Introduction
Females play an important role in the herd. Not only does she contribute 50% of her genetics to her calf, but she is also required to get pregnant, give birth, wean her calf and get back in calf, all while maintaining her own condition at an acceptable level. This article will examine the traits that make a good maternal female, and examine how genetics can help to improve compliance levels within the herd for each of these important life stages. In addition, this article will examine the current genetics of the average Australian Hereford female, thus providing Australian Hereford breeders with a tool to compare where their female herd sits in comparison to the current Australian Hereford breeding herd.
The Maternal Female
The job of a female (whether a maiden heifer or an older cow) in the breeding herd is to:
1. Get in calf (in the first or second cycle) and carry the calf to term.
2. Give birth to a live calf (without assistance).
3. Wean the calf.
4. Get back in calf, thus repeating the cycle in the next year.
In addition, she should do all of this without consuming excessive amounts of feed (in turn improving the stocking rate for the property, and thus giving producers the option to run more animals).
While beef producers will often cull cows from the herd that do not perform at each step, simply removing the individual cow does not remove the underlying poor genetics from within the herd (as the parents and/or progeny are not culled). Without making genetic improvement within the herd to improve compliance levels at each step, the problems will simply repeat themselves in subsequent calving drops.
A classic example of this is seen in the change in docility in Australian Limousin. While breeders were culling animals with poor temperaments from each calving drop, it wasn’t until the Docility EBV was introduced that breeders were able to make informed decisions about which sires and dams to select (previously poor temperament was passed on because the environmental effects confounded the underlying genetics of the trait – e.g. a “quiet” bull who was quiet because he had been broken in was still producing calves with poor temperament). As genetic progress was made within the breed for docility, the incidence of calves which needed to be culled for poor temperament decreased.
In a similar manner, genetics can be used to improve the percentage of females in the herd which are getting in calf, giving birth to a live calf unassisted, weaning the calf and getting back in calf. Let us explore which of the BREEDPLAN traits are important for a maternal female throughout her life, particularly during pregnancy, calving, while raising the calf to weaning and for her own maintenance.
1. Pregnancy
The first test for any female is to get in calf and carry the calf to term. Ideally, a female should be getting pregnant in the first or second cycle. This allows the producer to have a short joining period (in a fertile herd, this shouldn’t compromise pregnancy rates) and thus calve down over a shorter time (reducing the number of weeks the producer needs to check pregnant heifers and cows for calving difficulties). Calves born from matings in the first or second cycle also have a significant age, and thus weight, advantage over their late-born herd mates.
Failure of a heifer to get pregnant is often due to her not being sexually mature at the time she was out with the bull. A heifer may not be sexually mature because she is a late maturing type (e.g. the tall lanky animal that is still growing), or because she was born late in the season and is younger than the other heifers (e.g. the small young animal that is still growing). In both situations, the fertility traits (Days to Calving and Scrotal Size EBVs) are important.
The Days to Calving EBV describes the genetic differences between animals in the time from the start of the joining period (i.e. when the female is introduced to the bull) until subsequent calving, and is expressed in days. Most variation in this trait occurs in how long it takes the female to get pregnant (e.g. did she get pregnant in the first cycle, second cycle or not at all), with only a small amount of variation in this trait being due to gestation length (Figure 1). Lower, more negative Days to Calving EBVs are more desirable, as they indicate shorter Days to Calving (e.g. females that conceive earlier in the joining period).
Figure 1. Most variation in the Days to Calving EBV is due to the time taken for the female to get pregnant once she is out with the bull.
Similarly, Scrotal Size EBVs are another important indicator of fertility in the female herd. While this may seem counter-intuitive (after all, a heifer does not have a scrotum), research has shown that bulls with higher Scrotal Size EBVs tend to be more early maturing than those with lower Scrotal Size EBVs. In turn, bulls with higher Scrotal Size EBVs tend to have daughters that mature earlier than the daughters of bulls with lower Scrotal Size EBVs.
Thus, the ideal maternal female should have more negative Days to Calving EBVs (indicating a shorter Days to Calving) and more positive Scrotal Size EBVs.
2. Calving
The next important test for a female in the breeding herd is to give birth to a live calf, without assistance. Calving difficulty has a negative impact on the profitability of the herd due to increased calf, heifer and sometimes even cow mortality, slower re-breeding performance and considerable additional labour and veterinary expenses.
