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 season of the nutritional characteristics of an Alpine pasture with the objective of maintaining grazing sheep fed only on the available herbage.Four homogeneous areas of an Alpine pasture located in northeast Italy 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 pasture changed as the vegetative season advanced, with a progressive increase in grass species. The protein content decreased from 16.3 per cent 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 increased 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 wethers housed in single metabolic cages. The voluntary intake of herbage was 1151 g d-' at the end of June, decreasing significantly to values below the recommended requirement for maintenance in the subsequent periods of the study. No selectivity was observed for specific botanical 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 the recommended maintenance requirements for grazing only in the earlier period of pasture consumption. The late use of the pasture and the corresponding underfeeding of the animals would necessitate a feed supplementation to limit excessive loss of bodyweight. The conclusion is that the objective of maintaining grazing animals in mountain areas without any supplementation can be carried out exclusively by adopting an efficient grazing management able to provide good quality pasture throughout the vegetative season.

Spring cut Italian ryegrass was harvested at two different stages of maturity: lake vegetative (EARLY) and flowering (LATE). The wilted forage was round baled and then ensiled by wrapping in plastic film. EARLY harvest reduced dry matter (DM) yield significantly as compared to LATE (5.6 vs. 10.5 t ha"'; P < 0.01). However, forage quality both before and after ensiling was better for EARLY with higher crude protein (CP) and non-structural carbohydrates content and a lower amount of cell walls (NDF). Higher pH and the fermentation characteristics confirmed the poor quality of LATE silage, having higher content of butyrate, propionate and acid detergent insoluble nitrogen and a lower concentration of lactic acid.Dry matter intake of EARLY silage by sheep (average 65.0 + 7.3 kg LW) fed solely forage ad libitum was 37 % higher than LATE (1386 vs. 1011 gDM day"'; P < 0.05) due to its better palatability and digestibility. In vivo DM digestibility of EARLY silage was 76.1 % while it decreased to 58.2% for LATE silage. Estimated metabolizable energy content of EARLY silage (11.5 MJ kg-' DM) was 29% higher than LATE (8.9 MJ kg"' DM) resulting as similar to the reference value of a high quality perennial ryegrass silage. The forage conservation system of ensiled round bales is effective and recommended when spring cut Italian ryegrass is harvested at an early stage of maturity.

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