Yield, milk quality and physiological variables of dairy cows in rainy and dry seasons

The objective of this study was to analyse the effect of the dry and rainy seasons on the production, milk quality (lactose, fat, protein, total solids, TBC and SCC) and physiological (rectal and surface temperature and respiratory and heart rate) of crossbred cows (holstein/ zebu) in lactation, under rotational grazing regime in cultivated pasture, using 10 crossbred cows (holstein / zebu) in lactation, average live weight of 500 ± 30 kg, and in the rainy season they were between the fourth and fifth months of lactation and in the dry period were between the seventh and eighth months of lactation with an average initial production of 18 ± 4kg of milk / cow / day, maintaining batch homogeneity in both seasons. The animals were kept in a semi-intensive rearing system, using rotational grazing on pasture of Brachiaria decumbens, in an area of 3 hectares, where there was a conglomerate of trees that provided 5m² / animal with natural shade, to shelter the animals in the warm shorelines The seasons and times of the day significantly influenced (P < 0.05) the ambient temperature, relative air humidity and the black globe temperature index and humidity. The respiratory rate and surface temperature were higher (P < 0.05) in the dry season and the values for rectal temperature and respiratory rate were similar (P > 0.05) in the seasons. Milk production and protein showed a significant difference (P < 0.05) depending on the seasons. With the aid of physiological variables (rectal and surface temperature and heart and respiratory rate), even so, cows decreased their production and increased the concentration of protein in milk.