Effect Of Dietary Potassium Level And Source On Physiological Status of Heat Stressed Lactating Diary Cows

Forty eight healthy lactating Holstein cows, past the peak were used to study the effect of increasing dietary K level and sources on physiological status of heat stressed lactating dairy cow. Animals were housed in an open shaded barn, and were assigned equally and randomly to one of eight dietary treatments containing two levels of potassium (1.25 vs. 1.75) and four different sources. Results showed that levels of K in the diet have no significant effect on any of cellular or non-cellular components of blood, while cholesterol decreased with increasing K level. Plasma content of Na, K, Mg and P were not affected by dietary K level, whereas plasma Ca level increased by increasing dietary K level, (0.35+0.01, 0.38+0.01 for 1.25 and 1.75 K level respectively). Source of K supplementation did not affect the concentration of Na, K and Mg in blood, but Cl and Ca and P levels were affected (p<0.05). Plasma electrolyte balance was higher in cows fed the 1.25% K diets compared to the 1.75% K diets. Level of K in the diet showed no significant effect on the concentration of cortisol, T4 and T4/T3 ratio. Concentration of T3 was reduced (P