Meta-analysis of the energy and protein requirements of hair sheep raised in the tropical region of Brazil

Abstract

The objective of this study was to estimate, through mathematical models, energy and protein requirements for maintenance and gain of hair sheep raised in the tropical region of Brazil. To determine the equation parameters, a meta-analysis of seven independent experiments of nutrient requirements was performed, comprising a total of 243 experimental units (animals), which were conducted under tropical conditions, using hair sheep in growing and finishing phases and endowed of the following quantitative data for each animal: body weight (BW), empty body weight (EBW), average daily gain (ADG), empty body gain (EBG), heat production (HP), metabolizable energy intake (MEI), retained energy (RE), metabolizable protein intake (MPI) and body protein content. The regression equations generated were as follows: for Net Energy for maintenance, (NE_m ): LogHP(MJEBW-0.75day-1)=-0.6090(±0.07470)+0.5149(±0.07216)×MEI(MJEBW-0.75day-1); for Net Energy for gain, (NE_g ): LogRE(MJEBW-0.75day-1)=0.03084(±0.05334)+0.8455(±0.04355)×LogEBG(kg/day); for Metabolizable Protein for maintenance,(MP_m ): MPI_(g/day) = 24.8470 (±7.3646) + 560.28 (±99.6582) × EBG_(kg/day) ; for Net Protein for gain, (NP_g ): NPg(kg/day)=0.1941×EBW(kg)-0.1058. The NE_m requirement was 0.246 MJ EBW^-0.75 day^-1 . The metabolizable energy for maintenance requirement was 0.391 MJ EBW^-0.75 day^-1 . Considering an ADG of 100 g, the NE_g requirement ranged from 0.496 to 1.701 MJ/day for animals with BW ranging from 10 to 40 kg respectively. The efficiencies of use of the metabolizable energy for maintenance and gain were 0.63 and 0.36 respectively. The MP_m requirement was 3.097 g EBW^-0.75 day^-1 . Considering an ADG of 100 g, the NP_g requirement ranged from 12.4 to 10.5 g/day for animals with BW ranging from 10 to 40 kg respectively. The total metabolizable energy and protein requirements were lower than those reported by the NRC and AFRC systems. Thus, our results support the hypothesis that nutrient requirements of hair sheep raised in tropical regions differ from wool sheep raised in temperate regions. Therefore, the use of the equations designed in this study is recommended.

Keywords: meat sheep; nutrient requirements; prediction equations.