Productive performance and milk quality in cattle herds of the Amazon Savanna

This study aimed to investigate phenotypic trends and the effects of environmental factors on milk yield and composition in herds located in the Amazon Savanna. Milk recording data and samples collected between 2022 and 2024 were analyzed from three cities in the state of Roraima, Brazil (Boa Vista, Cantá, and Iracema), including cows of different breed compositions, predominantly Gir and Girolando crossbreds. Phenotypic trends were estimated using linear regression, and the effects of location and season (dry and rainy) were evaluated by analysis of variance followed by Tukey’s test at a 5 % significance level. In the experimental herd, average milk yield was 2.66 kg/ cow/day, and mean contents of fat, protein, lactose, mineral salts, and solids-not-fat were 3.79 %, 3.43 %, 4.80 %, 0.81 %, and 9.04 %, respectively. The phenotypic trend indicated a slight reduction in daily milk yield (-0.0021 kg), whereas milk components remained phenotypically stable: fat (-0.0006 %), protein (0.0003 %), lactose (0.0004 %), and mineral salts (0.00006 %). In commercial herds, no significant interaction was observed between location and season. A significant effect of location was detected for all milk components, with Iracema presenting higher mean contents of protein (4.79 %), lactose (5.21 %), mineral salts (0.88 %), and solids-not-fat (9.89 %), whereas Boa Vista showed the highest fat content (3.81 %). The dry season presented higher values for protein (4.05 %), lactose (5.04 %), mineral salts (0.85 %), and solids-not-fat (9.54 %) compared to the rainy season. It is concluded that average milk yield in the experimental herd remains low under tropical conditions of the Amazon Savanna, although relevant phenotypic variability exists, and milk composition is influenced by geographic location and climatic seasonality, with greater concentration of solids during the dry season.

Keywords:
tropical climate; milk components; variability; seasonality.