Costing a shorter calving period

Fertility is one of the most important aspects of a beef breeding business.  Fertility tends to be an overarching term applied to the number of calves that are born each year. Maximising the number of calves born and weaned annually requires attention on several areas in the herd.

While bull fertility is a significant contributor, there is also the aspects of female fertility.  Female fertility is impacted directly by daily energy intake.  This influences her condition score, and her ability to produce the hormones required to trigger ovulation and place the female in cycle for conception when exposed to a bull.

One area that I have often wanted my clients to focus on is the time between calving and re-joining.  This period is a critical window for producers, as it determines if you will achieve a calf born every 12 months.  A 12-month calving is the key benchmark for many herds striving to maintain or improve fertility and ultimately herd productivity.

“A 12-month calving is the key benchmark for many herds striving to maintain or improve fertility and ultimately herd productivity.”

This window is set by several boundaries.  The first is the actual period taken by gestation.  In cattle, gestation length is an average of 282 days.  As an average, this means there will be some animals that calve earlier, and some a bit later.  The other time component is the length of time that females require to recovery from calving ahead of a return to oestrus.   

This period can be influenced by the nutritional levels of feed on offer.  It is also impacted by the age of the female as well as a sight genetic influence.   

There are some significant advantages in having females which can join earlier.  An early joining which in turn results in an earlier calving buys the female some time ahead of the next calving season.  For instance, joining over a 6 – 9-week period would see those early calving females have several additional weeks to recover and return to oestrus for the next joining.   

As well as this advantage, naturally enough, those females who calve earlier will have several weeks advantage for their calves who can express additional growth compared to those born in the middle and end of the joining period.  This adds significantly to weaning weight and offers a chance to select replacements from animals that are slightly older and heavier from the new generation. 

A shorter calving interval offers significant financial benefits as well.  Research shows significant differences between herds that calve over 2 months and those with a longer (5 month) calving period.  The average difference in calf weaning weight is around 28kgs, which on the current EYCI values is $9.96 / kg translates to $278.88 / head 

A calf every 12 months should be the major target for breeding herds

Shortening calving is therefore a financially rewarding ambition for beef herds.  There are several ways to approach this ambition. 

Management Targets

Ideally females should be calved in a Fat Score of 2.5 – 3.5.  This means carefully managing pre calving nutrition.  It also means that heifers or cows that are lighter in condition will take longer to recover before returning to oestrus.   

For producers with lighter females, this could be addressed by increasing energy in the daily ration for lactating cows.  It’s important to remember that once calving occurs, females’ energy intake doubles.  This extra energy is often provided by metabolising fatness.  So, producers with light cows should supplement to make the ration meet the increased demands for the females. 

Selection Targets

While fertility is strongly influenced by environmental impacts – particularly nutrition, it is possible to select for those animals which are genetically suited to be more fertile and likely to conceive earlier.  

This can be done through using selection tools such as the Days to Calving EBV and the Gestation Length EBV. 

The Days to Calving EBVs are estimates of genetic differences between animals in the time from the start of the joining period (i.e., when the female is introduced to a bull) until subsequent calving. Lower, or more negative, Days to Calving EBVs are generally more favourable. 

Gestation Length EBVs address the time between the bull entering the herd and conception.

Gestation length can be defined as the period from the date of conception (i.e., when the female gets in calf) to when the subsequent calf is born. Shorter gestation length is generally associated with lighter birth weight, improved calving ease and improved re-breeding performance among dams. In addition, calves born with a shorter gestation length may be heavier at weaning due to more days of growth post-birth. Lower or more negative Gestation Length EBVs are more favourable. 

Improving fertility requires addressing long and short term goals in the herd

Combining long term selection with strategic management is the most effective way to move fertility levels towards more productive and financially rewarding levels.  The process should be seen as a combination of short- and long-term goals. 

Think about the raw data sheet at bull sales

The Spring Bull sales are well underway in Northern NSW. There have been a lot of successful sales in 2020, and this reflects a few things. Firstly there is a strong sense of optimism in the cattle industry, largely due to seasonal changes and strong market values. There’s also the influence of the intense selection placed on bulls over the last few years.

2020 bull sales have been highly successful to date

Breeders have definitely had a much greater level of selection placed on their bulls. Anything not making the grade has not been kept on for this years catalogue of sires. So this year is the year many people are using as the chance to upgrade their bull battery.

One message I have been providing for many years to producers is the importance of doing some research and preparation ahead of the bull sales. Its vital to think about the performance of your herd, and to look closely at the traits you want to improve or adjust to meet your environment and your markets. Performance records are a really important tool that can make these decisions more focussed and help refine selection of bulls for a program.

However not all data is the same, and it’s important to remember the difference between raw data (often provided on sale day) and performance records (published EBVs).

Consider selection of bulls as a process that starts well before the sale

EBVs are generated through the collection of large amounts of data that include not only the bull you are interested in, but the performance records of progeny, siblings and pedigrees. Collected over many herds and in many environments, EBVs are essential in describing the potential a sire can offer your future calves.

In contrast, raw data is really just a series of measurements taken at a single point in time, on one animal. There are people who use raw data in their comparisons, but if you do this, it’s important to realise that this data is a reflection of the nutrition and the pedigrees of animals in that particular program. However there are other factors that are in play as well.

These include:

• The age of the bull

• The age of the dam

• Was the bull a single calf or a twin

• Was the bull produced as a result of ET

These are all non genetic influences on the animal over and above nutrition and genetics.  It’s very difficult to know what these additional influences are or how to account for them in a selection decision. The combination of these factors can mean producers looking at raw data are really looking at differences that are a result of these multiple factors, rather than for the genetic differences in animals.  

“Selection on raw data is further complicated by the heritability of individual traits.  Highly heritable traits such as coat colour can be an easy selection decision, as these traits can be easily passed on to progeny.
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Selection on raw data is further complicated by the heritability of individual traits.  Highly heritable traits such as coat colour can be an easy selection decision, as these traits can be easily passed on to progeny.

However, as a trait becomes less heritable it is harder to see these differences reflected on the basis of raw data alone.  Producers attempting to manipulate traits to meet breeding objectives in areas such as female fertility have a harder job to select for improvement when they are reliant on raw data and visual observation.  It’s not an impossible task, however it is a much more difficult, and drawn out process over several generations.

Selection includes analysis of EBVs, physical inspection and looking at raw data

There is also a third consideration. What is the relationship between the trait that has been recorded and the traits that are the focus of breeding decisions?  Not all traits follow linear progressions.  In the case of scanned data for EMA.  The size of EMA at a particular point in time may not be reflective of increased muscularity, but rather a result of growth rate to that point in time.  A larger EMA may be more reflective of the growth and weight of the animal when it was scanned. 

I’m often concerned when producers place all their emphasis on the raw data of animals as the basis for their selection decisions.  Without knowing the cumulative impact of the environment, feed, and other non-genetic factors, bulls are being selected more on reflection of the year’s circumstances, rather than on their genetic capability.  This often works in a counterproductive manner to selection pressure placed on the breeding group at home.

Bidding on bulls should be the final step in a process that started at home thinking about the traits you need to meet your breeding objectives

Early planning allows time to consider a wider range of more accurate information and to consider the availability of data from Breedplan rather than reliance on raw data on sale day.  Combined with selection pressure these two areas do have a positive influence on genetic progress in any herd.