Influence of dietary particle size on chewing activity and reticulo-ruminal motility in goats and sheep fed wheaten ( Triticum aestivum) hay

Abstract

Wheaten hay, prepared into two physical forms was used to formulate four diets for goats and sheep. Hay was either chopped into 1 cm lengths or ground (3.2 mm screen) and pelleted and fed in either form or as a 2:1 or 1: 2 ratio, respectively. Responses in chewing activity and reticulo-ruminal motility were compared in a replicated 4 × 4 Latin square design. Goats ate 14% less DM than sheep (28.8 g/kg bodyweight vs. 33.5) yet spent 55% more time eating (251 min/d vs. 162), and 15% more time ruminating (635 min/d vs. 552). Frequency of primary and secondary reticulo-ruminal contractions were similar in both species when corrected for intake and digestible DM intake, respectively, but there were fewer secondary contractions in goats during eating and rest. Eating was associated with the highest frequency of both contraction types. There were no significant species by treatment interactions. In both species, feed intake and number of primary contractions increased linearly as the particle size of the diet decreased. In contrast, frequency of secondary contractions was not affected by physical form of the diet but was highly correlated ( r=0.97) with digestible DM intake. The digestive physiology of the two species appears to differ in regard to feed intake and chewing activity but goats did not clear digesta from the rumen as rapidly as sheep and, therefore, the extra particle size reduction of feed and rumen digesta did not enhance intake or digestion of the wheaten hay. However, these characteristics may provide a survival advantage for goats when limited to very poor quality roughage.