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Abstract Before lambing and up to 8 wk during lactation, ewes experience a temporary loss of immunity to gastrointestinal nematodes (GIN). This can result in a periparturient increase in fecal egg counts (FEC) along with clinical symptoms of parasitism. This increase in FEC can lead to greater larval numbers on pasture, consequently exposing lambs to a greater level of infection that can impair production. Adequate supplementation during late gestation and lactation has been shown to reduce the impact of this temporary loss in immunity and decrease GIN infection levels in ewes. This study evaluated the supplementation of an agro-byproduct (soy hull) on GIN infection parameters in hair sheep ewes. Pregnant ewes (n = 36) were allocated, balanced by breed, parity and fetal numbers to either corn/soybean (CS) or soy hull (SH) supplementation during the last trimester of pregnancy. Ewes rotationally grazed predominantly fescue pastures subdivided into 6 sections (0.13 ha) using electro-netting (3 sections of 6 ewes/supplement type). Ewes were supplemented at either 0.75% BW (late gestation) or 1.5% BW (lactation) using a single feeder per section. Ewes lambed on pasture and lambs were weaned at approximately 63 d. Lambs had access to the supplement provided to their dams. Blood and fecal samples were collected in prepartum, postpartum and at weaning for determination of packed cell volume (PCV) and FEC. Pooled treatment group feces were also collected and cultured to determine GIN genera. Body condition scores (BCS) were also recorded at each sampling. Data were analyzed in a model with supplement type and breed as the main effects and FEC were log transformed before analysis. There was a mixed population of GIN throughout the study with H. contortus (49.5%) and Tricostrongylus spp. (46.6%) being the most common. Supplement type had no effect on ewe BCS prepartum, postpartum or at weaning (averaging 2.6 ± 0.1, 2.3 ± 0.1 and 2.0 ± 0.1, respectively). Supplement type influenced PCV at weaning only, with ewes supplemented with CS having a greater (P 0.03) PCV than those supplemented with SH (33.0 ± 0.7% and 30.8 ± 0.7%, respectively). PCV was similar between treatments prepartum (38.4 ± 1.3%) and postpartum (34.4 ± 0.9%). Ewe FEC was similar between CS and SH supplemented ewes prepartum (271.6 ± 0.5 epg) and at weaning (298.5 ± 80.5 epg); however, at postpartum sampling CS ewes tended (P = 0.09) to have reduced FEC (234.1 ± 62.0 epg) compared with SH (414.1 ± 59.6 epg) supplemented ewes. At weaning, lamb FEC was not influenced by supplementation or breed and averaged 502.3 ± 83.2 epg. Data indicate that substituting SH for a more traditional corn-based supplement in landrace hair sheep ewes managed in a pasture-based system had no influence on GIN infection. Agro-byproduct supplementation should be explored further for their use in sustainable, forage-based sheep production systems.
Robertson et al. (Fri,) studied this question.