MILK PROGESTERONE LEVELS AND REPRODUCTION RESULTS ON 2 DIFFERENT DAIRY FARMS

The reliability of progesterone tests (PT) is affected by a wide range of factors, including a complex of conditions for the farm or localit y. The aim of this report was the comparison of PT results in two bree dings of cows conducted over two years. One study was carried out on a farm in a potato-growing region (farm A) and another in a sugar-beet growing region (farm B). Milk samples for PT were taken twice a week w ithin two hours following the morning milking. Four samples were colle cted from each cow: sample I - on the day of insemination or 1 to 2 da ys after insemination, sample II - on the 8th to the 12th day after in semination, sample III - on the 18th to the 22nd day after inseminatio n and sample IV - on the 22nd to the 25th day after insemination. The direct radioimmunoassay (RIA), not requiring previous extraction, was used to quantify progesterone (P4) in whole milk. Conception was found by rectal palpation between the 60 th and the 90th day after insemina tion. In the evaluation, pregnant (nonpregnant) cows were divided into groups according to the below mentioned ranges of P4 levels in milk: for sampling I (ng/ml): 0 - 1.1, 1.2 - 2.0, 2.1 - 4.0, > 6.0, and for samplings II, III, IV (ng/ml): 0 - 2.0, 2.1 - 4.0, 4.1 - 6.0, > 6.0. I n total, 11,400 milk samples were processed during two years (farm A - 4,656, farm B - 6,744). Mean values of relative frequency for the ind ividual years under study on farms A and B in pregnant and nonpregnant cows are presented in Figs. 1 to 4. In sampling during insemination t he best conception was recorded in cows with P4 concentration up to 1. 0 ng/ml. The proportion of these dairy cows was 78.1 % in the first ye ar and 85.4 % in the second year on farm A and 87.8 % or 94.8 % on far m B, in the 1st or 2nd year respectively. Only 0 to 1.5 % of cows on f arm A and 0.4 to 0.8 % of cows on farm B with the P4 concentration ove r 4 ng/ml conceived. In the group of nonpregnant cows, the proportion of cows with the level of P4 up to 1.0 ng/ml was 61.8 % or 75.0 % on f arm A, and 74.6 % or 87.1 % on farm B. A high proportion of pregnant c ows on both farms in the years under study was recorded in sampling II with P4 concentration over 6 ng/ml (farm A - 81.1 % or 76.7 %, farm B - 69.6 % or 77.8 %). Cows with the level of P4 up to 2 ng/ml became p regnant only exceptionally (0.3 to 2.3 %). In nonpregnant cows, despit e the fact that the highest proportion of cows was observed with the P 4 concentration over 6 ng/ml, their relative numbers increased in grou ps with lower P4 levels, in particular with the concentration up to 2. 0 ng/ml (P < 0.01). In sampling III and IV the P4 concentration over 6 ng/ml indicated pregnancy (87.7 to 95.5 %). On the other hand, P4 lev els up to 2 ng/ml resulted in nonpregnancy (55.3 to 76.2 %). There was a relatively high proportion of cows (11,3 to 36.5 %) with the P4 con centration over 6 ng/ml in nonpregnant cows. Contrary to the conclusio ns of Heap et al. (I 976) and Noiser et al. (1992), no statistically s ignificant differences (P < 0.01) were found between farms A and B, if their mutual comparison was conducted according to the ranges of P4 l evels in whole milk selected by us. Our results indicate that in proge sterone tests, if we keep to the condition of the given operational me thods, a similar distribution of dairy cows be expected according to P 4 levels, independent on the character of farm, efficiency, production s region and breed of cows.