Cattle transhumance to summer farms: milk yield, pasture management and biodiversity conservation

This study aimed to analyze the interactions between cattle husbandry, pastures management and arthropods biodiversity in the summer farms of Trento province (Italian Alps). Twenty-one summer farms used by dairy cattle were sampled during the summer 2012. Data collected were: utilized pasture surface (UPS, georeferenced on GIS), herd size and composition (breed and livestock categories), supplementary feeding (quantity and quality), milk yield and quality. In addition, in each pasture butterflies and grasshoppers were sampled and counted, and weed encroachment was estimated at the end of the summer season. Average UPS was 82.8 ha (SD=70.5), average elevation 1,687 m asl (SD=307) and average slope 16.7° (SD=4.6). The average herd size was 65 Livestock Units (LU) (SD=34), with a prevalence of Brown Swiss and Simmental breeds. All the farms with cows on milk used supplementary feeding, with an average of 4.0 kg of concentrates/cow per day (SD=1.2). The stocking rates varied widely from 0.4 to 2.1 LU/ha (average:1.1 LU/ha). The amount of supplementary feeding was positively correlated with milk yield; for both these variables no correlations were found with stocking rate, weed encroachment and insect biodiversity indexes. Pastures used only by heifers showed higher levels of weed encroachment than those used by dairy cows. Insect biodiversity indexes were weakly influenced by differences in average stocking rate and weed encroachment between pastures, but within pastures increased with increasing distance from the farms buildings. In conclusion, livestock productivity seems more supported by supplementary feeding than by pastures management and therefore cannot be directly related to pastures conservation, as indexed by weed encroachment, and to insect biodiversity.