An 84-day experiment was conducted to determine the influence of crude protein degradability (CPD) and supplementation frequency (SF) on the performance of beef cows consuming low-quality forage during the last third of gestation. Treatments included an unsupplemented control (CON) and degradable intake protein (DIP; 18% UIP) or undegradable intake protein (UIP; 60% UIP) provided daily, every 3 days, or every 6 days. The DIP supplement was composed of soybean meal and the UIP supplement was composed of expeller processed soybean meal and blood meal. The experiment used 84 cows (512 ± 42 kg BW) during the last third of gestation in a randomized complete block design (21 pens/ 4 cows per pen). The DIP treatments were calculated to provide 100% of the estimated DIP requirement while UIP treatments were provided on an isonitrogenous basis compared with DIP treatments. The basal diet consisted of low-quality (5% CP) meadow hay. Cow pre- and post-calving (within 14 days and 24 hours of calving, respectively) weight and body condition score change were more positive (P < 0.05) for supplemented groups compared with CON. No differences (P > 0.10) were observed for CPD or SF. Results suggest crude protein supplements consisting of 20 to 60% UIP can be effectively used by ruminants consuming low-quality forage without adversely affecting cow performance, even when provided as infrequently as once every 6 days.
Bohnert, D.W., C.S. Schauer, T. DelCurto. 2002. Influence of rumen protein degradability and supplementation frequency on performance and nitrogen use in ruminants consuming low-quality forage: Cow performance and efficiency of nitrogen use in wethers. J. Anim. Sci. 80:1629-1637 (DWB PDF#10)