Performance recording in drought conditions

Performance Recording in Drought Conditions 

Many regions of Australia have received below average rainfall throughout 2024. Given the seasonal conditions, we thought it would be timely to discuss some of the issues that come up in regards to recording performance information in drought conditions. This article will discuss whether performance information recorded under drought conditions is valid for genetic evaluation purposes, and outline some of the trait specific considerations for sheep producers as they continue to record during these challenging seasonal conditions. 

Can I still record performance information in a drought? 

Yes. Many producers are worried that lights weights on their animals will lower their ASBVs, but this is not the case. The genetic evaluation only compares animals within contemporary groups; that is, animals that have had equal opportunity to perform. It is not the raw weight of an animal that is important, but rather how that animal has performed relative to the rest of its peers. Furthermore, for most traits the analysis transforms the data prior to analysis so that all groups have the same average level of performance. This methods has been proven to produce more reliable ASBVs across the diversity of production environments we see in Australia and New Zealand. 

Consider the weights of the 12 animals shown in Table 1. In a non-drought year, under normal seasonal conditions, the average weaning weight of these animals is 32 kg. The animals range from 39 kg (Animal 4) to 26 kg (Animal 10); there are a number of animals that have performed above the average and a number of animals that have performed below the average of the contemporary group. Their ASBVs will reflect their performance relative to the other animals in their contemporary group. 

Now consider the weights of the 12 animals shown in Table 2. In a poor year under drought conditions with limited feed the average weaning weight of these animals is 27kg. While the weights are lower than they would be in a non-drought year, we still see a spread in weights, with the heaviest animal weighing 34 kg, and the lightest animal weighing 20kg. As was the case in the non-drought year, some animals perform above the average, while others perform below the average of their contemporary group.  

Table 1. Non-Drought Year Weaning Weights			Table 2. Drought Year Weaning Weights
Animal	Weight		Animal	Weight
Animal 1	38		Animal 1	33
Animal 2	27		Animal 2	22
Animal 3	37		Animal 3	32
Animal 4	39		Animal 4	34
Animal 5	28		Animal 5	23
Animal 6	32		Animal 6	27
Animal 7	31		Animal 7	26
Animal 8	30		Animal 8	25
Animal 9	35		Animal 9	30
Animal 10	26		Animal 10	20
Animal 11	36		Animal 11	31
Animal 12	29		Animal 12	24
Average	32 kg		Average	27 kg

 

Can drought conditions impact performance recording? 

While the poor performance of animals due to drought conditions can be handled by the OVIS analysis, there are numerous factors that have the potential to compromise the effectiveness of performance recording under drought conditions. Usually, these factors revolve around the forced implementation of management practices and supplementary feeding that can cause considerable disruption to routine stud operations and/or the poor condition of stock. 

For example: 

• Animals may be placed on agistment, often on a number of properties. This can make performance recording difficult (e.g. yards and/or scales not available on all properties) and can result in animals that would normally be managed together being split into multiple management groups (e.g. one or more management group per property). 

• Flocks may have an increased and varied incidence of disease and/or sickness. Were animals are sick and this has had an effect on performance, the sick animal should not be directly compared to other health animals. Thus, increased incidence of sick animals will impact contemporary group formation for the flock. 

• A large number of animals may be sold. Once again, this may impact contemporary group structure and the amount of performance records available for key trait groups. 

What management practices can be taken to reduce the disruption of drought? 

There are a number of strategies that can be applied to minimise the disruption drought conditions has on the effectiveness of performance recording. 

• Where possible, the number of animals within each contemporary group should be maximised and/or maintained. The analyse will use the performance information of an animal more effectively if there are more animals to compare it against 

• If a contemporary group has to be spilt for management reasons (e.g. splitting weaned lambs into different paddocks) create the new groups based on criteria such as sex, prior management groups and measurement dates so that animals that are automatically part of the same contemporary group are kept together. In addition, try to get a measurement on all animals before splitting the group (e.g. weigh all lambs before splitting into different paddocks). 

• Care should be given to submit accurate management group information. A different management group should be entered for any animal or group of animals that have been treated differently or exposed to different non-genetics influences on performance. For example animals that are supplementary fed more should be placed in a different group to those that do not receive as much supplementary feed. 

What other considerations should be made when recording performance information under drought conditions? 

In addition to the above strategies, there are several other considerations when recording performance information in drought conditions. 

