Vegetable proteins enhance the growth of milk-fed piglets, despite lower apparent ileal digestibility

This experiment compared the replacement of whey protein with isolated soy protein (ISP), or 2 levels of a hydrolyzed vegetable protein mixture (Lo HVPM and Hi HVPM, containing a partially hydrolyzed blend of soy, wheat, and other proteins) in liquid milk-replacer diets fed to neonatal pigs from 2 to 19 d of age. Piglets fed the vegetable protein diets weighed 20% more (8179 +/- 211 g, P < 0.05) at the end of the study than piglets fed the whey diet (6805 +/- 244 g). Growth rates were 35% higher for piglets fed the Hi HVPM diet than for piglets fed the whey diet. Similarly, intakes of the vegetable protein diets exceeded that for the whey diet (P < 0.05). Although the apparent ileal digestibilities of most amino acids were greater for the whey diet, digestible amino acid intakes (especially Arg, Phe, Met, and His) were greater in pigs fed the Hi HVPM and ISP diets (P < 0.01). Furthermore, carcasses of piglets fed the whey diet contained a higher percentage of fat and ash, whereas piglets fed the vegetable protein-containing diets accreted protein 42% faster (P < 0.01). Villus height and area and leucine aminopeptidase activity in the small intestine were greater in piglets fed the Lo HVPM diet than in those fed the ISP diet. Collectively, these data support the conclusion that some processed vegetable proteins may be good alternatives to whey protein in liquid diets formulated for neonatal pigs and that an appropriate balance of amino acids is more important than the source of protein per se.