Beef cattle research overview

By Jocelyn Coventry, Pastoral Production Officer, Alice Springs

Updates on beef cattle research help cattle managers review ongoing management strategies, as well as assess new strategies so they can adapt to change or adopt improved practices. This article provides an overview, to help the busy beef cattle producer scan the relevance of Australian beef cattle research on productive breeder cows, i.e. maternal productivity, as reported early 2018 in Animal Production Science, and cited in the reference list at the end of this article. Two department examples are given to help illustrate some points.

The research question

A Beef Co-operative Research Centre (Beef CRC) was tasked with looking at whether recent pursuit of “genetic improvement in feedlot and abattoir performance of cattle” could lead to “a decline in maternal productivity (of breeding herds), especially under variable nutritional conditions1. Therefore a Beef CRC Maternal Productivity Project (Beef CRC ‘project’) with Angus (Bos taurus) cattle was undertaken over five years in southern Australia.

Driving factors for maternal productivity

In the Beef CRC ‘project’, maternal productivity was defined as output (calf plus cow) versus input (feed intake), as measured by:

  • weight of calf-weaned,
  • cow weight change,
  • energy intake, and
  • progeny post-weaning production2.

Figure 1. Major driving forces for Maternal Productivity

Figure 1. Major driving forces for Maternal Productivity

Finding the balance for maternal productivity

The Beef CRC ‘project’ noted that the balancing of cattle requirements for maternal productivity and feedlot or abattoir performance “is not straight forward, (but) is of critical importance3. The researchers believe that producers should target management of “heifer pregnancy rates and interactions between the cow herd and (a variable) nutritional environment”3.

Suggestions for how to do this focused on heifer and cow genetics, in particular, estimated breeding values (EBVs) for rib fat and residual feed intake. The latter is an indicator of efficiency in feed conversion, and is defined as the difference between actual post-weaning feed consumption and the expected feed requirement for growth and maintenance.

Heifers with a higher EBV for rib fat had “significant (higher) pregnancy rates4. Cows with higher EBVs for rib fat and intramuscular fat were more likely to be “earlier calving cows5. This highlighted the importance of a heritable (genotypic) capacity to store feed energy as body fat. Similar to observations for physically (phenotypically) small-framed cows with lower feed maintenance requirements that allow them to store more feed energy as body fat, increased genotypic capacity to store body fat is perceived to provide a resilience for maternal productivity under variable seasonal conditions.

Cows with a lower EBV for residual feed intake had a lower weaning rate and delayed calving, but produced “heavier calves at weaning”5 and were “more efficient at producing weaner calves”6 under the range of ‘normal’ seasonal conditions in the Beef CRC ‘project’. This may sound counter-intuitive, but if the weaning rate is only slightly lower while the weaning weight of each calf is much higher, the average calf-weight weaned per breeder cow can still be higher. This latter finding illustrates the challenge in design of a breeding program that provides a regional balance between EBVs for improved reproduction (to increase the number of progeny), versus high growth (to increase the weight of individual progeny).

NT DPIR case study for heifer fertility and productivity

With regards to heifer fertility, the Beef CRC ‘project’ showed that “weight and fat depth were the largest contributing factors to variation in (heifer) pregnancy rates4. The following example from the department’s Droughtmaster cattle at the Arid Zone Research Institute (AZRI sentinel heifers) illustrates the importance of managing nutrition for heifer fertility, i.e. to reach a target weight for mating, with moderate body condition to promote re-conception after calving.

Between 2013 and 2016, supplementary feeding of pellets with coccidiostat at weaning, enabled the AZRI sentinel heifers to sustain steady post-weaning growth, averaging 0.5 kg per head per day in the first 12 months and meeting a target average critical mating weight of 300 kg at 12 to 14 months of age. For these moderate frame-sized breeders, this target is within the recommendations reviewed for the Beef CRC ‘project’ (56 to 66% of mature cow weight 4). Controlled mating commenced in early December and after three months, resulted in pregnancy percentages ranging from 87 to 100% (see Table 1 ).

