Optimizing lactation length for dairy cows to improve health and performance

Project: PhD

Project Details

Description

Modern dairy cows are managed to have a typical one year lactation cycle, with a lactation length of 305 d and a dry period (DP) length of 60 d, which is considered to result in the greatest economic output. Within such a lactation period, cows have a 40-60 d voluntary waiting period (VWP) from calving until the first insemination to allow them to recover from calving and start of the lactation. However, it can be questioned whether one year is the ideal length of a lactation cycle for modern dairy cows. Nowadays, high milk yield at dry-off has become a challenge to udder health and cow welfare. Also, a yearly calving event is associated with a yearly peak in risk for disease related with both the calving process and the start of a new lactation. The start of a new lactation, with a high milk production and a limited dry matter intake is accompanied by a negative energy balance (NEB). Altered metabolic and inflammatory status play a role in the relationship between NEB and an increased risk for diseases in early lactation. Shortening and omitting the DP can reduce the NEB in early lactation through a reduced milk production with similar feed intake, but increase the risk of fattening in the subsequent lactation. Adjusting the dietary energy level to correct for lower milk production in cows without a DP was reported to result in less body weight gain and fewer days open compared with cows fed a standard energy level. However, the underlying relationships between metabolic changes and fertility remain to be elucidated. Extending the VWP is another strategy hypothesized to improve fertility, because at the delayed insemination moment milk production is lower and energy balance is better than earlier in lactation. It is unclear how extending the VWP would affect udder health of cows, as udder health might be negatively affected by longer lactations, but positively affected by a lower milk yield at dry-off. Both strategies, shortening the DP and extending the VWP, are expected to improve cow health, because they reduce the NEB in early lactation (after no or a short DP) or the frequency calving events (with extended VWP). The aims of this thesis were 1) to evaluate relationships between inflammation biomarkers, metabolic status and clinical health problems in early lactation, 2) to evaluate effects of omitting the DP in cows fed 2 different dietary energy levels in early lactation on fertility, 3) to evaluate consequences of extending the VWP on fertility of dairy cows, and 4) to evaluate effects of extending VWP period on udder health of dairy cows.
StatusFinished
Effective start/end date1/03/1812/10/22

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