Influência da ingestão de água por vacas leiteiras durante a ordenha em diferentes estágios de lactação

Abstract

This study aimed to evaluate the water consumption during milking on blood gas analysis and metabolic parameters of dairy cows at different stages of lactation. 40 third lactation animals were kept in semi-intensive system and randomly assigned to the treatments, remaining 10 animals in each. The experimental factors were represented by the days in milk (DIM) with animals between 60-120 (DIM 60-120) or above 150 (DIM > 150), and providing water during milking (WDM). The groups remained as: CA: DIM 60-120 without WDM; CB: DIM > 150 without WDM; TA: DIM 60-120 with WDM; TB: DIM > 150 with WDM. The water was supplied during the two daily milkings through mobile drinkers positioned in front of the cows of the TA and TB groups, and empty water drinkers for cows CA and CB, recording the consumption (yes or no). Milk and blood samples were collected on days 0, 7, 14, 21 and 28 to determine the levels of fat, protein, lactose, total solids and urea in milk and biochemical and blood gas analysis. The oxygen partial pressure (pCO2) differed between CA and TA treatments throughout the experimental period. The physiological pCO2 values for cattle ranged 35 to 44 mmHg, observing that samples TB were slightly below physiological parameters. The tCO2 values were within the physiological patterns. No changes were observed in the variables related to the electrolyte balance of the blood. The results of BE, pO2 and Be, SO2, Na, K did not differ between treatments. Urea levels did not differ between CA and TA, but differed between CB and TB. The qualitative milk parameters were not affected by treatments. Supplementation of water for milking did not affect the electrolyte balance in dairy cows in different stages of lactation. The reduction of pCO2 seen in the TA group was not enough to alter blood electrolyte balance.