as one factor in a factorialized arrangement of treatments. In Exp. 1 and 2, the second factor was supplement CP concentration (10, 20, 30, and 40% CP), altered by changing the ratio of soybean meal to sorghum grain in supplements. Supplements were fed at 13.9 and 14.1 kg of DM/wk for Exp. 1 and 2, respectively. In Exp. 3, the second factor was supplement grain type (sorghum grain or corn) and supplements containing 21% CP were fed at 14.8 kg of DM/wk. In Exp. 1, eight ruminally fistulated steers (456 kg) consumed wheat straw ad libitum. Pregnant beef cows grazing dormant tallgrass prairie were used in Exp. 2 (475 kg; n = 128) and 3 (504 kg; n = 120). In Exp. 1, reducing supplementation frequency decreased (P < .01) straw intake but increased (P < or = .03) DM and NDF digestion. As CP concentration in supplements increased, straw DMI (P = .06) increased quadratically, whereas DM and NDF digestion increased linearly (P < .01). In Exp. 2, increasing CP concentration in supplements enhanced cows' ability to maintain BW and condition up to calving, with decreasing magnitude of difference between treatments at higher CP concentrations (P < .01). Increasing CP in supplements fed to the dams linearly (P = .05) increased calf weaning weight in Exp. 2. In Exp. 2 and 3, reducing supplementation frequency increased (P < or = .02) winter weight loss through calving. Grain type did not significantly affect most performance variables. In summary, response to supplementation frequency was not dependent on supplement CP concentration or grain type. Daily supplementation maximized forage intake and cow performance, although the magnitude of performance differences was not large.

Frequency of concentrate supplementation for cattle fed barley straw. 2. Ruminal dilution rates, pH and metabolite concentrations

“…There were no effects of either protein intake or feeding frequency on dilution rate of either Co-EDTA or chromiummordanted fibre, which is similar to results obtained by other researchers (Chase and Hibberd 1989;Hunt et al 1989;Beaty et al 1994). …”

“…The study of Beaty et al (1994) supports our results since the lowest rumen pH they obtained in steers fed concentrate three times weekly was just below pH 6.2. Similarly, Chase and Hibberd (1989) found that lowest ruminal pHs reached on days when concentrate was provided were approximately 6.3 and 6.15 in heifers fed 2.8 kg or 4.1 kg of maize, respectively, on alternate days.…”

“…1). Similar results were obtained by Chase and Hibberd (1989), Hunt et al (1989) and Beaty et al (1994). The lowered ruminal ammonia concentrations 13 h after feeding on days when the low-protein concentrate was fed in comparison with days when concentrate was not fed is consistent with increased ammonia utilization as a result of additional microbial growth.…”

“…First, although lactate did not accumulate when the frequency of feeding concentrates was reduced to less than once daily in the study of Beaty et al (1994), lactic acidosis is of such importance that the effect of alternate day feeding of concentrates on ruminal lactate concentrations needs to be re-examined. Second, additional information on ruminal parameters is required to aid in our understanding of why less-frequent feeding of concentrates did not negatively affect intake or digestibility of diets containing 70% straw.…”

BEEF SPECIES SYMPOSIUM: An assessment of the 1996 Beef NRC: Metabolizable protein supply and demand and effectiveness of model performance prediction of beef females within extensive grazing systems1,2,3

“…Köster et al (2002) indicated that inclusion of urea in supplements at less than 45% of DIP would not significantly depress performance of prepartum cows grazing dormant tall grass prairie in Kansas. Others (Beaty et al, 1994;Farmer et al, 2001) observed that infrequent (i.e., 2 to 3 times/wk vs. daily) DIP supplementation can be practiced without greatly affecting performance outcomes of winter grazing beef cows. Farmer et al (2004b) found that inclusion of NPN (30% or less of DIP concentrations) in protein supplements fed on alternative days to beef cows grazing dormant tallgrass prairie did not compromise beef cow performance.…”