Return to OESTRUS after first insemination in sow herds (incidence, seasonality, and association with reproductivity and some blood parameters)

Summary

As no systematic study has been done to get an accurate estimate of the incidence of return to oestrus after first insemination in sows in the Netherlands, the objectives of this investigation were:

1) to obtain an estimate of the incidence of return to oestrus after insemination at the herd level;

2) to investigate the association between incidence of return to oestrus after first insemination and reproduction characteristics in order to get an impression of the economic importance of reproductive failure.

These objectives were investigated by using the reproduction results of 240 swine breeding herds in the Southern Netherlands in 1987. This information was obtained from CBK plus computerized herd management records. The average incidence rate of return to oestrus after first insemination at a herd level was 16.9 per 100 first inseminations. The occurrence of return to oestrus after first insemination was distinctly higher in the insemination months July and August compared to the rest of the year. An increased incidence, with 10 returns per 100 first inseminations corrected for confounders in a multiple linear regression model, was associated with a decrease of approximately 0.3 live born piglets/sow/year. A prospective longitudinal study was started in 1988 and 1989 in 37 sow herds. Individual sows were monitored from weaning to first insemination, to the occurrence of return to oestrus, or not, after first insemination, and to farrowing. The investigation focused in particular on the relationship between return to oestrus after first insemination and seroconversion against porcine parvovirus (PPV) and Leptospira interrogans serovar bratislava (L. bratislava). During a number of consecutive farm visits, blood samples were taken from sows at weaning and again 6 weeks later. The final data set analysed consisted of 161 animals that did not return to oestrus and 158 animals that did return to oestrus after first insemination. Seroconversion was defined as a 4‐fold increase in titre between the two successive blood samplings: sera were investigated at dilutions of 1:100 to 1:3200 (L. bratislava) and 1:4 to 1:16384 (PPV).

There was no indication of an association between the occurrence of return to oestrus after first insemination and seroconversion against PPV or L. bratislava with the serodiagnostics used in this study. However, it should be noted that L. bratislava infected sows can have a titre below the widely accepted minimum titre of 1:100 used in laboratories, and recently from sows without a titre L. bratislava was isolated. It is suggested that the most appropriate way to assess the influence of infection with L. bratislava on reproductive failure in swine at this moment is to use culture or other methods (e.g. PCR). Litter size and between‐farrowing time of the last farrowing before the study period was not associated with the occurrence of return to oestrus after first insemination in the study period. However, an increased weaning‐to‐first‐in‐semination interval, a high progesterone level at weaning, a low albumin concentration at weaning, and a decrease in albumin concentration between the consecutive samplings and an increase in gamma globulin concentration between the two blood samplings increased the risk of occurrence of a regular return to oestrus after first insemination.

An increased weaning‐to‐first insemination interval, an increase in leucocyte and gamma globulin concentrations and a reduction in alpha_1,2 globulin concentration between the consecutive samplings increased the risk of occurrence of an irregular return to oestrus after first insemination.

Notes

Animal Health Service in the Southern Netherlands, P.O. Box 4. 52X0 AA Boxtel.

Dept. of Population Medicine, Ontario Veterinary College, University of Guelph, Ontario, NIG 2W1 Canada.

Dept. of Herd Health and Reproduction, Faculty of Veterinan Medicine, P.O. Box 80151, 3508 TD Utrecht, the Netherlands.

Additional information

Notes on contributors

Armin R.W. Elbers

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Martin J. M. Tielen

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