Effects of Colostrum Source, Dose and Processing on In Vitro Rumen Fermentation in Weaned Lambs

Young dairy ruminants often have limited rumen fermentative capacity, which can impair adaptation to solid diet during weaning. This study evaluated the effects of ruminant colostrum supplementation to enhance in vitro rumen fermentation at weaning. A batch culture system using rumen inoculum from artificially reared lambs was incubated with ovine, bovine, or reconstituted bovine colostrum at 4 and 20 mL/L. Sequential colostrum fractionation was used to identify the main functional components. Whole colostrum supplementation at high doses reduced ruminal pH (p < 0.001) and increased gas production (+18%), ammonia-N (+41%) and butyrate proportion (+10%) across colostrum sources, indicating enhanced microbial fermentation. Responses were dose-dependent and consistent across colostrum sources. Lipid removal had minimal effects, whereas depletion of high-molecular-weight molecules, mostly IgG, markedly reduced gas production and protein degradation. Removal of medium-size proteins such as lactoferrin produced minor changes. Residual activity in low-molecular-weight fractions was retained likely associated with the presence of fermentable substrates and bioactive compounds. These findings indicate that colostrum may exhibit both nutritional and modulatory effects on in vitro rumen fermentation, with IgG identified as a key component. These findings support the preservation of IgG in colostrum-derived products to enhance rumen fermentation, although further in vivo validation is required to evaluate the effects in weaned ruminants.