Use of an In Vitro Digestibility Approach to Assess Bombyx mori and Camelina sativa as Alternative Feed Ingredients for Poultry Species

The present study investigated the in vitro digestibility of diets for broiler chickens (Ross308) and broiler and laying Japanese quails (<i>Coturnix japonica</i>). The diets contained unconventional feedstuffs such as silkworm (<i>Bombyx mori</i>) meal (SWM) and meals obtained from different <i>Camelina sativa</i> lines (Pearl and Alan, characterized by reduced linoleic acid and glucosinolates content, respectively). An in vitro technique was tested in order to assess its potential for replacing in vivo studies. To test this, the digestive tracts of fifty broiler chickens and four hundred Japanese quails were sampled to extract digestive enzymes to be used for in vitro digestibility assessments, including dry matter digestibility (DMd), organic matter digestibility (OMd), and crude protein digestibility (CPd). Diets including SWM exhibited comparable digestibility values to those of Control diet for broiler chickens, highlighting its potential as a valuable protein source in poultry nutrition. The study also found strong correlations between DMd and OMd (<i>p</i> < 0.01), indicating a logical relationship in nutrient breakdown. A 5% or 10% inclusion of the two camelina lines in the diet for broiler quails did not significantly alter the digestibility parameters (<i>p</i> ≥ 0.05), whereas in laying quails, diets with a 15% inclusion level of camelina resulted in a significant difference in digestibility (<i>p</i> < 0.05). Specifically, oil diets provided the best outcomes, while the diet Pearl Spring 15 showed the lowest DMd, CPd, and OMd (<i>p</i> < 0.05). Overall, results from the present study indicate that the tested alternative feedstuffs (SWM and camelina) have a good potential for poultry feed formulations. In addition, the tested in vitro technique was shown to be more suitable to predict the digestibility of single feedstuffs (i.e., SWM) rather than complete diets, which is consistent with the existing literature. For this reason, this in vitro technique is not adequate to replace in vivo digestibility experiments.