title: Quality traits and modeling of coagulation, curd firming, and syneresis of sheep milk of Alpine breeds fed diets supplemented with rumen-protected conjugated fatty acid.
abstract: The aim of this study was to test the modeling of curd-firming (CF) measures and to compare the sheep milk of 3 Alpine breeds supplemented with or without rumen-protected conjugated linoleic acid (rpCLA). Twenty-four ewes of the Brogna, Foza, and Lamon breeds were allotted to 6 pens (2 pens/breed) and fed a diet composed of corn grain, corn silage, dried sugar beet pulp, soybean meal, wheat bran, wheat straw, and a vitamin-mineral mixture. The rpCLA supplement (12 g/d per ewe plus 4 g/d for each lamb older than 30 d) was mixed into the diet of 1 pen per sheep breed (3 pens/treatment) to provide an average of 0.945 and 0.915 g/d per ewe of the cis-9,trans-11 C18:2 and trans-10,cis-12 C18:2 conjugated linoleic acid isomers, respectively. The trial started at 38 ± 23 d after parturition, and individual morning milk samples were collected on d 16, 23, 37, 44, and 59 of the trial. Milk samples were analyzed for composition, and duplicate samples were assessed for milk coagulation properties (MCP). A total of 180 CF measures for each sample (1 every 15s) were recorded. Model parameters were the rennet coagulation time, the asymptotic potential CF, the CF instant rate constant, the syneresis instant rate constant, the maximum CF achieved within 45 min (CFmax), and the time at achievement of CFmax. The data were analyzed using a hierarchical model that considered the fixed effects of breed, diet, lamb birth, and initial days in milk, which were tested on individual ewe (random) variance; the fixed effect of sampling day, which was tested on the within-ewe sample (random) variance; and the fixed effect of instrument or cuvette position (only for MCP), which was tested on the residual (replicates within samples) variance. The local Alpine sheep breeds displayed similar milk compositions, traditional MCP, and CF modeling parameters. Supplementation with rpCLA triggered changes in milk composition and worsened MCP (e.g., delayed rennet coagulation time, slower CF instant rate constant, and a doubling of syneresis instant rate constant), but did not influence potential CF. Overall, our results indicate that rpCLA supplementation reduced the actual maximum CF (CFmax) but did not modify the interval between rennet addition and CFmax or time to CFmax.
authors.affiliation: Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Bittante
authors.affiliation: Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Pellattiero
authors.affiliation: Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Malchiodi
authors.affiliation: Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Cipolat-Gotet
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100 Sassari, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Pazzola
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100 Sassari, Italy.
authors.forename: G M
authors.initials: GM
authors.lastname: Vacca
authors.affiliation: Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Schiavon
authors.affiliation: Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy. Electronic address: alessio.cecchinato@unipd.it.
authors.forename: A
authors.initials: A
authors.lastname: Cecchinato
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001947:Breeding; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D005260:Female; D007774:Lactation; D044243:Linoleic Acids, Conjugated / Q000378:metabolism*; D008892:Milk / Q000737:chemistry*; D008954:Models, Biological; D011897:Random Allocation; D034561:Sheep, Domestic / Q000235:genetics / Q000378:metabolism*
chemical_list: D044243:Linoleic Acids, Conjugated
keywords: conjugated fatty acid; curd-firming modeling; milk coagulation property; ovine milk