title: The Norwegian Healthier Goats program--modeling lactation curves using a multilevel cubic spline regression model.
abstract: In 2001, the Norwegian Goat Health Service initiated the Healthier Goats program (HG), with the aim of eradicating caprine arthritis encephalitis, caseous lymphadenitis, and Johne's disease (caprine paratuberculosis) in Norwegian goat herds. The aim of the present study was to explore how control and eradication of the above-mentioned diseases by enrolling in HG affected milk yield by comparison with herds not enrolled in HG. Lactation curves were modeled using a multilevel cubic spline regression model where farm, goat, and lactation were included as random effect parameters. The data material contained 135,446 registrations of daily milk yield from 28,829 lactations in 43 herds. The multilevel cubic spline regression model was applied to 4 categories of data: enrolled early, control early, enrolled late, and control late. For enrolled herds, the early and late notations refer to the situation before and after enrolling in HG; for nonenrolled herds (controls), they refer to development over time, independent of HG. Total milk yield increased in the enrolled herds after eradication: the total milk yields in the fourth lactation were 634.2 and 873.3 kg in enrolled early and enrolled late herds, respectively, and 613.2 and 701.4 kg in the control early and control late herds, respectively. Day of peak yield differed between enrolled and control herds. The day of peak yield came on d 6 of lactation for the control early category for parities 2, 3, and 4, indicating an inability of the goats to further increase their milk yield from the initial level. For enrolled herds, on the other hand, peak yield came between d 49 and 56, indicating a gradual increase in milk yield after kidding. Our results indicate that enrollment in the HG disease eradication program improved the milk yield of dairy goats considerably, and that the multilevel cubic spline regression was a suitable model for exploring effects of disease control and eradication on milk yield.
authors.affiliation: TINE Norwegian Dairies, PO Box 58, NO-1431 Ås, Norway; Department of Production Animal Clinical Science, Norwegian School of Veterinary Science, PO Box 8146 Dep., NO-0033 Oslo, Norway. Electronic address: gunvor.elise.nagel_alne@nvh.no.
authors.forename: G E
authors.initials: GE
authors.lastname: Nagel-Alne
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, PO Box 8146 Dep., NO-0033 Oslo, Norway.
authors.forename: R
authors.initials: R
authors.lastname: Krontveit
authors.affiliation: Norwegian Institute of Public Health, Division of Epidemiology, Marcus Thranes gate 6, PO Box 4404, 0403 Oslo, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Bohlin
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, PO Box 8146 Dep., NO-0033 Oslo, Norway; Kontali Analyse AS, Industriveien 18, 6517 Kristiansund, Norway.
authors.forename: P S
authors.initials: PS
authors.lastname: Valle
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, PO Box 8146 Dep., NO-0033 Oslo, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Skjerve
authors.affiliation: TINE Norwegian Dairies, PO Box 58, NO-1431 Ås, Norway.
authors.forename: L S
authors.initials: LS
authors.lastname: Sølverød
mesh_terms: D000818:Animals; D003612:Dairying / Q000379:methods*; D005260:Female; D015511:Goat Diseases / Q000382:microbiology / Q000517:prevention & control* / Q000821:virology; D006041:Goats; D007774:Lactation; D016180:Lentivirus Infections / Q000517:prevention & control / Q000662:veterinary* / Q000821:virology; D008199:Lymphadenitis / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*; D008892:Milk; D008954:Models, Biological; D009664:Norway; D010283:Paratuberculosis / Q000382:microbiology / Q000517:prevention & control*; D012044:Regression Analysis
keywords: cubic splines; eradication program; goat; lactation curve