After calving, a cow’s uterus takes anywhere from 25 to 50 days to recover, her body to re-establish normal reproductive hormone levels and for her to return to normal cyclic activity.
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Traumatic calving, ill-health and several nutritional factors can delay a return to normal function, preventing cycling and affecting submission rates.
This can be incredibly frustrating to manage and have a significant impact on herd reproductive performance.
'Non-cycling’ is a term used to describe cows within a herd that do not return to visible oestrus (show no detectable signs of heat) within two months of calving.
Australian industry figures suggest most high-performing herds have 90 per cent of cows cycling within 40 days of calving (or 10 per cent non-cycling).
Some of the main reasons for non-cyclers are listed below.
● Pregnancy (cows don’t continue cycle when pregnant, although small numbers may still show behavioural signs of oestrus when pregnant).
● Late calving cows (have not had enough time to recover post-calving before mating start date).
● Uterine infection (the presence of infection/inflammation can affect normal return to cyclicity).
● Poor heat detection (cows are cycling but not being recorded).
● Poor body condition score (BCS) at time of calving/low plane of nutrition post-calving. (Energy balance is directly related to a cow’s ability to ovulate. Ideally, you should be calving cows in BCS 5-5.5/8 and joining in BCS 4.5-5.5/8, losing no more than 0.6 of a score during the post-partum period.)
● Trace element deficiencies (uncommon, usually associated with overall energy deficit).
● Silent heats (ovulation without visible/behavioural signs).
● Ovarian pathology (follicular or luteal cysts, causing irregular cycles or preventing ovulation altogether).
● Ill-health (including lameness) influencing apparent cyclicity.
● Undersized/poorly grown heifers (delayed puberty).
● Congenital abnormalities (most commonly freemartinism).
Pre-mating heat detection (using tail paint, mount detectors, activity monitors or a set of well-trained eyes) will give you the best chance of identifying non-cyclers as early as possible, optimising submission rates and maximising their chances of getting back in calf.
Dairy Australia estimates that every true heat detected is worth about $200 to your operation.
Vet-checking non-cyclers is advisable to determine uterine and ovary health, rule out unexpected pregnancies and formulate a management plan.
If no pre-mating heat detection has occurred, any cows that have not cycled or been joined in the first 21 days of mating should be checked.
Non-cyclers not managed in a timely fashion will protract your joining period, increase your veterinary costs, slow your rate of genetic gain, reduce lifetime milk production and increase your number of late calving/carry-over/empty cows.
2011 In-Calf Data shows that cows calved nine to 12 weeks before mating start date (MSD) have a 40 per cent higher in-calf rate than cows calved only three weeks prior to MSD.
This is due to the additional time this allows the cow’s body to recover from the last calving and prepare for the next.
Commonly, non-cyclers are enrolled in a treatment program involving the insertion of an intra-vaginal progesterone releasing device combined with timed injections of prostaglandin (PG) and gonadotropin-releasing hormone (GnRH).
When this program is commenced 10 days prior to MSD — and with enough time between calving and joining — most non-cyclers can then be bred to fixed time artificial insemination within the first few days of joining.
This program has the advantage of treating both cystic and inactive ovaries as well as silent heats, and increases submission rates over using PG alone.
Industry accepted standards are a 21-day herd submission rate of >85 per cent for all cows in a seasonal/split calving herd, and an 80-day submission rate of >73 per cent for year-round herds.
Regardless of your calving pattern, early detection and treatment of non-cyclers greatly improves a herd’s reproductive performance and profitability.
As always, prevention is better than treatment so good transition management and ensuring body condition is maintained throughout lactation is key.
Lucy Collins is completing her dairy residency with the University of Melbourne. She works as an on-farm veterinarian in Kyabram with Apiam Animal Health, and alongside her partner on his 600-cow dairy farm in Dixie.