Performance and health of dairy cows incompletely milked during the first five days in milk

During the transition period in dairy cows, energy demands for milk production are very high, while energy intake is low, leading to a physiologically unavoidable negative energy balance. Physiological imbalance or dysfunction appears to be one of the main factors leading to increased risk for transition diseases, and together, these problems have a great impact on subsequent reproductive performances and culling. This leads to the urgent need for alternative management strategies to help dairy cattle to cope with the intensive systems in which they are raised. Although there has been great improvements in managing the source of energy for the cow, little work has been done in controlling energy expenses to improve energy balance. An incomplete milking in early lactation could help limiting negative energy balance in dairy cattle. The objective of this project was to measure, in a context of commercial dairy farms, the impact of an incomplete milking (without altering the milk frequency) during the first five days in milk (DIM), on performance and health. Specifically, the aims were to quantify its impact on: culling and milk production; on incidence of infectious diseases; on reproductive performance; and on udder sensitivity. A randomized controlled trial was conducted on multiparous cows from a convenient sample of 13 commercial dairy farms. In each herd, all multiparous cows (n = 878) calving between December 2013 and March 2015 were randomly allocated at the time of dry off to a treatment or a control group using a random number generator. Cows in the treatment group were milked incompletely during the first five DIM, with a maximum of 10, 10, 10, 12, and 14 L/d collected on DIM one, two, three, four and five, respectively. Cows in the control group were milked conventionally. Culling hazard and milk yield did not differ among treatment groups. When investigating differences in energy corrected milk yield per week throughout the lactation, incompletely milked cows produced as much as conventionally milked cows during most weeks. Incomplete milking did not affect the odds of new intramammary infection from 11 to 18 DIM, the odds of reproductive tract disease at 35 DIM, or clinical mastitis incidence in the first 90 DIM. The odds of eliminating an existing intramammary infection from 11 to 18 DIM for incompletely milked cows were 2.9 (95% confidence interval: 1.4, 6.0) times those of conventionally milked cows. The incomplete milking protocol had no effect on postpartum luteal activity and it had a positive impact on pregnancy hazard in second parity cows from herds with voluntary waiting period lower than 55 days (180/775 cows). The hazards of pregnancy (95% confidence interval) in incompletely milked cows were 576.3 (240.0, 1383.7), 36.9 (18.9, 72.1), 6.8 (3.3, 13.8), 2.5 (1.0, 5.9), and 0.13 (0.07, 0.26) times that of conventionally milked cows at 1-21, 22-43, 44-65, 66-87 and >87 d after voluntary waiting period, respectively in second parity cows from herds with voluntary waiting period lower than 55 days. The pressure algometer was validated for measuring changes in udder sensitivity due to udder distension. The instrument was shown to be only moderately repeatable for quantifying mechanical nociceptive threshold on the udder and was influenced by extraneous covariates, therefore its use should be considered cautiously or it should be further developed. Consequently, to assess potential increased udder pain due to incomplete milking, we used the resting behavior data of incompletely and conventionally milked animals. There was no effect of incomplete milking on lying time. However, the effect of incomplete milking on frequency of lying bouts and on mean lying bout duration varied by parity level, suggesting that an incomplete milking may be slightly problematic for second parity cows and, possibly, slightly beneficial for older cows.

Keyphrases: Nociception, Dairy cattle, Incomplete milking, Culling, Milk production, Mastitis, Reproductive tract disease, Luteal activity, Pregnancy, Algometer, Resting behavior, Accelerometer