EFFECT OF POTASSIUM LEVEL AND SOURCE ON PERFORMANCE OF LACTATING DAIRY COWS DURING SUMMER SEASON

The adverse effect of hot climate on the productivity of dairy cows is being addressed. Evaporative cooling in regions with limited water supply is costly, so incr¬easing dietary K content from different salts sources has been tested as an alternative method for alleviat¬ing heat stress-induced low lactation performance. Forty-eight Holstein-Friesian cows, 118-134 days post partum, were used. The animals were housed in a partly shaded open lot, and were allotted to eight equal groups, matched for calving date, lactation number and daily milk yield. These groups were assigned randomly to one of eight treatment diets, half containing K at the level of 1.25% of dry matter (DM) and the rest containing 1.75% K. The salts used as sources of supplemental K differed within each K level, while dietary electrolyte balance for the treatment groups ranged from +19.4 to 31.0 meq/lOOg DM. The experiment was performed during the hot summer season, with average daily maximum and minimum ambient temperatures of 45.44 and 22.36°C, and average maximum and minimum relative humidity levels of 27.23 and 14.15%, respectively. Rectal temperature was higher in cows fed the higher rather than lower K diets, with no change in their feed intake. Average daily milk yield per cow decreased with increasing dietary K level (P