Genetic progress in litter size has been rapid over the last 15 years, with an annual improvement in the range of 0.2 – 0.3 total born. For many producers, litter size is no longer a limiting factor to achieving a high number of pigs born per sow per year. Today’s challenges now centre around maximizing piglet survival and, increasingly, ensuring the sow has a long, productive lifetime.
There is now increasing focus on gilt development and reproductive management programs that can improve sow herd retention rate, increase pigs per sow per year and, more importantly in this context, maximize piglets weaned per sow lifetime.
North American herd-recording systems show unacceptably high dropout rates for young females which is inconsistent with a long and productive life in the herd. Retaining females through the most productive three to six parity range will boost herd performance and reduce production cost per pig weaned. To achieve this goal, good gilt management practices are essential, but there is no widespread consensus about the routines that are most effective in improving sow herd retention.
In a recent issue of Michigan State University’s Pork Quarterly, state swine specialist Ronald O. Bates reviews the results of a Japanese research study (Kaneko and Koketsu, 2012) that evaluated sow productivity in 96 herds and related gilt management practices to sow performance. The study analyzed the farms’ sow productivity records and evaluated 15,574 gilt records. Each farm completed surveys that detailed their gilt management program.
Farms were categorized 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 and farms that were categorized as “Low” sow productivity farms produced 20.7 or fewer pigs per sow.
“Age at mating was lower among High and Intermediate sow productivity farms compared to Low sow productivity farms,” comments Bates (Table 1). “Gilts from high sow productivity farms also had higher farrowing rates than gilts from farms in the other two categories. This was true for gilts that farrowed to their first service as well as those that recycled and subsequently farrowed after a later service.”
In describing the gilt management programs 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,” Bates explains. “Therefore, it appears all farms were trying to mate gilts at their second estrus 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 (zero 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 estrus 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,” Bates notes.
Farms also listed the time gilts were mated after being 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,” points out Bates. “This may be because ovulation occurs sooner within the estrous period of gilts than sows. Therefore, mating immediately after gilts are detected in heat may allow for sperm to go through the process of capacitation and be ready to fertilize eggs at ovulation.”
Although the gilt development practices identified as being beneficial in this study are not the only ones that can improve subsequent reproductive performance, it does suggest that the following be considered for gilt development programs:
- The use of specialist gilt development diets.
- Commencing estrus detection at approximately 6.5 months of age, with gilts mated at their second or later estrus.
- Estrus detection should be carried out with direct boar contact.
- For the heat in which gilts will be mated, mating should occur soon after they are detected in heat and while they are in standing heat.
- Gilts that have been served should be limit fed until pregnancy is confirmed and then fed to body condition.
- 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,” concludes Bates.