Curvas de desidratação e valor nutricional de fenos de Urochloa spp.

Abstract

Haymaking constitutes a technical strategy to support forage and feeding planning for livestock during off-season periods, as well as in feedlot and semifeedlot systems. Currently, the market offers new forage hybrids that promise superior agronomic characteristics, higher nutritional value, and resistance to pests, in addition to easier dehydration, which is the key factor for successful haymaking. In this context, the use of mathematical modeling can be a strategic tool to assist in the haymaking process, as it allows the estimation of the dehydration rate of this material. The objective of this study was to evaluate the accuracy of nonlinear models in predicting the dehydration rate of Urochloa spp. cultivars, as well as to investigate the effects of cultivars and post-cut grinding on the nutritional value and potential quality of these forages for haymaking. Conducted in Dourados-MS, the experiment used a completely randomized design in a 2 × 4 factorial scheme, testing two processing methods (ground forage - GF and non-ground forage - NGF) and four cultivars (Ruziziensis, Convert 330 Sabiá, BRS RB331 Ipyporã, and BARG156 780J) through dehydration curves and bromatological analyses over 80 hours after forage cutting. The Gompertz, Logistic, Newton, Page, Modified Page, Bicompartimental Logistic, Thompson, Henderson and Pabis, Two-term Exponential, Two-term, and Midilli et al. models were used to estimate the dehydration rate of the hays. The Modified Page, Newton, and Henderson and Pabis models were excluded for not meeting the assumptions of residual normality and biological interpretation. The Gompertz (R² = 0.88 and AIC = 3419.40), Logistic (R² = 0.87 and AIC = 3441.78), and Bicompartimental Logistic (R² = 0.86 and AIC = 3469.81) models showed the best performance, presenting statistical and biological adequacy to model the dehydration process, evaluating the overall dehydration rate and, in the bicompartimental model, the rate in the fast and slow drying phases. Ground forage (GF) increased the dehydration rate in the fast phase (k₁ = 0.271 g/h) compared to non-ground forage (NGF = 0.135 g/h). However, GF delayed the onset of water loss, taking 89 minutes to begin dehydration, compared to only 42 minutes for NGF. Nutritionally, the Sabiá cultivar showed the highest cumulative loss of crude protein (CP), with an average of 4.49 g of CP lost per hour, significantly higher than the others, while Ipyporã showed greater stability. The bicompartimental logistic model proved suitable for estimating the dehydration rate of Urochloa spp. hays, allowing characterization of drying dynamics among different cultivars. In nutritional terms, the Sabiá and 780J cultivars stood out as the most recommended for haymaking, although all evaluated cultivars produced hays of satisfactory quality, with crude protein (CP) and neutral detergent fiber (NDF) contents compatible with desirable nutritional standards. Post-cut grinding altered the drying kinetics and contributed to preserving nutritional integrity, reducing losses of carbohydrates and proteins.