Sex effects on net protein and energy requirements for growth of Saanen goats.
Requirements for growth in the different sexes remain poorly quantified in goats. The objective of this study was to develop equations for estimating net protein (NPG) and net energy (NEG) for growth in Saanen goats of different sexes from 5 to 45 kg of body weight (BW). A data set from 7 comparative slaughter studies (238 individual records) of Saanen goats was used. Allometric equations were developed to determine body protein and energy contents in the empty BW (EBW) as dependent variables and EBW as the allometric predictor. Parameter estimates were obtained using a linearized (log-transformation) expression of the allometric equations using the MIXED procedure in SAS software (SAS Institute Inc., Cary, NC). The model included the random effect of the study and the fixed effects of sex (intact male, castrated male, and female; n = 94, 73, and 71, respectively), EBW, and their interactions. Net requirements for growth were estimated as the first partial derivative of the allometric equations with respect to EBW. Additionally, net requirements for growth were evaluated based on the degree of maturity. Monte Carlo techniques were used to estimate the uncertainty of the calculated net requirement values. Sex affected allometric relationships for protein and energy in Saanen goats. The allometric equation for protein content in the EBW of intact and castrated males was log10protein (g) = 2.221 (±0.0224) + 1.015 (±0.0165) × log10EBW (kg). For females, the relationship was log10protein (g) = 2.277 (±0.0288) + 0.958 (±0.0218) × log10EBW (kg). Therefore, NPGfor males was greater than for females. The allometric equation for the energy content in the EBW of intact males was log10energy (kcal) = 2.988 (±0.0323) + 1.240 (±0.0238) × log10EBW (kg); of castrated males, log10energy (kcal) = 2.873 (±0.0377) + 1.359 (±0.0283) × log10EBW (kg); and of females, log10energy (kcal) = 2.820 (±0.0377) + 1.442 (±0.0281) × log10EBW (kg). The NEGof castrated males was greater than that of intact males and lower than that of females. Using degree of maturity for estimating NPGand NEG, we could remove the differences between sexes. These results indicate that NPGand NEGdiffer among sexes in growing Saanen goats, and this difference should be accounted for by feeding systems. Including the degree of maturity as predictor cancels out those differences across sexes in protein and energy requirements.
Department of Animal Sciences, Universidade Estadual Paulista, Jaboticabal, SP 14884-900, Brazil.
A P
AP
Souza
Department of Animal Sciences, The Ohio State University, Columbus 43201.
N R
NR
St-Pierre
Department of Animal Sciences, Universidade Estadual Paulista, Jaboticabal, SP 14884-900, Brazil.
M H R M
MHRM
Fernandes
Department of Animal Sciences, Universidade Estadual Paulista, Jaboticabal, SP 14884-900, Brazil.
A K
AK
Almeida
Department of Animal Sciences, Universidade Estadual Paulista, Jaboticabal, SP 14884-900, Brazil.
J A C
JAC
Vargas
Department of Animal Sciences, Universidade Estadual Paulista, Jaboticabal, SP 14884-900, Brazil.
K T
KT
Resende
Department of Animal Sciences, Universidade Estadual Paulista, Jaboticabal, SP 14884-900, Brazil. Electronic address: izabelle@fcav.unesp.br.
I A M A
IAMA
Teixeira
D000821:Animal Feed; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake / Q000502:physiology*; D005260:Female; D006041:Goats / Q000254:growth & development*; D008297:Male; D009010:Monte Carlo Method; D009751:Nutritional Requirements; D009919:Orchiectomy / Q000662:veterinary; D012737:Sex Factors
D004044:Dietary Proteins
allometry; comparative slaughter; degree of maturity; mature weight; nutrient requirement