The non-bulling cows in the herd or the ‘problem cows’ can often cause frustration, but every herd has them.
However, every farmer deals with these cows effectively, as they will require immediate identification and corrective action.
Usually cows will return to normal cyclic activity within 30-35 days after they have calved, with the first heat being silent and the first cycle after that usually occurring quite quickly, about 8-12 days later.
This means that most cows should have displayed behavioural heat by, at the very latest, 38-47 days post calving.
When a cow fails to show signs of heat 60 days after calving, it is called postpartum anoestrus and can be due to true anoestrus or suboestrus.
Non-bulling cows
There are a number of factors that can contribute to poor cow fertility, which may be down to genetics, management, or husbandry.
If there is a large number of non-bulling cows each year in the herd, the farmer should examine the genetic merit of the herd and see if the fertility of the herd is an issue. The farmer can begin to rectify this by using high fertility and health positive bulls.
Ahead of breeding, examine the body condition score (BCS) of the cows, targeting a BCS at mating start date (MSD) of 2.9.
If there are cows in the herd that are not cycling and have a low BCS, their energy status needs to be improved by increasing their grass allowance and concentrate supplementation, and milking them once a day for a few weeks until they are served.
Farmers need to make sure that the diet is properly balanced for energy, protein, and minerals, and that pre-grazing covers and post grazing residuals are optimal.
If the non-bulling cows are also cows that had difficult calvings, retained membranes, metritis, milk fever, or any metabolic issue, these cows should be metrichecked by your vet and treated if necessary.
Blood tests should be completed prior to the start of breeding, as this allows for any mineral issues to be dealt with before it all kicks off. Farmers should blood test 7-10% of the herd to identify what minerals and trace minerals are deficient.
Phosphorus (P) deficiency can cause issues with fertility and lead to low conception rates. This deficiency can be identified through the cows’ behaviour – if they are licking stones and exhibiting depraved appetite, farmers need to react.
Farmers should also find out the disease status of their herd and vaccinations for bovine viral diarrhoea BVD, infectious bovine rhinotracheitis (IBR), Leptospirosis, Salmonella, Neospora, Mycoplasma, etc., should have been administered well in advance of breeding if they are issues.
As lameness affects the cow’s normal behaviour and causing her to lie down more to rest the affected hoof or limb, she will eat less and be less likely to show normal oestrus behaviour, so hoof trimming and foot bathing needs to continue as well as keeping roadways and gathering yards in good condition.
Mastitis can also have negative impact on fertility, as studies have shown that it reduces conception rates, alters the timing of ovulation, and results in irregular interoestrus intervals.
To deal with weak/silent heats, farmers need to improve their heat detection techniques and ensure that observation periods are long enough – of about 30 minutes – and frequent enough – about three to four times a day according to Teagasc.
The resumption of ovarian cyclicity after calving is influenced by the nutritional status, BCS milk yield, calving difficulty, uterine infection, breed, age, and concurrent disease.
Farmers could choose to synchronise these non-bulling cows to stimulate the resumption of cyclicity, and is the most effective and efficient way getting these cows back in calf early combined with increase energy intake.
It is important that these cows are dealt with early to try and maximise the 6-week submission rate and get the cows calving down early in 2026 to turn them out to grass straight away and to save on costs of production.
