The effects of cold exposure, food allowance and litter size on immunity of periparturient sheep toTeladorsagia circumcinctaand Trichostrongylus colubriformis

Abstract

Sixty twin- and 60 single-bearing ewes were used in a 2 ✕ 2 ✕ 2 factorial design incorporating nutritional and shearing-cold exposure treatment (no. = 15 per subgroup) to study the effects on periparturient immunity against nematode infection. From week –8 to week –4 relative to parturition, animals grazed ryegrass-white clover pastures at allowances designed to provide either 0·8 (low allowance) or 1·2 (high allowance) of estimated metabolizable energy requirement for a ewe carrying 1·5 lambs. During week –4, half the sheep from each reproductive effort and nutritional group were shorn and exposed to artificial wind and rain for 4 h on each of 4 days consecutively. During the same week, all animals were challenged twice with 1·5 ✕ 104 Teladorsagia circumcincta and 1·5 ✕ 104 Trichostrongylus colubriformis infective third stage larvae to supplement the natural infection from pasture. From week –3 to week + 5 relative to parturition the sheep were run together and offered pasture at rates estimated to enable them to meet their nutrient requirement.Shearing and cold stress reduced ewe body weight (by up to 4·66 kg per sheep), and temporarily reduced the levels of IgA against T. circumcincta (by proportionately 0·24) and T. colubriformis (0·34), and raised faecal egg count (1·6 to 4·4 fold) but did not affect the parasite-specific total antibody levels in the serum. The low allowance during pregnancy was associated with a 6·09-kg decrease in ewe body weight, decrease in the levels of total antibody and of IgA against both T. circumcincta and T. colubriformis, and increased faecal egg count (by 1·5 to 10·6 fold) during pregnancy and lactation. Faecal egg count was consistently higher (up to 8·8 fold) in twin-bearing and rearing ewes than in single-bearing and rearing ewes except during the first 4 weeks of the experiment. A significant effect of litter size on antibody levels was relatively small when compared with short-term changes (reductions) in antibody levels immediately around parturition. There were significant negative correlations between faecal egg count during late pregnancy and ewe body weight in lactation and significant negative correlations between the levels of total antibody against T. colubriformis and faecal egg counts near the end of the experiment. We conclude that litter size is likely to have greater influence on the resistance of ewes to nematode infections in the periparturient period than either pasture allowance or cold stress within the range of parameters used in this work.

Analysis of weaning‐induced stress in Saanen goat kids

“…By contrast, albumin and antithrombin III significantly decrease in animals under inflammatory conditions (Bertoni et al., 2008), infections (Cheryk et al., 1998) or cold stress (Hernández‐Espinosa et al., 2007). Similarly, cold stress after shearing reduce the level of serum IgA in periparturient sheep (Xie et al, 2004), and plasma IgG concentration significantly decreases in water buffalo calves under space restriction (Grasso et al., 1999), the same in heifers subjected to heat stress (West, 2003).…”

Influence of periparturient nutritional demand on resistance to parasites in livestock

“…Effect of litter size on PPRI seems to be sensitive to the parasite species involved, especially in mixed infections. The latter show consistently that effects of nutrient demand on T. circumcincta are smaller than those on Trichostrongylus colubriformis (24,37,39,40). Whether this relates to differences in parasite species per se , parasite niche or nutritional costs of associated expression of immunity remains to be elucidated.…”

“…The fact that improvement in resistance following reduction in reproductive effort can be achieved without affecting food intake (38,41,42) supports the view that improvement in resistance is likely achieved through effects of increased nutrient availability on expression of immunity, and not through changes in the gastrointestinal environment per se . However, consistent effects of reproductive effort on measured immune responses, including mucosal mast cells, eosinophils, globule leucocytes, and plasma, colostral and milk antibodies, have not been observed (24,38,40–42). The local nature of expression of immunity to gastrointestinal nematodes may suggest that changes in mucosal immunity would not necessarily be reflected in changes in plasma constituents (69).…”

Genetic variation in resistance to mixed, predominantly Teladorsagia circumcincta nematode infections of sheep: from heritabilities to gene identification

“…This increase in nematode egg production appears to be signalled by the poor nutritional status of the mother in late pregnancy and early lactation. It can be reversed by supplementary feeding of the pregnant ewe (17–21). Whether the nematode responds directly to the poor nutritional status of the ewe or the poor nutritional status weakens the immune response and allows the nematode to escape immune regulation is unknown.…”