Physiological and biochemical responses of West African dwarf sheep to partial feed restriction

Abstract

An experiment was conducted determine the effects of partial feed restriction on the body physiology and blood biochemistry of West African Dwarf (WAD) sheep. Adult ewes (18) were randomly assigned to undergo 3 levels (4,8 and 12 days, from 0600-1200 hr ) of partial feed restriction with the remaining 12 divided into pre-restriction (control) and post-restriction (recovery) animals. Blood samples (40ml) were collected from each animal at 0800 hr every 4 days for 16 days. Over the 12 days, pulse rate increased significantly in the feed restricted sheep from 90.33 beats/min to 116.0 beats/min, but returned near to control values (71.0 beats/min) by the beginning of the post-restriction (day16) period and thereafter, was not different from control values of 65.68 beats/min. Mean respiration rate decreased significantly from 45.0 breathdinin to a nlininlum of 19.0 breathslniitl during the first 4 days ofpartial feed restriction but increased to 42.06 beaths/min during the post-restriction period. Rectal temperature did not vary from control values over the entire experiniental period. There were statistically significant increases in sedimenation rate and differential white blood cells (neutrophils, eosinophils, basophils, monocytes and lymphocytes) counts, with significant decreases in haematocrit, haemoglobin concentration, oxygen content, plasma protein, osmolarity, Ca, K, and CI values. There was no change in plasma Mg, pH, PCO2, HCO3 ,, except for PO2, which increased constantly over time. The results of this study suggested that West African Dwarf sheep has good capacity to withstand prolonged (12 days) partial feed restriction, most likely because of a large reserve of hematopoeotic cells in the spleen, coupled with the animals effective use of its physiological mechanisms for stress adaptation.