The effect of dietary fish-meal supplementation on parasite burdens of periparturient sheep

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Abstract
Pregnant ewes were offered 0·80, 1·0 or 1·25 of estimated protein requirement, groups P80, P100 and P125, respectively and trickle infected with Teladorsagia circumcincta (average of 10000 larvae per day) and Trichostrongylus colubriformis (average of 7000 larvae per day) for 42 days prior to parturition. Eleven days after lambing half (group TC) received a single challenge infection of 25000 T. circumcincta and 17500 T. colubriformis larvae and the remainder (TO) no further larval challenge. Worm burdens were determined 21 days post partum.Worm burdens were inversely related to dietary protein concentration. Mature worms (L5) of T. circumcincta recovered were (log10 (count + 1)) 4·002, 3·806 and 3·444 in TO sheep and 3·812, 3·633 and 3·113 in TC sheep from P80, P100 and P125 groups, respectively. The corresponding burdens of T. colubriformis were 2·665, 2·893 and 2·029 for TO and 3·985, 2·363 and 1·188 for TC sheep. The numbers of L4 larvae recovered from TC sheep were (log10 (count + 1)) 3·532, 3·288 and 3·127 for T. circumcincta and 3·080, 2·180 and 0·949 for T. colubriformis on P80, P100 and P125 diets, respectively. There was no evidence of inhibition of larval development or egg laying with either worm species suggesting that the major effect of protein supply in enhancing resistance was operating at the larval establishment stage. There was evidence that the post-partum challenge infection affected the fecundity and survival of the established adult worm population of T. circumcincta but not of T. colubriformis.

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