Beef producers have to determine the best allocation of a limited resource of high-quality forage. This analysis assessed the most profitable way of incorporating high-quality forages into the whole-of-life steer growth path on forage systems in central Queensland, using property-level, regionally relevant herd models that determine whole-of-business productivity and profitability over a 30-year investment period. Twenty-two growth paths (liveweight change over time) from weaning to marketing were investigated for steers grazing buffel grass (Cenchrus ciliaris) pastures with and without access to leucaena–grass pastures (Leucaena leucocephala spp. glabrata + perennial, tropical grass (C4) species) or forage oats (Avena sativa) for varying intervals throughout their growth path. The production, economic and financial effect of each growth path was assessed by comparison to a base scenario that produced finished, slaughter steers (605 kg) from buffel grass pastures. The relative profitability of marketing steers at feedlot entry (feed-on) weight (474 kg) instead of slaughter weights was also assessed. The growth paths were applied within two beef enterprises, namely (1) steer turnover and (2) breeding and finishing. For both enterprises, grazing steers on leucaena-grass pastures from weaning until they achieved feedlot entry weight (474 kg) was substantially more profitable than any other growth path. Compared with the base scenario, this optimal growth path improved profitability by 121% and 37% for the steer turnover and the breeding and finishing enterprises respectively. The purchase of additional breeders for the latter enterprise was required to optimise utilisation of the leucaena–grass pastures immediately. Incorporating leucaena–grass pastures at any steer age improved the profitability of the steer turnover enterprise (AU$7368–AU$106508 extra profit/annum), and similarly for the breeding and finishing enterprise (AU$1754–AU$31383 extra profit/annum) except for two scenarios where leucaena–grass pastures were provided to older steers targeted at the feed-on market (AU$4816 and AU$23886 less profit/annum). However, incorporation of leucaena–grass into steer growth paths also resulted in increased peak deficit levels and financial risk to the business compared with buffel grass-only production systems, with payback periods for the most profitable growth path of 8 and 14 years for the steer turnover and the breeding and finishing enterprise respectively. All growth paths that incorporated forage oats and leucaena–grass resulted in lower economic and financial performance than did comparable growth paths that incorporated leucaena–grass only. Furthermore, incorporating oats into buffel grass-only growth paths always reduced the enterprise profitability. There was no relationship, across scenarios within an enterprise, between change in profit and the number of extra weaners produced or the amount of extra beef produced per hectare.
Existence of an optimal growth path with endogenous technical change
