Introduction

The objective of the present study was to test the efficacy of two treatments for ovulation induction (PG600® (400IU PMSG and 200IU HCG) and hCG (Chorulon®) followed by a single artificial insemination (AI) on fertility and prolificacy of gilts previously synchronised with Matrix®. Target is to obtain high reproductive performance while simplifying fertility management, i.e. less time spent for oestrus detection, less AIs and a more predictable timing of farrowing).

Materials & Methods

Thirty-six (36) Large White × Landrace pubertal gilts (129kg average bodyweight and 180 days old) were randomly assigned to three treatment groups, each including 12 animals. All gilts were synchronised by oral administration of Matrix (15 mg altrenogest per animal) once daily for 14 consecutive days. Four days (96 hours) after the last administration of Matrix (day 0), animals were treated for ovulation induction as follows:

• Group 1: Non-treated animals (control)
• Group 2: I.m. administration of PG600
• Group 3: I.m. administration of hCG (500 IU)

At 32 hours after ovulation induction, gilts from groups 2 and 3 were inseminated once, while those of group 1 (control) were inseminated twice, 12 hours apart, at detected oestrus. Ovaries were scanned (ultrasonography) starting immediately before treatment and then twice daily for the next 48 hours in order to check ovulations (based on the disappearance of the large pre-ovulatory follicles present at earlier scans). Blood samples were collected before treatment, and two, four and seven days later, to assess changes in plasma progesterone concentrations and to document the quality of ovulation. Twenty-two days after AI (Day+23), the pregnancy status of the gilts was checked by ultrasonography. At about 30 days after AI, all pregnant gilts were slaughtered, their ovaries collected and the numbers of total and normal foetuses were determined.

Results

A few gilts were not successfully synchronised by Matrix, reducing group size to n=9 in all three treatment groups.

At 48 hours after treatment, ultrasonographic scans demonstrated that ovulation was successfully induced over a 16-hour time window in 100 and 78 per cent of the animals treated with hCG and PG600, respectively. Only 22 per cent of the control gilts ovulated during the same time window. AI was closely synchronised with ovulation in all hCG-treated gilts and in six of the nine PG600-treated gilts. The remaining PG600-treated gilts ovulated, respectively, 12 (n=2) and 24 hours (n=1) later.

There was no treatment effect (P=0.11) and no treatment × time interaction (P=0.09) for changes in progesterone concentrations. Progesterone concentrations were low on day 0 and 2, and increased similarly in the three treatment groups to reach 22.8 ± 6.6, 18.8 ± 4.2 and 21.0 ± 5.0ng/ml in gilts treated with hCG, PG 600 and placebos, respectively.

When the reproductive features of the gilts of the three groups were compared, no significant differences were demonstrated for fertility assessed by ultrasound 23 days after insemination or for the number of corpora lutea and live embryos observed 29 days after insemination.

A summary of the data describing ovulation rate, fertility, number of live embryos at slaughter and of embryonic survival (ratio between ovulation rate and total number of embryos at slaughter) is presented in the table below:

Discussion & Conclusion

These results show the ability of an injection of PG600 or hCG to induce ovulation (when injected 96 hours after the end of Matrix), hence allowing to obtain high fertility and prolificacy after a single fixed time AI (similar to that generated by multiple AIs at detected oestrus).

Although these findings need to be confirmed on a larger sample, this study establishes that the LH activity intrinsic to the hCG and PMSG molecules is suitable for ovulation induction in swine.

This paper was presented at the 21st International Pig Veterinary Society (IPVS) Congress 2010 on 19-21 July 2010 in Vancouver, Canada.
For more information about the Congress, click here.

July 2010