The role of lactose in weanling pig nutrition: a literature and meta-analysis review

Abstract

Lactose plays a crucial role in the growth performance of pigs at weaning because it is a palatable and easily digestible energy source that eases the transition from milk to solid feed. However, the digestibility of lactose declines after weaning due to a reduction in endogenous lactase activity in piglets. As a result, some lactose may be fermented in the gastrointestinal tract of pigs. Fermentation of lactose by intestinal microbiota yields lactic acid and volatile fatty acids, which may positively regulate the intestinal environment and microbiome, resulting in improved gastrointestinal health of weanling pigs. We hypothesize that the prebiotic effect of lactose may play a larger role in weanling pig nutrition as the global feed industry strives to reduce antibiotic usage and pharmacological levels of zinc oxide and supra-nutritional levels of copper. Evidence presented in this review indicates that high dietary lactose improves growth performance of piglets, as well as the growth of beneficial bacteria, particularly Lactobacillus, with the positive effects being more pronounced in the first 2 weeks after weaning. However, the risk of post-weaning diarrhea may increase as pigs get older due to reduced lactase activity, high dietary lactose concentrations, and larger feed intakes, all of which may lead to excessive lactose fermentation in the intestine of the pig. Therefore, dietary lactose levels exert different effects on growth performance and gastrointestinal physiological functions in different feeding phases of weanling pigs. However, no formal recommendation of lactose for weanling pigs has been reported. A meta-analysis approach was used to determine that diets fed to swine should include 20%, 15%, and 0 lactose from d 0–7, d 7–14, and d 14–35 post-weaning, respectively. However, sustainable swine production demands that economics must also be taken into account as lactose and lactose containing ingredients are expensive. Therefore, alternatives to lactose, so called “lactose equivalents” have also been studied in an effort to decrease feed cost while maintaining piglet performance with lower dietary lactose inclusions. In summary, the present review investigated dose-response effects of dietary lactose supplementation to exert positive responses and begin to elucidate its mechanisms of action in post-weaning pig diets. The results may help to replace some or all lactose in the diet of weanling pigs, while improving production economics given the high cost of lactose and availability in some swine production markets.

Reduced concentrations of limestone and monocalcium phosphate in diets without or with microbial phytase did not influence gastric pH, fecal score, or growth performance, but reduced bone ash and serum albumin in weanling pigs

“…The lack of differences in fecal score or diarrhea frequency between pigs fed diets with adequate or deficient concentrations of Ca and P reflects the results from stomach pH and further indicates that a reduction in dietary Ca and P failed to change gastric and intestinal conditions. It is possible that this observation is a result of the fact that phase 1 diets used in this experiment contained 15% lactose, which may have resulted in production of lactic acid from microbial fermentation ( Suiryanrayna and Ramana, 2015 ), and therefore, reduced stomach pH, as has been recently reported ( Zhao et al, 2021 ). If that was the case, lactic acid production could have reduced the possibility for a further reduction in gastric pH by reducing Ca and P in the diet.…”

Shen-Ling-Bai-Zhu-San (SL) and SL Derived-Polysaccharide (PL) Ameliorate the Severity of Diarrhea-Induced by High Lactose via Modification of Colonic Fermentation

“…Tran et al showed that a high concentration of dietary lactose (20%) increased the relative abundance of Lactobacilli and reduced E. coli in the large intestine of piglets ( Tran et al, 2012 ). Furthermore, lactose feeding increases the proportions of fecal Lactobacilli and Bifidobacteria in lactose maldigesters ( Szilagyi et al, 2010 ; Ito and Kimura, 1993 ), which are considered to be colonic microbes adapting to the presence of lactose in the colonic lumen ( Forsgård, 2019 ; Zhao et al, 2021 ). In our study, we found the similar results that included the relative abundance of Lactobacillus and Bifidobacterium being significantly increased in the HLD group compared to the control group.…”

Invited review: strategic adoption of antibiotic-free pork production: the importance of a holistic approach

“…Typically, 15 to 20% lactose is included in the phase 1 diet of pigs weaned at approximately 3 wk of age and fed for 7 d, followed by a phase 2 diet containing 10% to 15% lactose for the subsequent 7 to perhaps 14 d. There appeared to be almost no limit to the pig’s response to increasing levels of lactose during the first week after weaning. Interestingly, the presence of antibiotic growth promotants in the diet muted the lactose response ( Zhao et al, 2021 ). Beyond phase 2, lactose is rarely recommended, unless the feed is being directed to pigs with compromised health or performance, or are lighter in weight than normal.…”

“…Furthermore, researchers have investigated alternative carbohydrates with interesting results. Dextrose, sucrose, liquid lactose and molasses have all been proposed as full or partial replacements for dried lactose ( Dunmire et al, 2020 ; Zhao et al, 2021 ). Recently, Clouard et al (2018) reported that using maltodextrin in place of lactose in a liquid milk replacer improved cognitive performance 8 wk later and did not impact growth performance.…”