Characterization and feeding value of mixed broccoli by-product silage for finishing lambs in confinement

Abstract

The use of agricultural by-products in animal nutrition is increasingly being considered to address livestock feed shortages, reduce feed costs, and diminish environmental pollution. While some studies have investigated broccoli by-products as livestock feed, few have focused on the nutrition of finishing lambs. This study aims to evaluate the characteristics of broccoli by-product silage (BBS) and the effect of the complete replacement of forage with BBS in the diet of male Mehraban finishing lambs on growth performance, nutrient intake, digestibility, and meat characteristics. Sixteen Mehraban ram lambs (270.7 ± 1.4 days old; body weight of 28.3 ± 1.5 kg) were individually housed for 60 days and adapted to feed and housing for 14 days. The experimental diets included the control diet (diet without BBS) and the BBS diet (diet containing 330 g/kg DM BBS). The broccoli by-product before ensiling was mixed with wheat straw and ground barley grain in a ratio of 80:15:5 on a fresh weight basis. The pH, aerobic stability and Fleig point of BBS were 4.9, 71 h and 75.9, respectively. The values for dry matter intake and live weight at slaughter (LWS) were lower in lambs fed the BBS diet than in those fed the control diet (P < 0.001 and P = 0.03, respectively). Average daily gain and feed conversion ratio did not differ between lambs fed the experimental diets. The feed cost per kg and cost per kg of LWS in the BBS diet were 19.5 % and 25.7 % lower than in the control diet, respectively. Digestibility of nutrients (DM, OM, CP, EE, and NDF) did not differ between treatments. Most carcass traits and cuts did not differ between treatments (P > 0.05) but the longissimus lumborum m. (LL) muscle area (cm²), skin, brisket, and tail fat (as a percentage of LWS) were lower in lambs fed BBS than in those fed the control diet (P < 0.01). The internal organs (a percentage of LWS) of lambs fed the experimental diets were not affected by the treatments except for the heart (P = 0.005), which was higher in lambs fed the control diet. For meat color stability, no significant differences were observed in the values of lightness (L*), redness (a*), yellowness (b*), chroma, red color (R), green color (G), and blue color (B) between the two treatments, however, the hue angle (h*) was greater in lambs fed BBS than in those fed the control diet (P = 0.002). In conclusion, BBS can be fed to finishing lambs; however, further dose-response studies may be needed to determine the optimal levels and mixtures of BBS for inclusion in lamb diets.