Prolific sow and suckling piglet nutrition
Over the last few decades, litter sizes and the number of weaned piglets per sow per year (PSY) have been improved considerably, especially driven by improved sow's prolificity via selection. With an increase of 0.2 piglets/year over the past 20 years, which we already observe in practice with large litters at birth (Quiniou, 2012), the PSY in the United States (23.2 to 25.0) and European Union (24.0 to 27.8) has increased considerably from 2008 to 2017 (PigCHAMP and AHDB-BPEX yearly report 2008-2017).
Figure 1. Development in weaned piglets per sow per year (Seges, 2018).
The increased litter size has inevitably led to a reduction in average piglet birth weight and an escalation in heterogenicity within a litter. Indeed, Boulot et al. (2008) reported that average piglet birth weight is reduced by 100 g/pig for every extra pig above 9 piglets (9 piglets; 1.89 kg/piglet, 16 piglets; 1.38 kg/piglet). This can in part be explained by the limitation in uterus size whereby a growing number of the developing fetuses are subjected to intra-uterine growth retardation (IUGR). The IURG piglets now represent up to 30-40% of piglets in large litters. These piglets can be identified by low birth weight and disproportionate body shape, including a characteristic 'dolphin shape' head morphology. Moreover, increasing litter size generally increases parturition time and consequently increased number of piglets, particularly those born later, are often exposed to hypoxia and thus increases the number of less viable pigs and still borns. Reproductive performance can also be adversely affected if low birth weight piglets are selected as replacement gilts. Low birth weight pigs have been shown to have fewer primary and secondary follicles than normal weight littermates. Whilst only few long-term studies are reported, sows born with less than 1 kg birth weight had 4.5 fewer piglets in the first 3 parities and had a shorter herd longevity (Magnabosco et al., 2015). Longer farrowing time may also affect sow longevity, which is a key factor for the profitability of a commercial swine herd (Stalder et al., 2004). Currently, in the USA, annual sow culling and mortality rates are 42.3% and 10.7%, respectively (PigCHAMP, 2018). Since uterine capacity is limited, nutritional strategies must be adapted to mitigate the negative impacts of these physiological changes on sow longevity and lifetime performance of their progeny.
Probiotics and prebiotics
Considering the beneficial effects on intestinal microbial balance, dietary administration of probiotics and prebiotics are reported to relieve the stress of sows in gestation and lactation. Probiotics are known for many beneficial health effects including antioxidant defence mechanisms thereby ameliorating oxidative stress (Cai et al., 2014; Dowarah et al., 2016). Pregnancy and lactation pose a considerable metabolic challenge for sows, particularly in highly prolific sows. The demand for energy increases with oxygen uptake, and increased release of stress hormones (glucocorticoids) associated with pregnancy and farrowing contributes to the increased production of reactive oxygen species that induces oxidative stress. Oxidative stress may also be associated with the litter size as Wang et al. (2018) found that oxidative stress status in the low litter sows was higher than that in the high litter sows, particularly during the perinatal period.
The addition of live yeast to the ration is one of the potential nutritional approaches that can influence the gut microbiome in a manner that supports a stable pH and fiber fermentation in both sows and piglets.
Live yeast products can be broadly split into two categories. Yeasts predominantly selected for use in the baking and brewery industry are often referred to as first-generation yeasts and are also used in animal nutrition. Yeasts specifically selected to work in animal nutrition are commonly referred to as second-generation yeasts. The selection of second-generation yeast involves a series of screening tests, with the first step being selection of smaller cell size, or a "micro yeast", and the second step being the selection of most metabolically active yeast strain. Small yeast cells have a larger cell surface area per gram product, allowing for a greater potential to scavenge oxygen. Moreover, metabolically active yeast strain demonstrates better oxygen scavenging capacity (i.e., higher redox potential). Therefore, selection of smaller cell size and metabolically active yeast strain enables a higher level of colony-forming units (CFU) per gram to be delivered and highest redox potential, providing the best possibility for live yeast to change and optimize the gut environment through the removal of oxygen concentration. The potential of live yeast to remove or "scavenge" for oxygen can be evaluated by measuring the redox potential (Eh). The more negative the Eh value indicates the greater the potential to scavenge oxygen. During ingestion of feed and water or under stress, oxygen concentration is higher due to increase oxygen ingestion and oxygen emission from the epithelial cells, respectively. Feeding live yeast maintains a lower Eh, even at times of feeding (Krizova et al., 2011). Live yeasts are mostly active dry yeasts (typically Saccharomyces cerevisiae). Its effects depend on a combination of strain specificity and quantity of live yeast (CFU) surviving and performing in the right part of the gastrointestinal tract. In this sense, a product with a higher CFU concentration would be more beneficial as it would need less inclusion to achieve the target CFU number (Desnoyers et al., 2009).
Live yeast is a probiotic and acts as pathogen binder via its unique mannan oligosaccharides in the outer cell wall which reduces the pathogen population in the intestinal lumen. As an oxygen scavenger, live yeasts suppress the growth of undesirable bacteria whilst shifting gut environment to more favorable for fiber fermentation, as most of the fiber fermenting microbiota are anaerobic and prefer a lower pH than pathogenic microbiota. The favorable luminal environment for fiber-degrading bacteria can results in increased hydrolysis of neutral detergent fiber, higher levels of volatile fatty acids production and, thus, a higher level of energy extraction in feed materials, that can be wasted (Lizardo et al., 2012). Both these modes of actions are key in supporting the needs of the animal through stressful periods.
Figure 2. Volatile fatty acids (VFA) production at different pH levels (Vervaeke., 1973)
A study by AB Vista examined the effect that live yeast (20 billion CFU/g) can have on sow farrowing performance when dosed at 0.5 kg per ton during gestation. Live yeast fed sows had more piglets born alive (17.0 vs. 16.3) due to decreased still born, heavier average birth weight (1.29 vs. 1.13 kg, P=0.016) and, more critically, live yeast fed sows had a lower percentage of piglets weighing less than 1 kg (27 vs. 12%, P<0.001) (refer to Graphs 1, 2 and 3).
Graph 1, 2, 3: Effect of supplementing 0.5 kg of live yeast (Vistacell) on live born, % still born, birth weight and % of piglets with less than 1.0 kg live weight.
This shows the potential role that live yeast may play in mitigating the number of small pigs in a litter specifically in the highly prolific breeding herd and justifies an evaluation in larger-scale commercial systems.
With a higher percentage of hyper prolific sows in the commercial breeding herd, the need to support the sows during gestation and lactation to maintain the reproduction efficiency for long term production is even more critical. This has seen producers look at different technologies and with live yeast offering the ability of combining the effect of a yeast cell wall with the added beneficial effect of being metabolically active it offers the producer a unique feed technology that can help support the sow through pregnancy and lactation.
For more of the article, please click here.
Article made possible through the contribution of Gustavo Cordero, Jae Cheol Kim and AB Vista