Introduction

Improving sow productivity is an on-going challenge across the pork industry. Improving pigs per sow per year is not only about improving litter size but also improving female retention.

It has been recognised that an effective gilt development and reproductive management program can improve sow herd retention rate which in turn should improve such characteristics as pigs per sow per year. This is due to the sow herd maintaining a high proportion of parity 2 and greater sows. However, there is poor agreement as to what gilt management practices are necessary to improve sow herd retention.

There was a recent research study (Kaneko and Kofetsu, 2012) that evaluated sow productivity in 96 herds and related gilt management practices to sow performance.

Results

This study worked with the sow productivity records from 96 farms and evaluated 15,574 gilt records. Each farm completed surveys that detailed their gilt management programme.

Farms were categorised into three sow productivity categories, based on pigs per sow per year. Farms classified as 'High' achieved more than 23.8 pigs per sow per year. 'Intermediate' sow productivity farms fell within the range of 20.8 to 23.8 pigs per sow per year. Farms that were categorised as 'Low sow productivity' farms produced 20.7 or less pigs per sow per year.

This study reported that age at mating was lower among High and Intermediate sow productivity farms compared to Low sow productivity farms (Table 1). Gilts from high sow productivity farms also had higher farrow rates than gilts from farms in the other two categories. This was true for gilts that settled on their first service as well as those that recycled and subsequently settled on a later service.

^a Adapted from Kaneko and Koketsu, 2012. ^b,c Means within a row with different superscripts differ (P<0.05).

In describing the gilt management programmes for these farm categories, High and Intermediate sow productivity farms began boar contact with gilts at approximately 203 days of age while Low productivity sow farms began boar contact with gilts at approximately 213 days of age. Therefore, it appears all farms were trying to mate gilts at their second oestrus but High productivity sow farms began boar contact with gilts sooner.

A greater proportion (32 per cent) of high sow productivity sow farms used gilt development diets than Intermediate (8.5 per cent) and Low (0 per cent) sow productivity sow farms. Also age at farrowing was 13.7 days younger for gilts on farms that used direct boar contact to stimulate oestrus versus farms that used indirect boar contact. This is in agreement with recent research from Michigan State University that reported that gilts that farrow at or before a year of age had improved sow longevity compared to females that farrowed after a year of age (Hoge and Bates, 2011).

Farms also listed the time gilts were mated after detected in heat. Farms that mated gilts immediately after detected heat had higher gilt farrowing rates than farms that waited either six to 12 hours or 24 hours to mate or inseminate gilts (Figure 1). This may be because ovulation occurs sooner within the oestrous period of gilts than sows. Therefore, mating immediately after gilts are detected in heat may allow for sperm to go through capacitation and be ready to fertilise eggs at ovulation.

Summary

The gilt development practices that significantly improved subsequent sow productivity in this study are not the only management practices that may improve subsequent reproductive capacity. Certainly, other gilt development practices have been suggested that could improve subsequent sow performance. However, this study identifies robust management practices that should be seriously considered for inclusion in gilt development programs. Specifically, this study suggests the following be considered for gilt development programmes:

1. Gilt development rations should be considered
2. Oestrus detection should begin at approximately 6.5 months of age and gilts mated at their second or later oestrus
3. Oestrus detection should allow for direct boar contact
4. For the heat in which gilts will be mated, mating should occur soon after detected in heat and while in standing heat
5. Gilts that have been serviced should be limit fed until pregnancy is confirmed and then fed to condition
6. Gilts should farrow at approximately 11 to 12 months of age.

Gilt development is an important aspect of sow farm productivity and attention to detail and consistent applications of fundamental gilt management practices should improve subsequent productivity and longevity.

October 2012