Hitting the grid with culled cows in the Northern Territory

Summary

The primary objective of this study was to generate and document both biological and economic data to estimate the potential economic benefits for feeding different classes of cull cows using feedlot or floodplain strategies to increase market value (based on a grid system) that might be obtained now, or at future costs, supplying a northern abattoir.

Data obtained during this study was also summarised to describe the variation in growth of culled cows for different ranges of body condition, dentition, and weight range. This information will provide stakeholders with baseline information to determine which cull cows classes are most suitable for feeding in a feedlot situation, and for how long.

Whilst significant average liveweight gains (0.5kg/d) have been reported for cows grazing floodplains, it is generally acknowledged that there is a period of adjustment when cows are transferred to floodplain. Changes to the ruminal structure have never been described in the literature for cattle transitioning to the floodplain and may partly describe the reduced performance of some cows during their adaption phase. This research studied rumen microbial populations during grazing the floodplain and investigated if these were associated with growth.   

In 2016, culled cows were purchased from several northern properties and transported to Beatrice Hill Farm where they grazed floodplain pastures.  Over a 138 d period, between June and November 2016, liveweight was recorded. On average, cows only gained 25.2 kg (SD 21.2) or 183 g/d. For the same time period, a 10.5 cm2 increase in eye muscle area and 0.3 mm rib fat depth was also observed for carcasses form similarly managed cows.

In 2017, 150 cows were purchased from a commercial station in the Stuart Plateau region and transferred to the Katherine Research Station where cows were randomly allocated to one of three treatments: Floodplain (FP) grazing for 102 days; 82 d of lot feeding on a high grain ration (HGR) ($729/T; 11% protein, 11.5 MJ ME) OR 82 d of lot feeding a locally sourced pellet (PEL) ($430/T; 14% protein, 10 MJ ME). Changes in liveweight was monitored using a 12 h curfew weighing policy. Cows were backgrounded for 14 d prior to commencing the pen study.

The cost of gains were estimated by calculating the average dietary intakes of individual pens over the entire trial period which was multiplied by the cost of diet and then divided by the average LWG of the pen. The increase in cow value was calculated by comparing an estimated slaughter values of cows at the start of the trial to their actual slaughter value at the end of the trial. The slaughter value at the start of the trial was estimated by using the slaughter grid prices received at slaughter and applying them to an estimated carcass weight of cows at the start of the trial. These results are presented in full in the final report.     

These results show that high input systems are often not profitable and will be highly dependent on market opportunities relating to the cost of feed and carcass values. Or, the undertaking pen feeding of culled cows has to result in increased profit in another part of the business to offset the cost of feeding cattle. When valued against a slaughter grid, lighter cows generally had the largest increase in value. Observations from this trial indicate that the floodplain provided the lowest cost of gain and provided the best returns.