The importance of performance recording and genetic selection

The importance of performance recording and genetic selection  Gaan terug


Many decades have passed  in which farmers have selected animals as parents for the future generation solely based on “the eye”.  The best looking animals are selected from the group to stay on and reproduce.  This has often been applied successfully…or has it?  Success cannot be measured if there are no historic or current records.  More successful progress could have been made with relevant measurements, fair comparison and additional information.  How would you know where you stand and what you’ve achieved if you don’t measure?

One of the most powerful tools in a farming system is therefore good recording, including measurements/weights of animals and reproductive information.  Weighing animals provides the ability to have a better description as well as idea of possible income.  It also allows the ability to compare animals more accurately.  Without knowing anything about your current herd, you cannot plan where you would like to be.  However, simply knowing the weights, measurements and records is not enough if not applied correctly.

The way an animal looks and performs is not an exact representation of its genetic potential, and genetics is after all what will be passed on to the next generation.  There are two main factors determining how an animal performs, namely environment and genetics.  An animal can have the best genetic potential for growth but if it’s not fed enough, it will not grow as fast as it can.  The proportion contribution of genetics to performance differs for traits, ranging from very small to very large.  Theoretically, what would happen if the “best” animals were selected out of a specific season’s ram lambs simply based on visual selection and no additional information?  Some animals will have an advantage due to environmental and other biological factors.  Single-born lambs will be bigger, as well as older lambs and those born from older ewes.  These animals don’t necessarily look better due to superior genetics.  They were just lucky.

Many decades have passed  in which farmers have selected animals as parents for the future generation solely based on “the eye”.  The best looking animals are selected from the group to stay on and reproduce.  This has often been applied successfully…or has it?  Success cannot be measured if there are no historic or current records.  More successful progress could have been made with relevant measurements, fair comparison and additional information.  How would you know where you stand and what you’ve achieved if you don’t measure?

One of the most powerful tools in a farming system is therefore good recording, including measurements/weights of animals and reproductive information.  Weighing animals provides the ability to have a better description as well as idea of possible income.  It also allows the ability to compare animals more accurately.  Without knowing anything about your current herd, you cannot plan where you would like to be.  However, simply knowing the weights, measurements and records is not enough if not applied correctly.

The way an animal looks and performs is not an exact representation of its genetic potential, and genetics is after all what will be passed on to the next generation.  There are two main factors determining how an animal performs, namely environment and genetics.  An animal can have the best genetic potential for growth but if it’s not fed enough, it will not grow as fast as it can.  The proportion contribution of genetics to performance differs for traits, ranging from very small to very large.  Theoretically, what would happen if the “best” animals were selected out of a specific season’s ram lambs simply based on visual selection and no additional information?  Some animals will have an advantage due to environmental and other biological factors.  Single-born lambs will be bigger, as well as older lambs and those born from older ewes.  These animals don’t necessarily look better due to superior genetics.  They were just lucky.

 

 

How should I then interpret the measurements?  Animals should be compared within a group of animals with the same environmental factors, including season, gender, age, birth and weaning status, age of dam (young = less than 3 years, old = more than 5 years), supplemental  feeding, etc.  This is the simplest step to at least account for some external factors.  The best, and only, way to account for all environmental factors is the use of estimated breeding values (EBV).  This uses measurements and information about the groups, pedigree information and genetic parameters (proportion of variation due to genetics and genetic links between traits) to determine the genetic merit of an animal.  Pedigree information is very important since this indicates the animals with shared genetics.  Measurements of related animals will contribute to each other’s breeding values.  Pedigree information is often difficult to determine due to the use of multiple sires in a flock of ewes.  Simply identifying the dam is valuable to both stud and commercial farmers because this can be used to build up a reproductive history of a ewe, including age at first lambing, lambs born, lambs weaned and total lambs weaned.  Only recording the dam is not sufficient for breeding value purposes.  Stud farmers participating in performance recording receive EBV’s and these values are often presented in auction catalogues to aid buyers in selecting their animals.

