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.

Related articles

Feeding sows and piglets for piglet resilience to weaning stress

Heat stress in sows – better lactation performance with Anco FIT

Heat stress in pigs – nutritional solutions that work

Plant extracts in animal feed – Why formulation matters

Plant extracts are often all thrown into the same pot, when in fact there are many different types of herbs and spices that could be used in products formulated for the use in animal feed. Plus, there are a multitude of possibilities to combine them and additional factors that will differentiate products containing plant extracts formulated for the use in animal feed. So, the reality is they are not all the same.

The type and combination of plant extracts is only one of the factors that determines the function and effectiveness of what is currently sold into animal feed as “plant extracts”.  What looks promising in an in vitro experiment might not always be practical and cost-effective in vivo.  The question will always be: have the plant extracts been tested at different dosages in the animal and in what species?

Here are 3 of the key factors that need to be considered when formulating and designing feed solutions based on plant extracts.


Herbs and Spices have many different bioactive components with different properties and functions. Even their essential oils can have something like 80 different components. Plants have evolved to cope with stressors and many of these components have a protective role supporting the resilience of plants, but they also evolved to attract pollinators to propagate. So, when you combine plant extracts derived from a number of different herbs and spices you can have a all cocktail of bioactive substances and their effect will ultimately also be determined on synergistic effects and not just concentrations of individual components. New research technologies have facilitated a more in depth understanding of the mode of action of plant extracts and their components at the animal level. As a result, it is now possible to formulate plant extracts with a more accurate idea of the outcome for their function in the animal and animal response, rather just working in a black box approach. This is speeding up the process of product development and evaluation. It also provides more potential for differentiation in function between products through formulation know how within the category of plant extracts.


Most plant extracts have sensory properties and they come with a distinctive flavour. That in itself can determine how effective the product will be and how much of it you can apply to animal feed, because the flavour can affect feed intake not just in a positive way.  For example, plant extracts with a strong bitter taste can lead to a lower acceptance of feed in pigs. Again, this will depend on dosage, but is it possible to apply the dosage required to achieve the desired effect in the pig without having a negative impact on feed intake? Only in vivo dose response trials will provide the answer. So, it is important to understand which plant extract compounds might have a negative impact on feed intake and find ways to determine the acceptable dose or mask their taste.


3.Concentration/dosage of plant extracts

Concentrations of individual components in the formula and concentrations ultimately added to the feed determine the dosage required to achieve the desired response in the animal. Dose response trials are required to determine the optimal and most cost-effective dosage. As is the case with other types of feed additives more is not always better in terms of performance, but there will be a minimum dose required to have an impact on the animal.

These are only some of the factors to consider when formulating products with plant extracts. But they highlight that how they are formulated matters, and the buck stops with the animal.

Relevant articles

Animal resilience – Harnessing the power of plant resilience

Evolution in the evaluation of phytogenics