Grazing season and forage type influence goat milk composition and rennet coagulation properties.
Two different types of pasture (cultivated and rangeland) and 2 different hay qualities (high and low quality) were examined for their effects on goat milk composition and rennet coagulation properties. Furthermore, the effect of dietary treatments in both the early and late grazing season was studied. As lactation stage is known to influence milk composition, the goats in the early and late grazing season were in the same lactation stage at the start of the experiment. The milk composition was influenced both by dietary treatment and season. Milk from goats on pasture was superior to those on hay by containing a higher content of protein and casein, and the goats on cultivated pasture had the highest milk yield. Casein composition was significantly influenced by forage treatment. Goats grazing on cultivated pasture had higher contents of αs1-casein and also of κ-casein compared with the other treatments, whereas goats grazing on rangeland had the highest content of β-casein. Factors such as milk yield, casein micelle size, αs2-casein, and calcium content were reduced in late compared with early season. More favorable rennet coagulation properties were achieved in milk from the early grazing season, with shorter firming time and higher curd firmness compared with milk from the late grazing season, but the firming time and curd firmness were not prominently influenced by forage treatment. The content of αs2-casein and calcium in the milk affected the firming time and the curd firmness positively. The influence of season and forage treatment on especially milk yield, casein content, and rennet coagulation properties is of economic importance for both the dairy industry and goat milk farmers.
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO Box 5003, NO-1432 Ås, Norway. Electronic address: raaboe@nmbu.no.
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Inglingstad
Norwegian Institute for Agricultural and Environmental Research (Bioforsk), Organic Food and Farming Division, Gunnars veg 6, NO-6630 Tingvoll, Norway.
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Steinshamn
Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Box 5003, NO-1432 Ås, Norway.
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Dagnachew
Department of Agricultural and Food Sciences (DISPA), University of Catania, via Valdisavoia 5, 95123 Catania, Italy.
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Valenti
Department of Agricultural and Food Sciences (DISPA), University of Catania, via Valdisavoia 5, 95123 Catania, Italy.
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Criscione
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO Box 5003, NO-1432 Ås, Norway.
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Rukke
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO Box 5003, NO-1432 Ås, Norway.
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Devold
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO Box 5003, NO-1432 Ås, Norway.
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Skeie
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO Box 5003, NO-1432 Ås, Norway.
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Vegarud
D000818:Animals; D002118:Calcium / Q000032:analysis; D002364:Caseins / Q000032:analysis; D012085:Chymosin / Q000737:chemistry*; D004032:Diet / Q000662:veterinary*; D005260:Female; D006041:Goats; D006863:Hydrogen-Ion Concentration; D007774:Lactation; D008274:Magnesium / Q000032:analysis; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis; D015999:Multivariate Analysis; D009584:Nitrogen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D011188:Potassium / Q000032:analysis; D012621:Seasons
D002364:Caseins; D008894:Milk Proteins; D010758:Phosphorus; C025350:rennet; D012085:Chymosin; D008274:Magnesium; D009584:Nitrogen; D011188:Potassium; D002118:Calcium
goat milk; individual casein composition; milk rennet coagulation properties; pasture