Abstract #341

Section: Small Ruminant
Session: Small Ruminant
Format: Oral
Day/Time: Tuesday 10:00 AM–10:15 AM
Location: 318
# 341
Net protein and energy requirements for growth according to the degree of maturity of Saanen goats.
I. A. M. A. Teixeira*1, A. P. Souza1, N. R. St-Pierre2, M. H. M. R. Fernandes1, A. K. Almeida1, J. A. C. Vargas1, K. T. Resende1, 1Universidade Estadual Paulista (Unesp), Jaboticabal, Sao Paulo, Brazil, 2Ohio State University, Columbus, OH.

We conducted a meta-analysis to develop equations for predicting net protein (NPG) and energy (NEG) requirements for growth of different sexes in dairy goats using the degree of maturity as predictor. A data set from 7 comparative slaughter studies including 238 individual records of Saanen goats (i.e., fed ad libitum and slaughtered at different BW) was used. We performed the study in 2 steps: first, using the traditional approach (i.e., allometric equations to determine protein or energy contents in the empty body weight (EBW) as dependent variables, and EBW as the allometric predictor, where the net requirements were estimated as the first partial derivative); second, we evaluated the relationship between protein or energy content of the EBW gain (g or kcal/kg EBW gain) and degree of maturity (calculated as a ratio between EBW and mature EBW of Saanen goats, considering mature EBW of 42.6, 34.9, and 26.0 kg for intact male, castrated male, and female, respectively). Parameter estimates were obtained using the MIXED procedure of SAS. 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). Using the allometric equations, sex affected the NPG (P = 0.08) and the NEG (P < 0.01), where the NPG for males were greater than for females, and the NEG of castrated males were greater than intact males, and lower than females. On the other hand, considering the degree of maturity, sex no longer affected the NPG (P = 0.26) and NEG (P > 0.05). The NPG general model was: Protein (g/kg EBW gain) = 176 (±12.8) + 3.25 (±19.0) × (EBW/mature EBW) (s2s 156.2; s2e 2,237), with an overall NPG of 176 (±12.8) g/kg EBW gain irrespective of degree of maturity. The NEG general model was: Energy (kcal/kg EBW gain) = 1,265 (±234) + 2,312 (±316) × (EBW/mature EBW) (s2s = 110,722; s2e = 459,166). The NEG (mean ± SD) increased from 1,726 ± 188 to 3,575 ± 197 kcal/kg EBW gain as degree of maturity ranged from 0.2 to 1.0. Including the degree of maturity as predictor of NPG and NEG canceled out the differences across sexes in Saanen goats.

Key Words: mature weight, nutritional requirements, sex