Front face fluorescence spectroscopy: a rapid tool for determining the effect of replacing soybean meal with scotch bean in the ration on the quality of Sicilo-Sarde ewe’s milk during lactation period

The present study aimed to determine the effects of substitution of a high degradable protein source, namely, soybean meal, with scotch bean, a Tunisian local product, on ewe’s milk quality. Twelve 5-year-old lactating Sicilo-Sarde ewes (third lambing) were kept in environmentally controlled sheepfold and were divided into two homogenous weight matched groups (n = 6). Ewes were fed ad libitum with two iso-energetic diets (20% barley, 3% vitamin and mineral premix, and 77% soybean meal or scotch bean). Physico-chemical analyses and fluorescence spectra were performed on milk samples during lactation period. The replacement of soybean meal by scotch bean induced a significant decrease in fat content (7.85 vs. 6.75 g 100 g⁻¹) and a significant increase in lactose level (3.49 vs. 3.61 g 100 g⁻¹). The principal component analysis (PCA) applied separately to the fluorescence spectral data set showed some discrimination between milk samples according to the lactation period and diet compositions. Finally, common components and specific weights analysis (CCSWA) applied to the physico-chemical data and spectral data sets allowed an obvious discrimination of milks of ewes fed soybean meal from those fed scotch bean throughout the whole lactation period.