Effects of rainfall and temperature on the feeding value of barley straw in a semi-arid Mediterranean environment

Abstract

Annual variation in the feeding value of barley straw (Hordeum vulgare L. subsp. vulgare) is economically significant in the Mediterranean region. The relationship between the feeding value for sheep of several winter-planted barley cultivars and monthly meteorological data was analysed at Tel Hadya, northwest Syria (mean annual precipitation 330 mm) in 11 years. Indicators of feeding value included contents of neutral detergent fibre, acid detergent fibre and nitrogen (11 years), voluntary straw intake by sheep (10 years), voluntary digestible organic matter intake (9 years), in sacco dry matter loss and lignin content (8 years), in vitro digestibility (7 years) and in vitro gas production (6 years). Monthly meteorological data included total precipitation, mean minimum and mean maximum air temperatures. Conditions likely to decrease grain yield tended to increase the feeding value of straw. Low mean minimum temperature in February, low precipitation in January, February, March and April, and high mean maximum temperature in March, April and May increased one or more indicators of straw feeding value (by both bivariate and multiple regression, P < 0.05). Precipitation before January affected grain and straw yield but had little effect on the feeding value of straw. Genotype x year interactions had a meteorological component; the superior feeding value of the straw of locally-adapted cultivars v. exotic cultivars was only seen in years with cool or wet springs. This has implications for the genetic selection of crops with better straw feeding value. Models based on monthly precipitation and temperature, calibrated for locations in the Mediterranean region, can predict the nutritive value of straw and aid the planning of rations for small ruminants.