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Abstract The protein requirements of hair sheep are a key factor in increasing profitability and decreasing the environmental impacts of nitrogen excretion. The objective of this study was to evaluate the protein requirements of hair sheep. A database with 382 individual records (269 intact and 113 castrated males) comprising information from 11 studies was used. The studies provided different levels of metabolisable protein intake (MPI) and of N retention, allowing the development of equations to predict the net protein (NP) and the metabolisable protein (MP) requirements. The efficiency of MP use for gain (k pg ) was calculated using the equation of daily protein retained against daily MPI above maintenance. The efficiency of MP use for maintenance (k pm ) was computed as the ratio between the NP for maintenance (NPm) and the MP for maintenance (MPm). The NPm (1.32 g/kg0.75 EBW) did not differ between sex. The k pm was 0.34, and the k pg was 0.25. The MPm estimated was 3.21 g/kg0.75 BW. Sex affects the protein requirements for gain (NPg). The protein requirements of hair sheep differ from those recommended by feeding systems for sheep. The equations provided herein may improve the optimisation of protein nutrition of sheep, thereby minimising the environmental impacts of sheep production.

Inadequate estimates of fiber and dry matter intake of sheep raised in tropical conditions may explain part of the inefficiency of those production systems. Therefore, we aimed to estimate dry matter intake (DMI) and neutral detergent fiber intake (NDFI) of hair sheep raised under tropical conditions. A meta-analysis of 61 independent performance experiments, comprising a total of 413 experimental units (treatment means or animals), was performed. Trials were conducted in tropical conditions, using hair sheep in growing and finishing phases and endowed with the following information: neutral detergent fiber (NDF) in diet, initial and final body weight (BW), average daily gain (ADG), DMI and NDFI of treatment means (51 studies) or individual data (10 studies). Data on organic matter and NDF digestibilities were collected to estimate D-value (Dv) and B-value (Bv) (20 and 33 studies, respectively). The equations obtained were: [Formula: see text] DMI (g/kg BW) as a function of Dv (g/kg DM) revealed a quadratic relationship, whose point of maximum DMI (38.69 g/kg BW) was obtained at 634.1 g/kg DM Dv. On the other hand, DMI decreased linearly as Bv (g/kg DM) increased. In conclusion, equations to predict DMI from BW and ADG as well to predict NDFI from dietary NDF were fitted with great accuracy and are recommended for hair sheep raised in tropical regions. DMI values were, in general, greater than those reported by the NRC, AFRC and INRA systems, which may be a reflection of the sheep breeds used in this study. Using Dv and Bv concepts was satisfactory to describe an integrated mechanism between metabolic and bulking regulation of DMI in sheep.

The objective was to determine the efficiency of utilization of metabolizable energy for maintenance (km) and weight gain (kf), the dietary requirements of total digestible nutrients (TDN) and metabolizable protein (MP), as well as, evaluate the Small Ruminant Nutrition System (SRNS) model to predict the dry matter intake (DMI) and the average daily gain (ADG) of Santa Ines lambs, fed diets containing different levels of metabolizable energy (ME). Thirty five lambs, non-castrated, with initial body weight (BW) of 14.77 ± 1.26 kg at approximate two months old, were used. At the beginning of the experiment, five animals were slaughtered to serve as reference for the estimative of empty body weight (EBW) and initial body composition of the 30 remaining animals, which were distributed in randomized block design with five treatments (1.13; 1.40; 1.73; 2.22 and 2.60 Mcal/kg DM), and six repetitions. The requirement of metabolizable energy for maintenance was 78.53 kcal/kg EBW0,75/day, with a utilization efficiency of 66%. The average value of efficiency of metabolizable energy utilization for weight gain was 48%. The dietary requirements of TDN and MP increased with the increase in BW and ADG of the animals. The SRNS model underestimated the DMI and ADG of the animals in 6.2% and 24.6%, respectively. Concludes that the values of km and kf are consistent with those observed in several studies with lambs created in the tropics. The dietary requirements of TDN and MP of Santa Ines lambs for different BW and ADG are, approximately, 42% and 24%, respectively, lower than those suggested by the american system of evaluation of food and nutrient requirements of small ruminants. The SRNS model was sensitive to predict the DMI in Santa Ines lambs, however, for variable ADG, more studies are needed, since the model underestimated the response of the animals of this study.