Effect of water restriction on feeding and metabolism in dairy cows

Abstract

We investigated how lactating cows are able to cope with a sustained water restriction. In experiment 1, body weight and meal patterns were recorded with ad libitum access to water (baseline) and during 8 days of 25 and 50% restriction of drinking water relative to ad libitum intake. In experiment 2, indirect calorimetry was combined with nitrogen and energy balance and plasma hormone and metabolite measurements to assess the effects of 50% water restriction on digestion and metabolism. In experiment 1, food intake and body weight declined during the first 3 days of water restriction depending on the restriction level and stabilized thereafter at a lower level. The daily food intake reduction with 50% water restriction was entirely due to a reduction of meal size. The size of the first meal on every day was markedly (>50%) reduced with 25 and 50% water restriction. In experiment 2, urea concentrations in milk and blood as well as plasma sodium and hematocrit were increased by 50% water restriction. Energy balance was not affected by 50% water restriction, but nitrogen balance became negative, because, relative to intake, nitrogen excretion via urine and milk was higher. The lower energy intake during 50% water restriction was compensated by a lower milk production, a higher digestibility of organic matter and energy, and, apparently, a more efficient energy use. Through these changes and a preserved water balance, the cows reached a new equilibrium at a lower water turnover level, which enabled them to cope with a sustained drinking water restriction of 50%.

Physiological and behavioral basis for the successful adaptation of goats to severe water restriction under hot environmental conditions

“…The increase in standing activity may reflect a thermoregulatory behavioral response: in the standing position, the goats may direct themselves to position with respect to the sun, so that lower proportion of their body surface will be exposed to direct radiation (Silanikove, 2000a). The reduction in meal size under water restriction explains the reduction in feed intake and is consistent with the results of Burgos et al (2001) in cows. The reduction in meal size may also explain the lower rumination in the water-restricted goats.…”

“…Similar moderate reduction in feed intake in proportion to considerable imposition of water restriction (33% and 67%) was found in breeds of tropical (Abioja et al, 2010) and desert goats (Alamer, 2009). In cows, with 50% drinking water restriction, the reduction in feed intake was 20% lower than that during when water was available ad libitum (Burgos et al, 2001). Thus, although in cows the reduction in feed intake upon water restriction was also lower than the level imposed by feed restriction, the relative reduction in feed intake was greater than that found in goats.…”

Diet effects on urine composition of cattle and N2O emissions

“…Urea is an important osmolite in the renal reabsorption of water. A rise in urea reabsorption to increase renal osmotic pressure and water absorption from the renal filtrate will increase plasma urea levels and may explain the increased plasma urea levels in dehydrated cattle (Steiger Burgos et al, 2001). The effects of increased mineral consumption and water intake on urinary N and urea content will be discussed in a subsequent section.…”

Effects of dehydration on endocrine regulation of the electrolyte and fluid balance and atrial natriuretic peptide-binding sites in perinatally malnourished adult male rats

“…In our study, food intake was not measured but other studies have reported that dehydrated rats ate significantly less food (35,64,65). Reduction of food intake during water deprivation reflects a homeostatic mechanism that minimizes the negative consequences of dehydration (66). Indeed, in dehydrated rats the intake of a conspicuous amount of dry food might further compromise osmolality and body fluid balance (67,68).…”