Effect of high daytime temperatures on the intake and utilisation of water in lactating Friesian cows

Abstract

Four primiparous Friesian cows in mid-lactation and housed in climate chambers were simultaneously exposed to three sequential climate treatments: 1, a three-week period in a thermoneutral environment (ambient temperature Ta 14-21 degrees C and relative humidity r.h. 60-70%); 2, a similar period during which they were exposed to Ta max. 38 degrees C/r.h. max. 80% for up to 7 h and Ta 14-21 degrees C/r.h. 60-70% for 17 h each day; and 3, a three-week period during which they were subjected once more to the thermoneutral conditions described for 1. Water and a complete feed were constantly available. Compared with water intake (drinking water + feed water) under thermoneutral conditions cows exposed to treatment 2 significantly increased their mean intake by 12.2%; in three cows, this involved a phase-shift of greater than 20% in drinking habits from day (hot) to night (cool) time. Water balance trials conducted at the mid-point of each treatment revealed that the mean losses of water via urine, faeces, milk, sweat and saliva as a percentage of water intake changed significantly resulting in a net gain (retention) of body water. An accompanying significant increase in live weight despite a 9.1% decrease in DM intake during treatment 2 confirmed the water retention results. On return to thermoneutral conditions (3), the cows exhibited a marked weight loss and a significant increase in urinary water excretion over treatment 1 and 2 values, signifying that a large proportion of the water retained during 2 was of extracellular origin.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrogen and Oxygen Stable Isotope Fractionation in Body Fluid Compartments of Dairy Cattle According to Season, Farm, Breed, and Reproductive Stage

“…The sampling time was planned to avoid the effect of the different water half-life (from 2.0 d for lactating cows to 7.5 d for non-lactating cows), starting from the beginning of steady climatic conditions between the different reproductive stages already highlighted [ 2 ]. For this reason, the sampling took place at least two weeks after relatively stable THI ( Fig 1 ), in a supposedly steady state of body water turnover and, during heat stress, not in the phase of increasing body water pool to adapt to increased Ta [ 1 , 28 ].…”

Reproductive physiology of the heat-stressed dairy cow: implications for fertility and assisted reproduction

“…Additionally, cooling cows during the summer increased circulating concentrations of progesterone (Wolfenson et al, 1988). Some effects of heat stress on peripheral blood concentrations of hormones could be the result of changes in water balance during heat stress and reduced hematocrit (Richards, 1985;Lamp et al, 2015).…”

Strategies for managing reproduction in the heat-stressed dairy cow

“…The extent to which heat stress affects these other physiological characteristics could lead to variable changes in steroid hormone concentrations in peripheral blood. For example, heat stress can cause either dilution, concentration, or no effect on blood plasma volume (Richards, 1985;McGuire et al, 1989;Johnson et al, 1991;Elvinger et al, 1992), and the nature of effect of heat stress on blood volume will affect steroid hormone concentrations in blood.…”