While non-genetic factors can contribute to calving difficulty (it’s still important to keep heifers and cows in optimal condition in the lead up to calving), there are a number of genetic factors that also
influence calving difficulty. These include birth weight, gestation length, shape of the calf, pelvic area and willingness of the cow to push. These factors are covered by several BREEDPLAN EBVs; namely Calving Ease Direct, Calving Ease Daughters, Gestation Length and Birth Weight.
The Calving Ease Direct EBV describes the genetic differences in the ability of a sires’ calves to be born unassisted from two-year-old heifers, while the Calving Ease Daughters EBV describes the genetic differences in the ability of a sire’s two-year-old daughters to calve without assistance. Both EBVs are reported as differences in the percentage of unassisted calving’s, with higher, more positive Calving Ease EBVs (indicating less calving difficulty) being more desirable. In a self-replacing herd system, where daughters are retained for breeding, both Calving Ease EBVs are of importance.
The Gestation Length EBV describes the genetic differences between animals in gestation length and is expressed in days. Lower, more negative Gestation Length EBVs indicate a shorter gestation length and thus are more desirable. In general, a shorter gestation length results in a smaller calf, which is usually born with less difficulty than a larger calf.
The Birth Weight EBV describes the genetic differences between animals in calf birth weight and is expressed in kilograms. Small, or moderate, Birth Weight EBVs are generally more favourable, as they indicate lighter birth weights. In general, a lighter calf at birth is likely to result in less calving difficulty than a heavier calf, although of course there can be exceptions. This is because birth weight, as mentioned above, is not the only factor that influences calving difficulty.
The ideal maternal female should have more positive Calving Ease Direct and Calving Ease Daughters EBVs (indicating less calving difficulty), more negative Gestation Length EBVs (indicating shorter gestation length) and a low to moderate Birth Weight EBV (indicating lower birth weight).
3. Raising the Calf to Weaning
The next test for the female is to raise her calf to weaning. A good maternal cow should provide adequate nutrition to raise the calf to weaning, and wean her calf with an adequate weaning weight. The Milk EBV provides an estimate of the maternal contribution of a dam to the 200 day weight of her calf. The Milk EBV is expressed in kilograms and indicates the expected difference in the weight of the calf at 200 days due to the maternal contribution of the cow.
However, it is important to note that the optimum Milk EBV is dependent upon the production system and the environment in which the cows are run. Selection for increased milk production may be warranted when cows are run under good nutritional conditions (e.g. improved pasture), while other poorer environments (e.g. scrubby rangeland) may not support cows with higher Milk EBVs. In addition, high milking cows may not get back in calf as easily as lower milking cows in the following year. Thus, while the ideal maternal female should provide adequate nutrition to raise the calf to weaning, the optimum Milk EBV for a maternal female will depend on the environment in which she is run.
4. Maintenance
In addition to getting pregnant, giving birth to a live calf, weaning the calf and getting back in calf, a maternal cow should perform all of these tasks without consuming excessive amounts of feed. Given that feed costs are among some of the most expensive costs on a farm, the weight of a mature cow will have a major influence on net profitability. This is because, in general, lighter cows will tend to eat less, thus having lower feed requirements and being less expensive to maintain. Conversely, given live weight is the major determinant in the value of cull cows, heavier cows may provide higher returns when selling cull cows. It is important to achieve an appropriate balance between feed requirements over the lifetime of the cow and her value as a cull animal.
The Mature Cow Weight EBV describes the genetic differences between cows in live weight at 5 years of age, and is expressed in kilograms. A higher, more positive Mature Cow Weight EBV indicates an animal that would produce progeny with a higher mature weight than an animal with a lower Mature Cow Weight EBV. While it is important for producers to optimise the balance between feed requirement and cull value, in general the maternal female should have a low to moderate Mature Cow Weight EBV, as this will reduce her feed requirements over her lifetime.
Another trait that gives a measure of cow maintenance is net feed intake. Net Feed Intake (NFI) EBVs are measures of genetic differences between animals in feed intake at a standard weight and rate of weight gain. The NFI-F EBV is a measure of feed efficiency when animals are in a feedlot finishing phase, with a more negative EBV indicating a more feed efficient animal (e.g. animal consumes less feed than expected given its weight and growth profile). While an EBV for net feed intake in cows is not available, research has shown that there is a positive relationship between NFI EBVs and feed intake and feed efficiency of cows. Simply put, selecting for more feed efficient animals using NFI EBVs should also lead to more feed efficient cows.
