Effects of Havardia albicans supplementation on feed consumption and dry matter digestibility of sheep and the biology of Haemonchus contortus

This study evaluated effects of Havardia albicans foliage intake on sheep dry matter digestibility (DMD) and included post-mortem evaluation of Haemonchus contortus infection (i.e., worm burdens, worm female length, fecundity). Fifteen hair sheep (16 ± 4.2 kg live weight (LW)) raised free of gastrointestinal nematodes were used. Sheep were fed a basal diet: grain based concentrate and Pennisetum purpureum grass (900 and 100 g/kg DM, respectively) and were infected on day 0 with 3000 H. contortus infective larvae. On day 28 post-infection (PI) sheep were distributed to three groups being: Control (100 g/kg DM of basal diet), HA group (basal diet 600 + H. albicans 400) and the HA + PEG group (basal diet 600 + H. albicans 400) + Polyethylene glycol (PEG). The H. albicans foliage was supplied for 13 d including 7 d of adaptation (i.e., day 28-40 PI). The content of condensed tannins (CT), total polyphenols (TP) and total tannins (TT) was determined in the foliage. Concentrate, grass and H. albicans intake (g DM/kg LW0.75), DMD and H. contortus egg excretions were determined. Sheep were slaughtered at day 41 PI to assess adult worm burdens, female worm lengths and fecundity (i.e., eggs in utero). Foliage had (g/kg DM): 71.5 CT, 61.3 TP and 66.9 TT. Experimental groups had similar feed intakes, and intake of H. albicans was not affected by PEG. The DMD of HA + PEG and HA groups was lower than Control (P<0.05). Post-mortem worm burdens were similar in all groups, but the H. contortus females in the HA group were shorter and had reduced fecundity (P<0.05). Adding PEG (HA + PEG) eliminated the effect of H. albicans intake on worm length. A short period of H. albicans intake affected the DMD of sheep and reduced the H. contortus female worm length and fecundity. The use of this type of tannin-rich foliage could bring nutritional and anti-parasitic benefits to the ruminants which consume them.