title: Milk fatty acids as possible biomarkers to early diagnose elevated concentrations of blood plasma nonesterified fatty acids in dairy cows.
abstract: Most cows encounter a state of negative energy balance during the periparturient period, which may lead to metabolic disorders and impaired fertility. The aim of this study was to assess the potential of milk fatty acids as diagnostic tools of detrimental levels of blood plasma nonesterified fatty acids (NEFA), defined as NEFA concentrations beyond 0.6 mmol/L, in a data set of 92 early lactating cows fed a glucogenic or lipogenic diet and subjected to 0-, 30-, or 60-d dry period before parturition. Milk was collected in wk 2, 3, 4, and 8 (n = 368) and blood was sampled weekly from wk 2 to 8 after parturition. Milk was analyzed for milk fatty acids and blood plasma for NEFA. Data were classified as "at risk of detrimental blood plasma NEFA" (NEFA ≥ 0.6 mmol/L) and "not at risk of detrimental blood plasma NEFA" (NEFA <0.6 mmol/L). Concentrations of 45 milk fatty acids and milk fat C18:1 cis-9-to-C15:0 ratio were subjected to a discriminant analysis. Milk fat C18:1 cis-9 revealed the most discriminating variable to identify detrimental blood plasma NEFA. A false positive rate of 10% allowed us to diagnose 46% of the detrimental blood plasma NEFA cases based on a milk fat C18:1 cis-9 concentration of at least 230 g/kg of milk fatty acids. Additionally, it was assessed whether the milk fat C18:1 cis-9 concentrations of wk 2 could be used as an early warning for detrimental blood plasma NEFA risk during the first 8 wk in lactation. Cows with at least 240 g/kg of C18:1 cis-9 in milk fat had about 50% chance to encounter blood plasma NEFA values of 0.6 mmol/L or more during the first 8 wk of lactation, with a false positive rate of 11.4%. Profit simulations were based on costs for cows suffering from detrimental blood plasma NEFA, and costs for preventive treatment based on daily dosing of propylene glycol for 3 wk. Given the relatively low incidence rate (8% of all observations), continuous monitoring of milk fatty acids during the first 8 wk of lactation to diagnose detrimental blood plasma NEFA does not seem cost effective. On the contrary, milk fat C18:1 cis-9 of the second lactation week could be an early warning of cows at risk of detrimental blood NEFA. In this case, selective treatment may be cost effective.
authors.affiliation: Laboratory for Animal Nutrition and Animal Product Quality, Ghent University, Proefhoevestraat 10, 9090 Melle, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Jorjong
authors.affiliation: Adaptation Physiology Group, Department of Animal Science, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors.forename: A T M
authors.initials: AT
authors.lastname: van Knegsel
authors.affiliation: KERMIT, Department of Mathematical Modelling, Statistics and Bioinformatics, Ghent University, Coupure links 653, 9000 Ghent, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Verwaeren
authors.affiliation: Universitat Politècnica de València, Camino de Vera, 46022 Valencia, Spain.
authors.forename: M Val
authors.initials: MV
authors.lastname: Lahoz
authors.affiliation: Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bremgartenstrasse 109ª, CH-3001 Bern, Switzerland.
authors.forename: R M
authors.initials: RM
authors.lastname: Bruckmaier
authors.affiliation: KERMIT, Department of Mathematical Modelling, Statistics and Bioinformatics, Ghent University, Coupure links 653, 9000 Ghent, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: De Baets
authors.affiliation: Adaptation Physiology Group, Department of Animal Science, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: Kemp
authors.affiliation: Laboratory for Animal Nutrition and Animal Product Quality, Ghent University, Proefhoevestraat 10, 9090 Melle, Belgium. Electronic address: veerle.fievez@ugent.be.
authors.forename: V
authors.initials: V
authors.lastname: Fievez
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002417:Cattle / Q000097:blood / Q000378:metabolism*; D016002:Discriminant Analysis; D042241:Early Diagnosis; D005227:Fatty Acids / Q000032:analysis*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005260:Female; D005410:Flame Ionization / Q000662:veterinary; D008892:Milk / Q000737:chemistry*; D049590:Postpartum Period; D011897:Random Allocation
chemical_list: D015415:Biomarkers; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified
keywords: biomarker; milk fatty acid; nonesterified fatty acid