5. Other Traits
In addition to the BREEDPLAN traits discussed above, it is important to remember that there are other traits that are important for a good maternal cow in the herd. A good maternal cow must still have good structural soundness; after all, she spends much of her life moving around the paddock feeding and thus needs good foot and leg structure to allow her to move about with ease. In addition, a cow with good structural soundness may last longer in the herd, thus potentially improving her longevity in the breeding herd. In a similar manner, a maternal cow should be in good general health.
While not strictly related to her maternal ability, the horn/poll status, genetic condition status and pedigree of the cow should also be a consideration. Keeping an eye on the pedigree of the cow (and the bull she is being mated to) allows producers to manage inbreeding in the herd at an acceptable level. Similarly, producers may be interested in the genetic condition status of the female as this will allow them to avoid carrier to carrier matings; although this becomes less important when the bulls being used in the herd have been tested free for the relevant genetic conditions. In the same way, producers breeding for polled animals may wish to know the horn/poll status of the females to avoid producing horned calves (unless using a homozygous polled bull). This is less of a consideration for those wishing to breed only horned calves – given horns are recessive, simply select bulls and females with visible horns.
The ‘Average’ Australian Hereford Dam
What does the average Australian Hereford dam look like? Where does she benchmark against the rest of the breed? To answer this question, let us examine the average EBVs of the dams of the 2016 Australian Hereford calving drop (Figure 2).
Figure 2. The EBVs and EBV Percentile Graph for the average Australian Hereford dam of the 2016 calving drop.
• Calving Traits – For the calving traits, shown in yellow, the average Australian Hereford dam is genetically harder calving than breed average for both calving ease direct and calving ease daughters. She also has a gestation length that is slightly longer than breed average, and a Birth Weight EBV that is slightly heavier than breed average.
• Growth Traits – These are shown in green. The average Australian Hereford dam is below breed average for 200, 400 and 600 day weight, being in the 62nd, 68th and 68th percentiles respectively. She is lighter than breed average for mature cow weight, being in the 58th percentile. However, as discussed earlier in the article, being below breed average for mature cow weight may be desirable for a maternal female. Her Milk EBV of +13 puts her below breed average, in the 62nd percentile. However, the optimum Milk EBV depends on the country that the female is being run in; some producers may be happy to have their females below breed average if they are running in tough country, while others in better country may want to have cows with above average Milk EBVs.
• Fertility Traits – These traits are shown in red. With a Days to Calving EBV of -1.6, the average Australian Hereford dam is in the 70th percentile and thus below breed average for this trait. This means that she has longer days to calving than breed average. She also has a Scrotal Size EBV that is below breed average, being in the 60th percentile. While the dam does not have a scrotum, she will pass on genetics that influence the scrotal size of her sons. Furthermore, as discussed previously, a larger scrotal size in a bull has been linked to earlier maturity in his daughters.
• Carcase Traits – The carcase traits are shown in pale blue. The average Australian Hereford dam is below breed average for carcase weight, EMA, rib fat, rump fat and IMF, being in the 72nd, 52nd, 65th, 60th and 68th percentiles respectively. The average Australian Hereford dam is just above breed average for retail beef yield, being in the 45th percentile.
• Docility – Docility is shown in dark blue. With a Docility EBV of +1, the average Australian Hereford dam is less docile than breed average, sitting in the 58th percentile.
• Selection Indexes – The four Hereford selection indexes are shown in pink. The average Australian Hereford dam is below breed average for each of the indexes, sitting in the 68th percentile for both the Grass Fed Steer and Grain Fed Steer Indexes, and the 70th percentile for both the Supermarket and EU Indexes.
While the average Australian Hereford dam does sit below breed average for all traits except retail beef yield, it needs to be remembered that there is less selection pressure on females than there is on males. This is because beef producers tend to keep more of their heifers as replacements than they do their male calves. Furthermore, the dams of the 2016 drop will have a spread of ages. Therefore, older cows may have been above breed average when they were selected as replacement heifers, but, assuming the breed has made genetic progress in subsequent years, they may no longer be above breed average now.
