Nutritive value of on-farm vetch-oat hays.: I.: Voluntary intake and nutrient digestibility

Forage hay from the common vetch-oat intercrop has the potential to meet the forage deficit and integrate crop and livestock production in Mediterranean cereal-sheep systems. Groups of three wethers (1-2 year-old) were randomly allocated to individual on-farm hays of a sample size of 12 with the aim of assessing variability of botanical and chemical fractions, digestibility of nutrients, and DM intake. Vetch content (g.kg(-1) DM) of hays (mean value = 557) ranged from 125 to 917. Mean contents (g.kg(-1) DM) of crude protein (CP), neutral detergent fibre (NDF) and acid detergent lignin (ADL) were 126, 486, and 45 respectively. Variations of chemical composition between bays, and especially those of CP and ADL were partially explained by vetch proportion. Voluntary intake (g DM.kg(-1).BW0.75) had a mean value of 64.2 and ranged from 49.0 to 78.9. Organic matter digestibility (mean value = 68.8%) ranged from 59.9 to 72.6%. The digestibility coefficient of nutrients and voluntary intake showed lower variability than that of chemical fractions, which, in turn, had a lower variability than that of botanical composition. The mean digestible energy (DE) concentration of the study sample was 11.72 MJ DE.kg(-1) DM. Low variability of this value (CV = 5.9%) indicated a compensatory effect between vetch and oat. Vetch proportion in hay gave a better explanation of the variation of CP intake (r(2) = 0.63) than of the variation of DE intake (r(2) = 0.37). On-farm hays with at least 50% of vetch contribution may be considered as a production objective. This criterion may contribute to standardisation and marketing operations at the farm level.