Effects of Graded Levels of Sunflower Hulls in Diets of Naemi Ewes During Late Gestation and Lactation on Colostrum Quality, Milk Composition, Lamb Performance, Survival, and Blood Metabolites

(1) Background: Sunflower hulls (SFHs) are an abundant agro-industrial by-product that may serve as an alternative fiber source in sheep diets, particularly in arid production systems. This study evaluated the effects of graded levels of dietary SFH during late gestation and lactation on colostrum and milk composition, lamb growth performance, neonatal survival, and serum biochemical parameters in Naemi sheep. (2) Methods: Seventy-two primiparous Naemi ewes (initial body weight = 55.0 ± 3.8 kg) were randomly allocated to four dietary treatments containing 0, 12, 20, or 28% SFH (n = 18 ewes per treatment) from late gestation until lamb weaning at 90 days postpartum. Data were analyzed using mixed-model procedures, and treatment effects were considered significant at p ≤ 0.05. (3) Results: Dietary SFH supplementation did not affect lamb birth weight or overall survival rate (p > 0.05). However, weaning weight declined from 28.03 kg in the control group to 25.11 kg in the 20% SFH group, showing a significant linear decrease with increasing SFH inclusion (p = 0.044). Likewise, average daily gain decreased linearly by 10.4% (p = 0.044). Colostrum composition was partially affected by dietary treatment, with fat and protein concentrations at 48 h postpartum increasing quadratically by 46.6% and 33.50%, respectively, in ewes fed 20% SFH compared with the control group (p < 0.05). In contrast, milk fat and total solids contents decreased quadratically by 30.7% and 13.4%, respectively, in ewes receiving 12% SFH (p = 0.01). Most serum metabolite variables were unaffected by dietary treatment and remained within normal physiological reference ranges. However, overall serum triglyceride concentration decreased linearly with increasing SFH inclusion (p = 0.023). (4) In conclusion, SFH can be incorporated into the diets of Naemi ewes during late gestation and lactation as an alternative fiber source without adversely affecting lamb birth weight, survival, or overall metabolic health. However, increasing dietary SFH inclusion reduced pre-weaning lamb growth despite improvements in selected colostrum quality traits. Based on the productive and physiological responses observed, 12% dietary SFH appears to be the optimal inclusion level, providing the best balance between animal performance and sustainable feed utilization.