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The effect of experimental metabolic stresses on ovulation and progesterone levels in cows

VINKLER A, DVORAK R, KUDLAC E
Veterinarni Medicina 41, 1996, 65-69

The effect of a long run subclinic metabolic stress of acidotic and alkalotic nature was examined with respect to the course of cloprostenol induced estrus, ovulation and progesterone levels in blood and milk. The stress of acidotic nature was induced by widening the ratio of digestible crude protein to total dietary energy to the value 1 : 8.1 in 11 cows, while the alkalotic stress was due to narrowing the nutrient ratio to 1 : 2.81 in eight cows. Control group with the nutrient ratio 1 : 4.5-5 comprised 11 cows. The stress of acidotic nature was accompanied by ovulation disorders in 4 out of 11 cows (36.4%), in the group with the stress of alkalotic type it was in 2 out of 8 animals (25%). No ovulation disorders were observed in control group. Within 7 days after estrus, the average progesterone levels were 1.26 +/- 0.84 ng/ml in the blood of cows with stress of acidotic type, 3.48 +/- 2.99 in cows with stress of alkalotic type and 3.12 +/- 1.98 ng/ml in control cows. The differences between acidotic stress and control were statistically significant (P < 0.05). During the whole pregnancy (18 to 276 days), average progesterone levels were lowest in the group subjected to stress of acidotic nature. They ranged from 1.9 to 3.8 ng/ml with the average value 2.65 +/- 1.40 ng/ml. In the group with stress of alkalotic type they ranged from 2.55 to 5.43 ng/ml with the average value 3.67 +/- 2.29 ng/ml. In the control group, they ranged from 4.00 to 8.68 ng/ml with the average value 5.62 +/- 2.24 ng/ml. Variations in cortisol concentrations indicated a certain stressing effect of feed rations on the internal environment of dairy cow organisms and activation of compensatory mechanisms


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