2006 Gambade Ipvs

Abstract No: P.34-18

IMPACT OF INJECTING A SYNTHETIC ANALOGUE OF PROSTAGLANDIN AT WEANING ON THE WEANING-TO-OESTRUS INTERVAL AND THE FERTILITY OF SOWS

P Gambade1, V Auvigne2, E Sallé3 1

Sanders Bretagne, PONTIVY, France 2 Ekipaj, ST GREGOIRE, France 3 Ceva santé Animale, LIBOURNE, France

Introduction The administration of prostaglandins in sows at weaning may help to obtain a better synchronisation of oestrus and/or to resolve problems of silent oestrus. Two action mechanisms are assumed: (a) an intrafollicular stimulation by PGF2α of enzymes such as collagenase and elastase, leading to a follicular rupture (1), and (b) lysis of the luteal bodies present at weaning. Materials and Methods The study was carried out in a breeding farm (590 sows, 14.4 total born piglets, 11.1 weaned in 2003). Farrowing was induced with a synthetic prostaglandin. Dinoprost (Enzaprost®, CEVA) was injected IM 24 to 48 hours after farrowing. Piglets were weaned at 27 days. The farmer’s objective was to inseminate a maximum number of sows between day 4 and day 6 post-weaning (PW). From the day of weaning to day 3 PW, the sows were stimulated by the brief visit of a boar. From day 3 PW, oestrus was determined by leading the sow past a boar and testing for immobility (standing heat). Semen was collected at the farm. Two to three inseminations were carried out in each sow: the first 24h after the first signs of oestrus, the second 24h later and a third depending on the duration of oestrus. Pregnancy diagnosis was carried out using ultrasonography on days 21 and 28 after the first insemination. The study was carried out in 11 batches weaned between March and June 2003. The sows, weaned and inseminated, were divided into two groups: a treatment group and a control group. The treatment group received an IM injection of 2 mg Alfaprostol (1 ml Alfabedyl®, CEVA) at weaning. The control group received no hormonal treatment. Statistical analysis was carried out using the nonparametric rank sum test (Mann&Whitney) in order to compare the quantitative variables and Fischer’s exact test for the two-class qualitative variables. Results Selection of sows: 247 sows were selected (121 treatment, 126 controls). There was no significant difference between treatment and control groups regarding parity (average =4.8), the number of piglets born and weaned (14.8 and 10.0) or the average period of lactation (26.6 days). The two groups were therefore comparable. Coming into oestrus: Four sows were not seen to come into oestrus: three in the control group and one in the treatment group (NS). The average interval between weaning and insemination was significantly reduced (p=0.02) in the treatment group (5.5 days) compared to the control group (6.3 days). This improvement in the coming into oestrus was due to a major reduction in the number of late oestrus and not to the increase of early inseminations (before day 3). Finally, the percentage of sows inseminated in the target period (days 4 to 6 post-weaning) was

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increased (p=0.01, Table 1). Table 1 Weaning to oestrus intervals Weaning to first AI Treatment group 0 to 3 days 4 to 6 days 7 days and more

1 (0.8%) 109 (90.8%) 10 (8.3%) 120 (100%)

Control Group 2 (1.6%) 96 (78.0%) 25 (20.3%) 123 (100%)

Fertility and prolificity: Gestation (as confirmed by ultrasonography) following the first service was defined as indicator of fertility. The average fertility rate was 86% (Table 2) and the difference between treatment and control groups was not significant (p=0.26). With an improved coming into oestrus interval in the treatment group and identical fertility, this means that the WCI (weaning-toconception interval), as confirmed by ultrasonography, and the farrowing interval were shorter in the treatment group (9.0 vs 9.5 days, p = 0.08 and 149.3 vs 151.3 days, p = 0.02, respectively). The total number of piglets and of dead piglets born at the subsequent farrowing were not significantly different (14.2 vs 14.4, p = 0.56 and 1.3 vs 1.6, p = 0.98). Table 2 Gestation rate after first service Success at first Treatment group Control Group AI NO 19 (15.8%) 15(12.2%) YES 101 (84.2%) 108 (87.8%) 120 (100%) 123 (100%) Discussion In this study, the administration of Alfaprostol at weaning led to a significant improvement of the interval between weaning and first insemination and of the synchronisation of inseminations. Fertility and prolificity rates remained unchanged. These results are similar to those obtained in Spain by Peña (1). The studied protocol increased the frequency of inseminations on day 5. This corresponds to the average time of maturation of a follicle starting at weaning, and is therefore compatible with the hypothesis of a luteolytic action mechanism. It seems unlikely that this concerns luteal bodies that persisted since pregnancy, as all sows already received two prostaglandin injections before weaning. The luteal bodies were probably formed subsequent to the lactational oestrus. This action mechanism is different from that of gonadotropins. It may therefore be presumed that these treatments are complementary. References 1. PEÑA et al. E., An. Reprod. Sc. 68 (2001) 77-83

Proceedings of the 19th IPVS Congress, Copenhagen, Denmark, 2006 · Volume 2