Grasping genetics: ‘Improved’ animals are like elite athletes or racing cars

Animals can be selectively bred to grow faster, grow to a specific size or even digest food better, among other things, but what most programs all have in common is the goal of feed efficiency. 

Dr Kim Bunter, senior scientist for the Animal Genetics and Breeding Unit at University of New England, Australia, said it was vital feed manufacturers and others working with these ‘improved’ animals, better understood animal genetics. 

“If you don’t understand genetics, you tend to have the global view that ‘one diet fits all’, at least within a class of animals,”​ she told FeedNavigator. “If you understand genetics, or even just the nature of variation between individuals - whether it be genetic or environmental in origin, then perhaps targeted or customized diets for animals would have more meaning.”​ 

Customized shortfall? ​

Bunter said that whilst the animal sector had customized diets for classes of animals – with differences in weaner, grower and lactation diets, for example – industry had yet to truly customize for “high performing animals within that class”.​

Animal longevity, she said, was an issue across industry with mortalities, lameness and culling for poor conditions commonplace, and this was something she believed could be remedied with improved, customized diets. 

“Dairy, pigs and poultry in particular have made enormous genetic changes and it is within these species we also see these issues. Some of this is genetic, but I have no doubt that some of it could be better managed, including dietary issues.”​ ​

Professor Dorian Garrick, chief scientist of the Institute of Vet, Animal and Biomedical Sciences at Massey University, New Zealand, agreed industry could and should adapt when working with improved stock. 

“Generally speaking, improved animals of any species are more like racing cars than family vehicles and are therefore more sensitive to having the right kind of fuel,” ​he said. 

Because genetics were vital in dictating things like body composition, growth and metabolism, Garrick said feed for animals genetically selected had to be customized accordingly. 

Genes controlled a number of very specific aspects within the animal - protein synthesis to produce muscle; the rate protein was deposited throughout the animal’s body; the rate fat or lipids were deposited; and how much the animal wanted to eat. 

Elite athletes wouldn’t eat junk food ​

Bunter said with any body composition changes through genetic selection, came altered nutritional needs.

“Perhaps a good example from a human perspective is that an elite athlete - who has created high muscle, low fat by training – does not remain elite for very long if they live off McDonald’s, because while their calorific needs might be met by simply increasing intake, other requirements won’t be. Most move into higher protein, higher antioxidant style diets.”​

However, she said some athletes had to eat more than others to sustain a constant weight and composition, and the same applied to animals.

Metabolizable energy (ME) and protein intake, as well as macro and micronutrient needs could all differ, she said, and so changing requirements and variability amongst individuals was something industry had to contend with.

Amino acid adjustments​

Garrick said one specific requirement change for improved animals was the amount of amino acid needed – an organic compound that assisted and optimized protein deposition.

Levels, he explained, had to be adjusted accordingly to achieve maximum protein deposition but had to also consider increased voluntary intake common amongst improved animals.

Restricting feed could help, he said, but this proved costly because the animal then took longer to reach harvest weight. Feed alterations, if timed well, were a better option to manage amino acid intake, and other nutrient intakes, in improved animals, he said.

“Since the requirements change with age, it is more cost effective to have diets that meet no more than the exact requirements at a particular age and physiological status.​

“…The most cost effective diets will vary over the lifetime and metabolic status of the animal,”​ he said.