In the present study, we evaluate the effects of different weaning strategies on intestinal health and growth performance. We observed that piglets weaned at 16 days of age and transferred to a pre-weaning facility, with provision of milk replacer had reduced growth performance at 24 days of age when compared to the other groups. Further, even though piglets from the ESW group were provided with milk replacer, and no litter mixing occurred, a decrease in ADG and BW at 24 days of age was observed. This further corroborate the notion that weaning age (Faccin et al. 2020) is an important factor influencing piglet growth performance. Indeed, there is positive correlation between weaning age and improved growth performance (Ming et al. 2021; Smith et al. 2010; Van Der Meulen et al. 2010). Maternal separation is another important factor that should be considered. Reported results demonstrate that maternal separation can altered subsequent behavior, physiology and neuroendocrine function in young pigs (Jarvis et al. 2008).
Low feed intake or even no feed consumption often occurs during the first days following weaning, and it can contribute to gut dysfunction and compromise performance (Pluske et al. 2007). Therefore, an early resumption of feed consumption has an important role to play in mitigating the adverse effects of weaning stress (Campbell et al. 2013). In our study, we observed that the SSW group had the greater percentage of piglets consuming feed in the first 24 hours after transference to the nursery facility. This result differs with those of Colson et al. (2006), who observed no differences in piglet feeding behavior when weaned at 21 or 28 days in the first 24 hours post-weaning.
In the nursery phase I, piglets from the CW group had the lowest DFI among experimental groups. In contrast with the other groups, CW piglets were weaned at 24 days of age and transferred directly to the nursery unit, therefore, the combination of sudden separation from the sow, abrupt change in diet, and living environment may have contributed to this result. Although no statistical difference was found in the final weight of ESW and CW piglets, there is a noticeable improvement in feed consumption for the former, even though early weaning is typically associated with a considerable decrease in this variable (Kobek-Kjeldager et al. 2021).
Damage to tight junction protein function can increase paracellular permeability and, consequently, trigger gastrointestinal disorders (Edelblum and Turner 2009). In this sense, weaning is one of the most critical periods associated with intestinal barrier disfunction, with detrimental effects more pronounced in early-weaned piglets (Modina et al. 2019). In our study, when the total experimental period is considered, ESW piglets had the lowest incidence of diarrhea. Although piglets from the ESW group were weaned at an earlier age compared to the other groups, the provision of creep-feed during lactation and milk replacer at the pre-nursery facility may have helped to ease the transition from the sow’s milk to a plant-based diet. Provision of milk replacer during the lactation period has been shown to significantly increased BW of piglets in the first 3 weeks of life and resulted in a significantly increased length and relative intestinal weight:length ratio of the small intestine (de Greeff et al. 2016). In our study, however, the beneficial effects of milk replacer provision on piglet performance were not observed.
Intestinal permeability is reported to increase in the first 24 hours post-weaning and gradually decrease thereafter. Similarly, Xia et al. (2022) stated that intestinal villi height decreases by 75% in the first 24 hours post-weaning and continues to gradually decrease until stabilization at 14 days post-weaning. Impairments in enzyme secretion are also reported, as amylase, trypsin, and chymotrypsin levels return to pre-weaning secretion levels about 9 days after weaning (Hedemann and Jensen 2004). Thus, due to the fact that samples were collected 9 days after ESW piglets were separated from the sow, these piglets may had been more adapted at that time, leading to a lower incidence of diarrhea. Piglets weaned at 15 days had higher intestinal permeability and a higher incidence of diarrhea in the 7th and 20th weeks post-weaning compared to piglets weaned at 28 days (Pohl et al. 2017). Early weaning causes hypersensitivity to intestinal stimuli (early mast cell activation and changes in the enteric nervous system secretion patterns), leading to the development of chronic diarrhea. Other authors also report higher intestinal permeability in piglets weaned early compared to those weaned after 21 days (Moeser et al. 2017; Smith et al. 2010). In our study, ESW piglets had lower intestinal permeability at 19 days of age. Although there is a consensus that intestinal permeability sharply declines after the first hour after birth, there are studies demonstrating that compounds present in milk and the microbiota itself stimulate an increase in permeability during lactation to encourage the enteric immune system to adapt to the presence of microbiota bacteria, with this permeability being more pronounced around the second week of lactation (Arnaud et al. 2020). The second and third assessments of intestinal permeability was conducted at 6 and 9 days, respectively, and no difference were found between weaning strategies. This might be due to the fact that piglets were in a more advanced physiological stage at that time compared to piglets evaluated at 19 days of age.
Overall, the results of our study showed that the weaning strategy, Segregated Strategic Weaning, can be used to mitigate the deleterious effects of early weaning. This weaning strategy may be implemented in commercial operations to optimize the use of nurse sows, and improve sow productivity, by increasing annual litter size. However, further studies are warranted to evaluate the effect of this weaning strategy on piglet behavior and gut morphology as well as its economic viability.