Índices fecais para estimativa de consumo e digestibilidade em bovinos e ovinos consumindo azevém anual

Abstract

The objective was to evaluate the use of mixed models for intake and digestibility markers in cattle and sheep, based on crude fecal protein as a marker. Five experimental periods were conducted with cattle in metabolism cages, fed with fresh Italian ryegrass (Lolium multiflorum Lam) forage, to evaluate the organic matter digestibility (OMD), organic matter intake (OMI), crude protein intake (CPI), total faecal output and faecal CP content. The treatments were constituted in different levels of supply (1.5, 2.25 kg of dry matter / 100 kg of live weight and ad libitum) with two repetitions in each period. Also, a sheep database (107 data) of tests in metabolism cages was used, consuming annual ryegrass, in supply levels and phenological stages. Models that describe the relationship between fecal CP, OMD, OMI and CPI were developed, divided by species and then together, and adjusted in the regression models, hyperbolic for OMD, and linear for OMI and CPI. The estimated data were compared with observed data, considering the species effect and evaluated by the parallelism test at the level of 5% probability and the variability assessed by the relative predictive error (RPE). In the mixed models for OMD, OMI and CPI, there were coefficients of determination of 0.72, 0.74 and 0.69 and relative error of prediction of 6.4%, 14.5% and 15.2% respectively, and there was no significant effect of species. The individual models, in the cross validation, presented parameters that indicated the viability of the application of the models with mixed data of cattle and sheep.