Effect of feeding complete feed block containing rumen protected protein, non‐protein nitrogen and rumen protected fat on improving body condition and carcass traits of cull ewes
Irrespective of breed, physiological stage of the animal and defined product utility (rearing for meat or wool production), all sheep are slaughtered at the end of their productive life cycle for meat production. In many developing or underdeveloped countries including India, approximately 40% sheep slaughtered are from culled categories (Sahoo and Bhatt, 2012). Herd owners do not regard them as valuable meat animals and dispose them at a lower price due to low body condition score (BCS) and poor dressing yield. Re‐alimentation by feeding concentrate up to 90 day improves their body condition including the improvement in carcass yield and quality traits for better consumer acceptability (Bhatt et al., 2012); however, higher feeding cost and increased fattening are the matter of concern at field level. Experiments were conducted to strategically reduce the feeding cost either by reducing the feeding period (Bhatt et al., 2013a) or by the use of non‐protein nitrogen (Bhatt et al., 2015) and by supplementing rumen bypass fat (Bhatt et al., 2013b) in diet. All these experiments were based on ad libitum feeding of concentrate. Higher concentrate feeding is associated with higher carcass fat content and carcass fat exceeding the limit will lower feed conversion efficiency, making the production uneconomical (Santra and Karim, 2009). It also alters fat composition and reduces lamb flavour intensity (Duckett and Kuber, 2001), changes the colour (Alcalde and Negueruela, 2001; Priolo et al., 2002) and has higher levels of ω‐6 fatty acids as compared to higher levels of ω‐3 fatty acids in forage‐fed lambs. Rapid fermentation of concentrate in the rumen also increases the incidence of bloat, acidosis, laminitis, liver abscesses and feed intake problems related to digestive upsets (Haddad and Nasr, 2007), whereas the complete feed stabilizes rumen fermentation, minimizes fermentation losses and ensures better ammonia utilization (Prasad et al., 2001). Level of roughage and concentrate in the complete feed is apparently of major importance for maintaining the desirable volatile fatty acid (VFA) patterns in the rumen for the efficient utilization of dietary nutrients. Increase in efficiency of microbial N synthesis (EMNS) was observed as the proportion of the concentrate increased from 40 to 70% (Nagireddy et al., 2012), and Tripathi et al. (2007) reported 70:30 (concentrate/roughage) ratio as most appropriate for higher gain in lambs. This experiment is an attempt to manoeuvre the body condition and modify the carcass traits and yield of cull animals before slaughter through nutritional intervention involving a balance between rumen degradable and non‐degradable nutrients.