Milk Production and Nutrient Utilisation Efficiency of Dairy Ewes Fed Alfalfa Hay, Sulla Hay or Sulla Haylage Under Pasture-Based Conditions

This study evaluated the effects of replacing alfalfa hay with sulla (Sulla coronaria (L.) B.H. Choi & H. Ohashi) hay or sulla haylage in pasture-based diets for lactating Sarda ewes on milk production, composition, and nutrient utilization efficiency. Seventy-two mid-lactation ewes were assigned to three dietary treatments: alfalfa hay (AH), sulla hay (SH), or sulla haylage (SHL), all combined with 3 h/day grazing and concentrate supplementation. Diets were formulated to be theoretically isoenergetic and isoproteic. Pasture quality was comparable among groups throughout the experimental period. Milk yield did not differ among treatments; however, fat- and protein-corrected milk (FPCM) and milk components were higher in AH compared with sulla-based diets. Nitrogen intake (NI) was greatest in AH, as reflected by higher milk urea concentration. Energy utilization efficiency (FPCM/UFL intake) differed among treatments, with lower values in SH compared with AH and SHL. Protein utilization efficiency (Milk N/NI) was highest in SHL, intermediate in SH, and lowest in AH (p < 0.001). Condensed tannins were not detected in conserved sulla forages, suggesting that conservation processes may reduce the characteristic tannin-related nutritional effects of fresh sulla. Results indicate that forage conservation method influences nutrient utilization efficiency, with sulla haylage improving nitrogen efficiency without impairing milk yield.