Effects of feeding prickly pear by-product silage as a partial replacement of concentrate on dairy ewes: Milk characteristics, nutrient utilisation and in vitro ruminal fermentation

Prickly pear fruit processing industries generate a substantial amount of fibrous by-products as waste rich in bioactive compounds, including polyphenols and tannins, and that contain considerable minerals and water-soluble carbohydrates. This study investigated the potential of prickly pear by-product silage as feed in the diet of Valle del Belice ewes and its effects on body weight, milk yield and composition, nutrient utilisation and degradability and in vitro ruminal fermentation characteristics. A total of 12 ewes (60 d in lactation) were selected and randomly divided into three experimental groups, homogeneous for parity, live weight and milk yield. Each group was fed for 14 d (9 d for diet adaptation + 5 d for sampling), with one of the three experimental diets based on a Latin square design. The diets with the same crude protein and NDF were: 1) control (CTR) diet with hay and concentrate; 2) prickly pear peels (PPP) diet with PPP silage, hay and concentrate; and 3) pulp, peels and seeds (PPS) diet with PPS silage, hay and concentrate. Nutrient intake varied between diets, with total DM intake being greater in the CTR and PPS (p < 0.01) diets than in the PPP diet. Daily milk yield tended to be lower in ewes fed the PPP and PPS diets than in those fed the CTR diet, whereas no differences were found for fat- and protein-corrected milk between diets. Protein and casein (p ≤ 0.05) levels were higher in the milk of ewes fed the PPP diet. Compared with the milk urea concentration of CTR-fed ewes, that of PPP-fed ewes was 15 % lower. The in vivo nutrient degradability, in vitro fermentation rate and volatile FAs were greater (p < 0.01) in the PPP diet than in the PPS diet. These results suggest that PPP silage can be partially incorporated into dairy ewe diets to reduce feeding costs and improve milk nitrogen efficiency.