Abstract
Alpine dairy farms are characterised by small-scale production units, which traditionally host various cattle breeds in different herd combinations. The aim of this study was to investigate the effect of the shift in herd structure on the variation of milk quality. To this purpose, bulk milk traits (gross composition, somatic cells, urea and fatty acid composition) of single- and multi-breed farms of South Tyrol (northern Italy) with either Brown Swiss (BS), Holstein Friesian (HF), Simmental (SI) or combinations of these breeds (BS + HF, BS + SI, HF + SI and BS + HF + SI) were considered. Bulk milk composition was predicted from spectra using mid-infrared spectroscopy. At least three bulk milk samples per month were available for all herds from January 2014 to December 2018. An ANOVA was carried out on milk traits accounting for the fixed effects of herd composition, month and year of sampling, and the interactions of herd composition with month and year of sampling; farm was included as random effect. Orthogonal contrasts were performed for single- vs multi-breed herds, specialised breeds vs dual-purpose breed, and multi-breed herds with SI vs multi-breed herds without SI. Overall, results showed that approximately two thirds of the farms in South Tyrol are single-breed herds and, according to herd size, only farms with more than 20 cows have changed herd structure over time, switching from multi- to single-breed herds. Farms with BS cows produced milk with higher fat, protein, casein and fatty acids contents than farms with SI and HF cows. Milk from single-breed SI herds was characterised by lowest somatic cell counts. Results demonstrated that BS farms were the best in terms of milk composition, and this supports the interest of using this breed in alpine dairy farming in both single- and multi-breed scenarios to improve cheese making properties and farmers’ profitability.