Effects of two levels of concentrate supplementation on milk production of dairy goats browsing Mediterranean scrubland

Effects of two levels of supplementation (low (LC) 750 g/d and high (HC) 1500 g/d from d 30 post-partum) on 4 months lactation of 17 Anglo-Nubian × Damascus goats were evaluated. Goats browsed 5–6 h daily on typical Mediterranean scrubland, dominated by Common oak (Quercus calliprinos) and shrubs (mainly Pistacia lentiscus, Sarcopoterium spinosum and Calicotome villosa), young Cupressus sempervirens trees but few grasses. Goats were separated from their kids 2 d postpartum. HC feeding depressed net grazing time at pasture (75.1% and 59.2%, P<0.05). Although goats in the HC group produced more milk (2.23 vs. 1.81 kg/d, P< 0.05), no significant differences were found in total production of fat, protein and solids for cheese manufacturing (SCM, 188 and 158 g/d, P=0.22). On d 38, milk yield of LC goats was lower (2.31 vs. 2.84 kg/d, P<0.05), and protein (5.54% vs. 4.74%) and fat (3.69% vs. 3.40%) contents were higher, compared to HC (P<0.05). No differences in milk composition between groups were detected later. However, from d 85 of lactation onward, LC goats yielded 26% less kg milk, 24% less kg protein, 25% less kg fat and 24% less kg SCM (P<0.10) than HC; LC goats produced less lactose throughout the experiment, but not significantly at d 51 (P<0.05). Plasma NEFA concentration was higher in the LC than in the HC group at d 38, 85 and 113. Energy balance, as calculated from plasma NEFA values, was negative in the LC goats in all periods but positive in HC from d 85 onward. Since no significant difference in SCM throughout lactation was found, and the main effect of HC feeding was an extra production of lactose, decision to provide HC feeding may be economically justified only if the extra income from lactose (as part of whole milk, yoghurt, or whey-cheese) exceeds the cost of 750 g concentrates.