Effect of the inclusion of fresh lemon pulp in the diet of lactating ewes on the properties of milk and cheese

Abstract

This study investigated the effects of fresh lemon pulp (FLP), as a natural antioxidant in the diet, on the intake of feed and the production of milk and cheese of Valle del Belice lactating ewes during the hot summer in Sicily. A total of 15 second-lambing ewes, kept individually in 3 × 3 m pens, were divided into 3 homogeneous groups fed with 3 diets in a 3 × 3 Latin square design, with 3 experimental phases of 21 days each. The diets were: mixed hay ad libitum plus 600 g/day of concentrate (FLP0); mixed hay ad libitum plus 400 g/day of concentrate and 1 kg/day of FLP (FLP1); and mixed hay ad libitum plus 200 g/day of concentrate and 2 kg/day of FLP (FLP2). Nine experimental Pecorino cheeses were manufactured with bulk milk collected at the end of each phase from each group. The ewes of each group showed the same dry matter (DM) intake (2 kg/day/head), but the FLP2 group received lower (P = 0.001) net energy for lactation (NEL) than other groups (2.13, 2.36, and 2.31 Mcal/day per head for FLP2, FLP0, and FLP1, respectively). The FLP constituted 9% and 16% of the total DM intake in the FLP1 and FLP2 groups, respectively. In general, the daily milk yield was low, reflecting the effect of the high environmental temperatures, and was lower (P = 0.001) in the FLP2 group than in the other groups (323, 355, and 369 g/day for FLP2, FLP1, and FLP0, respectively), probably due to the lower daily energy intake. Milk protein (P = 0.046) and casein (P = 0.033) percentages were higher in the FLP2 group than in the FLP1 group; the FLP-fed groups had higher levels of (P = 0.011) milk urea than the FLP0 group, due to a higher (P = 0.001) CP/NELratio in the ingested diet (96.4, 95.8, and 95.3 g/Mcal for FLP2, FLP1, and FLP0, respectively). The fatty acid composition of milk from FLP2-fed ewes was higher in vaccenic (10.6 vs. 7.96 mg/g fat; P = 0.031) and rumenic acids (6.21 vs. 5.30 mg/g fat; P = 0.048) than that in milk from FLP0 ewes. The characteristics of the cheeses were not influenced by the diet, with the exception of the total content of phenolic compounds (P = 0.011) and antioxidant activity (P = 0.051), both of which were higher in cheeses made with milk from FLP-fed ewes.