weaning-to-first service interval - anco fit

Weaning-to-first service interval in sows fed a gut agility activator

The weaning-to-first service interval is a key driver for improving farrowing rate and increasing litter sizes in subsequent litters. Heat stress is one of the factors that is known to have a significant impact on weaning-to-first service intervals. A gut agility activator was evaluated in commercial sow diets for response in sow reproductive performance post weaning in a hot climate.

Factors affecting the weaning-to-first service interval

Weaning-to-first service interval is economically relevant since it affects the number of non-productive days and hence maintenance cost and sow efficiency. Whereas estrus detection methods and the capabilities of breeding technicians play an important role for weaning-to-first service interval, there are other factors that need careful management and optimization to ensure short weaning-to-first service intervals in sows.

Lactation length for example needs to be optimized, since the shorter the lactation period the more likely the weaning-to-service interval is increased. Adequate feed intake, especially during the first 7 to 10 days of lactation, is key to replenish body reserves which controls subsequent reproductive performance. This is also why many studies have demonstrated that high ambient temperatures prolong weaning-to-first service intervals and reduce pregnancy rates, because they impact sow feed intake in lactation. Hence why ventilation design and supplemental cooling systems in the farrowing room and adequate water intake can also play an important part.

Impact of heat stress on weaning-to-first service interval

Researchers reported weaning-to-first service intervals of 2 to 4 more days in sows experiencing temperatures >35°C versus <30°C. Others showed that a high temperature humidity index (THI > 82) resulted in a greater percentage of gilts and sows with a weaning-to-service interval >8 days. This has been explained to be partly due to a reduction in feed intake in response to high temperatures, particularly during lactation.

More recent studies measured the impact of heat stress in sows on oxidative status at different stages of the reproductive cycle and reported increased oxidative stress in sows around late gestation in sows kept under temperatures above 25°C compared to sows kept at more moderate temperatures. This was associated with a reduction in reproductive performance in the form of a decrease in litter size at birth and litter weaning weights. Increased oxidative stress could however also lead to an increase in inflammatory responses in the sow and an increase in maintenance energy, which again could have an impact on subsequent weaning-to-first service interval.

Effect of Anco FIT on post-weaning sow reproductive performance

The gut agility activator Anco FIT was tested in a sow trial designed to evaluate the product for its impact on annual sow reproductive performance post-weaning on a commercial sow farm in Cordoba, Argentina.

Trial design

Anco FIT was added to sow gestation and lactation diets for a whole year starting in September 2019 on a commercial sow farm with 380 sows. Monthly post weaning KPIs (key performance indicators) for sows, such as weaning-to-first service interval and percent of sows returning to oestrus (when a sow was mated but did not become pregnant), were monitored until August 2020. No other dietary changes made. Performance was compared to that in the previous year, where there was no Anco FIT in the sow diets.


Adding Anco FIT to the sow diets reduced annual means for weaning-to-first service intervals by 31% (11.6 vs 8.0 days) and returns to estrus by 24%. The improvement seen in returns to estrus was particularly marked in the summer months (November to March) of Argentina (10.4% vs 6.3%).


Feeding Anco FIT to sows during gestation and lactation improved key annual post-weaning reproductive performance parameters in sows and the impact was particularly measurable during the hotter summer months in Argentina. Results may to some extent be explained by improving sow lactation feed intake under heat stress as shown in a previous sow lactation trial with Anco FIT.  On the other hand, Anco FIT includes components with antioxidative properties, which might have helped to reduce the negative impact of oxidative stress in sows at crucial stages of the reproductive cycle and make more energy available for reproductive performance.

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