Post-weaning changes in the digestive physiology and caecal fermentative activity in the greater cane rat (Thryonomys swinderianus)

Abstract

The greater cane rat is a recently domesticated monogastric herbivore, and the importance of the caecum in the functioning of its digestive tract has frequently been mentioned. However, no data are available on caecal fermentative activity of this animal and research on the digestive physiology was only performed in adult animals. The present work was initiated to describe some  parameters of the digestive tract anatomy and to study caecal fermentation of the growing cane rat. Thirty 40-day-old weaned  cane rats were used in this experiment. Six of them were immediately euthanased and 12 were housed in a collective pen for  gastrointestinal tract (GIT) parameters measurements. Twelve others were kept in individual cages to record growth and food intake. Captive cane rats received a pelleted diet containing 12.5% of crude protein and 16.7% of lignocellulose. Six of the 12 collectively housed animals were euthanased on day 82 and a further six on day 103. The growth rate increased with age (P < 0.01) with a linear growth curve (P < 0.001) while the feed intake (g/kg body weight) did not vary (P>0.05). The caecum   represented the largest compartment of the digestive tract constituting more than 40% of total GIT contents. Acetate was the most abundant short-chain fatty acid with more than 70% of the total, followed by propionate (less than 25%) and butyrate (around 5%). Short-chain fatty acid profiles varied with age: when age increased, the acetate proportion increased (P < 0.01), the propionate proportion decreased (P < 0.001) and the butyrate proportion remained unchanged (P>0.05). The propionate/butyrate ratio showed a decrease with an increase in age (P=0.05). Ammonia concentrations did not vary with age (P>0.05). It is concluded that the caecum is an important site of fermentation in the growing cane rat.

Key words: cane rat, digestive physiology, caecum, fermentative activity, Thryonomys.