Analysis of milking characteristics in New Zealand dairy cows

Abstract

The objective of this study was to describe the variation in milking characteristics, and factors associated with these traits, in grazing dairy cows milked without premilking stimulation. Milk yield, duration, and average and maximum milk flow rate data were collected from 38 farms in New Zealand at 2 time points (spring and autumn) during the 2010 to 2011 season. Subsequently, a second data set, allowing the generation of daily milk flow profiles, was collected from 2 farms in the 2011 to 2012 season. Corresponding animal data, such as breed, date of birth, and ancestry information, were extracted from the New Zealand Dairy Industry Good Animal Database (New Zealand Animal Evaluation Ltd., Hamilton, New Zealand). Residual milking duration (deviation from the regression line of milk yield on milking duration) was calculated, allowing the identification of fast-milking cows independent of milk yield. Variance components for the milking characteristics traits were estimated using an animal linear mixed model. The average milk yield was 10 kg/milking and the average milking duration was 360 s. The average milk flow rate was 1.8 kg/min and maximum milk flow 3.3 kg/min, with 44% of milk flow curves being classified as bimodal. Primiparous animals exhibited different milk flow profiles, with a lower maximum flow, than multiparous animals, possibly due to differences in cisternal capacity. Residual milking duration was shortest (-10s) in mid-lactation (121-180 d) and was 13s longer for Jersey compared with Friesian cows; however, it was 19s shorter when adjusted for energy content. Residual milking duration had a negligible genetic correlation (-0.07) with milk yield, indicating that selection for cows with shorter residual milking duration should have a negligible effect on milk yield. A heritability of 0.27 indicated that residual milking duration could be valuable as part of a breeding program. Knowledge of the distribution of milking durations for a given milk yield allows farmers to choose appropriate cluster-on time when using a maximum milking time strategy to improve milking efficiency.

Changes in milking parameters with robotic milking

“…Lee and Choudhary (2006) reported a similar MS, at 2.3 kg min −1 , to the one reported in the present study, especially in herd A. Edwards et al (2014), based on summary statistics, showed that MY, MD and MS increased with age, which is also supported by the results of the present study. At the same time, a strong negative correlation between MS and MD is observed, which is supported by the results obtained by Lee and Choudhary (2006).…”

“…Castro et al (2012) found that in Spanish herds, the average number of cows per robot was about 52.7, which was significantly less than in the Polish herds studied. Castro et al (2012), Edwards et al (2014) and Løvendahl and Chagunda (2011) found that the mean MY from cows during milking by an AMS was about 10.70 kg, which is similar to the figure found in this present study. A higher mean MY was obtained by Hogeveen et al (2001), at 11.8 kg, and in Korean studies (Lee and Choudhary, 2006), where it was more than 14.10 kg.…”

“…A study by Klaas et al (2003) concluded that high-yielding cows receive a large proportion of concentrates during milking in the AMS, which induced them to go to the milking machine more frequently. Edwards et al (2014), based on least squares means of milking characteristics at each stage of lactation (periods of 60 d) in 1500 animals in 4 herds found that the highest MY, at 12.07 kg, was until the 60th day of lactation; after this, it then fell. Likewise, MD was the longest in the first stage of lactation, at 416 s, and the shortest, at 316 s, in the last (days 241-300 of lactation) stage of lactation, and a similar trend was observed in the present study.…”

“…As emphasised by numerous authors (Hogeveen et al, 2001;Pirlo et al, 2005;Edwards et al, 2014;Lee and Choudhary, 2006), it is important that animals have a positive experience at milking time and do not mind using the AMS. The milking robots currently used allow cows to freely chose the time of milking and to dynamically adjust the intermilking interval throughout lactation as well as throughout the day (Carlström et al, 2013).…”

“…In some countries, this trait has constituted one of selection criteria and has been incorporated into breeding programmes of dairy cattle. An AMS allows farmers to monitor milking speed, milking flow and milking duration, which offers opportunities to improve their levels and hence provides a greater potential for profitable dairy production (Gray et al, 2012;Edwards et al, 2014). The aim of the present study was to identify changes occurring during the milking of cows in various periods following the introduction of an AMS.…”