Better oestrus detection

If heat is not detected properly in dairy cows, fertility will be reduced, leading to an extended open period and longer intercalving periods. Here are practical ways to detect heat accurately.

Accurate heat detection is essential where cows are bred by artificial insemination (AI). Cows can then be separated from the herd, and inseminated at the appropriate time.

The oestrus cycle lasts between 18 and 24 days, with an average of 21 days, and the cow should therefore show signs of oestrus every 21 days or so.

Oestrus activity normally recommences during the first three weeks after calving. The first observed oestrus (heat) occurs three to six weeks after calving, with considerable variation between cows and herds.

It is essential, however, to give the cow a voluntary waiting period (VWP) of 45 to 60 days after calving before rebreeding. This is necessary for uterine involution (the return of the uterus to the pre-gestation state) to take place. The process can last up to six weeks after calving.

On average, 50% of all heats are missed because the most reliable sign of oestrus – standing to be mounted – often goes unnoticed.

Several factors make accurate oestrus detection difficult:

• The cycle length can vary from 18 to 24 days and the duration can vary from two to 30 hours, with the average being 15 hours;

• Research shows that 70% of the mounting activity occurs between 6pm and 6am;

• The average standing time for a cow on heat is only four to six seconds.

What to look for

Observing a cow is the most common method to detect oestrus. Look for the following behaviour and signs:

• Sniffing the vulva or urine of other cows;

• A scuffed tailhead, dirty flanks and sweating; • Resting its chin on another cow, or licking it. In this case, both animals might be coming on heat;

• Bellowing and restlessness;

• Mounting head to head. Other signs include frequent urination, a red, swollen vulva with mucous discharge, and milk yield fluctuations. The yield usually drops by 12% to 16% on the day before oestrus.

tips for better detection

• Make one person responsible for observing for oestrus and recording the identity of those cows that come on heat. This employee should be made aware of the importance of the job, and should take prompt action accordingly;

• Observe the relevant group of cows or heifers for heat for 20 to 30 minutes, twice or three times a day, but not during other activities such as feeding or milking. Early morning, late afternoon or early evening are the best times for observation;

• Ensure that the cows are not on slippery, steep or rocky surfaces, or under a low roof. Cows will hesitate to mount one another if they do not have a sure footing;

• Record the oestrus periods of the cows one month before the end of the VWP (that is, one month prior to breeding) to determine if the cows are cycling;

• Bloodstained mucous may appear from the vagina two days after oestrus. Record this, as it is a valuable aid in predicting the next oestrus.

• Source: Van der Merwe, B. ‘Dairying in Kwazulu-Natal: Oestrus Detection’. Cedara Agricultural Development Institute. Retrieved from www.kzndard.gov.za/images/ Documents/RESOURCE_CENTRE/ GUIDELINE_DOCUMENTS/ PRODUCTION_GUIDELINES/ Dairying_in_KwaZulu-Natal/ Oestrus%20Detection.pdf.

UWEMUELL ABOVE: Ampules of frozen bovine semen in a liquid nitrogen canister. Accurate oestrus detection is a crucial factor in artificial insemination.