Weather, herbage quality and milk production in pastoral systems. 4. Effects on dairy cattle production

Prevailing weather conditions are one factor that influences herbage growth and quality, and therefore may have a substantial impact on animal production. The objective of the present study was to quantify the associations between weather, herbage quality and mineral concentration, and animal production. Daily weather data and weekly records of herbage quality and mineral concentration, as well as dairy cattle production, were available from a research farm and nearby weather station across the years 1995 to 2001, inclusive. Animal production variables of interest included individual cow milk production and composition, body condition score, and liveweight, as well as group herbage dry matter intake. Results indicate moderate relationships between some weather- and herbage-related variables and dairy cattle production variables, although most relationships appeared to be an artefact of temporal variation, as evidenced by weakening of correlations following adjustment for animal parity, stage of lactation, and week of the year at calving. Prior to adjustment for the confounding factors, the negative associations between milk yield and all temperature-related variables (r = -0.46 to -0.34) were most notable. Following adjustment for time of year, milk yield became positively associated with sunlight hours (r = 0.14). Negative relationships were demonstrated between temperature-related variables and milk protein concentration (r = -0.08), regardless of time of year. Milk protein concentration was positively associated with herbage metabolisable energy content (r = 0.06), water-soluble carbohydrate (r = 0.11), and organic matter digestibility (r = 0.06) concentrations, and negatively associated with ether extract (r = -0.07), acid detergent fibre (r = -0.06), and neutral detergent fibre (r = -0.05) concentrations. Weather, herbage quality and mineral concentration explained up to 22% more variation in dairy cattle production variables over and above farmlet and time of year, with a greater effect on dry matter intake than the other production parameters. © CSIRO 2009.