Tuesday, March 5, 2024

Tackling productivity cow by cow

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AgResearch scientists are contributing to a programme that aims to lift the productivity of India’s millions of dairy farms, one cow at a time.
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Picking the best cow to breed from with only two in your herd is being made more considered than a toss of the coin, thanks to work that includes input from AgResearch scientists in India.

In a country of 75 million dairy farms averaging 1.7 cows per farm, the push is on to lift cow productivity to keep the country self-sufficient in milk production.

Despite the country being able to claim that it is the world’s largest dairy nation, India’s dairy cows are relatively low producing, typically averaging only 6-8 litres a day. 

But AgResearch scientist and geneticist Roy Costilla has been part of an international team focusing on developing a means of identifying the cows with the best milking genes in small herds, to select for breeding future higher producing offspring.

The work is funded through the Bill & Melinda Gates Foundation to develop models that use genomic selection to identify the DNA markers for cows with a higher potential to deliver improvements in herd production. 

The international team working on the project includes Professor Ben Hayes from the University of Queensland (Australia), as well as researchers from the University of New England (Australia), INRAE (France) and the BAIF research foundation (India).

Costilla says the challenge for researchers in such small herds is to identify which cow is best selected, something the team’s genomic selection model – developed specifically for small-scale Indian herds – is proving effective at.

The selection model has proven to be accurate when calibrated against data from 4650 cross-bred cows. 

The model’s strength also lies in its ability to control the influence or the “nurture” side of the nature-nurture impact on production.

“Our model uses random effects for herds which allows us to circumvent the problem, one that is impossible to get rid of entirely when assessing, but you can get a good idea of its proportion of contribution.” 

The model is also significant in that it is not generated by artificial intelligence, and uses real breeding data, something never done before for smallholder systems.

“Our simulations are using real genotype data from animals with known phenotypes and all their known genetic effects. And we have shown that, using our model, we can identify the breeding values for cows with good accuracy when you have at least two animals per herd.”

The heritability of the milk production trait in India has been estimated at 16%, higher than Africa’s 12% but lower than New Zealand-Ireland’s 20-30%.

“Over time with breeding we would expect to see that figure increase.” 

He emphasises that genetics are not the silver bullet for India’s dairy productivity gains.

“Nonetheless, they help. When you have good genetics, the nurture side of things also improves – the stock are valued more, looked after even better.” 

The results of identifying cows with the best milking traits will feed back to better bull selection, and thanks to an extensive AB system in India the genetics can be distributed quickly and widely.

“In some respects, it is a system more advanced than NZ. India has had affordable, accessible sexed semen for several years ahead of NZ, for example.”

He says the diverse nature of India’s dairy sector is also a bonus, with breeds and bloodlines around that are specific to different states’ conditions.

Future work will include expanding the model to allow for “genotype by environment” interactions – that is, the genetic differences that result from an exposure to particular environments.

“We are looking for the best genetics for the particular environment, based on state-by-state conditions.”Because the work is for the BAIF research foundation, an Indian NGO backed by the Bill & Melinda Gates Foundation, there is no intention to commercialise the model. 

However, it is set to play a big part in helping India’s national effort to lift dairy herd productivity in coming years.

“The next phase involves working together with BAIF and the National Dairy Development Board of India to implement the breeding values in the field.” 

The researchers also intend to focus on the implementation of genomic selection on India’s large buffalo population, which also supplies about half of the country’s fresh milk.

This article first appeared in the December edition of our sister publication, Dairy Farmer.

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