Can you make more from a hill beef herd?

01-05-2010 | Contributor

A beef breeding herd run on hill country is asked to turn low-quality feed into calves.

Income occurs when calves are sold and can be quantified as kilogram of calf weaned and in turn is driven by the number of calves sold, times the weight of the calf, times price.

The price we have less influence over, but calf numbers and their weights at weaning are driven by factors that we can manage - for example:

• Fertility of the herd (number of calves born)

• Growth rate

• Carcase type.

Of these drivers it is fertility that has the greatest influence on the efficiency and income from a beef breeding herd.

Pregnancy rates, or in-calf rates, for herds scanned by our veterinary practice in the Fairlie and Mackenzie country averaged 87% in 2009 (in 2008 this was 88%) but you will note in the table there is plenty of variation around this average.

To maximise income from the breeding herd, a high pregnancy rate is not enough in itself. A high pregnancy rate can be achieved if the bulls are left out for long periods; as someone so succinctly put it, "any fool can get 100% of cows in-calf rate if they leave the bull out long enough".

However those later calves are smaller calves at weaning and this has a significant impact on the kilograms of calf sold.

This is where the calving span and pattern must be looked at.

For example:

A herd that has a mean calving day 20 days earlier than another will wean 10% more kilogram of calf at fixed weaning date.

To demonstrate, compare two 100-cow herds. Mean calving date of one herd is 20 days ahead of the other herd, overall in-calf rate is the same in both herds. More calf growing days from birth to weaning.

Assume a calf grows at 1kg per day (so weaning weight is about 220kg); 100 cows on average calve 20 days earlier =20 x 100= 2000kg of extra calf at weaning = 8-10 extra calves.

Put another way, a tight calving pattern from a condensed six-week mating period can have 10% more empties and still wean the same kilogram of calf.

This does not mean that bulls should be put out 20 days earlier. Rather it means that there are huge advantages in having a condensed calving pattern in terms of kilograms of beef weaned.

From our scanning records we have made calculated conception rates from the same herds scanned (see calculated conception rate 2009).

This is a calculation based around pregnancy rate and the number of days bulls ran with the cows. The higher the figure the better the conception rate (or number of cows that are pregnant in each 21-day period). This is a theoretical calculation but it does give us the ability to compare herds that have different mating periods.

For example, for our 100-cow herd a 60% conception rate would mean in the first cycle 60 cows would be pregnant; by the end of the second cycle (that is, 42 days) 60% of the remaining cows would be pregnant. Therefore at the end of two cycles a total of 84 cows would be in calf - a pregnancy rate of 84% of the herd. With another cycle another 60% of the remaining cows would be in calf or 94% in calf.

The average calculated conception rate from the herds in the table is 54% in 2009 (in 2008 this was 50%, suggesting bulls were in longer to achieve the same pregnancy rates). This indicates that we have a lot of potential on many breeding-cow units to improve fertility and increase income and profit.

How do you achieve this? A good place to start is to look at the pregnancy rate in conjunction with the length of time the bulls are run with the cows. Get your vet to help you work out your calculated conception rate and with him/her decide where you want to be. You can then establish a plan of how you want to get there and this should include some measurable targets that can be compared from year to year.

Nothing occurs overnight in terms of shifting breeding herds' calving patterns because once a cow calves late it is difficult to shift her calving date forward. She will invariably always wean a lighter calf. So a good place to start may be with your heifers.

Get heifers to the right weight at mating. By this I would emphasise that you do get actual weights of calves as they grow. Well-grown heifers also give you the option of mating heifers 1-2 weeks before the main herd.

Mate heifers for a maximum of six weeks - no more. This will mean all heifers going in to the herd are going to be all early calvers.

Mate more heifers than you need to keep. With a restricted mating period to ensure you have enough heifer replacements you will need to "over-mate".

For example, for a normal group of heifers allow a 60% in-calf rate per cycle (three weeks) so over six weeks or two cycles, the cumulative in-calf rate will be about 87% and will be the herd replacements. This way your herd is always made up of early calving cows.

For the mixed-age cows, if you have a long calving period, to determine which are the late-calving cows pregnancy test early - that is, 14-16 weeks after the "bull-in" dates. Empty cows may have to be retested but if feed is tight, or culling is required for other reasons, then these later calving cows can be the first to go.

Remember the first place to start is establishing the reproductive efficiency of your herd.

• Mark Colson is a vet with Aorangi Vet Services, Geraldine.

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