Epsilon Archive for Student Projects

Abstract

Cow–calf contact (CCC) systems, in which dairy cows nurse their calves while also being machine milked, are gaining increasing interest due to their potential welfare benefits. However, CCC systems are commonly associated with reduced machine milk yield, potentially related to altered milk ejection and milk partitioning between cow and calf. This study investigated daily machine milk yield and strip milk fat concentration as indicators of milkability and milk ejection in a whole-day, cow-driven CCC system.
Twenty CCC cows and 20 conventionally separated cows (separation ~ 12h after birth) were followed from early lactation until after calf separation. Daily machine milk yield was assessed during the contact period and strip milk fat concentration was assessed during the contact period, following the introduction of fenceline contact, and after complete separation. In addition, suckling characteristics such as the timespan between milking and the preceding suckling event, the duration of that suckling event as well as the number of suckling calves - were evaluated within CCC cows during the contact period.
During the contact period, CCC cows delivered 44% less machine milk than conventionally separated cows (−16.3 kg/day). Strip milk fat concentrations were 4.2 percentage units lower in CCC cows during the contact period (p < 0.001), with substantially greater between-cow variation compared with conventionally separated cows. Following calf separation, treatment differences in strip milk fat concentration disappeared.
Suckling characteristics changed markedly between the first and second sampling occasions during the contact period. Intervals between the last suckling event and subsequent milking increased from 4.6 (± 2.8) hours to 7.1 (± 3.6) hours, suckling duration increased from 8.1 (± 5.4) minutes to 12.5 (± 5.8), and the frequencies of allosuckling increased from 38 to 71% when calves were older.
Within CCC cows, longer intervals since the last suckling event were associated with higher strip milk fat concentrations (β = 0.0043 ± 0.0022 % units per minute, p = 0.053), whereas longer suckling durations were associated with lower strip milk fat concentrations (β = −0.002 ± 0.001 % units per minute, p = 0.058). These associations appeared more pronounced during the second sampling occasion prior to fenceline contact, suggesting that suckling-related effects on milk partitioning may become more established over time. Exploratory analyses further indicated that the occurrence of suckling between milkings, rather than the number of calves involved, was associated with lower strip milk fat concentrations.
Overall, the results suggest that CCC systems temporarily alter milk partitioning and milk ejection dynamics during periods of calf contact, but without clear carryover effects following calf separation.