Quality of drinking water for dairy cows

Abstract

When looking at different welfare assessment protocols for cows, clean drinking water always is ranked higher than water with a form of pollution. However, when looking at available literature, evidence from a welfare based viewpoint for this concept seem to be lacking. Aim of this randomised controlled trial was to determine if dairy cows, when given free choice, prefer tap water from a regularly cleaned container, or prefer water that contains some silage or manure, and thus has a different taste and properties in comparison to the clean tap water. The group consisted of nine heifers in various stages of gestation housed on pasture 24/7. Drinking water preference was measured for 6 days during a 12-hour period after an initial adjustment period of 14 days in which all water options were available, but no measurements were taken. Water options were (A) 90L clean water, (B) 90 L water mixed with 250 grams of corn silage, (C) 90 L water mixed with 1000 grams of corn silage and (D) 90 L water mixed with 500 grams of manure. During the experiment, temperature (°C), relative humidity (%) and sun minutes per day were recorded. Temperature Humidity Index (THI) was calculated. Analysis of data was done via a linear regression model and a Poisson model in R, using RStudio. On average, cows drank 84.6 L from the clean water, 44.4 L from the lightly polluted water (P<0.011), 49.2 L from the heavily polluted water (P<0.051) and 0 L (P<0.00011) from the manure polluted water. Mean drinking session per container per day were 15.5, 11.2 (P<0.052), 13.5 and 03 for container A-D. Liters per drinking session were respectively 5.6, 4.4, 3.8 and 0 L for container A-D. There was no significant effect of weather or THI on drinking water preference. These findings show that current assessment protocols for water quality for (dairy)cows are sufficient as cows do prefer clean tap water over contaminated water.

1 In comparison with water uptake (L) from the clean drinking water 2 In comparison with mean drinking sessions per container per day of the clean water 3 P was not possible to calculate due to all values being 0

Keywords: Dairy cows; drinking water; preference; free choice; water uptake; clean water; polluted water; welfare