A nutrition mathematical model to account for dietary supply and requirements of energy and other nutrients for domesticated small ruminants: The development and evaluation of the Small Ruminant Nutrition System

A mechanistic model that predicts nutrient requirements and biological values of feeds for sheep (Cornell Net Carbohydrate and Protein System; CNCPS-S) was expanded to include goats and the name was changed to the Small Ruminant Nutrition System (SRNS). The SRNS uses animal and environmental factors to predict metabolisable energy (ME) and protein, and Ca and P requirements. Requirements for goats in the SRNS are predicted based on the equations developed for CNCPS-S, modified to account for specific requirements of goats, including maintenance, lactation, and pregnancy requirements, and body reserves. Feed biological values are predicted based on carbohydrate and protein fractions and their ruminal fermentation rates, forage, concentrate and liquid passage rates, and microbial growth. For sheep, the SRNS accurately predicted gains and losses of shrunk body weight (SBW) of adult sheep (n = 15; mean bias (MB) = 5.8 g/d and root mean square error of prediction (RMSPE) = 30 g/d; and r(2) = 0.73) when diets were not deficient in ruminal nitrogen. Several evaluations indicated the SRNS had MB varying from 2.4 to 18 g/d, RMSPE varying from 21.4 to 41 g/d, and r(2) varying from 0.70 to 0.84 when predicting average daily gain (ADG) of growing lambs. For goats, the evaluation for lactating does indicated that predictions of ME intake (n = 21; MB = 0.04 Mcal/d; RMSEP = 0.24 Mcal/d; and r(2) = 0.99) and energy balance (n = 21; MB = 0.075 Mcal/d; RMSEP = 0.20 Mcal/d; and r(2) = 0.87) were adequate. Similarly, the SRNS accurately predicted ADG of kids (n = 31; MB = 6.4 g/d; RMSEP = 32.5 g/d; and r(2) = 0.85). In conclusion, the SRNS can accurately predict, ADG of growing lambs, and changes in SBW of mature sheep and ME intake and the energy balance of lactating and non-lactating adult goats and the ADG of kids of dairy, meat, and indigenous breeds. The SRNS model is available at http://nutritionmodels.tamu.edu. Published by Elsevier B.V.