A drop in milk production is a dairy cow’s first response to water restriction, and, because of this, it is vital to compensate water losses through water intake to retain optimal homoeostasis.
Anne Boudin, of the French national institute of agricultural research, explains losses of water are vital for many bodily functions, including evaporation for thermoregulation, excretion for digestion and milk secretion for reproduction.
Ms Boudin says studies which restrict a cow’s access to water by up to 50 per cent of requirements, have found milk dropped on the first day of the restriction, and this decrease was also correlated with a drop in the animal’s feed intake.
After seven days on the trial, analysis of the results showed milk production had decreased by between 1 and 2.5kg/day.
She explains further studies, where cows were granted access to water once or twice per day compared with ad-lib access, found water intake decreased by an average of 13.5 per cent, resulting in a decrease in milk production of 2.6 per cent.
This may not seem like much, but further analysis of the study shows milk production was influenced more by water restriction combined with hot weather and, in these conditions, milk dropped by an average of 15.6 per cent.
Evaporation increases with increased ambient temperature as this is a way to decrease body temperature. This is called latent heat loss. Drinking water intake is highly correlated to the amount of water evaporated.
In hot weather a lack of adequate drinking water is very detrimental to milk production, as it impairs latent heat loss through evaporation and also impairs the cow’s ability to adapt to the heat.
“Farmers must ensure that water is not the limiting factor in milk production,” says Ms Boudin.
Drinking water intake in dairy cattle is dependent on, but not exclusive to, parameters, such as the animal’s diet, physiological stage and production levels.
A dairy cow’s drinking water intake is the total water intake minus water ingested with feed.
Dry matter intake (DMI) is a strong determinant of drinking water intake, as the dry matter of the diet increases, DMI decreases, however drinking water intake increases.
Despite this, due to the lower levels of water in the diet and increased intake of drinking water, overall the total water intake stays relatively consistent.
Managing the correct water access for cows
IN order to provide cows with as close to ad libitum water supply as possible they require:
■ A water flow of at least 10 litres/minute/cow
■ The flow to allow 10 per cent of the herd to be able to drink at any one time
■ At least 4.5cm of water trough per cow
■ Access to drinking water at a minimum of two separate sites for each group of cows