The impact of short-term incomplete milking on dairy cows in peak to mid-lactation

The evolutionary-based genetic predisposition of dairy cows for milk production has been further enhanced by genetic selection and modern breeding programs. Resulting high milk production requires considerable energy supply, leading to a high lactation-induced metabolic load. Despite the fact that a high production level is only possible in healthy dairy cows, the vast need for energy and nutrients can be a burden to the cow, and high-yielding cows are more susceptible to certain diseases. In fact, in later lactation stages, dairy cows remain vulnerable to metabolic stress, especially when challenged by stressors, such as heat stress or insufficient feed supply. In this context, incomplete milking (IM) may be used to temporarily reduce milk production and mitigate the metabolic load of individual dairy cows. <br> In order to establish IM as a potential management strategy in peak- to mid-lactation dairy cows, comprehensive knowledge of its effects and potential limitations is essential. Therefore, the main aim of this dissertation was to implement an IM protocol and to investigate and characterize the effects on the lactation-induced metabolic load and the animal welfare of clinical healthy dairy cows. The experimental design included incompletely milked (INCL; n = 23,93 ± 46 DIM) and completely milked (COMP; n = 23, 95 ± 49 DIM) multiparous dairy cows. For the INCL cows, IM was implemented using a software module, enabling earlier cluster removal after a predefined amount of milk (kg) has been collected, rather than based on the milk flow rate (kg/min). The IM protocol included a gradual reduction phase (first IM phase: 9% daily reduction to ~40% over 5.5 d), followed by 3 complete milkings, and a constant reduction phase (second IM phase: 40% reduction over 5.5 d). Concentrate allocation was based on the feed-to-yield system (depending on the milk yield). Blood samples were collected on d -9, -2, 6, 13, 20, 27 relative to the start of IM. The present study demonstrates that the IM protocol was successfully implemented and that the reduction in milk yield increased with the duration and intensity of IM. Consequently, INCL cows received less concentrate, reflecting lower energy requirements. The milk yield remained reduced shortly after IM but increased again with the resumption of continuous complete milking. The reduced milk yield affected the concentration of two metabolic indicators in serum: Free fatty acids decreased during both IM phases in INCL cows pointing to a lesser mobilization of body fat reserves, and insulin-like growth factor-1 concentrations were elevated during both phases, indicating a reduced lactation-induced metabolic load. At the same time, consistently good udder health and no evidence of impaired animal welfare were observed according to the evaluated indicators. <br> This dissertation provides initial insights into the application of an IM protocol and its effects on milk production, metabolic indicators, and animal welfare parameters in dairy cows during peak- to mid-lactation. In order to establish IM as a potential management strategy for these lactation stages, it should be further evaluated under actual stress conditions such as heat stress or insufficient feed supply in future studies.