title: Lactose in blood plasma and the ability of dairy cows to tolerate once-daily milking in terms of milk loss and milk recovery.
abstract: This experiment described the variability among cows with the aim of studying the ability of dairy cows to tolerate once-daily milking (ODM) in terms of milk losses and milk recoveries observed when cows are switched from twice- to once-daily milking and then back to twice-daily milking (TDM). It also aimed to investigate whether or not lactose in blood plasma, which indicates the mammary epithelium permeability, is correlated with milk losses and recoveries and, consequently, a potential candidate assessor of dairy cow tolerance to ODM. The study used 86 crossbred dairy cows (Holstein × Normande) split into 5 groups over 2 yr. The trial consisted of 3 successive periods: a 1-wk control period of TDM, then 3 wk of ODM, followed by 2 wk of TDM. Blood samples were collected 1 to 1.5h before the morning milking and 5 to 6h after milking on d -3, 0, 1, 3, 7, 21, 23, and 28, where d 0 is the last d of the control period. Milk losses measured as kilograms per day were higher in cows with highest control-period milk yields (r=-0.66). When expressed in relative terms (%), milk losses were weakly correlated with the control-period milk yield (r=-0.22). When switched back to TDM, cows recovered only 47% of the milk lost. Milk recovery (kg/d) was weakly correlated with control milk yield (r=0.34) and not correlated with ODM milk yield. Milk recovery was correlated with milk yield losses: the higher the milk yield losses (kg/d or %), the higher the milk recovery (kg/d; r=-0.59 and -0.52, respectively). Rate of milk recovery expressed as the quantity of milk recovered per kilogram of milk lost, was not correlated with milk loss expressed as a percentage. This means that to be considered well-adapted to ODM scheduling, a cow must be well adapted to milk loss, and be well adapted to milk recovery. Blood plasma lactose concentration (log(10)-transformed data) was not correlated with milk production levels in either control, ODM, or back-to-TDM periods. It was poorly correlated with milk loss but was positively correlated with milk recovery (kg/d) and rate of milk recovery. We conclude that blood plasma lactose needs to be coupled with other indicators for evaluating dairy cow tolerance to ODM.
authors.affiliation: Agrocampus Ouest, UMR1080 Production du Lait, F-35042 Rennes cedex, France. Jocelyne.Flament@agrocampus-ouest.fr
authors.forename: J
authors.initials: J
authors.lastname: Guinard-Flament
authors.forename: Y
authors.initials: Y
authors.lastname: Gallard
authors.forename: H
authors.initials: H
authors.lastname: Larroque
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood; D002417:Cattle / Q000097:blood / Q000502:physiology*; D003612:Dairying / Q000379:methods*; D005260:Female; D007774:Lactation / Q000502:physiology*; D007785:Lactose / Q000097:blood*; D008892:Milk / Q000378:metabolism*; D013997:Time Factors
chemical_list: D015415:Biomarkers; D007785:Lactose