Pregnancy testing of beef cattle
Pregnancy testing is one method of monitoring reproductive efficiency and detecting any problems early in the breeding cycle.
The key to profitability for all beef breeding enterprises is high reproductive efficiency. This means achieving:
- 95% calves weaned to cows joined
- an average calving interval of 12 months
- a calving spread of 10 weeks or less
These are all realistic objectives in Victoria. This can be achieved by early detection of pregnant cows.
Pregnancy testing for cows
Manual rectal palpation is a proven effective and reliable technique. Using this method pregnancies can be reliably detected as early as 6 weeks.
Ultrasound has also become commonly used. The main advantage of ultrasound pregnancy diagnosis is it reduces operator fatigue and injuries. It is important to recognise that females identified as non-pregnant by ultrasound must then be confirmed by rectal palpation. As ultrasound is not as specific for non-pregnant’ s. Both methods can be used to age foetus’s however accuracy of ageing reduces as the foetus age increases.
Experienced operators can age foetuses accurately particularly in the first 4 months of pregnancy. Pregnancy testing is normally carried out 8-10 weeks after the end of mating. Cows need to be restrained in a race — it may not be necessary to headbail each one. In well designed yards and with labour provided to keep cattle moving into the race, up to 60 cows can be pregnancy-tested per hour.
Benefits of pregnancy testing your cows
Early detection of non-pregnant cows is the main benefit from pregnancy testing, but there are others.
Estimating calving dates
In many cases, the age of the calf and the likely calving date can be estimated during rectal palpation. Cows expected to calve early can then be separated from cows expected to calve late. This can provide a useful basis on which to cull cows if it is necessary to reduce herd size, perhaps in times of feed shortage. The calving spread can also be quickly reduced if late-calving cows are replaced with heifers that conceived early.
Detecting infertility and other abnormalities in cows
Various abnormalities responsible for infertility in cows can also be identified. The more common of these include cystic ovaries and uterine infection. The occasional freemartin heifer and other abnormalities of the reproductive organs may also be detected during rectal palpation.
Diseases and management problems affecting the whole herd can also be identified much earlier if cattle are pregnancy tested.
Low pregnancy rates in one particular mob, for example, might indicate problems with an individual bull. Poor fertility throughout the whole herd might be caused by an infectious disease, or perhaps inadequate nutrition prior to mating.
After pregnancy testing
Pregnancy testing is of little use as an aid to management unless the information gained is used to make management decisions.
Feed availability, current beef prices, and the management system used on the property must all be considered when deciding the fate of non-pregnant cattle.
By pregnancy testing, you are in a position to make the best possible decision.
In most situations non-pregnant cows are best culled as soon as possible. The cost of owning and maintaining a beef cow for a year is very high, so it is important that every cow on the property is fully productive. Even if they have calves at foot, non-pregnant cows are only partially productive. Mature cows sometimes fail to conceive after a late calving. Such cows wean the youngest, smallest calves, and are therefore best culled.
Under certain circumstances it might be better not to cull non-pregnant cows immediately. If feed is plentiful, and particularly if beef prices are depressed, the best strategy might be to draft off non-pregnant cows and fatten them for sale at a later date. Alternatively, the most profitable decision might be to sell them after their calves are weaned. It is a common practice to 'bang' the tails (that is, trim about 100mm of hair from the switch) of cows to be culled at some time in the future, so that they can be identified for up to six months. However, it is best to also record ear tag numbers to ensure non-pregnant cows are not lost in herd.
The other option is to re-mate non-pregnant cows, particularly young cows, for a later calving. This strategy may have application on properties that have more than one calving period each year. However, it may result in reduced genetic selection for fertility in the herd. On properties with one calving period, small groups of late calvers create management difficulties.
Where non-pregnant cows are re-mated, good records are needed to ensure that barren cows are not being kept and moved between mobs calving at different times.
On some properties, cows are not pregnancy tested but are simply culled when they reach some predetermined age. Quite often cows culled for age at 9, 10 or 11 are still rearing good calves each year. On the other hand, some of the younger cows retained in the herd fail to conceive.
Old, pregnant cows are obviously more productive than young 'empty' ones. Culling cows on the basis of a pregnancy test is much more efficient than simply culling on age.
Pregnancy diagnosis also has implications for marketing. Cows sold by live weight will attract a higher price if they have been certified by a vet to be non-pregnant. In addition, females sold for future breeding will be worth more if they have had their pregnancy status confirmed. PREGCHECK™ accredited veterinarians can also provide a tail tag indicating the pregnancy status which gives buyers greater confidence.
The two main considerations of whether non-pregnant heifers are given a second chance to conceive are the breeding value of the heifers and the cost of carrying the heifers over. When a group of heifers have been reared and mated under similar conditions, those that fail to conceive are less fertile than the group. It is possible that these heifers will fail to conceive if kept for a second joining, or if the heifers conceive, the tendency displayed toward lower fertility may be passed on to heifer daughters.
For maximum profitability, heifers should usually be brought into production as early as possible. The cost of feeding and maintaining non-pregnant heifers for an extra year cannot be justified.. Heifers that fail to conceive at first mating should therefore be culled.
It is desirable to mate heifers for a short period, (6-8 weeks) to ensure a compact calving. It is also a sound practice to mate more heifers than are needed for replacements. Heifers can then be pregnancy tested eight weeks after the end of mating, and only those pregnant need to be kept.