Breeding decisions to breed four- and five-star replacements

The female replacement requirements for the Beef Data and Genomics Programme have brought a greater focus to breeding decisions.

There are two important targets. The first is for farmers to have 20% of their reference number of animals (based primarily on the number of cows calved in 2014) rated as four- or five-star on the Replacement Index, on an across-breed basis, by 31 October 2018. The second target farmers must achieve is to have 50% of their reference number of animals classified as four- or five-star by 31 October 2020.

To put this in context, a farmer with a reference number of 18 calved cows in 2014 must have four animals rated four- or five-star on the Replacement Index by 31 October 2018 and nine animals rated as four- or five-star by 31 October 2020.

For a female to be deemed eligible for inclusion, she must be 16 months old, or greater, and have a four- or five-star rating on the Replacement Index on an across-breed basis at the time of purchase (for heifers purchased into the herd) or at the time of genotyping for replacements bred within the herd.

The ICBF explains that over 90% of herds already meet the 2018 replacement requirement, while in the region of 72% currently meet the 2020 target – that is assuming farmers continue with their present breeding strategies.

It is important that steps are taken to ensure herds stay on track and for those requiring improvement that the necessary changes are implemented in time. For many, this will take the form of sourcing four- and five-star heifers and purchasing from an outside source.

For another high percentage of suckler farmers, the preferred approach to meeting targets will be to breed from within the herd. This is where a high percentage of discussions and queries are currently stemming from and will be the focus for the remainder of this article.

Replacement Index

After a review of the Replacement Index earlier this year, the index is currently comprised of 71% cow traits and 29% calf or progeny traits. A full breakdown of these traits is detailed in Table 1. For an animal to be rated as four-star on the Replacement Index, it must currently achieve a minimum Replacement Index value of €74.

It is important to note that while a Replacement Index value of €74 currently classifies an animal as a four-star on the Replacement Index, this is not an absolute figure that is immune to change. The value of €74 can alter when more production information comes on stream and is particularly at risk to fluctuating once genomic values (from genotyping) are fed into the database and start contributing to evaluations.

It is envisaged by the ICBF that values will not change significantly but to reduce the risk of fluctuation and animals falling into lower indices, the advice is to target breeding animals with a replacement value well above the current minimum value for a four-star replacement of €74.

Calculating the Replacement Index

The Replacement Index value of progeny is calculated on the parent average of a dam and sire, as demonstrated in Figure 1. As touched upon above, this calculation is taken at a given point in time and could change. The greatest risk of values fluctuating stems from using new or unproven sires with low reliability.

The ICBF explains the way the system works is that all pedigree beef bulls when born start out with a predicted figure as to how they will breed based on their parents’ figures. This is called a “parent average”. As data is recorded on them (weights, body measurements (linear scores), feed efficiency, etc) their own figures change to reflect this data and the reliability percentage increases slightly. Then when the bull sires calves and they have data recorded on them, the bull’s figures change again and the reliability percentage goes up again. The more progeny that a bull has data recorded on, the more the bull’s parents’ figures are fading out of the equation. By the time a highly used AI sire reaches 90% reliability, his parents’ evaluation figures will have little or no effect.

Munster Cattle Breeding Group and Progressive Genetics recently launched a BDGP breeding advice booklet which contains AI and general breeding advice (it can be found on www.progressivegenetics.ie and www.munsterai.ie). The information has also been presented by Rosalish Goulding, NCBC, and Arthur Bredin, Progressive Genetics, at recent farmer meetings incorporating a live demonstration of livestock.

Their advice in the booklet, stemming from discussions with the ICBF and Teagasc, is for farmers to aim for a parent average Replacement Index value of at least €102.50. They say this will ensure you have an increased chance of meeting the €74 target post-genotyping.

Table 2 details the minimum bull index recommended for use for a range of Replacement Index values to deliver a parent average of €102.50. This is based on a minimum bull index with a reliability of 85%.

Lower reliability and teams of bulls

If breeding a cow with a lower Replacement Index value, three stars or lower, for example, it is useful to select a sire with high reliability, while if you want to use a test bull with a lower reliability figure, it is recommended to use with caution to reduce the risk on progeny values from a sire’s Replacement Index value falling. The advantages of using a young bull is that you are accessing the best new genetics. The best way of using a young AI bull while at the same time protecting yourself from the potential of his figures falling is to use him in a team of bulls, ie instead of using 15 straws from one Limousin bull, use five straws from three bulls.

If using sires with low reliability, Rosalish advises farmers to use a team of bulls that will serve in spreading the risk. She says the number of bulls on the team will vary according to the reliability of the individual bulls with the principle being that the greater the number of bulls on the team, the greater the reliability. “Aim for a bull team reliability of 85%. One bull with a reliability of 85% is equivalent to using four bulls at 40% reliability equally.”

Even with this principle, low-reliability bulls should still be used with caution and particularly where excess cows are not being bred to allow for greater choice and disregarding of heifers that don’t make the grade.

Aiming high

The conclusion can be summed up as follows: to maximise the chance of breeding four- and five-star replacement progeny, target your highest index cows in the herd for breeding with high-index sires. Aiming for as high a value as possible will also allow for some fluctuation in the ICBF’s Replacement Index values (stemming from genotyping) and also for fluctuations in an animal’s own replacement value stemming from more production data entering the ICBF database while also improving the genetic merit of your herd.

Opportunities

At a recent beef information meeting in Ballymote Mart, organised by Aurivo, Progressive Genetics and the Irish Farmers Journal, Rosalish Goulding, NCBC, advised farmers not to be afraid to look outside their normal selection of breeds when aiming to breed four- and five-star female replacements. For example, she said that beef Shorthorn sires are a good option to breed good-quality suckler cows with the added bonus of sires available with a proven favourable milk yield.

Rosalish highlighted Salers as being the breed with the highest average replacement values.

“High-index replacement sires can be found in all breeds. It is necessary to select your sires carefully as there are large variations within breeds. Fifty-seven high-index replacement sires are presented in the booklet from eight beef breeds.”

The higher values in bulls such as RIO, with a Replacement Index of €170 at 95% reliability, stem from proven fertility, calving ease, milk yield and favourable performance of progeny, making them a good choice to increase the parent average of replacements. She said daughters breed particularly well when crossed back to a good terminal Charolais bull to produce top-quality cattle that suit a number of markets.

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