Abstract :
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 r2 = 0.73) when diets were not deficient in ruminal nitrogen. Several
evaluations indicated the SRNS hadMBvarying from 2.4 to 18 g/d, RMSPE varying from 21.4
to 41 g/d, and r2 varying from 0.70 to 0.84whenpredicting average daily gain (ADG) of growing
lambs. For goats, the evaluation for lactating does indicated that predictions ofMEintake
(n = 21; MB= 0.04 Mcal/d; RMSEP= 0.24 Mcal/d; and r2 = 0.99) and energy balance (n = 21;
MB= 0.075 Mcal/d; RMSEP= 0.20 Mcal/d; and r2 = 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 r2 = 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 theADGof kids of dairy, meat, and indigenous breeds. The SRNS model is available
at http://nutritionmodels.tamu.edu.
