HERD IMPROVEMENT
Herd improvement is an active process where farmers are working towards a genetic improvement goal within their herd. For New Zealand dairy farmers, the measure of genetic improvement from one generation of cattle to the next is made through the industry’s Breeding Worth (BW) index.
BW incorporates a wide range of the data collected on-farm to provide farmers with an objective assessment of an animal or herd’s genetic merit. Farmers also readily select for specific characteristics like conformation or temperament using Breeding Values (BV), which are an estimate of a cow or bull's genetic merit for a trait.
Why is it important?
Genetic improvement has a direct economic value to farmers. The rate of gain in the national herd is increasing every year and the value of those gains accumulates over time. Each year, genetically superior heifers enter the milking herd.
They add value initially through their own performance and then through the genetics passed on to their daughters. This is why the impact of genetic gain on farm profitability accumulates over time. The difference between the genetic merit of the median herd, and a herd in the top 10% is estimated to be worth $12,600 in profit every year.
Breeding decisions have a permanent and compounding effect on a dairy herd, and making those decisions can be complex. The genetic merit of the herd will set the foundation for the profit they can achieve. When creating a herd improvement strategy, farmers and their advisors also have an opportunity to consider the impact genetic decisions can have on animal wellbeing.
Polled genetics
Disbudding is an invasive procedure that carries costs of time and money for the farmer and provides concerns for perception of the sector. Polled genes are dominant and can be utilised to reduce the need to disbud calves.
- The fastest gains are made by selectively mating to polled bulls. Currently, there are limited options available in New Zealand dairy bulls but there are great opportunities within beef bulls for cows not being bred for replacements.
- Bulls carrying one polled gene, rather than two, can be utilised in conjunction with the other breeding objectives for the farm to help reduce the on-farm cost of disbudding.
Thermal tolerance
The thermal comfort zone for New Zealand dairy cattle is between 4 and 20 degrees celsius and climate change is increasing temperatures but cattle throughout NZ are likely to be experiencing temperatures that cause thermal stress already.
Heat mitigation tools such as effective shade and altered milking frequency and time will continue to be important but genetics can also be used to develop a more heat tolerant herd.
- Jersey genetics have greater thermal tolerance so full Jersey animals or crossbreeds with a high Jersey component tolerate heat better.
- Gene mutations have been identified that support heat tolerance, e.g. the ‘slick’ gene. In hot conditions, cows with the ‘slick’ gene have been shown to have lower body temperatures and higher milk production compared to non-slick cattle. There is also preliminary evidence that ‘slick’ cows can have improved reproductive performance.
- A small number of bulls carrying the ‘slick’ gene are available in New Zealand. While ‘slick’ cows might not be the best choice for regions with cold winters, herds in hot areas and/or on farms where other heat-mitigation tools are difficult to implement may benefit from introduction of genetics which confer greater thermal tolerance.
Health traits
Preventing disease is generally better than trying to cure and there are already several heritable disease resistance and tolerance traits that have been discovered.
- Facial Eczema resistance genetics are available in New Zealand.
- Mastitis resistance is a heritable trait in cattle although currently most commercial genetic offerings only include Somatic Cell Count (not clinical mastitis) in their indexes – check with the breeding company how they calculate their udder health BV.
- Lameness/locomotion is the next largest health burden for dairy cattle although heritability of mobility traits in cattle is thought to be low , variation in breed and animal susceptibility to lameness could still be used to increase mobility traits within herds.
- Easy calving bulls improve welfare outcomes while also reducing financial and animal welfare costs.
How to improve?
Knowing your herd’s indexes and BV can help when planning your genetic strategy to improve the health and welfare of your herd.
Work with your herd improvement company as well as your advisors and veterinarian to consider the impact genetic decisions can have on animal wellbeing and formulate your herd improvement strategy.
Where to go for further information?
