Pastoral Research Station Herd Performance report for 2019 to 2020

The Northern Territory Government’s cattle research and management program is integrated across two agricultural research stations near Alice Springs, Old Man Plains Research Station (OMP) and the Arid Zone Research Institute (AZRI).

OMP is 525km² (includes Quarantine and Borefield areas) while AZRI is 6.5km². The cattle herd at AZRI has 30 heifers used as sentinels for arboviruses (monthly blood tests). The larger herd at OMP is used for research projects. Quality Graze is a long-term grazing strategies project that determines which animals are allocated to each paddock at any point in time. These include steers, breeders and calves. Bulls spend three months with the breeders for controlled mating and are in their own paddocks for the rest of the year. Most of the bulls are bred on property.

The Research Station Herd Performance report is an annual cattle production summary that celebrates our successes and highlights areas for improvement.

The season

Rainfall for the 2019 to 2020 period was low across OMP and AZRI, with 12-month totals ranging from 50 to 120mm.

In May 2019, approximately 30mm of rain fell across much of OMP, spoiling large areas of pasture that had grown in the previous summer. Approximately 20mm fell in February 2020 and another 20mm in March 2020. This was reasonably consistent across most of OMP with widespread modest growth of buffel grass, some annual grasses and some forbs (lots of caltrop). The best pasture growth occurred around Mulga Dam, where 57mm was recorded in February and 35mm in March.

There is regional concern that the extended dry period in Central Australia appears to have resulted in the death of mature buffel grass tussocks. On OMP and AZRI, mature tussocks in drainage lines are still growing but there is considerable tussock death in open areas. Pasture assessments done in April and May 2020 identified germination of buffel grass seedlings. However, this will be monitored closely as it can be tricky to re-establish perennial tussock grasses.

In summary, the eastern paddocks recorded good growth, particularly in the drainage lines, after the late summer rains. The western paddocks had lost carryover feed as a result of the 2019 spoiling rain with only moderate replacement growth from the rain in 2020.

Herd structure

There is typically little variation in stock numbers on OMP as most of the grazing strategies involve set stocking rates (there are only two strategies with variable stocking rates). At the end of each summer, forage budgets are completed. So far, there has been sufficient carryover feed available for the numbers of stock held. However, given that carryover feed is being consumed, the decision was made to sell all the 2019-branded heifers rather than keep any as replacement breeders. In addition, empty breeders were culled in May 2020 and conformation or temperament defects were culled more stringently.

Table 1: Cattle numbers on OMP and AZRI at 1 July 2019 and 30 June 2020

Herd performance indicators

Like most extensive rangeland production systems, inputs are low. It is worth noting that, while the herd had access to urea licks at all times, there was no supplementary feeding of energy for the OMP herd and no agistment. Grass hay was only offered to stock while held in yards overnight at musters and during weaning. The 30 sentinel heifers located at AZRI had substantial hay feeding.

The breeder herd on OMP is control mated. The weaning rate reported here for 2020 relates to mating around December 2018, when 527 breeders went to the bull. Pregnancy testing in May 2019 recorded 439 pregnancy tested in calf (PTIC) (see Table 2). Of these breeders, the youngest cohort was the 2018-branded heifers that were 12 to 14 months old at mating. After culling in May 2019, 400 PTIC breeders were retained. Calving occurred between September and November with 354 calves tagged in December. Subsequently, 353 calves were weaned in March 2020. Weaning rates are typically expressed as a percentage of cows that were exposed to the bull, however, because we sold some PTIC we had to do some maths to work out our weaning rate. It is interesting to note that the pregnancy rate in the maiden heifers was only 63 per cent.

Weaner training of the heifers and young bulls was particularly effective this year and was conducted at Mulga Dam. Those weaners were regularly tailed out and became very quiet (Figure 2).

Table 2.  Breeder herd performance for OMP/AZRI 2019-2020 financial year.

The production system at OMP and AZRI is designed to supply  30-month-old steers straight to abattoir. Steers are branded for the year they  are weaned, then grazed in mixed herds until 30-months of age and sold in about  April each year. The goal is to meet MSA specifications with as many steers as  possible. Cattle numbers are based on long-term carrying capacity however, the  ongoing dry conditions have seen some decline in forage quality and live weight  gain was a little below target (Figure 1).

Figure 1: Lifetime live weight gain for the three cohorts of  steers grazing OMP and AZRI (solid black line indicates average of all steers 2010 to 2020)

Steers are sold by year brand and all steers in that age  group are sold at the same time. The 2018-branded steers were sold in May 2020  and, even though they were produced during three very dry years, they still  performed well at slaughter.

One of the key indicators for MSA compliance is P8 fat depths of 5mm, or greater. A good pasture growth event in November 2018, when  the steers were about a year old, led to the initial development of fat. Dry,  nutritious pasture kept the steers in good condition and, in May 2019, 41 per  cent of steers were on track to meet fat targets. In May 2019, winter rain  spoilt a lot of pasture on OMP and as feed quality declined, so did the  condition of the steers. When the steers were assessed in late  February 2020, a mere 8 per cent met the 5mm P8 fat depth threshold.  In preparation for sale in March 2020, the steers went onto feed in a paddock  that hadn’t been grazed for about nine months. At the same time, moderate falls  of late summer rain provided a supply of fresh green pick. The decision was  made to hold the steers for an additional five weeks.

When the steers were slaughtered in late May, 71 per cent achieved a P8 fat score of 5mm or greater. In total,  62 per cent of the herd achieved MSA grading (Table3), a much better  outcome than seemed possible in February. We believe that this good outcome is  a result of having land in good condition that can respond well to rain and because  we had sufficient reserved feed to maintain cattle in reasonable condition, even  in a dry year. Then, when we got lucky with a little bit of rain, the steers  put on weight and did well at market. Visit 2018 steer performance for a  more detailed account.

Table 3: Average MSA performance for 2018 branded steers  when slaughtered in May 2020

Sales

Given the ongoing dry conditions, the decision was made to  sell all 2019 and 2020 branded heifers, with the exception of the sentinel  heifers required annually for disease investigation (30 at AZRI and 62  transferred to the Katherine Research Station).

Table 4. Sales and transfers of cattle from OMP and AZRI, 2019-20

1. Sentinel  heifers supplied to the Katherine Research Station (KRS) could potentially have  sold for an equivalent $500 per head. This would have generated an additional  $31,000, bringing the total to $422,102.

Production measures

It can also be useful to maintain measures of production  that can be used for comparison with other investment information.

Table 5. Production measures for OMP and AZRI, 2019-20

Contacts

Jocelyn Coventry
Cattle Production Officer
08 8951 8142

Jocelyn.conventry@nt.gov.au

Chris Materne
Pastoral Production Officer
08 8951 8135

Chris.materne@nt.gov.au