19 October 2022

Examining Weight for Age

Pearse Kelly, Head of Drystock Knowledge Transfer, Teagasc, explains how weight for age is a very good indicator of the performance of a group of animals.

Unfortunately most beef farmers do not get to see this until the day they sell an animal.  If it is below target, you can only guess when their performance was poor.

• Was it while they were being reared either on the cow or artificially?
• Was it while they were indoors over their first winter?
• Was it at grass as yearlings?
• Was it during the finishing period?
• Were they below target at all stages over their lifetime?

Farm Results

The Teagasc Beef Roadmap figures show at a national level the average carcase weight for steers slaughtered from suckler herds was 395kg at 28 months of age.  For suckler heifers the average carcass weight was 333kg at 25 months of age.  We know from work done in our research herds and from demonstration farms across the country that steers can achieve a similar carcase weight (394kg) but at a much younger age (22 months) while heifers slaughtered on these farms are closer to 20 months of age at a carcass weight of 328kg.  While some farmers will make the decision not to push cattle for slaughter at a younger age (in order to keep costs to a minimum) a delay of 4 to 5 months to end up with no heavier a carcass does also show that there are significant stages in the growth of steers and heifers where their performance is well below average on many farms.

Weight for Age Targets

In a standard suckling to beef system Teagasc over the years has set the target of producing a 400 kg steer carcase at two years of age. The Table below shows the target live-weights that need to be met throughout the lifetime of a spring born suckled steer to achieve this.

Many different things will influence whether or not these targets will be met.  Overall the breeding of a steer will have a huge influence throughout the animals’ lifetime.  By this I am particularly referring to the genes a beef animal inherits from both its mother and father for growth rate.  Different breeds have different growth rates but also within breeds there are large differences for growth rate.  The health of the animal will also have a huge influence throughout its lifetime.  For example a non-fatal outbreak of pneumonia at the weanling stage can have a hugely negative influence an animals weight gain for the rest of its life.

Main Influences on Weight for Age

Leaving aside breeding and lifetime health issues though what are the main influences at different stages on whether or not a steer achieves the above targets.

Up to Weaning

1. Milking ability of the suckler mother.
2. Amount and quality of grass availability.
3. Level of meal feeding

Housing to Turnout (1^st Winter)

1. Quality of winter forage fed
2. Amount of meals fed
3. Parasites controlled

Turnout to Housing (2^nd Summer)

1. Turnout date
2. Amount and quality of grass availability 

Housing to Slaughter (2^nd Winter)

1. Quality of winter forage fed
2. Amount of meals fed

Over the coming weeks weanlings will start to be housed.  The aim with them is to put up 70 kg between now and turnout next spring or 0.6 kg of liveweight on average per day.  This level of performance should not affect compensatory growth at grass the following spring.  It has always been suspected that weanlings are not achieving this target at farm level.  A number of years ago a Teagasc study on farms investigated this very question.

Teagasc Weanling Study

Teagasc examined the performance of weanlings across 17 monitor farms by weighing them at housing and again at turnout.  The main results to come from it showed:

• Only one farm achieved 0.6 kg of liveweight per day
• Half had a satisfactory performance at 0.55 kg per day on average
• The other half had a poor performance at an average daily gain of 0.20 kg.

The nine farms in the satisfactory group housed their weanlings on average at 348 kg and they gained 82 kg over the winter to come out at 430 kg.  The eight farms in the poor group had a lower daily gain from birth and housed theirs at an average of 302 kg and then only put on 32 kg over the winter.  Their turnout weight was only 334 kg.  Almost 100 kg already behind the weanlings in the satisfactory group at much the same age!

This study clearly showed that as far as weight for age was concerned the first winter indoors is a period that can cause a serious setback to the lifetime performance of cattle.

So why was there such a big difference in performance?  Remember the three main influences mentioned already for this stage.  These were forage quality, amount of meals fed and parasite controls.

There was very little difference between the satisfactory and the poor groups in the quality of silage fed.  Both were feeding on average 67% DMD silage.  This by the way is the average quality of silage cut in this country over the last couple of decades.  All 17 farms also had a satisfactory parasite control programme in place at this time of the year.

The main difference between the two groups was in the amount of meals being fed.  The better group fed on average 280 kg of ration over the winter while the poor group only fed 160 kg on average.  This is not really that surprising.  Weanlings are very good converters of meal compared to older cattle.  Money spent on meals for weanlings is money well spent.  A subsequent on farm Teagasc study carried out some years after this one found that the amount of lying space given to weanlings can also have a big impact on their performance.  Putting too many weanlings in a pen is one sure way of reducing performance.  Taking one or two out of each pen can be a big help to the performance of the whole pen.

Meal Levels for Weanlings

To achieve 0.6 kg per day over the winter with weanlings you need to match your meal feeding level to your forage quality.  Take three different silage qualities.  The TABLE below shows the amount of meal that should be fed per day over a typical 140 day winter.  It shows the amount per day, the total amount for the winter and the recommended feeding pattern.

For example if you are feeding 68% DMD silage, weanlings should get 2 kg of meal per day with it to achieve 0.6 kg ADG.  However, rather than giving this amount every day right up to turnout it is better to feed more of it at the start of the winter and less towards the end.

Table 2 – Meal feeding recommendations for weanlings on grass silage

* 140 day winter

What Ration?

After you have decided on your level of meals to be fed the next question is what ration.  Whether you are buying in a commercial ration or are deciding yourself on the ingredients, aim for a ration that is high in energy.  There is no reason in the world why your weanling ration should not be approaching the energy levels of a finishing ration.  It makes very little sense to feed a ration that is considerably lower in energy.  So meals that have a high content of cereals, maize, pulps, distillers, gluten and soya are all good bets.

As far as protein is concerned, there is evidence from research work done in Grange that the overall diet of weanlings need not be as high in protein as might have previously been thought.  They are recommending an overall crude protein in the winter diet of the weanling of 14%.  With high protein grass silages (16% +) you would in fact get away with straight cereals if you were not feeding high levels.  With more typical grass silages (12 -14% C.P) a ration containing 14 – 15% C.P. should be adequate.

Finally

As I said at the start, quite often the first indication of poor weight for age is on the day of sale.  The only way around this is to start weighing stock at least three times a year i.e. at housing, at turnout and half way through the grazing season.  There are a number of platform cattle weighing scales on the market now that you put down at the front of your cattle crush.  When you are finished using them you just lift them up (by hand) wash them and put them away until the next day you are weighing.  This relatively in-expensive piece of equipment is I believe a must for all beef farmers serious about their business going forward.  It will I guarantee you give a better return than any other machine you have or will buy over the coming years and if you don’t want to buy one there is now the option of renting one in many co-ops across the country for as little as €50 per day.

Teagasc Beef Specialists issue an article on a topic of interest to Suckler and Beef farmers every Wednesday here on Teagasc Daily.  Find more on Teagasc Beef here