Replacement gilts represent about 20% of all farrowings on most farms. As such, they are a critical part of the production system, though in many operations all females in the breeding herd are treated similarly. Gilts intended to be used as replacements should be treated as the special animals that they are. After all genetic decisions are made, they should be provided a better nursing environment, more space and separate feeds than their counterparts intended for market. Health should be monitored and actively managed. Through the strategic use of mature boars, the gilt age at puberty should be stimulated early and recorded. They should be mated and managed after mating as parity one females, receiving a different diet than older sows. These steps require extra time, and in some cases greater investment, but the payoff in long term productivity can be great.

The data suggest a split on the impact of fast gilt growth rate on reduced longevity. Based on the large data sets and variety of farms and genetics included, it is more likely that as long as gilts are within a desired range for growth, puberty and even longevity may not be the issue. However, both fertility and longevity can be influenced by gilt parameters at time of breeding which would have consequences for gestation and lactation performance. The data also strongly suggest that very low growth rates (<500 g/d) are less likely arise in modern production systems today. These gilts would be far below weight and should not be selected for the gilt pool. Farms that do observe problems with excessive body condition as a result of fast growth rates, can choose to limit feed access or change diet as long as restriction of energy is not below 75% of ad libitum, and protein is not limiting. Several studies implicate age at first farrowing, first litter size, and litter weaning weight as key measures for gilt longevity. First litter production is an important milestone for gilts and relies on breeding decisions and management of the female. The factors involved in litter production include gilt fertility at estrus, her ovulation rate, fertilization rate, embryo survival and uterine capacity. Some of these processes are complex, and therefore farms should focus on what can be assessed and controlled by management. The considerable body of evidence implicating troublesome variation in estrus expression suggests problems in how farms deal with this problem and how estrus expression is performed in gilts. The genetic and seasonal effects on estrus symptoms also suggest that more stringent culling could be helpful. However, industry data indicates high performance is possible and not infrequent for early age at puberty and gilt puberty induction. Problems then appear to be further downstream when gilts fail to farrow early in their lifetime, when they produce a small litter in the first farrowing, or when they wean a light litter in their first parity.

There can be a number of challenges to productivity on the sow farm including: labour, nutrition, genetics, health, facilities, environment, gilt management, etc. The biggest factor affecting productivity is the number of pigs weaned.  The number of sows farrowing has the biggest impact on the number of pigs weaned. The number of sows farrowing is in turn impacted the most by the number of gilts farrowing and management of the Gilt Developer Unit (GDU).  How can pre-weaning survival be enhanced and what factors influence weaning weight variation of pigs?

Enhancing reproductive performance of the breeding herd is a daily challenge. Today’s sows and gilts are expected to farrow and wean a large number of pigs per litter and have a large accumulated number of pigs weaned per sow per year. Caretakers need to continuously be alert and look for major and minor problems that can affect reproductive performance. Although numerous factors can influence reproductive performance, this paper only deals with some of the factors affecting preweaning survival and growth rate, such as: managing colostrum intake, effect of colostrum intake on growth rate, managing mammary gland development, identification and management of non-functional mammary glands, effect of litter size on growth rate, and use of creep feed to improve the adaptation of weaned pigs to solid feed.

You have static group and dynamic groups with sows. It seems that dynamic groups is becoming the favourite one, especially if sows are introduced in the group housing directly after insemination.