Nevertheless, taking the time to sit down and work out where your replacement heifers and breeding cows are sitting, particularly for the maternal traits, is a valuable exercise and highly recommended. Your BREEDPLAN herd report contains the average EBVs for the dams in your herd. This allows you to identify the average genetic merit of your dams, and compare the average dam in your herd to the average Australian Hereford dam shown in Figure 2. In addition, this report allows you to identify whether you have made genetic progress in your dams over the years. To compare an individual female to the average Australian Hereford dam, first bring up the EBV Percentile Graph of the female you wish to examine (if unsure of how to do this, see the SBTS & TBTS Technical Note ‘Where Does This Animal Rank? Introducing the EBV Percentile Graph’ or contact SBTS for support). You can then compare the individual female to the average Australian Hereford dam shown in Figure 2. While not the only criteria to consider (structure is important too), this is a particularly useful exercise to consider when deciding which of your heifers you will keep as replacement females. Similarly, this is a useful exercise to undertake when considering which of your breeding cows to cull.
Although a lot of thought goes into selecting the right sire(s), and rightly so, it is important to remember that the female also passes her genetics onto the resulting calf. Even if the average Australian Hereford dam was mated to a bull in the Top 1% of the breed for all traits, the resulting calf will be, at best, around the 25th-30th percentile (e.g. halfway between the two parents). Having desirable genetics in your females is just as important as selecting the right bull.
For those wishing to improve the genetics of their females, there are several options to consider. Assuming that genetic progress is being made in each generation, the heifers in a herd should have
greater genetic merit than older cows. Therefore, increasing the replacement rate to keep more heifers could help to improve the average genetics of the female herd. Another option to consider is mate selection, where a certain bull is strategically mated to a certain female. Programs such as MateSel and TGRM can assist producers to make optimal mate selection decisions. In addition, the Mating Predictor on Internet Solutions (Figure 3) allows producers to see the expected average progeny values for the progeny of a particular mating. While the EBVs of the resulting progeny will usually shift away from the expected average progeny values depending on how the progeny performs once it is born, the expected average progeny values give producers an indication of how the progeny of a particular mating may perform.
Figure 3. The Mating Predictor on Internet Solutions allows producers to see the expected average progeny values for the progeny of a particular mating.
Conclusion
A maternal female in the Australian beef herd should get in calf, give birth unassisted to a live calf, raise that calf to weaning and then get back in calf, all the while maintaining herself without needing to consume excessive amounts of feed. BREEDPLAN produces a number of EBVs which are of importance when considering a maternal female; namely Days to Calving, Scrotal Size, Gestation Length, Calving Ease Direct, Calving Ease Daughters, Birth Weight, Milk and Mature Cow Weight. Ideally, a maternal female will have shorter Days to Calving and Gestation Length EBVs than average (more negative EBVs are more desirable), while having larger Scrotal Size, Calving Ease Direct and Calving Ease Daughters EBVs (more positive EBVs are more desirable). She should also have a moderate Birth Weight (lower or moderate EBVs being more desirable), and a moderate Mature Cow Weight (lower or moderate EBVs being more desirable). The optimal Milk EBV will depend on the environment, where producers in good country may prefer more positive Milk EBVs, while producers on more scrubby marginal country may prefer more moderate Milk EBVs.
This article has provided a snapshot of the average Australian Hereford dam, using the average dam of the 2016 calving drop as an example. The average Australian Hereford dam is below breed average for all traits bar retail beef yield. This may be explained in part by less selection pressure on females compared to males, and the spread of ages of Australian Hereford dams (e.g. older dams may be below breed average now, but may have been above breed average when selected as a replacement heifer). The provision of the EBVs and EBV Percentile Graph of the average Australian Hereford dam will enable Hereford producers to benchmark both their replacement heifers and current breeders against the average Australian Hereford dam. To improve the genetics of the female herd, beef producers could consider increasing the replacement rate (keeping more heifers) and/or using mate selection tools to make more informed mate selection decisions.
For further information on using genetics to breed maternal females, or to further discuss any of the topics raised in this article, please contact Catriona Millen, SBTS Technical Officer for Hereford, on (02) 6773 3357 or via email catriona@sbts.une.edu.au
