Use of Low Protein Diets for Weanling Pigs

The practice of using antimicrobial growth promoters (AGP) to manage incidences of post-weaning diarrhea in piglets is becoming increasingly untenable in many parts of the world, including North America. Thus, there is a concerted effort to develop alternative nutritional strategies to profitably raise pigs without AGP. To this end, utilization of a low-crude protein (LCP) diet fortified with crystalline amino acids (AA) has been suggested as an important piece in the overall strategy of raising weanling pigs without in-feed AGP. This is because dietary protein is an important risk factor for post-weaning diarrhea in piglets. Undigested dietary protein is subjected to bacterial fermentation in the large intestine, which produces metabolites with toxic effects and favours the proliferation of pathogenic bacteria. Thus, feeding a LCP diet to weanling pigs limit the amount of substrate entering the lower gut, which restricts the proliferation of pathogenic bacteria and the associated toxic metabolites that pre-dispose the weanling pig to diarrhea. Indeed, many studies have shown that feeding a LCP diet reduces the proliferation of pathogenic bacteria in the gut and favors those with potential gut health benefits. Also, a feeding LCP diet minimizes the attachment of enterotoxigenic E. colito the intestinal mucosa, which is an important step in its ability to cause disease. Existing evidence suggests that a LCP diet may be used in combination with other dietary interventions such as probiotics and fermentable fibre to further enhance gut health outcomes in piglets. A practical consideration for using a LCP diet for weanling pigs is that, reduction in dietary protein content invariably leads to deficiencies of essential AA beyond those that are typically limiting (i.e. Lys, Met, Thr and Trp) in high protein nursery pig diets, including Val and Ile. An alternative view is to accept the short-term loss in performance as a result of feeding a LCP diet as pigs might be able to “catch up” later on in life through compensatory growth. A minimum reduction of dietary protein by 4 percentage units coupled with supplementation of those AA that might become limiting is necessary to effectively utilize a LCP diet as part of the overall strategy to control piglet diarrhea.