PSX-23 Predicting feedstuff associative effects in goats

Abstract

Abstract The objective was to develop means of predicting effects of supplementation on forage and total ME intake in goats. A database of treatment mean observations from the literature currently has 529 individual animal observations with ad libitum intake from 24 studies. Essential data were supplement and forage OM digestibility without supplementation or sufficient information for estimation, total diet OM digestibility, forage and supplement CP concentration and OM intake, and BW. Intake of ME was assumed 15.104 MJ/kg digested OM. For observations with supplementation, forage ME intake was the difference between total and supplement ME intake. The original database had 134 observations, although 24 were omitted because of questionable values and(or) unlikely estimates. Forage averaged 9.4 MJ/kg DM of ME (SD=1.77, 4.6–12.6), 59.1% OM digestibility without supplementation (SD=8.67, 42.9–77.1; AOMDIGFOR), and 8.1% CP (SD=3.72, 2.1–17.1) (PTCPFOR), and supplement was 12.3 MJ/kg ME (SD=1.38, 7.1–15.1) and 28.4% CP (SD=41.5, 0–288). Forage ME intake (MEIMBWFOR, kJ/kg BW0.75) was regressed against supplement ME intake (MEIMBWSUP, kJ/kg BW0.75), with inclusion of other variables tested. The equation explaining most variation (R2=0.77) was 155.9 ± 135.75 – (0.5403±0.04381 × MEIMBWSUP) – (41.0063±20.71841 × PTCPFOR) + (5.3497±2.31608 × AOMDIGFOR) + (0.74056±0.345002 × PTCPFOR × AOMDIGFOR), with P values of 0.253, < 0.001, 0.050, 0.023, and 0.034, respectively. The mean difference between observed and predicted MEIMBWFOR (379±15.0 and 382±12.8, respectively) was -3±7.4, with minimum and maximum values of -181 and 167, respectively. The equation for the regression of residual MEIMBWFOR (observed – predicted) against predicted values was -10±22.3 + (0.018±0.0553 × predicted MEIMBWFOR), with the intercept and slope not different from 0 (P = 0.670 and 0.739, respectively). Equations describing associative effects can be used to predict the quantity of a particular supplement with a given forage necessary to meet nutrient requirements of goats in specific production settings.