Effects of Supplement Type and Breeding Season on Parasite Load in Hair Sheep Ewes

Abstract Proper supplementation in late gestation and lactation helps reduce the effects of temporary immunity loss from increased gastrointestinal nematode (GIN) parasitism around lambing. This study evaluated effects of supplementing soyhulls (SH) or a 50:50 combination of SH and corn gluten (SH-CG) on GIN infection parameters in hair sheep ewes mated in November, March and July. Pregnant St. Croix (STX) and Barbados Blackbelly (BB) ewes (n = 30-36) were allocated, balanced by breed, parity and fetal numbers, to either SH or SH-CG supplementation during the last trimester of pregnancy. Ewes rotationally grazed predominantly fescue pastures subdivided into 6 sections (0.13 ha with 3 sections of 5-6 ewes/supplement type) and 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 nursed lambs for 63 d. Blood and fecal samples were collected pre- (PRE), post-partum (PP) and at weaning (WEAN) 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 recorded at each sampling. Data were analyzed with supplement type, mating season, and breed as the main effects, and FEC were log-transformed before analysis (means reported). Haemonchus contortus (71.0%) was the most common GIN throughout the study. Although there was no effect of diet, season or breed on PRE-FEC (overall mean 431±55 epg) and PRE-PCV (overall mean 30.1±0.4%), there was an effect of breed (P 0.0001) and season (P 0.005) on PRE-BCS with STX ewes (2.7±0.06) having higher scores than BB (2.3±0.07) and the highest scores observed in March (2.7±0.08 vs 2.4±0.08 for July and November). There was no effect of diet, breed, or season on PP-FEC (442.1±60.2 epg). There was an effect of season (P 0.007) on PP-PCV (March lowest at 29.7±0.7, others similar at 31.5±0.7 for July and 33.0±0.7 for November) and an effect of breed (P 0.003) on PP-BCS (2.4±0.06 and 2.2±0.06 for STX and BB ewes, respectively). There was no effect of diet, breed, or season on WEAN-FEC (overall mean 635.6±124.5 epg) nor on WEAN-BCS (overall mean 2.1±0.05). Weaning PCV was highest (P 0.02) in July (31.8±0.7%) compared to November (29.5±0.7%) and March (29.5±0.7%). There was a tendency (P = 0.05) for diet to influence WEAN-PCV, with SH-CG (31.0±0.74%) higher than SH (29.3±0.7%) supplemented ewes. Under the conditions of this study, SH alone could serve as an adequate supplement for ewes pre- and immediately post-lambing regardless of breeding season, though packed cell volume and body condition scores should be monitored closely if used as the only supplement during lactation.