Intensification strategies for temperate hot-summer grazing dairy systems in South America: Effects of feeding strategy and cow genotype

摘要

Pasture-based dairy systems present the opportunityto increase productivity per hectare through increasingstocking rate and forage utilization. However, inthe temperate hot-summer region of South America,different productive strategies are being adopted byfarmers. The aim of this study was to quantify theeffect of feeding strategy (FS) and cow genotype (G)on individual animal and whole-farm biophysical performance.A design with 2 × 2 levels of intensificationaiming to increase home-grown forage utilization andmilk output per hectare was evaluated. The experimentwas a randomized complete block design with a2 × 2 factorial arrangement of treatments, combining2 feeding strategies with varying proportions of grazingin the annual feeding budget [grass fixed (GFix) andgrass maximum (GMax)] and 2 Holstein Friesian cowgenotypes [New Zealand (NZHF) or North AmericanHolstein Friesian (NAHF)]. The effects of FS, G, andtheir interaction were analyzed using mixed models.New Zealand Holstein Friesian cows presented lowerindividual milk yield and higher milk component concentrations,maintained higher average body conditionscore, and increased body weight (BW) throughoutthe experiment, while presenting a better reproductiveperformance compared with the NAHF cows. Althoughall farmlets were planned at the same stocking rateon a per kilogram of BW basis, the current stockingrate changed as a result of animal performance andgrass utilization resulting in NZHF cows achievinggreater BW per hectare. The superior stocking rate ledto greater milk solids production and feed consumptionper hectare for the systems with NZHF cows. TheGFix feeding strategy resulted in greater total homegrownforage harvest and conserved forage surplus thanGMax. Overall, it was feasible to increase stocking rateand increase milk production per hectare from homegrownforage with differing feeding strategies andHolstein Friesian cow genotypes within grazing systemslocated in the temperate hot-summer climate region ofSouth America. The interactions reported between FS× G highlight the superior productivity per hectare ofNZHF cows within the GMax feeding strategy basedon maximizing grazed pasture, which could represent acompetitive intensification strategy in terms of cost ofproduction for this region.