title: Response to dietary-induced energy restriction in dairy sheep divergently selected for resistance or susceptibility to mastitis.
abstract: Dairy ruminants experiencing a severe postpartum negative energy balance (NEB) are considered to be more susceptible to mastitis. Although the genetic variability of mastitis resistance is well established, the biological basis of the link between energy metabolism and resistance is mostly unknown. The aim of this study was to characterize the effect of NEB on metabolism and immune response according to the genetic background for mastitis resistance or susceptibility. Forty-eight ewes from high and low somatic cell score (SCS) genetic lines were allocated to 2 homogeneous subgroups 2 wk after lambing: one group (NEB) received an energy-restricted diet to cover 60% of their energy requirements, and the other group received a control (positive energy balance: PEB) diet. Both diets met the protein requirements. After 10 d on either the NEB or PEB diet, all ewes were injected with a Pam3CSK4/MDP solution in one half-udder to induce an inflammatory response. The ewes were monitored for milk production, somatic cell count (SCC), body weight (BW), body condition score (BCS), and blood metabolites. Differential milk cell counts were determined by flow cytometry. Plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), and triiodothyronine were determined. Energy restriction resulted in an increased fat:protein ratio in milk and decreased milk yield, BW, and BCS. The NEB ewes had significantly higher NEFA and BHB and lower plasma glucose concentrations than PEB ewes, reflecting a mobilization of body reserves and ketone body synthesis. High-SCS ewes had a higher SCS than low-SCS throughout the experiment, except after the inflammatory challenge, which resulted in similar SCS in all 4 groups. A noteworthy interaction between genetic background and diet was evidenced on metabolic parameters and BW. Indeed, high-SCS ewes subjected to NEB showed greater decrease in BW and increased NEFA and BHB concentrations compared with low-SCS ewes. Thus, NEB in early lactation led to extensive mobilization of body reserves and intense ketone body synthesis in mastitis-susceptible sheep. These results reinforce the hypothesis of a genetic association between mastitis susceptibility and energy metabolism and open the way to further studies on the biological basis for this association.
authors.affiliation: INRA, Unité Mixte de Recherche (UMR) 1388 Génétique, Physiologie et Systèmes d'Elevage, F-31326, Castanet-Tolosan, France; Université de Toulouse, École Nationale Vétérinaire de Toulouse (ENVT), INRA, UMR 1225, Interactions Hôtes-Agents Pathogènes (IHAP), F-31076 Toulouse, France.
authors.forename: J
authors.initials: J
authors.lastname: Bouvier-Muller
authors.affiliation: INRA, Unité Mixte de Recherche (UMR) 1388 Génétique, Physiologie et Systèmes d'Elevage, F-31326, Castanet-Tolosan, France.
authors.forename: C
authors.initials: C
authors.lastname: Allain
authors.affiliation: INRA, Unité Mixte de Recherche (UMR) 1388 Génétique, Physiologie et Systèmes d'Elevage, F-31326, Castanet-Tolosan, France.
authors.forename: F
authors.initials: F
authors.lastname: Enjalbert
authors.affiliation: Université de Toulouse, École Nationale Vétérinaire de Toulouse (ENVT), INRA, UMR 1225, Interactions Hôtes-Agents Pathogènes (IHAP), F-31076 Toulouse, France.
authors.forename: G
authors.initials: G
authors.lastname: Tabouret
authors.affiliation: INRA, Unité Expérimentale 0321 Domaine de La Fage, F-12250 Roquefort sur Soulzon, France.
authors.forename: D
authors.initials: D
authors.lastname: Portes
authors.affiliation: Université de Toulouse, École Nationale Vétérinaire de Toulouse (ENVT), INRA, UMR 1225, Interactions Hôtes-Agents Pathogènes (IHAP), F-31076 Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Caubet
authors.affiliation: Université de Toulouse, École Nationale Vétérinaire de Toulouse (ENVT), INRA, UMR 1225, Interactions Hôtes-Agents Pathogènes (IHAP), F-31076 Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Tasca
authors.affiliation: Université de Toulouse, École Nationale Vétérinaire de Toulouse (ENVT), INRA, UMR 1225, Interactions Hôtes-Agents Pathogènes (IHAP), F-31076 Toulouse, France.
authors.forename: G
authors.initials: G
authors.lastname: Foucras
authors.affiliation: INRA, Unité Mixte de Recherche (UMR) 1388 Génétique, Physiologie et Systèmes d'Elevage, F-31326, Castanet-Tolosan, France. Electronic address: rachel.rupp@toulouse.inra.fr.
authors.forename: R
authors.initials: R
authors.lastname: Rupp
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000097:blood; D000818:Animals; D001835:Body Weight; D004032:Diet / Q000662:veterinary; D004198:Disease Susceptibility / Q000662:veterinary; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D007328:Insulin / Q000097:blood; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism; D008413:Mastitis / Q000276:immunology / Q000662:veterinary*; D008892:Milk / Q000166:cytology / Q000378:metabolism*; D049590:Postpartum Period; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology*; D014284:Triiodothyronine / Q000097:blood
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014284:Triiodothyronine; D020155:3-Hydroxybutyric Acid
keywords: dairy ruminant; mastitis susceptibility; negative energy balance