Comparative digestion in deer, goats, and sheep

Abstract

Comparisons were made between castrated male red deer, Angora × New Zealand feral goats, and Border-Leicester × Romney sheep fed chaffed lucerne hay ad libitum during summer and winter. Measurements were made of apparent digestibility, fractional outflow rate (FOR) of rumen digesta, rumen pool size, and particle size breakdown in the rumen, at voluntary feed intake (VFI) during both summer and winter. Both deer and sheep selected a diet lower in fibre and greater in nitrogen than the feed on offer, whereas goats showed no evidence of diet selection. Sheep did not show evidence (P > 0.05) of seasonal cycles (summer versus winter) in voluntary dry matter (DM) intake and apparent DM digestibility, whereas deer showed marked increases during summer in voluntary DM intake (35%) and rumen pool size of DM + liquid (51%), with no reduction in apparent DM digestibility. Goats showed evidence of a summer increase in VFI (17%), which did not attain significance, and in rumen pool size of DM + liquid (+ 27%; P < 0.01), which was associated with a decrease in the apparent digestibility of DM (P < 0.01). Deer digested total fibre better than sheep, especially in summer, and consistently had a higher digestibility of lignin. Goats digested total fibre better than sheep during winter when voluntary intakes were similar (P < 0.001) and to a similar extent during summer when voluntary intake was much higher than for sheep. However, goats digested lignin more efficiently than sheep in both seasons. Particles had to be reduced in size to pass a 1 mm sieve, in order to leave the rumen of sheep, deer, and goats. Deer had a faster rumen FOR of water (l5.6%/h) than sheep (1O.4%/h) and goats (1O.0%/h), both in summer and in winter (P < 0.01). The FOR of particles from the rumen of deer showed a reduction during summer compared to winter, whereas sheep and goats showed no change with season. The ratio FOR Cr-EDT A/FOR lignin was greater in deer than in goats and sheep, indicating that water left the rumen proportionately faster than particulate matter in deer compared to sheep and goats. Relative to sheep, it was concluded that goats would use low-quality fibrous feeds more efficiently, whereas red deer would be likely to use feeds with high contents of soluble carbohydrate and protein more efficiently.