The effect of a protein energy supplement on pasture protein and fibre digestion in the rumen of grazing steers

• Published in: Animal feed science and technology Vol. 25; no. 1; pp. 39 - 53
• Main Authors: Napoli, G.M., Santini, F.J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1989
• Subjects: BOEUF; BUEY; BULLOCKS; CONCENTRADOS DE PROTEINA; CONCENTRE DE PROTEINES; CRUDE FIBRE; CRUDE PROTEIN; DIGESTION; FIBRA BRUTA; FIBRE BRUTE; GRAZING; PASTOREO; PATURAGE; PROTEIN CONCENTRATES; PROTEINA BRUTA; PROTEINE BRUTE; RUMEN
• ISSN: 0377-8401; 1873-2216
• DOI: 10.1016/0377-8401(89)90106-5

The effects of a protein-containing concentrate supplement on rumen environment, crude protein and fibre digestion and passage with two fresh forages were studied. The trial was designed as a crossover, with two treatments (T0, 0 kg supplement; T1, 3 kg supplement), two periods (17 days each) and six randomly distributed Aberdeen Angus steers. Animals grazed together with lactating Holstein cows. From 0900 to 1500 h they were on an oat pasture ( Avena sativa L.), while from 1630 to 0730 h they grazed a ryegrass ( Lolium perenne L.)-white clover ( Trifolium repens L.) pasture. There were no differences ( P > 0.05) between treatments and periods for rumen liquor pH (mean 5.93). Ammonia N concentration was higher ( P < 0.05) for T0 (16.36 mg dl −1) than for T1 (15.26 mg dl −1). Total VFA concentration (mean 193 mmol l −1), VFA proportion (C2, 44%; C3, 31%; C4, 17%) and C2 C3 ratio (mean 1.42) were not affected by treatments but showed variations during the day. Neither the rate of protein degradation nor the effective protein degradability showed differences ( P > 0.05) between treatments. The value of ryegrass-white clover pasture were 60 and 3% h −1, and for the oat pasture 72 and 3.5% h −1, respectively. Protein potentially digestible fraction was affected by treatments ( P < 0.05) in oat pasture (T0, 75.5%; T1, 73.4%), but not in ryegrass pasture (mean 61%). Readily available soluble protein fraction in ryegrass-white clover was higher ( P < 0.05) for T1 (16.6%) than for T0 (7.5%). Rye grass-white clover fibre potentially digestible fraction ( D o) was not different ( P > 0.05) between treatments and periods (mean 73%); lag time ( L) was different ( P < 0.05) between periods (I, 3.9 h; II, 0.4 h); rate of fibre digestion ( k d) was lower ( P < 0.05) for Period II (2.7% h −1) than Period I (3.7% h −1). In forage oat, concentrate significantly ( P < 0.05) reduced D o fraction from 82.4 to 79.4%, and increased k d (T0, 3.8% h −1; T1, 4.2% h −1). Differences between periods have also been observed. For the rye grass-white clover pasture actual extent of digestion (AED) was significantly higher ( P < 0.05) in Period I (41 vs. 35.1%). In forage oat there were differences in AED ( P < 0.05) for treatments (T0, 49.4%; T1, 41.5%) and periods (I, 54.7%; II, 43.9%). Rate of passage in reticulo-rumen (mean 2.6% h −1), caecum-proximal colon (mean 10% h −1) and small intestine transit times (mean 5.15 h) were not affected ( P < 0.05) by treatments and periods. The concentrate used affected rumen environment, protein and fibre digestion kinetics very little.