Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Milk yield and pasture nutrient availability associated with milking order in commercial dairy herds.

Monique Berkhout , Martin Auldist, Meaghan Douglas , Anna Thomson , Khageswor Giri, Joe Jacobs, M. M. Wright

Abstract

Context. On pasture-based dairy farms, herd behavioural dynamics result in a milking order that remains consistent over time. Previous research has demonstrated that cows that are consistently early in the milking order routinely access pasture of greater biomass and nutrient density than later-milked cows, since they access the paddock first. This effect likely explains why early cows commonly produce more milk than later cows. We hypothesised that in commercial dairy herds milk yield would decline as milking order progressed, and there would be a reduction in pasture mass and nutritive value before the last cows returned to the paddock. Aims. This study aimed to validate observations previously demonstrated under controlled experimental conditions, in commercial dairy herds in Gippsland, Victoria. Methods. This research was repeated across three commercial farms with four grazing sessions observed per farm. Cows were milked twice daily, with daily individual milk yields and milking times obtained. Pasture measurements were collected pre-grazing, hourly for the first 3 h of grazing after the morning milking (while cows progressively entered the paddock), and post-grazing after the cows exited the paddock. At each sampling, pasture mass was estimated using a calibrated rising plate meter, and pasture samples collected for analyses of nutritive characteristics. Key results. Milking order was consistent, and the last cows produced on average 4.7 L/cow.d less milk than the first cows. As grazing progressed, pasture mass, crude protein concentrations and metabolisable energy declined and fibre concentrations increased. Conclusions. This study demonstrated a decrease in pasture mass and nutrient density as grazing progressed. The earliest cows had access to more pasture of higher nutrient density and produced more milk than later-milked cows. Implications. This study validated that the milk yield of cows in commercial herds is influenced by milking order, which is likely mediated at least in part by the quantity and nutrient density on offer to earlier versus later-milked cows. Other factors may also influence milking order and milk yield, but these factors were not accounted for in this research. Future research should focus on mitigation strategies to negate this effect by improving nutrient intake of later-milked cows.

AN24285  Accepted 13 December 2024

© CSIRO 2024