Protein supplementation improves the performance of parasitised sheep fed a straw-based diet.

A study was made of the benefits of protein supplementation for parasitised and non-parasitised lambs. Sixty, 5-month-old crossbred wether lambs were placed in individual pens indoors for 9 weeks. Half of the animals were experimentally dosed with 1500 Haemonchus contortus larvae per head per week and were fed ad libitum and the other half were worm-free, pair-fed controls. Diets were formulated to be iso-energetic (9.0 MJ of calculated metabolisable energy per kg dry matter) with five levels of protein (10, 13, 16, 19 and 22% crude protein). These diets were based on oaten chaff, with barley, cotton-seed meal, urea and mineral mix (except for the 22% crude protein diet which did not contain barley). Dietary crude protein content increased live-weight gain, feed intake, rumen fluid ammonia-N, packed cell volume, eosinophil counts and antibody responses to H. contortus L3 antigen and decreased faecal worm egg counts significantly. Infection did not significantly affect packed cell volume of animals on diets with 16, 19 and 22% crude protein content. We conclude that extra dietary protein can prevent the adverse effects of H. contortus infection on animal production.