• Animals should only have ultrasound scanning information recorded if they are in adequate condition. To obtain effective results, a group of animals should have a minimum average fat depth and weight of 1.5mm and 30kg respectively. This ensures there will be sufficient variation between animals to allow their performance to be reflective of genetic differences. If the animals are not meeting these requirements the measurement may have to be pushed back an age stage for this drop. 
• Performance information should be recorded for animals even if they have lost weight. Animals are only directly compared to other animals that have been treated alike. It is how the animal performs relative to the other animals in the contemporary group that is important, not the raw measurement itself. 
• Feed strategies are also important. They way in which sheep are fed can also contribute more variation in intake and performance, such as using lick/self-feeders compared to trail feeding. The aim from the breeding program perspective is to try and obtain as consistent intake as possible. Any shy feeders should be put into a different paddock and thus management group. 

What if I am making selection decisions earlier than usual, how to I reduce the impact on data quality? 

Making selection and culling decisions earlier while minimising the impact on data quality can be achieved.  

Having as many traits recorded earlier in life before the culling decisions are made will reduce the impact of those animals not appearing for later in life traits. By having early in life traits (i.e. weights, visual scores like wrinkle or cover) the relatives of the culled animals still within the flock will benefit from this information being used within the analysis. The analysis can account to some degree that these culled animals existed and the flock moving forward are a selective group. However, for this to be taken into account the analysis needs to know they existed and have some work of measurement on them to compare against the remaining animals.  

On the proportion remaining in the flock care must be taken to ensure management groups do not be come ineffective with smaller numbers. When taking measurements ensure to measure every animal available to reduce further impact on data quality.  

This is an opportunity to further define, concentrate and focus on keeping animals that suit your breeding objective. Using strict parameters on structural and ASBV performance when making selection decisions during dryer season can allow a “reset” of your flock and ensure that moving forward only the animals that will benefit your flock achieving that breeding objective are kept. In the long run this will allow genetic potential of animals that are matching your flock production goals to be retained and bred from.   

What if I am genotyping a smaller proportion of the flock than usual 

Genotyping for pedigree 

Within Sheep Genetics we have different levels of pedigree accepted, with a known sire and dam (full pedigree) considered the gold standard. Pedigree information is important to the evaluation as it describes the genes that the animal has to inherit and pass along to progeny influencing production.  For a proportion of Sheep Genetics flocks, the use of DNA parentage is the main method of obtaining pedigree.  

If you are using genotypes to inform pedigree, reducing the number of animals genotyped during these drought conditions may create different tiers of pedigree levels within a flock. 

 Tiers with less specific pedigree information (i.e. syndicate pedigree) or missing a sire and dam will have the “gap” in pedigree filled in but your genetic group. Think of genetic groups as one parent who adopts all the lambs with missing pedigree. This genetic group gets a breeding value like all the other animals submitted, but with reduced accuracy and potentially ASBVs not as high as they really are genetically. Additionally, some animals may not meet the accuracy and linkage thresholds to be reported.   

It is important that this is considered when making selection decisions and deciding which cohort to genotype.  

Strategic Genotyping 

When it comes to strategic genotyping (getting the best bang for buck on a smaller proportion of animals genotyped) there are a few considerations to make: 

• Are there some animals that can be removed from consideration to genotype (as they will be culled and not continue in the flock)? 

• Culls on structure and physical attributes 

• Animals that do not suit the breeding objective 

• Low genetic merit on ASBVs or as estimated by the mid-parent breeding values if a measurement and ASBVs are not available yet 

• What is the purpose of genotyping? 

• Pedigree 

• More accuracy on hard to measure traits 

• Being able to make earlier selection decisions with more accuracy 

• What proportion of the flock are going to be genotyped? 

• Young rams 

• Maiden ewes joining the ewe flock 

• Mixture of both for selection decisions 

• A mixture of sires and genetics to get good representation across the flock 

These considerations will assist in identifying which animals to genotype for this cohort.  

Conclusion 

Sheep producers are able to continue to record performance information in drought conditions. As it is the relative performance of an animal that is important (e.g. how did the animal perform relative to the rest of the animals in the contemporary group) and not the raw data, a decrease in production due to drought conditions will not lower an animal’s ASBVs.  

The amount of quality of the pedigree and phenotypic information records is vital to maintain progress in the breeding program and as always this need to be carefully balanced with the commercial reality of running the sheep on-farm.  

Sheep Genetics are happy to try and help with any decisions you have to make so for further information on recording performance information in drought, please sign up for a One on One with the Development Officers to talk more in depth about your particular flock circumstances and concerns.  

Book a One-on-One with the Development Officers.