Optimizing growth paths of beef cattle in northern Australia for increased profitability

Dr Stuart McLennan Queensland Alliance for Agriculture and Food Innovation University of Queensland - Meat & Livestock australia

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

This research article looks at optimizing growth paths of beef cattle in northern Australia for increased profitability. Research intended that the Australian feeding standards could not currently be relied upon to predict intake of grazing cattle in the tropics.

What is the problem?

Over the last 2 or 3 decades, there has been increasing emphasis on improving beef quality for both the domestic and export markets and this trend is only likely to continue into the future. However, growth rates of cattle in northern Australia often do not support the desire for younger turnoff of carcasses to meet this increasing demand.

This plan was aimed to:

• Classify and compared (including a full economic assessment and sensitivity analysis) different feeding strategies for increasing growth rates of steers in the tropics of northern Australia to a common liveweight/age end-point.

• Determined growth response relationships for mature-aged (finishing) cattle to supplements, based on high protein and/or high energy, and fed in conjunction with forages of low or medium quality and incorporate them into the ‘WhichSupp’ decision support spreadsheet.

• Verify an existing intake prediction spreadsheet (‘QuikIntake’) for use in predicting intake of pasture by cattle grazing tropical or sub-tropical pastures.

• Expand a supplementation optimisation model for use by producers and extension officers.

What did the research involve?

-The pasture-based trial was carried out between August 2008 and June 2012 primarily at Swans Lagoon Research Station, Ayr but with 1 treatment partly located at Brian Pastures Research Station, Gayndah. Two drafts of Brahman crossbred (~75% B. indicus) steers were used, 12 months separated in time, covering the period between weaning and slaughter.

-The growth paths represented various combinations of treatment applied in the first and second dry seasons (DS1 and DS2) post-weaning. Three of the treatment groups received supplement inputs of low (L), medium (M) or high (H) order in DS1 followed by H in DS2, denoted as L-H, M-H and H-H, respectively. These groups were slaughtered at the end of the second wet season post-weaning (WS2) at about 30-33 months of age.

-Within treatments, all steers were slaughtered at the same time at 1 of 2 commercial abattoirs. Steers from L-H, M-H and H-H treatments were killed on the same day late in WS2, and L-nil steers about 12 months later, in an abattoir near Townsville, northern Queensland, about 120 km from Swans Lagoon. L-leuc steers were slaughtered in an abattoir at Beenleigh, south-eastern Queensland, about 350 km from Brian Pastures.

-A full economic analysis of the growth paths generated in the grazing study described above (Component A) was carried out using 2 approaches. First, the treatments were assessed according to their effects on the increase in net value per head, i.e., the value-added method. This method calculated the final value achieved for individual steers and deducted the costs of achieving that value including cash and non-cash costs.

What were the key findings?

-The combination of these dry seasons had a marked impact on the results obtained. With Draft 1 the experimental protocol of equalizing LWs by the end of DS2 for the L-H, M-H and H-H treatments was achieved but in Draft 2 the second dry season was too short for the L-H group to catch up in LW with the other groups. In addition, the difference between the L-nil and L-H groups at the end of DS2 was not significant.

Liveweight change
-Feeding MUP to steers at high intakes increased growth rate when compared with that of others either fed US (as weaners; DS1) or no supplement (as yearlings; DS2) by 0.39-0.43 kg/day in weaners or 0.48 kg/day in yearlings;

-The conversion rate of MUP supplement to additional liveweight gain was between 7.9 and 9.9 kg/kg (as fed) for weaners (controls fed US) and 11.8 kg/kg for yearlings (controls not fed), with respective costs of $1.72, $2.16 and $2.57/kg extra gain;

• Skeletal growth (height)
-Steers grew skeletally even during periods of nutritional stress when liveweight change was only at maintenance, for instance during the prolonged, harsh 2009 dry season when both weaners and yearlings had zero LW gain but grew 39 and 32 mm/100 days, respectively.

• Fat and eye-muscle depth
-Trends in the depth of rib or P8 fat cover and in eye-muscle depth (EMD), determined using ultrasound scanning, closely followed those of LW in that, where LW change was greater during the dry seasons for high plane treatments receiving MUP compared with those of steers on low plane nutrition (e.g., L-nil), the depth of rib fat, P8 fat and eye-muscle were also greater.

• Carcass characteristics and MSA chiller-assessed traits
-Because treatment groups were slaughtered at different times and abattoirs, the only growth path treatment comparisons possible were for the 3 high plane treatments killed together (L-H, M-H and H-H).

Final comment

An economic analysis showed that leucaena, but not high-input supplements, increased profitability – the use of improved forages, combined with manipulation of body composition and associated compensatory gain offer the most cost-effective options for reducing slaughter age.

2014 - Australia - Dr Stuart McLennan Queensland Alliance for Agriculture and Food Innovation University of Queensland - Meat & Livestock australia
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