Voluntary Feed Intake and Digestion in Farmed Red Deer Stags: A Comparison with Goats and Sheep

Abstract

Castrate male red deer (Cervus elaphus), sheep, and goats, aged 2 to 3 years and fistulated in the rumen, were fed chopped lucerne (Medicago sativa) hay during experimental periods in winter (w) and summer (s) to determine effects of seasonality. All animals were fed at hourly intervals. Deer showed a marked (+ 34%) increase in voluntary food intake (VFI) and rumen pool size (+51%) during s, and this was accompanied by nonsignificant but consistent decreases in fractional outflow rate (FOR) of both rumen liquid and particulate matter, resulting in no change in apparent digestibility. Goats also showed an increase in VFI (+ 19%) and rumen pool size (27%) during s, accompanied by nonsignificant but consistent increases in FOR of rumen liquid and particulate matter, causing apparent DM digestibility to markedly decline. Sheep showed no differences between s and w in VFI, apparent dry matter (DM) digestibility, rumen pool size, and FOR of liquid or particulate matter. Rumen FOR was much greater for deer than for goats and sheep, both for liquid (0.16 vs 0.10/h) and for particulate matter (0.044) vs 0.035/h), and the ratio FOR liquid/FOR particulate was consistently higher for deer (3.6) than for sheep and goats (3.0). In a second experiment, implants of melatonin were given to the red deer for a 10-week period during spring. These resulted in a reversal of seasonal patterns during the ensuing 12 months, with VFI, rumen pool size, rumen capacity, and heart rate being depressed during summer and then rising at maximum values during winter. These data show seasonality in castrate male red deer in both VFI and a number of rumen criteria, and their strong entrainment by a period of high plasma melatonin concentration.