title: Individual responses of dairy cows to a 24-hour milking interval.
abstract: Some dairy farmers opt to omit one milking, either incidentally or weekly, without changing other milking times. This practice entails an extended milking interval of 24h (24h-MI), which is associated with a decrease in milk yield. This decrease varies among cows and could be partly due to factors such as stage of lactation and milk yield level. The aim of this study was to describe the average and individual responses in terms of loss and carryover effects of a 24h-MI on milk yield. The influence of factors such as parity, stage of lactation, and milk yield potential were investigated, together with response repeatability. Our trial used 292 Holstein-Friesian cows, and consisted of 3 successive periods: 1 wk of twice-daily milking (TDM) as a control, one 24h-MI, and then 13d of TDM. The number of observations per cow ranged from 1 to 9, with no more than three 24h-MI per lactation. The 24h-MI reduced milk yield by 23% (7.8 kg on average) and milk lactose content by 2.6g/kg on the 24h-MI day. Milk fat and protein content, and somatic cell score increased by 3.0 g/kg, 0.5 g/kg, and 0.4 units, respectively. No significant carryover effect was found of a 24h-MI on milk yield or milk composition 2 wk after resumption of TDM. Milk yield loss and recovery varied widely (coefficient of variation 62%), and the relationship between milk loss and milk recovery showed substantial variation (residual standard deviation 2.1 kg/d). Cows with a greater milk potential level lost more milk yield but recovered more milk, with no influence on recovery:loss ratio. Cows in early lactation recovered the lost milk yield faster. Repeatability of the responses to a 24h-MI was 44% for milk yield loss (kg/d), 57% for relative milk yield loss (%), 33% for milk yield recovery (kg/d), and 0% for milk recovery:loss ratio (%), suggesting a genetically determined ability to limit loss when one milking is omitted. To conclude, a 24h-MI caused higher milk yield losses than reported in previous studies. Stage of lactation, estimated potential milk yield level, and parity explained the cows' response to the 24h-MI, but did not account for all the individual variability.
authors.affiliation: INRA, UMR 1348 PEGASE, 65 Rue de Saint-Brieuc, F-35042 Rennes Cedex, France; AGROCAMPUS OUEST, UMR 1348 PEGASE, 65 Rue de Saint-Brieuc, F-35042 Rennes cedex, France; INRA, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31326 Castanet-Tolosan, France; Université de Toulouse, INP, ENSAT, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31326 Castanet-Tolosan, France; Université de Toulouse, INP, ENVT, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31076 Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Charton
authors.affiliation: INRA, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31326 Castanet-Tolosan, France; Université de Toulouse, INP, ENSAT, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31326 Castanet-Tolosan, France; Université de Toulouse, INP, ENVT, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31076 Toulouse, France.
authors.forename: H
authors.initials: H
authors.lastname: Larroque
authors.affiliation: INRA, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31326 Castanet-Tolosan, France; Université de Toulouse, INP, ENSAT, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31326 Castanet-Tolosan, France; Université de Toulouse, INP, ENVT, UMR 1388 GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), F-31076 Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Robert-Granié
authors.affiliation: INRA, UMR1213 Herbivores, F-63122 Saint-Genès-Champanelle, France; Clermont Université, VetAgro Sup, UMR1213 Herbivores, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: D
authors.initials: D
authors.lastname: Pomiès
authors.affiliation: Institut de l'Elevage, UMT 3G, Domaine de Vilvert, Jouy-en-Josas, France.
authors.forename: H
authors.initials: H
authors.lastname: Leclerc
authors.affiliation: INRA UMR 0791 Modélisation Systémique Appliquée aux Ruminants, 16 rue Claude-Bernard, Paris 75231, France; AgroParisTech UMR 0791 Modélisation Systémique Appliquée aux Ruminants, 16 rue Claude-Bernard, Paris 75231, France.
authors.forename: N C
authors.initials: NC
authors.lastname: Friggens
authors.affiliation: INRA, UMR 1348 PEGASE, 65 Rue de Saint-Brieuc, F-35042 Rennes Cedex, France; AGROCAMPUS OUEST, UMR 1348 PEGASE, 65 Rue de Saint-Brieuc, F-35042 Rennes cedex, France. Electronic address: Jocelyne.Flament@agrocampus-ouest.fr.
authors.forename: J
authors.initials: J
authors.lastname: Guinard-Flament
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying / Q000379:methods*; D005260:Female; D007774:Lactation / Q000502:physiology*; D007785:Lactose / Q000032:analysis; D008892:Milk / Q000737:chemistry; D010298:Parity; D011247:Pregnancy; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D007785:Lactose
keywords: 24-hour milking interval; dairy cow; milk loss and recovery; repeatability