For a long time, the topic of fibre supplementation for the sow was only discussed in connection with the prevention of constipation in the period close to birth. In recent years, fibre supplementation has been increasingly used in the context of positively influencing the performance of sows and piglets.
The genetic progress made in sows in recent years represents a major challenge for management. The number of weaned piglets is increasing worldwide (Fig. 1). Modern sows wean 33-35 piglets per year, with the most productive herds already producing more than 40 piglets per year per sow (PSY).
Figure 1: Development of the number of PSY in selected countries (Sanz-Fernández et al. 2024)
At the same time, piglet mortality remains high. In Denmark, the number of PSA rose from 30.3 to 35.3 between 2013 and 2023. However, piglet mortality remains relatively unchanged at over 20% (Fig. 2).
This high piglet mortality rate is an economic and increasingly also a social problem, with production methods being increasingly scrutinised by society. This increases the need to limit loss rates, especially as the continuing upward trend in the number of piglets born per sow each year also implies a risk of further increases in piglet losses. Large litters imply a longer farrowing period with lower individual birth weights, associated with a higher risk of stillbirths or weak piglets. At the same time, the amount of colostrum available per piglet decreases, which reduces the immune status of the animals and reduces their overall growth potential.
However, successful management determines the production of large litters of (over)live piglets. There are many ways of adjusting this - feeding the sow is an important way of influencing this.
Figure 2: Development of the number of weaned piglets per sow per year and piglet mortality in Denmark between 2013 and 2023 (Vinther 2023, Hyttel 2024).
The farrowing period as an important factor
Large litters are closely linked to longer farrowing times. A long birth means stress for the sow and the piglets and is associated with several negative consequences. An extended farrowing period increases the proportion of stillborn piglets. According to Theil (2015), an extended farrowing from 300 to 400 minutes means the loss of 2 piglets or more. The correlation is also illustrated in Figure 3 below.
Figure 3: Relationship between farrowing duration and stillbirths (Schoos et al. 2023)
In their study, Schoos et al. (2023) identify longer farrowing times (> 300 min) and > 20 min as the most important factors contributing to both an increased stillbirth rate and increased mortality before weaning in hyperproliferative sows.
Oliviero et al. (2013) demonstrated the negative effects of an extended farrowing period on the fertility of sows. Sows that did not become pregnant at the first insemination needed 100 minutes longer for the previous farrowing than the sows for which the first insemination was successful. Impaired fertility is associated with delayed placental detachment, which has a negative effect on postpartum uterine health and thus influences the development of postpartum dysgalactia syndrome (PDS). If PDS reduces colostrum and milk production in the first few days after farrowing, this means an additional risk for the piglets in the critical neonatal phase (Maes et al. 2010). A prolonged labour period also reduces the vitality of the piglets, which are also more likely to die from hypoxia (lack of oxygen). According to findings by Langendijk and Plush (2019), 15 to 20 % of piglets born alive later suffocated due to a prolonged farrowing period.
Providing the sow with fibre in the period around birth offers an approach to reducing farrowing duration and has various other advantages. Adequate fibre supply increases the sow's water intake around birth and feed intake during lactation and therefore also has the potential to increase colostrum intake and thus piglet performance (Oliviero et al. 2009; Quesnel et al. 2009).
The fibre effects can be summarised as follows:
1) Improved intestinal motility and energy supply: Fibre increases intestinal motility and prevents constipation, which can otherwise prolong farrowing. In addition, the fermentation of fibre produces short-chain fatty acids (SCFA), which serve as an energy source and help sows to maintain their strength during parturition. The sow can meet up to 25% of her energy requirements (maintenance) through the fermentation of fibre in the large intestine (Shi and Noblet, 1993). Bacteria in the large intestine metabolise dietary fibre into volatile fatty acids and lactic acid. These are absorbed by the animal and serve as additional sources of energy. The great advantage here is the time delay with which the energy from the fermentation is provided. Enzymatic digestion in the small intestine provides energy up to five hours after feed intake, while the fermentation products from the large intestine are provided over a period of 24 hours. For the sow, this additional energy in the period close to birth means a reduction in hunger - and therefore stress - and above all additional energy for the birth process. The energy supply has a strong influence on the duration of the farrowing period, which has a significant effect on the number of stillborn and weak piglets (Feyera et al. 2018).
2) Hormonal and metabolic benefits: a high-fibre diet improves insulin sensitivity and glucose regulation, which ensures a steady energy supply during farrowing, reduces exhaustion and promotes stronger uterine contractions (Xu et al. 2020; Li et al. 2024).
3) Reduced stress and increased satiety: Dietary fibre increases satiety by slowing gastric emptying and stabilising blood glucose levels. This reduces stress and restlessness in the sows, which can lead to a smoother farrowing (Huang et al. 2020).
In Hirtenlehner et al (2021), the supplementation of lignocellulose as a fibre source in sow feed resulted in a significant reduction in farrowing duration, a shortening of the birth interval and an increase in the number of piglets born alive. The positive effects of supplementation were greater in highly productive sows of Danish genetics compared to standard hybrids.
When supplementing with fibre, it is important to consider both the quality and quantity of the fibre. The balance between soluble and insoluble fibre is crucial for improving intestinal motility, preventing constipation and ensuring a consistent energy supply during farrowing.
Soluble fibres support fermentation and energy supply. They form a gel-like structure in the intestine, which slows down digestion and enables fermentation in the hindgut. They are fermented into short-chain fatty acids, which serve as a source of energy during labour. Sources of soluble fibres include dried/molassed beet pulp, soybean hulls or alfalfa. Insoluble fibres improve intestinal motility and reduce constipation. Sources include lignocellulose, wheat bran or oat hulls.
And the quantity? A minimum of 10% soluble and 15-20% insoluble fibre is required to achieve a balance. Li et al (2019) recommend a ratio of insoluble to soluble fibre of 3.9:1 in the diet of gestating sows to increase the birth weight of the piglets and the litter weight at weaning. More general recommendations deal with 3:1 or 2:1 but the concrete ratio hasn’t yet been scientifically proven.
However, the "but" follows immediately: data on the soluble and insoluble fibre content is not generally available. The standard parameter in the characterisation of feed for pigs is still crude fibre, although neutral detergent fibre (NDF) and acid detergent fibre (ADF) are also increasingly being taken into account, even if it is agreed that the dietary fibre is more suitable.
Conclusion
The high genetic potential of today's sows should result in well-developed and fast-growing piglets, while at the same time reducing the proportion of stillborn and underweight piglets. The farrowing process, in particular the length of farrowing, can be a significant influencing factor here.
A prolonged farrowing process increases the number of stillbirths and weak piglets and has a negative effect on the health, fertility and performance of the sow. Sows have an increased risk of post-partum dysgalactia (PDS), which is characterised, among other things, by insufficient colostrum and milk production after farrowing. The interrelationships are very complex, but targeted fibre supplementation can have a positive influence on the farrowing process and thus positively affect the performance of sows and piglets.
