The impact of the installation of an automatic milking system on female fertility traits in Holstein-Friesian cows

Abstract

The objective of the study was to compare 305-day lactation milk yield in first and second lactations and selected fertility traits (number of services per conception, service period (days between first and last insemination), age at insemination and calving, gestation length, calving to conception period, calving interval period) in 2620 conventionally and automatically milked Polish Holstein-Friesian cows during the first two reproductive cycles. The study was conducted in 16 dairy herds that had been transitioned from a conventional milking system (CMS) to an automatic milking system (AMS) in the years 2010–2013. Sources of variation for the traits measured, including the milking system, were tested by multifactorial analysis of variance and the generalized linear model using a Poisson and negative binomial models and log link function using SAS. After switching from a conventional to an automatic milking system, milk yield increased by 1078.35 and 1182.24 kg in first- and second-lactation cows, respectively. In terms of fertility traits, the change in the milking system had a significant effect only on service period in the first reproductive cycle (CMS–22 days; AMS–15 days) and the number of inseminations needed for pregnancy (CMS–2.01; AMS–1.79) and on age at calving (CMS–1244; AMS–1226 days) in the second reproductive cycle. It must be emphasized that more favourable fertility traits (except for the calving to conception period in the second reproductive cycle) were observed in the group of automatically compared to conventionally milked cows. The interaction between herd and milking system was significant for most of the examined traits.