Does genetic selection of animals really work?

 

If only a proportion of the trait’s expression is due to genetics and the flock is already performing well, why should I bother with all these record-keeping and selecting on genetic merit?  The flock may be performing well but it could have done better.  Yes, the environment can be improved or manipulated to give quick results, but this good performance is not carried over to offspring.  Furthermore, even in the best environments, there are still animals that do better.  Out of the group of ewes, some don’t lamb at all and some have multiple lambs.  Some lamb every year while others don’t lamb even though they were treated exactly the same under the same conditions.  Some rams grow to an impressive size and others don’t.  Clearly genetics still has an influence and selecting based on genetics while also maintaining good management practices will deliver greater results.
Genetic change is a slow process since it takes time for animals to reach puberty, reproduce and have offspring with measurements.  But selection over generations can truly make a difference.  The Merino breed is a great example where drastic change took place over a few decades.  The Merino used to have pleats all over their bodies to increase fleece weight.  These pleats became problematic for health reasons, dirty wool and shearing difficulty.  Strict selection against this trait led to Merino’s that look completely different.  The iconic horns are selected against, drastically increasing the proportion of polled rams.  Another example is the Angus.  In the 1960’s an Angus bull was considerably smaller than one of today.  Selection based on measurements and breeding values can deliver great results.

 

What do I need to get results?

Firstly individual identification is important.  Without identification, measurements and other information cannot be linked to the relevant animals.  The identification must never change, even when owners change.  This is to ensure that all the records of the animal can be linked to only one number/name throughout its life and even after death.  There is a standard method of individual identification:

Stud nr/tattoo + Birth year + Sequence nr = ID 5571 + 12 + 0123 = 5571120123

Performance information must then be recorded and assigned to the relevant animals.  Information such as birth date, weaning date, birth status and weaning status should be recorded along with weights.  Compare animals within a group exposed to the same environment and biological factors (gender, birth status, age, age of dam).  The effect of birth status, age and age of dam become much smaller as the animal becomes older.  Pedigree information is essential for breeding value estimation, but even simply recording the dam is helpful for general management and valuable reproductive information.

A basic step often forgotten is the need for well-formulated breeding objectives/goals.  The general objectives of the overall breed is not necessarily suitable to all farmers.  The environment greatly determines the type of animal the breeder should aim for.  Very challenging environments cannot support large animals and therefore a medium-framed animal might be best.  Keep breeding objectives realistic and constant.  Breeding takes time to show results.  Constantly changing goals will not be productive.  Well-balanced goals are important for sustainability and animal health.  Dairy cows have been selected strongly for milk production, which was successful, but other factors became a problem.  Fertility decreased, health deteriorated and cows had shorter productive lives.  Fertility is the most important trait since the least profitable animals are those that were not born.  It is strongly advised to cull ewes that do not lamb and give preference to those who raised multiple lambs.  Strict selection must happen to maintain or improve fertility in a herd.
 

Conclusion:

Having accurate measurements and applying them correctly takes commitment and dedication but will bear fruits.  Identify animals and measure them to keep track of the current state of the herd.  Measurements alone don’t mean much if not compared fairly.  Compare animals that have been exposed to the same environment to compensate for some external factors influencing performance.  Record information such as birth date, birth status, weaning date, weaning status, number of lambs born (dead or alive), number of lambs weaned, dam and the traits of interest.  Selecting only on visual factors does not select true genetic potential since genetic potential can be masked by the environment.  Have well-defined breeding objectives and stick to them.  Apply strict selection on fertility since this is the main trait of importance in livestock systems.  Measuring your animals is the only way to evaluate your herd, identify weaknesses, develop a plan to address these weaknesses and monitor progress towards your goal.

 



Artikel Indeks  Terug na bo

© SA Stamboek. All Rights Reserved.
No article or picture may be reproduced\published
without the written consent of SA Stamboek.