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Forage level influences milk fat production in dairy sheep

Tim Lundeen



The milk fat content and fatty acid profile in sheep milk can vary considerably but can be manipulated through diet, according to an international team of researchers writing in an upcoming issue of Livestock Science.


Lead author Juan C. Angeles-Hernandez with the Universidad Autónoma del Estado de Hidalgo in Mexico, along with colleagues from the University of California-Davis, Iowa State University, the University of New England in Australia and the Universidad Autónoma del Estado de México, conducted a meta-analysis to determine the effect of forage concentration ratio and dietary fat supplementation on milk yield production, fat, protein, lactose and conjugated linoleic acid (CLA) content in dairy sheep.


According to Angeles-Hernandez et al., compared to sheep fed diets with a concentrate content greater than 40% dry matter, sheep fed high-forage diets (forage content greater than 40% dry matter) had 0.087 liters per day lower milk yield (P = 0.001) and milk lactose content of 0.065 g/100 g (P = 0.02).


However, they said fat content and CLA concentrations were greater in dairy sheep fed high-forage diets (0.32 g/100 g and 2.28 mg/g, respectively). Angeles-Hernandez et al. reported that adding fat to sheep diets had a positive effect on fat (0.22 g/100 g; P = 0.005) and CLA concentrations (0.78 mg/g; P = 0.001) in milk, but protein concentration was reduced by -0.20 g/100 g of milk (P < 0.001).


Angeles-Hernandez et al. concluded that low-concentrate rations induce a significant increase in fat and CLA content in sheep milk, likely associated with alterations in rumen function, including biohydrogenation processes governing fatty acid saturation level and CLA synthesis promoted by concentrate-based rations.


They added that including fat in the ration of dairy sheep produces an increase in milk yield and fat and CLA contents, which may improve the milk quality in terms of human health.


Other researchers involved in the study include Rodolfo Vieyra Alberto with the Universidad Autónoma del Estado de Hidalgo, Ermias Kebreab with the University of California-Davis, Jayasooriya A.D. Ranga Nirosha Appuhamy with Iowa State University, Holland C. Dougherty with the University of New England and the New South Wales Department of Primary Industries and Octavio Castelan-Ortega and Manuel Gonzalez-Ronquillo with the Universidad Autónoma del Estado de México.


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