18 September 1998



Good fertility results can

help boost profits and

reduce cull rates. ADAS

senior dairy Consultant

Cate Barrow looks at top

tips for good fertility

ACHIEVING good cow fertility results takes more than just a balanced ration. Cow nutrition may be top of the list, but there are many other factors producers need to consider to ensure good fertility.

Good nutrition

Body condition at calving and changes in condition over the service period will affect a cows ability to conceive, so minimise weight loss by adequate feed intake in early lactation.

The balance between dietary energy and protein is also critical. Excess levels of dietary protein are believed to reduce embryo survival.

Several minerals and trace elements are also important for herd fertility, particularly copper, selenium, phosphorous, cobalt, manganese and iodine.

Heat detection

Improving heat detection will have the greatest effect on herd fertility. Both quality and quantity of heat detection are important. Three periods of 20 minutes a day are needed to observe bulling cows, with the last period after 9pm as sexual activity tends to be greatest at night.

Cows must also be easy to identify by freezebrand, tail tag or ear tag.

Know all signs of heat

The most positive sign of heat is when a cow stands to be mounted by another cow. However, the number of mounts an oestrus can vary from five to 140. There are also several secondary signs, such as chin resting, sniffing, licking and bunting. Bulling cows may also solicit attention and separate themselves from the group.

Time insemination correctly

Serving cows too early in their heat period may be less of a problem than serving cows too late. It is unwise to delay service for more than 24 hours after a cow is first seen on heat.

The practical difficulty in timing AI is that when a cow is first seen in oestrus there is no reliable way of telling how long ago oestrus began, or how long it will continue. However, most cows first seen in oestrus in the morning will have ovulated by noon the next day. Optimum time for insemination is five to 20 hours after the cow was first seen standing to be mounted.

Keep good records

Recording the sexual cycle of each cow will ensure she is cycling normally and allow you to seek veterinary input if no bulling activity is seen by 42 days after calving.

Historical records will aid problem solving and allow comparisons with acceptable performance targets. These targets include submission rate – a measure of how quickly cows are served after becoming eligible for service. Submission rate should be 80% and is a good measure of how effective heat detection is.

Pregnancy rate is also useful. It is usually measured as a proportion of cows diagnosed pregnant, expressed as a percentage of total services. Overall pregnancy rate should be 55-60%.

Submission rate and overall pregnancy rate together provide the best indication of reproductive performance. However there are other ways of measuring herd fertility, including calving to conception interval, calving index and pregnancy rate to first service.

Dynamic records are essential. These include three-week calendars, Bray circular calendars and action lists, which promote good heat detection by acting as memory joggers.

When choosing a fertility recording system consider the follwing questions:

How much time will it take to run?

&#8226 How much duplication of records is there?

&#8226 Where will records be kept?

&#8226 Can you look up individual cow information?

&#8226 Does the system provide day-to-day action lists?

&#8226 Can the system measure herd performance?

Use aids when possible

Heat detection aids are no substitute for good observation, but can be useful when combined with good records.

The most commonly used aids are:

&#8226 Kamars/Beacons – these paint filled pads are glued to the cows rump bone. They must be correctly positioned and false positives can occur if pads are knocked.

&#8226 Tail paint – rubs off when a cow is mounted.

&#8226 Pedometers – though expensive, these are successful as physical activity increases in a bulling cow.

&#8226 Marker animals or a vasectomised bull – particularly when fitted with a chin ball marker.

Reduce environmental stress

In winter housing, where floors are slippery, cows will not show normal bulling activity. Also poor lighting, lack of loafing area and competition for food and/or water, will reduce activity.

Seek prompt and regular veterinary advice

Cows not seen bulling at all since calving should be offered to the vet soon after the second expected heat. Problem cows should be seen regularly by the vet and treated as advised, but remember that treatments such as Estrumate and PRIDs are an expensive substitute for good fertility management.

Carry out pregnancy diagnosis at the earliest possible date.

Provide good insemination facilities

Management of the cow on her service day is vital for good conception rates. Reduce stress levels by offering food and water, and isolating cows from others for the shortest possible time. Good AI facilities are essential. Restrain cows from sideways movement and present them at the same floor level as the inseminator.

Ensure regular refresher courses for DIY AI

DIY AI operators must keep good records and monitor conception rates, so that they can go on refresher courses where necessary. When the herd is breeding seasonally, a refresher course before the breeding season starts may be worthwhile. &#42