Nowadays the reproduction of cattle is getting more and more topical. The question of optimal age for the first insemination and first calving, the duration of service- and inter-calving periods, which provide high level of cows productivity, should be considered in specific conditions of use. According to that the aim of research was to study the dependence of cows milk production on Ayrshire cattle reproductive ability indicators.

The research was conducted at the LLC "Agricultural firm "Uhryniv" in Sokal district of Lviv region on the Ayrshire cattle. The assessment of cows productivity and reproductive ability was performed according to the zootechnical registry data (for the last 20 years) for the I, II, III and the best lactations.

The milk yield of the 1-st lactation cows was 4034,3 kg, during the II – 4280,1 kg, during the ІІІ – 4337,0 kg, during the best – 4588,2 kg, the milk fat quantity was – 165.4; 180,6; 181,7 and 191,3 kg respectively, duration of service period – 89,8; 92,1; 82,9 and 90,1, inter-calving – 369,2; 372,2; 362,4 and 369,9 days. The age of the first insemination and the first calving was 17,4 and 26,6 months respectively. Indicators of reproductive ability had some impact on the formation of milk production of Ayrshire cattle. Thus, the highest yield andamount of milk fat were observed in animals with age of first insemination up to 16 months. However, these indicators set their probableadvantage (P <0,05–P <0.001) only in cows with age of first insemination 20,1-22,0 months for the first and second lactation animals over the age of first insemination 22,1 a month or more – for the first, second and third lactation. Significant differences for milk yield and the number of milk fat was found between animals with age of first insemination: 16,1-18,0 and 22,1 months or more; 18,1-20,0 and 22,1 months and more - for the first, second and third lactation; 18,1-20,0 and 20,1-22,0 months - for the first and second lactation. As for the age of first calving, the better milk production was observed by cows, which did not exceed 25 months. However, their likely advantage (P<0,05-
P <0,001) was observed only on animals of the first calving age - 31,1 months and more with milk yield and the number of milk fat during the first, second and third lactations. The last ones had worse indicators of lactation periods even than the cows with the age of the first calving of 25,1-27,0 and 27,1-29,0 months. The difference among other groups of animals by the indicators of milk production was negligible. The animals whose service period duration was within 81-100 days had top milk yield and milk fat. According to the mentioned indicators they likely dominated (P<0,05-P<0,001) during the first, second and the best individuals with lactation with service period duration up to 40 days, 41-60, 121-140 and 141 days or more, cows with the service period duration of 61-80 days for the first and second lactation and the cows with the service period duration of 101-120 days during the second and the best lactations. The difference was found between the indicators of other animals but it was unreliable in most cases.

The difference among other groups of animals wasn't significant. There is need to be said that the milk yield of cows with age of the first insemination - 20 months was allmost the same, but starting from the 20,1 month it got much more reduced. Animals which had their inter-calving period of 361-380 days had the highest yield and quantity of milk fat. These animals were dominative by above named inicators during the І, ІІ and the best lactations (P<0,05-P<0,001) comparing to the cows of other groups: with the inter-calving period of 320; 321-340; 341-360; 381-400; 401-420 and 421 days and more. The difference was found  between the indicators of other animals but it was unreliable in most cases. Thus, the Ayrshire cattle had the highest milk production with age of the first insemination - 16, age of the first calving – up to 25 months, the duration of service period – 81-100 days , and inter-calving period – 361-380 days.

Key words: breed, milk yield, milk fat, first insemination age, first calving date, service period, intercalving period.