Thursday, March 28, 2024

Genetic gain facilitates lower cow numbers

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The national dairy herd already contains the calibre of cows that will be required in the future to allow farmers to reduce cow numbers without losing total farm productivity or profitability.
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“We already have cows with the desired levels of productivity, we just need more of them,” LIC’s general manager of New Zealand Markets Malcolm Ellis said.

LIC says genetics are a big part of the dairy industry’s response to the Climate Change Commission’s targets for greenhouse gas reduction in agriculture.

NZ is already a low-emissions dairy producer, but the commission is signalling a 15% reduction in stock numbers in nine years.

“We will need to be more efficient at a per cow level and look to produce at least as much milk from less cows to maintain profitability and competitiveness,” he said.

Over the past 25 years it is acknowledged that the average rate of genetic gain within the sector has been in the order of 9BW units (dollars) a year.

LIC says if the rate of genetic gain was to increase to within the range of 15 to 20BW a year, the associated productivity gains captured would go a long way to counteract declining cow numbers.

Ellis says the current 9BW a year is worth approximately 5.9kg milksolids per year, of which 2.7kg is directly attributable to genetic gain.

But while the sector average is currently 9BW, it is clear that many farmers are achieving in the order of double this rate of genetic gain.

Individual farms that are incorporating the use of sexed semen and genomically-selected bulls and have a desirable reproductive performance are achieving up to 32BW gain between their R1 and R2 replacement animals.

There is currently noticeable growth in the uptake of genomically-selected sires on the back of farmers increased confidence from the validation of teams once they have matured to daughter-proven status. 

LIC reported 1.4 million inseminations from genomic sires took place last year, up from just under 400,000 in 2017.

Validation includes all contemporary groups of bulls across all traits, production and non-production (TOP), in order to verify the claims of superiority of the young genomic bulls. 

Ellis then turned to the BW spread within herds to show what genetic gains are available by sharpening the selection pressure within the herd improvement equation and tightening the bell-shaped curve of distribution.

Following decades of cow population growth a number of dairy herds within the country have a long tail of genetic merit and indeed productivity. 

He says the objective should be to avoid breeding the next generation of replacements from tail-end cows.

“It is a reality that in a national herd averaging 385kg MS a cow, the difference in productivity between the top and bottom quartile of all herd tested cows corrected for age, breed and location, is a staggering 160kg a cow,” he said.

In order to create the desired number of replacements, farmers could mate a portion of the top end of the herd to sexed semen in order to better utilise those high BW cows. 

Yearling matings would also accelerate this rate of gain. 

“We have long known that poor cows very often come from poor mothers – that is genetics 101,” he said.

Ellis says the combination of MINDA LIVE and herd testing can generate very informative cow analysis to sharpen that selection pressure in herd improvement.

Once the distribution of herd quality is well-known and understood, more emphasis can be put on the reproductive outcomes of those top cows. 

“With limited selection pressure, often we see too many poor quality cows being trusted with the creation of the next generation, which ultimately holds back the rate of gain achieved,” he said.

Ellis listed the options available to farmers wanting to increase the rate of genetic gain – the use of genomic bulls, sexed semen and yearling matings along with a sharpened  focus on reproductive performance. 

Underpinning all of it was enhancing selection pressure.

“It is a reality that in a national herd averaging 385kg MS a cow, the difference in productivity of four to eight-year-old cows, adjusted for age, breed and location, is a staggering 160kg a cow,” he said.

“This represents a significant opportunity as an increased spotlight goes on the principles of herd improvement.” 

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