Table 1 . Summary of annual outcomes for management of AZRI sentinel heifer fertility

Year Brand … to 12 months old … to 18 months old
Growth
(kg/day)
Average weight
(kg)
Control-mated? Growth
(kg/day)
Median body condition
(scale: 1 to 5)
Pregnancy
(%)
2013 0.62 327 yes 0.54 3 94%
2014 0.51 325 yes 0.56 3 100%
2015 0.44 304 yes 0.48 2.5 87%
2016 0.36 343 yes 0.64 3 93%
2017 0.26 274 not mated 0.79 2.5 na

In 2017, supplementary feeding of pellets with coccidiostat was withheld at weaning and the heifers only grew at an average of 0.29 kg per head per day for four months post-weaning. They failed to meet the target average critical mating weight in time for controlled mating over summer 2017-18. At assessment in May 2018, these heifers were within the expected hip height range-for-age (medium frame), but the sub-optimal median body condition (fat) score of 2.5 (on scale of 1 to 5) and the absence of prospective calf production in 2018, is a legacy of their previous slow post-weaning growth.

Department research in the Top End7 has previously modelled the relationship between pre-mating weight and pregnancy percentage in yearling and two year old Brahman heifers, where pre-mating weight was recorded in either October or December (see Figure 2). In each case, pregnancy rates were higher with higher pre-mating weights. The average weight at conception for the yearling heifer groups that were used for the modelling, ranged from 300 to 333 kg. This weight range represented reproductive success (conception) in up to 36% of the control-mated heifers. In comparison, the slightly wider average weight range (304 to 343 kg) that was reported pre-mating for the control-mated AZRI Sentinel heifers, resulted in reproductive success in over 80% of heifers. So although those two weight ranges provide slightly different retrospective views of the interaction between management, nutrition and heifer fertility in the NT, they both emphasize the importance of weight targets over 300 kg for reproductive efficiency in moderate framed Bos indicus or Bos indicus-infused heifers.

Modelling of pre-mating weight vs. predicted pregnancy rate in Top End yearling and two year old Brahman heifers

A productive department breeder cow with good mothering ability in Alice Springs … feeding one calf and grooming another in 2013!

Figure 2 . Modelling of pre-mating weight vs. predicted pregnancy rate in Top End yearling and two year old Brahman heifers7

Figure 3. A productive department breeder cow with good mothering ability in Alice Springs … feeding one calf and grooming another in 2013!

Footnote

Research findings from the described Beef CRC ‘project’ provide new insights into ‘feeding vs. breeding’. Together with examples from department research cattle, this highlights the importance of balancing a breeding program to manage nutrition and to consider EBVs in cattle selection.

Because selection and introduction of beef cattle sires with Bos taurus genetics forms an important base for many cattle herds in central Australia, this adds relevance to the Beef CRC ‘project’ findings for Centralian cattle producers.

For more information, please contact:
Jocelyn Coventry, (b/h) ph. 08 89518142.

1 Animal Production Science, Volume 58, Issue 1: Genesis, design and methods of the Beef CRC Maternal Productivity Project http://www.publish.csiro.au/AN/AN13054 (Pitchford et al 2018, pp. 20-32)

2 Animal Production Science, Volume 58, Issue 1: A review of factors influencing key biological components of maternal productivity in temperate beef cattle http://www.publish.csiro.au/an/an12428 (Walmsley et al 2018, pp. 1-19)

3 Animal Production Science, Volume 58, Issue 1: Modelling systems to describe maternal productivity, with the aim of improving beef production efficiency by eliciting practice change http://www.publish.csiro.au/an/an14874 (Walmsley et al 2018, pp. 193-205)

4 Animal Production Science, Volume 58, Issue 1: Divergent breeding values for fatness or residual feed intake in Angus cattle. 1. Pregnancy rates of heifers differed between fat lines and were affected by weight and fat http://www.publish.csiro.au/an/AN14583 (Jones et al 2018, pp. 33-42)

5 Animal Production Science, Volume 58, Issue 1: Divergent genotypes for fatness or residual feed intake in Angus cattle. 3. Performance of mature cows http://www.publish.csiro.au/an/AN13295 (Copping et al 2018, pp. 55-66)

6 Animal Production Science, Volume 58, Issue 1: Divergent breeding values for fatness or residual feed intake in Angus cattle. 5. Cow genotype affects feed efficiency and maternal productivity http://www.publish.csiro.au/AN/AN14034 (Hebart et al 2018, pp. 80-93)

7 Animal Production Science, Volume 57, Issue 10: The effect of weight and age on pregnancy rates in Brahman heifers in northern Australia http://www.publish.csiro.au/an/an16212 (Schatz & Hearnden 2017, pp. 2091–95)

Last updated: 06 December 2018