The Effect of the Dietary Inclusion of Crude Glycerin in Pre-Starter and Starter Diets for Piglets

SIMPLE SUMMARY: The surplus of crude glycerin and the rising cost of feedstuffs have encouraged the nutritional valorization of this by-product as an interesting alternative ingredient in pig feed. We tested the addition of 2.5 and 5% glycerin to pelleted piglet diets to assess the effects on growth performance and digestibility of weaned piglets and to determine the serum concentrations of hormones related to energy metabolism and feed intake. Crude glycerin was included as a replacement for sheep sweet whey and wheat in pre-starter and starter diets, respectively. Growth data and fecal samples were collected at the end of each feeding phase. At the end of the study, blood samples were taken to analyze insulin and ghrelin concentrations. Over the whole period, our results showed that the average daily gain and the feed conversion ratio were not affected negatively by the dietary glycerin inclusion. There were also no differences between dietary treatments in terms of blood metabolites measured while the digestibility coefficients of dry and organic matter improved as glycerin increased. Therefore, crude glycerin could be used as an energy source to replace sweet whey and wheat and be added to pre-starter and starter diets. ABSTRACT: The aim of this study was to evaluate the effect of the inclusion of crude glycerin in post-weaning diets for piglets on growth performance and digestibility. The study was carried out with a total of 360 piglets over a 39 day period. Animals were blocked by body weight (7.7 ± 0.86 kg) and allotted randomly to one of three dietary treatments containing 0, 2.5 or 5% glycerin (G0, G2.5 and G5, respectively). Considering the whole period, glycerin did not affect the average daily gain. However, the average daily feed intake (ADFI) and the feed conversion ratio (FCR) tended to decrease or decreased linearly as the amount of glycerin increased, respectively (p = 0.060 and p = 0.039). The apparent total tract digestibility (ATTD) of dry and organic matter (DM, OM) increased linearly with increasing glycerin in both periods (p ≤ 0.05). At the end of the study, there were no differences between treatments for any of the hormones measured. In conclusion, the FCR and digestibility of DM and OM were improved although the ADFI tended to be lower when glycerin was included at 5%. Consequently, crude glycerin could be used as an alternative ingredient to partially replace sweet whey and wheat in post-weaning diets.