Effect of physical particle size on ruminal and postruminal disappearance of nutrients of a mixed concentrate in Holstein steers

Abstract

In situ ruminal and post-ruminal disappearance [dry matter (DM), crud<br><br>protein (CP) and ether extract (EE)] of a mixed concentrate prepared as<br><br>fine mesh (fm), fine pellets (fp) and coarse pellets (cp) were studied. All<br><br>pellets were provided in a condition of 70°C with pressure of 3 bars in<br><br>7 seconds. Concentrate was composited of cereal grain, soybean meal,<br><br>canola meal, fish meal, urea, wheat bran, beet pulp, bagasse, salt, sodium<br><br>bicarbonate, mineral and vitamin premix, anionic salt, molasses, sugar,<br><br>protected fatty acid and Mg oxide (318, 60, 150, 15, 3.6, 250, 33, 40, 6.7,<br><br>8.6, 8, 15, 55, 30, 5 and 2.1 g/kg DM, respectively). Four Holstein steers<br><br>(430±50 kg, BW) fitted with ruminal fistulae and T-shaped intestinal<br><br>cannulae were used. Steers fed (DM basis) 2.5 kg of alfalfa hay, 2.1 kg<br><br>of corn silage, 1.5 kg of straw and 2.5 kg of concentrate (170 g CP/kg<br><br>of DM). Approximately 5 g of sample (DM) was placed in polyester bag<br><br>(12×19 cm, pore size of 48 μm,<br><br>n=8), then incubated in the rumen for<br><br>12 h. After removal from the rumen, bags were washed and dried. Then,<br><br>1 g DM of un-ruminal disappeared sample was weighed into a mobile<br><br>bag (3x6 cm, pore size of 48 μm,<br><br>n=8) and inserted in small intestine,<br><br>then removed from the voided feces and rinsed in cold tap water. DM,<br><br>EE and CP of intact and incubated samples were determined. Data were<br><br>analyzed using completely randomized design. Ruminal DM, CP and<br><br>EE disappearance of fm was significantly (P&lt; 0.01) lower than fp and<br><br>cp. Ruminal DM, CP and EE disappearance of fp was significantly (P&lt;<br><br>0.01) higher than cp (0.71, 0.61 and 0.65 vs. 0.67, 0.58 and 0.59, respectively).<br><br>Post-ruminal DM, CP and EE disappearance of fm concentrate<br><br>(0.45, 0.50 and 0.80, respectively) was significantly (P&lt; 0.01) higher<br><br>compared with fp (0.35, 0.38 and 0.68, respectively) and cp (0.39, 0.38<br><br>and 0.57, respectively). Results of the present study indicated that the<br><br>physical particle size of a mixed concentrate might impact on ruminal<br><br>and post-ruminal disappearance of DM, CP and EE.