Probiotics are used in all stages of porcine production: sow herd, nursery and growing-finishing pigs. Generally speaking, the use of probiotics aims to establish a healthy gut microbiota, improve health, well-being and productivity of the animals (Cho et al. 2011). However, if we are more specific, the practical application (or result) of using probiotics can be distinct in every context (see table 1). This article briefly describes main applications for which probiotics have been evaluated in different productive stages of swine production.
Table 1. Main applications of probiotics in the swine industry. Adapted from Barba-Vidal et al. Practical aspects of the use of probiotics in pig production: A review. Livestock Science 223 (2019) 84–96.
Sow herd and piglets
Administering probiotic treatments to sows has demonstrated a dual potential, including benefits for themselves and for piglets. Supplementation of sows with probiotics may increase feed consumption during late pregnancy stages or lactation, improving body condition at the end of lactation (Bohmer et al. 2006). This situation is desirable, because it can cause a reduction of the necessity of energy mobilization at lactation. This, in turn, could be the explanation of the reduction in the weaning–estrus interval that has also been reported with probiotics (Hayakawa et al. 2016). Reproductive-performance-related benefits have also been reported with the use of probiotics in sows. For example, an increase in the number of piglets (Apic et al. 2014) or higher piglet growth rates with greater body weight at weaning (Alexopoulos et al. 2004). Furthermore, a reduction of gut pathogens (Kritas et al. 2015), clinical signs of uterus and/or udder disease (Apic et al. 2014), together with fewer clinical signs of diarrhea in piglets (Taras et al. 2006) have also been described. Finally, there is an ongoing scientific interest to assess the capacity of sows to deliver probiotics to piglets in early-life stages (Scharek-Tedin et al. 2015).
Up until today, the nursery period is where the use of probiotics is receiving more interest in swine production, with the aim to improve weaning outcome (de Lange et al. 2010). Weanling piglets have low disease resistance, which makes them vulnerable to stress reactions and invasion by pathogenic microorganisms (Konstantinov et al., 2006). This can be a serious problem, as this period is considered critical in terms of productivity, because performance parameters at the first week post-weaning can be correlated to subsequent performance of the pigs up to the market weight (Kats et al., 1992).
Probiotics can potentially act beneficially in these animals in several ways. For instance, it has been reported that supplementing weanlings with probiotics may prevent or improve diarrhea (Bhandari et al. 2008), re-establish microbial balance after a transient drop in favorable bacteria (Krause et al. 2010), protect against pathogenic bacteria (Casey et al. 2007), enhance intestinal barrier function (Guerra-Ordaz et al. 2014) and stimulate immunity (Lessard et al. 2009). As a consequence of one or a combination of the before-mentioned reasons, probiotics have been reported to improve productive parameters of post-weaning piglets in many occasions (Ahmed et al. 2014, Bhandari et al. 2010).
The main objective to use probiotics in this phase would be to enhance productivity. Scientific literature published until now would support the idea that although older pigs have more developed immunity, and capacity to resist intestinal disorders, there is still a margin for probiotics to act and potentiate growth; especially in early growing phases or high-density diets (Meng et al. 2010). Improvement of the final meat quality and organoleptic properties could also be another target for probiotics in this phase, as probiotics have been described to affect meat color, marbling and firmness scores (Černauskienė et al., 2011); and reduce potentially zoonotic infections such as Salmonella spp. (Casey et al., 2007). Finally, a weakly explored but interesting potential of probiotics is to reduce environmental pollutants from animal manure. Several probiotics have been reported to be capable of reducing potential pollutants from manure such as fecal noxious gas (H2S) or ammonia (NH3) content, particularly in pigs fed high-nutrient density diets (Yan and Kim, 2013). The direct mechanisms for these effects are still unknown, although indirect mechanisms such as improving feed efficiency, nutrient retention and modulation of gut microbiota are probably involved.