Effect of two protein sources of different rumen degradability on growth and digestive processes in beef cattle
Two trials were conducted to evaluate the effects of two dietary protein sources on liveweight gain, ruminal fermentation and digestion kinetics of beef cattle. In the first trial, 100 young Salers bulls (200 1.72 kg BW) and 60 Salers heifers (207 2.16 kg BW) were blocked by initial body weight in pairs and randomly assigned to one of the following treatments: 1) grazing in rye grass-oat pasture, oat hay and a ruminal degradable protein supplement (RDP); and 2) rye grass-oat pasture, oat hay and a ruminal undegradable protein supplement (RUDP). No differences between treatments were observed (p>0.05) in daily gain over a 112 d feeding period, which presumably means that the nitrogen requirements of the animals were met with both diets. In the second study four steers with ruminal and duodenal cannula were assigned to a Latin square design 4 X 4. The treatments were: T0, a control diet with RDP using a poultry manure-urea supplement; T150, a diet with a low level of RUDP (150 g/d of blood meal); T300, a diet with a intermediate level of RUDP (300 g/d of blood meal); and T450, a diet with a high level of RUDP (450 g/d of blood meal). In general, all the treatments presented a similar pattern in ruminal fermentation, liquid and solid kinetics, digestion, outflow of nutrientes to the duodenum and microbial protein synthesis.