The skinny on genes

What genetic change has the New Zealand beef cow herd made and are we improving? Amy Hoogenboom writes.

In Livestock11 Minutes

What genetic change has the New Zealand beef cow herd made and are we improving? Amy Hoogenboom writes.

Genetics set the potential for the upper and lower production limits an animal can achieve. Alongside animal health and nutrition, it is one of the most economically important production components of the modern beef system.

Genetic change is easy, one only has to look at the Angus New Zealand champion national sale bulls from the 1960s to the present day, to see that we can change the genetic make-up and ‘type’ of cattle we have.

The key is to make genetic improvement. Genetic improvement is about producing the best genotypes of cattle to suit a specific beef system, and importantly this genetic gain is cumulative and permanent.

So, what genetic change has the NZ beef cow herd made and are we improving?

Where we’ve come from and where we are now?

First, let’s look at some general trends of the NZ beef cow herd from a breed composition aspect. Using information from Beef + Lamb NZ’s Compendium of NZ Farm Facts (between 2010 and 2020) cattle numbers, breeding cows and heifers have remained relatively stable.

What has changed is the breed composition of the nation’s cattle population, with the percentage of straight-bred Angus increasing by 10%. The percentage of Hereford and Angus/Hereford cross cattle have stayed similar. Mixed breed cattle dropped at a similar rate to that which Angus has increased.

The percentage of Friesian (in the form of bull beef) has reduced slightly but still hovers about 20% of NZ beef cattle numbers.

Another genetic trend, possibly overlooked, is the increasing number of polled cattle within the population. This is partly due to the change in breed composition towards a breed which is naturally polled. It is also through conscious effort by breeders to breed for the polled trait in their herd. Introducing the polled gene to a herd is one which rewards the farmer for decreased input costs in the form of reducing or removing the need for dehorning and improving the animal welfare aspects.

Focusing on the Angus and Hereford breeds, what way have the lines been trending for recorded traits of economic importance?

To find the answers I went searching for the two breed associations’ trend graphs for the various estimated breeding value (EBV) traits reported. These were less readily available than hoped, but fortunately a couple of helpful breeders were willing to share their Breedplan reports. They include the breed average genetic trend Information from the early 2000s to present day. While we cannot directly compare EBV values between breeds due to the genetic base for each breed being different, the units the traits are expressed in are the same, therefore we can compare the rate of genetic gain between breeds.

Both breeds have increased growth from 2000 to 2020, with Angus having a slightly higher rate of gain (about 0.3kg/year) than the Hereford breed for 200- and 400-day weight EBV average. The carcaseweight EBV breed average has also lifted from 2000 to 2020 at a rate of 1.45kg per year for NZ Hereford and 1.15kg per year in NZ Angus cattle. As is well-documented, the high correlation of mature cow weight with growth and weight traits, means increase in growth has also resulted in an increase in mature cow weight EBVs at a rate of 0.95kg/year in Angus and 1.05kg/year in Herefords.

Premiums pushed marbling

Intra-muscular fat (IMF) was the big on-trend word for the 2021 bull selling season. This was off the back of announcements from some meat companies of better premiums for carcases displaying higher eating quality attributes for which marbling was a key criterion.

Both breeds have made improvement to their IMF EBV breed averages, though Angus breeders have pursued both IMF and eye-muscle area more aggressively than Hereford breeders.

The rate of genetic gain in the Angus breed being almost double that of Hereford for these two traits. Only very small changes to external fat cover EBV averages have been made in both breeds.

When we look at birth traits and traits of maternal importance, we have already mentioned the increased mature cow weight. Milk EBV breed averages for both breeds have also increased which, depending on the production system and environment in which the cows are run may not necessarily be desirable, especially when combined with an increased mature cow weight.

Birthweight for both breeds has, after trending upwards in the early 2000s, come back to the same, if not slightly less than where the breeds were at in 2001. This is most likely driven by a shift in some breeders’ focus towards supplying bulls to the dairy market. The same can be said for gestation length and days to calving where downward pressure has been applied by breeders supplying the dairy industry, in turn reducing the breed average for each of these.

If we diverge from traits recorded for a moment, but to one of high maternal importance, the NZ national calving percentage (calculated as, the number of calves weaned, as a percentage of cows mated) has remained almost stagnant at ~82% over the past 30 years.

Varying factors on each farm impact this across the three production components of genetics, nutrition, and animal health, but there is considerable potential for increased reproductive performance and efficiency of the national beef herd to be made through something as ‘simple’ as increased calving percentage. Having the genetic potential for increased growth and carcase merit is of little value if you cannot get a calf on the ground in the first instance.

In summary, we’ve made good improvements in terminal traits which have led to higher weaning weights, yearling weights, and carcase weights. We’ve done a variable job on improving the traits that add value to the end product beyond carcase weight. However, we are probably falling short on improvement of key maternal traits that are becoming increasingly important with regards to more efficient production and a smaller environmental footprint.

Where are we going or where should we be heading?

One of the great challenges of the beef cattle industry is that the dollar benefit of these terminal trait improvements made by the bull buyer/cow-calf producer are very rarely seen by them, unless they are a breeder-finisher which is of low occurrence in the NZ beef system. What the cow-calf producer does experience is the increased feed cost or maintenance associated with these bigger cattle.

To widen our profit margins, we cannot always count on increasing our income, but rather decreasing our inputs. Which raises the question: where is the sweet spot between maternal and terminal traits to realise a more efficient and profitable beef system across the whole chain?

Let’s say you’ve bought an Angus bull to put over your 15-month heifers and he has a +2.0kg for BW and a CE direct of +5.0 %. For the past few years, you have not pulled calves from any heifers or are pulling less than 2%, do you need to keep driving those numbers up/down? When does it become detrimental to other parts of the operation?

If there are no onfarm issues with the related application of these traits you are using in your bull selection process, it is probably okay for you to keep buying at this threshold for these two traits, allowing for more selection on other traits where improvement is wanted. You can apply this same principle to other traits to help prioritise selection decisions.

If we wish to improve the efficiency of the beef cow herd population, undoubtedly some changes in the slope of these genetic trend lines are needed. Adding another 10kg to mature cow weight over the next 10 years will not improve efficiency of the beef system from any standpoint, most particularly at the cow-calf producer level where it is most needed, nor is it likely to stand the scrutiny of beef production’s impact on the environment. What traits are we not recording for and giving adequate attention to that with small change could make significant improvement to the efficiency of beef production?

The modern beef cow herd needs to be a low-cost calf factory that produces an end product that meets market demand.

  • Amy Hoogenboom is a veterinarian and Zoetis beef genetics area manager.