Response profiles of dairy cows to a single 24-h milking interval in relation with milk proteolysis, udder expansion and immune traits.

An extended milking interval of 24 h (24-h milking interval (24h-MI)) constitutes the acute phase of cow adaptation to once-daily milking (ODM). A recent trial including 724 24h-MI challenges demonstrated that milk yield responses to this acute phase of ODM are highly variable (from+22% to -52% of milk yield when switching to the 24h-MI, mean=-25.3%) and that factors such as stage of lactation parity and milk yield level influenced cows' responses but did not account for all individual variability. Additional traits related to physiological, immune and behavioural adaptation were measured on a subset (96 observations) of this data set. This study aimed to determine (1) the relationship of these traits with cows' milk yield responses, (2) their ability - combined with previously identified traits - to help predict milk yield responses to 24h-MI (adaptive profiles). The 24h-MI challenge consisted of three successive periods: one control week of twice-daily milking (cTDM), one single day of 24h-MI and then 13 days of TDM (pTDM). Milk yield responses to the 24h-MI (corrected for effects of stage of lactation, parity, milk yield level and milk yield) were related to physiological traits measured during cTDM (milk flow rate, presence or absence of interleukin-8) and to their changes during the 24h-MI (absolute increase in milk flow rate and relative udder distension). Analysis of associations between milk yield responses, stage of lactation, parity, milk yield level, proteolysis, udder expansion and immune traits found three adaptive cow profile clusters. Cows in cluster 1 had a less compliant udder than cows in cluster 2, and they lost more milk during the 24h-MI than cluster-2 and cluster-3 cows. After resuming twice daily-milking (TDM), cluster-2 cows fully recovered the milk they had lost during the 24h-MI. On the opposite, cluster-3 cows did not recover the milk they lost, likely due to udder inflammation during cTDM, as suggested by elevated concentrations of interleukin-8 in their milk. These results combining new traits with stage of lactation, parity and milk yield level constitute a first step towards predicting individual cow responses to a 24h-MI.

Treatment of naturally occurring bovine respiratory disease in juvenile calves with a single administration of a florfenicol plus flunixin meglumine formulation.

The efficacy and safety of a florfenicol plus flunixin meglumine formulation in the treatment of respiratory disease was evaluated in calves less than six weeks of age, compared with a positive control group treated with a well-established florfenicol formulation. A total of 210 calves, selected from nine sites in Belgium, France and Spain, showing severe signs of respiratory disease, were randomly assigned to treatment with either florfenicol plus flunixin meglumine (Resflor; MSD Animal Health) or florfenicol (Nuflor; MSD Animal Health), both administered subcutaneously once. Animals were clinically observed daily for 10 days following treatment initiation. The predominant respiratory pathogens were Pasteurella multocida, Mycoplasma bovis, Mannheimia haemolytica and Histophilus somni. All isolates were subject to in vitro sensitivity testing and found susceptible to florfenicol. In both groups, rectal temperature dropped and clinical index (depression and respiratory signs) significantly improved after treatment. Specifically, for the change in rectal temperature from pretreatment to six hours post-treatment, the florfenicol-flunixin formulation was found significantly superior to florfenicol. Moreover, the florfenicol-flunixin formulation alleviated the clinical signs of disease more rapidly, and was demonstrated to be non-inferior to florfenicol on days 4 and 10. The use of the product combining florfenicol and flunixin in calves is safe and efficacious in the treatment of outbreaks of bovine respiratory disease.