Growth & Maternal

Glosssary

Average Growth/Maternal EBV’s for 2004 born calves*

*Based on the January 2006 results.

When considering growth traits, commercial producers have to balance their customers’ growth requirements for steer progeny with the need to ensure viable replacement females keep coming through the system. At Millah Murrah we lean towards a long term “production” (as opposed to “market”) focused view, maintaining an easy keeping female herd as the number one priority.

It is worth considering the genetic trend lines for growth and maternal attributes of the Angus breed over the past 20 years, by examining the graph below (Source Angus Australia Website).

The 1st message to take from this graph is that growth EBV’s are strongly correlated. (There are animals that defy such genetic correlations, and Breedplan identifies such animals for us.)

The 2nd message is that the Angus type has changed. Growth rates have increased greatly and the maturity pattern of the breed (represented somewhat by the mature cow weight line) has been extended. This is in line with the requirements of the Feedlot industry which requires a leaner, larger and later maturing animal than was typical of British breeds 20 years ago.

Two example production systems are outlined below to allow discussion of the use of EBV growth figures in bull selection.

Growth EBV’S and Bull Selection

1. PRODUCTION SYSTEM:

Self replacing female herd turning off 250 – 320kg male progeny, direct from their dams, as 7-9 month vealers, or for domestic slaughter after 100-150 days on feed.

Typical of the colder regions of the NSW Tablelands, we would advise a breeder with these production targets to select older style sires. In EBV terms, in many cases the best animal for this role will in fact carry EBV’s at or below today’s breed average for growth traits. Aiming too high for 200 day weight EBV’s will almost inevitably translate into later maturity patterns and difficulty presenting a soft type at weaning.

For this sector, consideration of milk (discussed below) as well as carcass traits (especially the desire for positive fat cover and adequate muscling) is also prudent.

The female replacement portion of the progeny will likely retain the easy doing traits traditionally associated with the breed when using this style of sire. As lower growth sires are likely to be used, in most cases this will translate into a smaller framed cow at maturity.

2. PRODUCTION SYSTEM

Self replacing female herd weaning 270 – 340kg male progeny, destined for back grounding and lot feeding for export, often for the B3 Japanese market.

Currently most temperate Australian Angus cattle breeders would operate under a similar system to this.

Compared to production system 1, growth is a more important variable for consideration. The challenge is to balance the desire to produce high growth, later maturing steer progeny with the need to retain functionality in the replacement female crop.

Today’s average EBV set (shown above) is perfectly adequate in terms of growth to satisfy the balance described in the previous paragraph. Providing the animal is physically satisfactory, variations above or slightly below average will be acceptable, but in EBV growth terms, the Angus breed “has arrived” at its goal of satisfying the demands of the feedlot sector.

The greatest trap for breeders targeting this market is to lose focus on the cow base. Pushing growth genetics too hard will often cause deterioration in the ability of the cow herd to produce easily under commercial conditions. Phenotypically, +100 cows (referring to the 600 day weight EBV) are often big framed, hard doing animals with high nutritional requirements. In other words cows that need careful management to get them back in calf when it turns dry. There are individuals with high growth genetics that retain doing ease and fertility, but they are the exception rather than the norm. Therefore it is sensible to take only modest steps each year to increase herd wide growth genetics. This ensures retention of easy doing females, whilst maintaining adequate growth genetics to satisfy feed lot requirements.

MATURE COW WEIGHT

The Mature Cow Weight EBV is designed to predict the size of the cows an animal will leave. Theoretically we should be able to develop a herd of small cows that produce fast growing calves to 600 days that then stop growing. This would keep a check on nutritional requirements of the cow herd, whilst optimizing the growth of the steers at the right time. One day it should be an excellent tool. To date however, it has been an unreliable EBV, penalizing some of the breed’s greatest female sires in terms of doing ability and fertility, whilst rewarding some harder doing types. At this stage it is wise to emphasize visual inspection for decision making in this regard.

MILK

What does the Milk EBV mean in terms of calf weight at 200 days.

(from the Angus Society Website)

“ Research has demonstrated that a 1 kg increase in Milk EBV equates to a 0.1 kg increase in daily milk production. This means an extra 20 kg of milk over 200 days of lactation.

Given that a calf converts milk to body weight at around 10% efficiency, this 20 kg extra milk equates to an extra 2 kg calf weight at 200 days of age. Sounds trifling at that level perhaps but take a +10 kg cow and we are looking at an extra 20 kg of weaning weight that results from Mum’s extra milk, compared to a cow with a 0 milk figure.”

Some widely used recent US sires have carried very high figures for the milk trait, and breeders need to be aware of the potential deleterious side effects of high milking cows, depending upon how they are grazed.

Consider the animals below:

Breeders can instinctively fall into the trap of seeing the milk EBV for cow C and thinking, “Cow C is a great cow, she gives so much to her calf. I’ll choose her over cow A & B, who are below average for milk.”

If nutrition is unlimited, this thinking should stand up, however over the long term in typical temperate Australian conditions it is likely Cow B will be the best cow and in Northern environments it may well prove that Cow A is the most profitable of the three.

For a relatively small weight advantage attributable to milk genetics at weaning, the negative impact of high milking performance on the ability of a cow to re breed can be profound. Provided a cow supplies adequate milk to allow its calf to grow on normally to weaning age, the only situation where one might actively select for such high milk as cow C is under a reliable high rainfall or irrigation, vealer production system. For all other systems the weight advantage created by a high milking dam at weaning is usually lost to growth performance during the grow out phase and has negligible impact by feedlot entry time.

Milking ability must be kept in balance with the environment in which cattle are run.