Abstract/Summary

Interest in organic cows’ milk has increased, due to the perceived superior nutritional quality, and improved sustainability and animal welfare. However, there is a lack of simultaneous assess-ments of the influence of organic dairy practices and dietary and breed drivers on productivity, feed efficiency, health parameters and milk nutritional quality at herd level. This work aimed to assess the impact of organic vs conventional management and month on milk yield and basic composition, herd feed efficiency, health parameters and milk fatty acid (FA) composition. Milk samples (n=800) were collected monthly from the bulk tanks of 67 dairy farms (26 organic, 41 conventional) between January and December 2019. Data on breed and feeding practices were gathered via farm questionnaires. Samples were analysed for basic composition and FA profile using FTIRS and GC, respectively. Data were analysed by linear mixed model, repeated measures design and multivariate redundancy analysis (RDA).Conventional farms had higher yields (kg/cow per day) of milk (+7.3 kg), fat (+0.27 kg) and protein (+0.25 kg), and higher content (g/kg milk) of protein, casein, lactose and urea. Conventional farms produced more milk (+0.22 kg), fat (+8.6 g) and protein (+8.1 g) per kg offered dry matter (DM). Organic farms produced more milk per kg of offered non-grazing and concentrate DM offered respectively (+0.5 kg and +1.23 kg), fat (+20.1 g and +51 g) and protein (+17 g and +42 g). Organic milk had higher concentration of sat-urated fatty acid (SFA;+14 g/kg total FA), polyunsaturated fatty acid (PUFA;+2.4 g/kg total FA) and nutritionally beneficial FA alpha linolenic acid (ALNA; +14 g/kg total FA), rumenic acid (RA; +14 g/kg total FA), eicosapentaenoic acid (EPA; +14 g/kg total FA); while conventional milk had higher concentrations of monounsaturated FA (MUFA; +16 g/kg total FA). Although conventional farms were more efficient in converting the overall diet into milk, fat and protein; organic farms showed better efficiency in converting conserved forages and concentrates into milk, fat and protein, as a result of reduced concentrate feeding. Considering the relatively small differences in FA profiles between systems, increased pasture intakes can benefit farm sustainability without negatively impacting consumer nutrition and health.