AVOIDANCE OF DEGRADATION OF ALPINE PASTURE THROUGH GRAZING MANAGEMENT- INVESTIGATIONS OF CHANGE IN VEGETATION NUTRITION CHARACTERISTICS ASA CONSEQUENCE OF SHEEP GRAZING AT DIFFERENT PERIODS OF THE GROWING-SEASON

The maintenance of animal husbandry in mountain areas can prevent the general degradation of the landscape due to the disuse of pastures and meadows. This study investigated the changes over the productive seas on of the nutritional characteristics of an Alpine pasture with the ob jective of maintaining grazing sheep fed only on the available herbage . Four homogeneous areas of an Alpine pasture located in northeast Ita ly were cut at the end of June, July, August and September, simulating different grazing periods by the animals. The herbage was sampled to estimate the botanical and chemical composition and fed to four Lamon breed wethers (76.5 kg average bodyweight) measuring voluntary intake, digestibility and energy value. The botanical composition of the past ure changed as the vegetative season advanced, with a progressive incr ease in grass species. The protein content decreased from 16.3 per cen t dry matter in the first grazing period, to 9.6, 9.9 and 7.9 per cent , respectively, in the following, while the neutral detergent fibre in creased from 62.1 per cent in the first period to 78.4, 77.7 and 79.4 per cent in July, August and September, respectively. The nutritional evaluation of the forage material was carried out using four Lamon wet hers housed in single metabolic cages. The voluntary intake of herbage was 1151 g d-1 at the end of June, decreasing significantly to values below the recommended requirement for maintenance in the subsequent p eriods of the study. No selectivity was observed for specific botanica l species. The in vivo digestibility of the herbage was lowered by the delay in the use of the pasture and the resulting energy intake met t he recommended maintenance requirements for grazing only in the earlie r period of pasture consumption. The late use of the pasture and the c orresponding underfeeding of the animals would necessitate a feed supp lementation to limit excessive loss of bodyweight. The conclusion is t hat the objective of maintaining grazing animals in mountain areas wit hout any supplementation can be carried out exclusively by adopting an efficient grazing management able to provide good quality pasture thr oughout the vegetative season.