Composition and quality of milk and cheese from sheep grazing on dry pasture: effects of feeding supplementation

Introduction: The increasing summer drought stress linked to climate change represents a threat to livestock rearing and biodiversity conservation [1]. This work evaluates the influence of feeding supplementation on sheep dairy products quality, adopted in order to achieve an environmental and economic sustainable management of grassland productive ecosystems. Methods: 50 lactating adult female sheep were divided in 2 groups of 25: a control group (CG) fed with fresh hay and an experimental group (EG) fed with fresh hay supplemented with 600g/day/head of barley and corn (1:1). During one month we compared the yield and chemical composition of the milk samples, the volatile and sensorial profiles of their cheese. Levels of retinol and α-tocopherol were also studied. Results: Daily milk production showed a less pronounced decrease in EG than in CG (P two tail test 0.0368) but the chemical composition (fat content, lactose and protein) did not change significantly. At the end of the study, the concentrations of retinol and α-tocopherol in milk and cheese from EG were higher than CG (p<0.05). Moreover, supplementary feeding had a clearly positive effect on the fatty acid composition of the sheep milk. Indeed, on most of the sampling days, the EG milk showed a lower total % of saturated fatty acids and a higher % of polyunsaturated fatty acids due to the increase of linolenic acid. The volatile profile of the EG cheese presented an increment of esters and a reduction of carboxylic acids while it was the opposite for CG cheese. Carboxylic acids are associated with an unpleasant and rancid note while esters have a positive odor profile [2]. Conclusions: This study confirmed that expected worsening of pasture features could have deleterious effects on the chemical characteristics of sheep milk products. The food supplementation proved to be an approach to maintain and improve dairy product quality and could be taken into consideration in planning how farming systems should adapt to the increased heat and aridity associated with climate change. References 1. Giorgi, F., & Lionello, P., Global and Planetary Change, 63, 90-104 (2008). 2. Rodriguez-Campos, J., Escalona-Buend, H. B., Orozco-Avila, I., Lugo-Cervantes, E., & Jaramillo-Flores, E., Food Research International, 44, 250–258 (2011