A study of reproductive failure in dairy cattle

Soedjiharti Tjondronegoro

The overall objectives of this project were: (1) to study the epidemiology of reproductive failure in a number of dairy herds operating under commercial conditions, (2) to investigate whether the reproductive performance of dairy cows was affected by factors such as herd size, lactation number (age), season, month of calving or herd management and (3) to investigate a means of inducing synchronized oestrus and advancing the time of insemination in cows not observed to be in oestrus by 49 days postpartum. The reproductive performance of dairy cows in 4 dairy herds in Western Australia and the epidemiology of infertility in these herds was described by measuring the: a. Inter-calving interval b. Interval from calving to first observed oestrus c. Interval from calving to first service d. Number of cows observed in oestrus by 60 days postpartum e. Number of services per conception f. First service conception rates g. Prevalence of reproductive disorders Retrospective analysis of data from each farm based on lactation listing, and monthly and annual dairy herd health reports from 1977 to 1985, revealed that reproductive efficiency and the performance of the dairy herds studied is unsatisfactory when compared with recognized targets of performance for dairy herds in Australia (Blood et al., 1978; Radostits and Blood, 1985). The mean inter-calving interval of the 4 herds was approximately 400 days, which was 35 days above the target of 365 days. The mean interval from calving to first service was prolonged by 15 days above the target of 65 days. The mean conception rates to first 1 service also fell short of the target (40% vs a target of 70%). Failure of cows to exhibit behavioural oestrus (’no visible oestrus’) in the postpartum period, inadequate oestrus detection, inaccurate time of insemination, failure to rebreed cows in the early postpartum period, delayed interval from calving to first service after calving, increased number of services per conception and poor conception rates to first insemination were the major contributing factors in prolonging intervals from calving to conception, hence inter-calving intervals. Poor first service conception rates can be attributed to a number of causes such as insemination at the wrong time during oestrous periods, poor oestrus detection, failure to conceive and early embryonic mortality. The size of the herd, month of calving lactation number or body condition scores at calving did not affect inter-calving intervals. Seasons of the year did not influence the conception rates to first service or the number of cows observed in oestrus by 60 days postpartum. The month of calving and lactation number had a significant effect on the incidence of reproductive disorders. In the second part of this study, behavioural oestrus was synchronized in postpartum dairy cows using two types of intravaginal devices which released progesterone. Groups of lactating dairy cows were treated with intravaginal devices containing either progesterone only or progesterone plus an initial dose of oestradiol benzoate for 9 or 12 days. Milk samples were taken at frequent intervals before and after the removal of the devices to obtain profiles of progesterone. The proportion of cows showing oestrus within 5 days after removal of the devices was greater for groups of cows treated with progesterone plus oestradiol benzoate. Within 5 days after removal of the intravaginal device, the mean milk 5 progesterone level of all cows which did not show oestrus (NVO) was significantly greater than that of cows which showed oestrus. However, about 61 % of NVO cows had a decrease in milk progesterone concentrations after removal of the devices followed by a typical post-ovulatory rise, which indicated that these cows were cyclic, though behavioural oestrus was absent. Poor reproductive performance of the dairy herds in the present study, which reflects a general lack of concern by the farmer of problems that limit their cow’s reproductive performance, causes major economic losses to the dairy farmers by reducing the farm's milk production and decreasing the number of calves born per year. The procedures adopted in the second part of the present study represent a programme which can be applied to enhance control over reproduction in the dairy herd so that the efficiency of reproduction and production in dairy herds can be improved.

A study of reproductive failure in dairy cattle

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