Genetic gain in a tough season

February 6, 2019 12:05 pm

The lack of rain over much of the winter and spring months throughout Australia has seen significant pressure applied to the Australian cow herd. The seasonal conditions have meant many breeders have had to make hard calls around the future of cows, resulting in many herds reducing in size. This reduction in cow numbers is however not without a potential silver lining for the long-term genetic improvement of the herd.  

The opportunity presented during these difficult times is the ability to apply significantly more selection pressure on the females through the removal of a greater proportion of bottom end cows, which over the coming years could result in a significant increase in the rate of genetic gain the herd achieved (Refer to figure 1).

Figure 1. Shows the trend for genetic gain over time, comparing the herd with and without culled cows

Selection pressure is all about the criteria used to identify which individuals are kept within the breeding program and increases as the criteria to be chosen on become harder to meet. Rate of genetic gain is influenced by selection pressure and programs which apply greater selection pressure have the potential to achieve greater rates of genetic progress. 

Ultimately if we are to realise this benefit we need to not only ensure that the females we remove are the bottom proportion of the herd, but also that when we build numbers back up, that we maximise the opportunity towards our breeding objectives.

Females, females, females

As the conditions improve there will be greater demand for replacement females, as breeders look to increase their herd size. This increase in herd numbers to the ‘normal’ level is where the opportunity for increased genetic gain exists. The opportunity to make a step increase in genetic merit of the herd is through replacing the cow you removed due to poor seasonal conditions, with a heifer of greater genetic merit when times improve.  

Producers are able to achieve this either by buying in females or breeding their own, both these approaches present an opportunity to both increase or reduce the herds rate of genetic gain. Importantly whilst the ability to apply significant pressure has the potential to deliver benefit to the herd, if genetic conditions are brought in or poor selection decisions are made this potential upside can result in herd going backwards.

1. Buying in females 

Not all heifers are created equal and the value to an operation of one animal over another can be significant, even if they are by the same sire. When purchasing females it is important to consider the return on investment they will deliver to the operation and if cattle prices are high the importance of this increases.  

Research has shown the significant difference high and low genetic merit animals have in potential return to a business but even put simply, a cow with greater longevity is worth more to the business then a cow who will produce less calves in her lifetime.  

Being able to assess the suitability of an individual is not always simply as the two considerations, the genetics and the phenotype can be difficult to adequately assess at the point of sale, due to limited information. The key when buying in females though is to plan ahead and ask questions.  

If you are sourcing replacement females consider getting them genomically testing before sale, if they are commercial angus females then a product like HeiferSELECT should be very seriously considered. Genomic testing does take time and producers will need to plan ahead, but the benefit of identifying the top proportion can be significant. An alternative approach if time is limited could be to purchase females and then sell off some once you have tested them yourself and made selection decision based on the results.  

Not only will a product like this confirm some important checks such as angus content, but will also provide valuable information for later breeding decisions, such as who the sire is (important for inbreeding management) and some values representing the genetic merit of the animals.  

Seedstock producers have access to high density SNP panels and full parentage verification which if purchasing seedstock females is of increased importance.  

Understanding the genetic merit of purchased animals is critical if breeding programs are going to continue to make genetic gain towards their breeding goals, failing to consider the genetics carried by the herd can result in a greater spread in the performance of calves by a program and a potential reduction in suitable animals to make selection decisions on.

2. Breeding replacements 

Breeding replacements is a longer approach then purchasing in animals, however offers benefits of increased selection pressure, capitalising on genetic gain previously made by the herd and the reduced risk of purchasing new animals.  

When breeding replacements, you have the ability to benefit from the genetic gain you have already made within the herd and it is important that breeding decisions made when breeding replacements consider this.  

It is also worth considering whether sexed semen is right for you, to increase the number of replacement females available for selection and the number of females by elite sires. Typically, sexed semen comes with an additional cost compared to conventional A.I or use of a herd sire, so it is about understanding if its right for your herd and at what level.  

Within any cattle breeding program there will be female lines that are more desirable to the goals of the operation and whilst ensuring diversity of line within a program is an important management strategy, having strong influence from these elite lines and females can significantly benefit the herd. Seedstock breeders should consider technologies like embryo transfer when both making difficult culling decisions, to preserve genetics, and when building the herd up. To a lesser degree sexed semen can also be used to build greater influence from particular cow lines within your herd, by producing heifers from your top cows.  

The bulls you buy

Up until this point we have really focused on the female side and largely the focus of maximising rate of genetic gain from the increased selection pressure on females requires this. The question however when we do examine the bulls we use is, if you are going to retain more daughters out of the bull then in a normal season, do you have the same selection focus?  

This question is significant because traits such as gestation length and calving ease may have a greater significance if you are retaining females compared to if you are just performing selection towards your breeding objective. Remembering the cows you breed this year will be influencing your herd for years to come.  

For further information or support contact staff at Angus Australia on (02) 6773 4600 or