BRIEF COMMUNICATION: Ad libitum fodder-beet and pasture beef-finishing systems -intake, utilisation, grazing behaviour and liveweight gains

摘要

Traditionally, New Zealand (NZ) beef-production systems rely almost solely on pasture production. However, the seasonality of pasture growth, which affects quality and quantity, impacts the productivity of the system, with mean slaughter age of 26-36months. In accelerated beef-finishing systems internationally, cereal grains are used to maintain energy intakes across the production cycle, at a lower cost than is possible in NZ. A recent NZ development in beef-production systems involves ad libitum intakes of fodder beet (FB; Beta vulgaris) with minimal supplement for 130 d from weaning to spring, and then 90 d of grazing on grass-based pasture before slaughter. This system, developed by Gibbs at Lincoln University, allows finishing of spring born animals at 12-18 months of age (Gibbs et al. 2015; Gibbs & Saldias 2014a). Ad libitum intakes after appropriate transition to FB are critical to system profitability, and prevention of rumen acidosis (Gibbs & Saldias 2014b). However, previous NZ crop-feeding experience with brassicas suggests that increased intakes require reduced utilisation of feed (Rugoho 2013). There is no published information on FB utilisation in ad-libitum systems, where high pasture residuals at 24 h post-allocation are used to ensure maximal intakes. Therefore, this study was designed to determine utilisation, grazing behaviour and intake patterns, and liveweight (LWT) gains, in steers grazing FB and then spring perennial ryegrass {Lolium perenne) and white clover (Trifolium repens) based pasture.