Prospective cohort study of the relationship between milking machine liner slip, milking performance, and cow characteristics

We conducted a prospective cohort study to investigate the associations of machine milking liner slip with (1) milking performance and (2) cow characteristics. Parlor data including milk flow characteristics and data on the occurrence of milking machine liner slips from a 4,000-cow dairy with a thrice-daily milking schedule were obtained with electronic on-farm milk meters over a 2-mo period. We analyzed data from a total of 686,330 milking observations. A multivariable general linear mixed model revealed no association between liner slip and milking unit on time. Least squares means (95% confidence intervals, 95% CI) were 237 (235-238) s for milking observations with and without a liner slip. We observed statistically significant differences in average milk flow rate; however, these were biologically irrelevant. Least squares means were 3.40 (3.37-3.42) kg/min for a milking observation with and 3.42 (3.40-3.44) kg/min without a liner slip. A multivariable generalized linear mixed model showed an association between liner slip and cow characteristics. Compared with late-lactation cows, the odds ratios (OR, 95% CI) of occurrence of a liner slip were 2.03 (1.59-2.59) in early lactation cows and 1.26 (0.97-1.64) in cows from 101 to 200 days in milk. Presence of a nonlactating quarter increased the odds of liner slip occurrence [OR, 95% CI: 10.35 (8.02-13.35)]. Bimodal milking observations had higher odds of occurrence of a liner slip compared with milking observations with a unimodal milk flow curve [OR, 95% CI: 1.05 (1.005-1.09)]. A 1-kg increase in 2-min milk yield increased the odds of a liner slip [OR, 95% CI: 1.26 (1.25-1.28)]. We conclude that, in the study cohort presented herein, the negative effect of liner slips on milking performance can be diminished. The identified cow characteristics could offer unique opportunities to identify and manage cows at increased risk of liner slips.

Bimodal milk flow and overmilking in dairy cattle: risk factors and consequences

To maximise the return on capital invested in the milking parlour, the largest number of cows should be milked gently and completely in the shortest possible time. Bimodal milk flow and overmilking negatively influence the efficiency of the milk removal process and teat health. This observational study had the objective of investigating the prevalence of bimodal milk flow and overmilking, determining which individual and farm-related variables are associated with these occurrences, and determining the association of overmilking and bimodal milk flow with milk yield and with short- and long-term teat changes. Twenty-one farms were visited once during the study period, wherein the milking routine was timed, the teat condition was assessed, and dynamic evaluation of the milking vacuum was performed. A total of 606 vacuum graphic records were obtained, with an average of 29 ± 3 records per farm, in order to indirectly evaluate the milk flow and thus determine the occurrence of bimodal milking and overmilking time. The average percentage of bimodality per farm was 41.7%. The median overmilking time was 59 seconds, and on average, 78.3% of the cows in a herd were overmilked longer than 30 seconds. An association was found at cow level between the occurrence of bimodal milk flow and days in milk, the total stimulation time, parity, and the preparation lag time. The increase in the mean total stimulation time and the number of passes during preparation were associated with a decrease in the proportion of bimodality in the herd. Parity, reattachment of the milking unit and milking in manual mode were associated with an increase in overmilking time of an individual cow. The presence of a clogged air bleed hole in the claw and the reduction of the cluster removal milk flow threshold were associated with an increase in the herd's median overmilking time. The average milk flow decreased with the increase in overmilking time and with the occurrence of bimodal milk flow. An association was also found between the occurrence of bimodal milk flow and decreased milk yield. A mean of 78.4% of cows per farm had short-term teat changes in at least one teat, and 33.6% of evaluated cows per farm displayed at least one teat with hyperkeratosis. These results emphasise the association of bimodality and overmilking on milking efficiency and reinforce the importance of the milkers' actions and the functioning of the milking parlour for its prevention.

Vacuum Dynamics as an Alternative Method for Detection of Bimodal Milk Ejection in Dairy Cows

Simple Summary

We investigated the relationship between vacuum dynamics and milk flow curve characteristics using portable vacuum and milk flow recording devices, respectively, for the assessment of bimodal milk flow curves in dairy cows. For this purpose, we analyzed 241 vacuum and milk flow curve recordings that we collected concomitantly during eight milking center evaluations on five New York dairy farms. We found that vacuum dynamics could be a suitable measure to assess bimodal milk flow curves in dairy cows.

Abstract

The primary objective of our study was to assess the ability of a vacuum recorder to detect the presence of bimodal milk flow curves in dairy cows compared with a portable milk flow meter. In a cross-sectional study, 241 individual cow milking observations were analyzed. We simultaneously collected (1) individual cow vacuum events during milking using portable vacuum recorders, and (2) individual cow milk flow curves by attaching a portable milk flow meter to the same milking unit. Presence of bimodality was assessed with the vacuum recorder visually (BIM_VA) and with the gold standard method of a milk flow meter through automatic detection (BIM_LA). Kappa statistics revealed moderate agreement between BIM_VA and BIM_LA [κ, 95% confidence intervals (95% CI) = 0.59 (0.46–0.71)]. Diagnostic test statistics for BIM_VA for detection of bimodality indicated moderate performance for sensitivity [0.65 (0.52–0.76)] and positive predictive value [0.71 (0.58–0.82)] and high values for specificity [0.92 (0.87–0.95)] and negative predictive value [0.93 (0.84–0.93)]. We conclude that milking vacuum dynamics are a suitable measure to assess bimodal milk flow curves in dairy cows.