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Production aspects of hay of tropical pasture of Urochloa brizantha, Megathyrsus maximus and Andropogon gayanus: forage mass yield characteristics, evaluation of losses, dehydration and nutritional value of hays

ABSTRACT Context. Tropical pasture have been little explored for haymaking, due to lack of information regarding loss of nutrients and of forage dehydration. Aims. This study aimed to evaluate the production aspects of tropical pasture hays. Methods. To characterise forage dry mass yield and dehydration rate, we studied the grasses Marandú, Xaraés, Massai, Paredão, Planaltina and Tupã. The water soluble carbohydrates concentration curve, chemical composition and in situ rumen degradability of dry mass, crude protein and neutral detergent fibre were also determined. Key results. The highest forage dry mass yield was observed in 2018, when Planaltina and Paredão performed best (6.28 and 5.26 ± 0.41 t of dry matter ha−1, respectively). There was no genotype × dehydration time interaction (P = 0.81) on water soluble carbohydrates. Exposure to sun resulted in a linear decreasing effect (P < 0.01) on water soluble carbohydrates content, with loss of 5.03 g kg−1 for each hour of exposure to the sun during the haymaking process. There was an interaction effect (P < 0.01) between type of material and genotype on the content of dry matter, mineral matter, crude protein and neutral detergent fibre (P < 0.01). In situ degradability of Massai grass dry mass was higher for the hay (758.0 and 253.8 ± 7.9 g kg−1 for hay and in natura material, respectively). Conclusions and implications. The greater amount of leaves in relation to stem indicates that Massai grass is more efficient in dehydration during the first hours of exposure to the sun, as well as sustaining lower losses.