Increasing productivity in goats grazing Mediterranean woodland and scrubland by supplementation of polyethylene glycol

A single daily oral dose of polyethylene glycol (PEG) - a tannin-binding ag ent - has been shown to substantially improve feed intake and efficiency of utilization by sheep and goats consuming tannin-rich forage. The aim of th is study was to quantify the effect of supplementing 10 g/day of PEG on the performance of does grazing on Mediterranean woodland and scrubland. The e xperiments were carried out in production systems based on Mamber goats rai sed only for the production of slaughter kids (Experiment 1), dual-purpose Mamber goats raised for slaughter kids and milk (Experiment 2) or Damascus x Anglo-Nubian goats raised mainly for milk (Experiment 3). in Member goats , PEG supplementation was associated with higher body weight (BW) gain duri ng pregnancy (p<0.01), higher kid birth-weight (p<0.05) and daily BW gain u ntil weaning (p<0.10 and p<0.05 in Experiments 1 and 2, respectively), and no difference in milk yield. In contrast, the response of Damascus x Anglo- Nubian goats to PEG was a 43% increase in milk yield (p<0.001) but no respo nse in kid weight at birth. These responses are consistent with previous fi ndings that show the resilience of Mamber goats to practices aimed at incre asing their milk production while these goats respond well to practices tha t improve the probability of successful reproduction in harsh environments. In contrast, Damascus x Anglo-Nubians respond to increased available nutri ents by increasing their milk production. Supplementation with PEG has the potential to improve the profitability of systems in which liberally supple mented and high-yielding dairy goats feed on Mediterranean browse. However, its contribution to production systems exploiting well adapted but low-yie lding local goats is limited. (C) 2000 Published by Elsevier Science B.V.