Introduction

The vast majority of matings on swine farms in the US are done using artificial insemination. This is also true in those countries that have adopted modern swine production technology. For the most part, sows are inseminated with fresh semen that is diluted and extended in various semen extenders and used within a few days after collection from a boar. There has been ongoing research to better understand what ingredients should be put within extenders to improve semen storage and maintain fertility. Recently, there was a publication^a that reported studies evaluating the inclusion of gelatin in extenders for fresh semen.

Method

This study evaluated the inclusion of gelatin in a Beltsville Thawing Solution (BTS) type extender. A BTS extender is commonly used in the pork industry as a short-term extender. The gelatin used was a commercial, colourless and unflavoured gelatin containing one per cent energy and three per cent protein. Semen was collected from four crossbred boars and pooled for these experiments. In all experiments, sperm concentration was adjusted to 3.5 billion sperm per 100ml.

In the initial experiment, semen was compared in extenders that included zero gelatin, 1.5 per cent or 3.0 per cent gelatin. Sperm motility and morphology was evaluated over 72 hours after extension.

In a subsequent experiment, semen was extended in either zero per cent or 1.5 per cent gelatin and compared over 108 hours for sperm motility, normal sperm morphology and sperm membrane integrity.

In the final experiment, semen extended in a BTS extender with 0 or 1.5 per cent gelatin was inseminated into sows. Semen backflow was collected during and after insemination and farrow rate and litter size born were evaluated.

Results

In the initial experiment, sperm motility and sperm morphology was not different over the 72 hours evaluated regardless of the extender used (Figure 1). This suggests that neither sperm motility nor sperm morphology was negatively impacted by the inclusion of 1.5 per cent or 3.0 per cent gelatin in the extender.

In the second experiment, extender with zero per cent and 1.5 per cent gelatin were compared and sperm was evaluated for a longer period of time and included sperm membrane integrity. Over the 108–hour (4.5 days) time course, sperm motility was only slightly improved after 108 hours when sperm was extended with 1.5 per cent gelatin compared to a BTS extender with no gelatin. However, normal sperm morphology was dramatically improved after 108 hours when kept in extender with 1.5 per cent gelatin. Semen extended in the BTS extender with 1.5 per cent gelatin had approximately seven per cent greater motility than semen extended in BTS alone. The difference for sperm membrane integrity was even larger. Semen extended in BTS extender with 1.5 per cent gelatin had approximately 200 per cent greater membrane integrity after 108 hours compared to semen stored in BTS extender without gelatin.

Figure 1. Comparison of extenders with differing amounts of gelatin

In the breeding experiment, 26 sows were inseminated for each of the two treatments of semen extended in BTS extender or BTS extender with 1.5 per cent gelatin. Sows were inseminated three times, 12 hours apart after detected in behavioural oestrus.

Inseminations with semen extended in BTS took one minute longer than those with semen extended in BTS with 1.5 per cent gelatin (7.8±0.4 minutes versus 6.8±0.4 minutes, respectively; P<0.05). In addition, backflow of inseminations with 1.5 per cent gelatin in the extender was lower than inseminations that did not have gelatin in the extender (Figure 2).

Farrowing rates were high for sows inseminated with semen extended with either the zero or the 1.5 per cent gelatin extender and did not differ (92.6 per cent versus 88.5 per cent, respectively). The same was true with total size born (12.0±0.6 versus 13.2±0.7, respectively).

Figure 2. Comparison of insemination backflow

Conclusions

As the pork industry looks for ways to improve efficiency and cost of production, the inclusion of gelatin in semen extender may improve storage life and sperm cell integrity. This may allow for fewer doses to be thrown out due to reduced sperm cell viability. In addition, the reduced backflow during and after insemination may take some of the guesswork out of inseminating sows.

Furthermore the possible increased litter size born observed for sows inseminated with semen that included gelatin in the extender may be an added bonus. This simple idea looks very promising; however, further research is needed to determine how well the differences observed in this study carry over to commercial production.

^aCorcini, C.D., F. Moreira, R. Pigozzo, A.S. Varela Jr., N.U., Torres, T. Lucia, Jr. 2011. Semen quality and reproductive performance after artificial insemination with boar sperm stored in a gelatin-supplemented extender. Livestock Science. 138:289-292.