Energy and protein requirements of weaned male and female Saanen goats

Abstract

The objective of this research was to estimate the energy and protein requirements for maintenance and growth in male (castrated and intact) and female Saanen goat kids between 15 and 30 kg BW. To determine the net energy requirements for maintenance (NE_m) and the net protein requirements for maintenance (NP_m), 75 goats (25 castrated and 26 intact males and 24 females) were used. Twenty‐one goats (seven castrated and eight intact males and six females) were randomly assigned for slaughter to estimate the initial empty body composition. The 54 remaining animals (18 castrated and 18 intact males and 18 females) were randomly assigned in a split‐plot design using a 3 × 3 factorial arrangement with three sexes and three levels of intake (<i>ad libitum</i> and restricted feed to 75% or 50% of the <i>ad libitum</i> intake). Within each sex, six blocks (three goats per block) were formed and one goat was randomly assigned to each level of intake. The 75% and the 50% of <i>ad libitum</i> rationing were determined daily, based on the DMI of the animal fed <i>ad libitum</i> on the previous day. All animals within block were slaughtered when the animal fed <i>ad libitum</i> reached 30 kg BW. The net energy requirements for gain (NE_g) and the net protein requirements for gain (NP_g) were obtained using 58 animals (20 castrated and 20 intact males and 18 females). The animals were fed <i>ad libitum</i> and slaughtered at targeted BW (15, 23 or 30 kg). Sex did not affect NE_g and NP_m (277.8 kJ/kg^0.75 BW day and 2.98 g CP/kg0.75 BW day respectively), as well as NP_g (180.9 ± 6.48 g/kg EBW gain) in Saanen goat kids. However, castrated males and females had similar NE_g (varied from 12.6 ± 0.424 to 17.9 ± 1.38 MJ/kg EBW gain), greater than intact males (varied from 9.74 ± 0.420 to 10.7 ± 0.984 MJ/kg EBW gain), as the BW increased from 15 to 30 kg.