Poor fertility is a vicious cycle, with fertility problems in one lactation programming further issues in the next.
This is according to Professor Jo Leroy of Antwerp University, who says fertility needs to be a long-term planning process in order to break the cycle.
“Low fertility will induce a longer calving interval. That leads to fat cows in the last trimester of lactation, which increases metabolic disease and stress in early lactation, and that will drastically reduce fertility.
“That’s why we speak about low-fertility herds, because it’s a repeating cycle.”
Bad feed bank management, such as overstocking, also causes cows to be in the incorrect condition at calving and predisposes them to metabolic disease, he adds.
Speaking on a recent Mole Valley webinar, Prof Leroy explained how management affects fertility and how to optimise it.
1. How management affects ovulation
Before understanding how to optimise fertility, farmers need to understand how management can affect ovulation.
Follicles need to be in good condition to produce sufficient oestrogen for ovulation to take place (see diagram). If they are, the oocyte will be ovulated and will arrive in the oviduct, where it needs to be for successful fertilisation, he explains.
But without sufficient oestrogen the oocyte will be captured in the follicle. If the oocyte is low-quality, after fertilisation the embryo will die within days and there won’t be successful fertilisation.
It takes 90 days for the follicle to reach the dominant follicle stage before ovulation can happen. If the cow is overwhelmed with stress, disease, antioxidative stress, or bad feeding, that will disrupt the growing phase and will lead to poor breeding results.
If the oocyte is of low-quality you will never be able to improve that with synchronisation protocols because the real problem is the history of the oocyte.
- Oocyte is ovulated
- Cow inseminated, sperm will swim up to the oviduct
- Will fertilise the oocyte and form an embryo
- Embryo arrives in the uterus 5-6 days later and healthy corpus luteum supports pregnancy.
2. The role of antioxidants
Antioxidants such as beta carotene and vitamin E aid oocyte development.
However, a study carried out by Prof Leroy found that if the cow is low in antioxidants three weeks before calving, she will be low throughout the transition period.
The study also showed:
- One in four cows had deficient beta carotene concentrations
- One in three had insufficient vitamin E
- The majority of these were in early lactation (54%)
- 60-70% of deficient animals were fully housed, fed a total mixed ration and didn’t have access to grass.
Cows that have optimal concentrations of antioxidants will maintain higher levels throughout transition.
“The period before breeding will determine the quality of that oocyte,” Prof Leroy adds. “If you really want to invest in management to improve fertility results on your farm you have to focus on this phase.”
3. Importance of body condition score (BCS) in the last trimester
As the two points above show, good fertility starts in the last trimester of pregnancy.
This period is a key driver of optimal body condition, which is a major factor determining appetite in early lactation.
If dry matter intakes (DMI) are insufficient during the transition period, this will cause negative energy balance (NEB). This is caused by a tremendous increase in energy loss around parturition, coinciding with a reduction in energy intake.
“Healthy, well-fed animals reproduce. If we can manage cows so they keep eating, we can minimise the impact of NEB,” he explains.
Tips on how to maintain good BCS:
- Ensure cows are not overstocked. Crowding causes dominant cows to eat too much too quickly, making them fat. This will also hamper saliva production and may lead to acidosis. Meanwhile, subordinate cows and young heifers will eat too little, which will lead to significant fertility issues 60+ days after calving.
- Watch out for cows perching – not lying down in cubicles. This can be a sign the cubicles are too small. These cows will have raised non-esterified fatty acid (NEFA) levels due to increased stress, which can cause infertility.
- Avoid cows losing weight in the dry period. This is dangerous because the liver is preoccupied with pregnancy and the cow will mobilise fat before calving. Instead, aim to achieve optimal condition before drying off cows, by body scoring them in the last trimester of pregnancy and rectifying it in the coming weeks before drying off.
4. Avoid NEB
DMI is a major determinant of metabolic health in early lactation, with studies showing that cows in higher condition at calving will mobilise fat in the first weeks after calving.
“Energy balance early post-partum needs to be pre-programmed during the previous lactation and dry period and cannot be adjusted in real-time,” says Prof Leroy.
Avoiding NEB centres around three questions: whether or not the cow is eating, when she is eating, and what she is eating.
- First, ask yourself if the cow is able to eat. Is she lame or is something else such as dominant cows preventing her from eating? Is there enough feed?
- When are cows eating? If cows eat too much during the last trimester of lactation or during the dry period, they will become fat at calving. They should be fed to eat and not too fat to eat.
- What are they eating? The diet composition is important; cows should love what they eat to maximise DMI.
NEB is not a simple calculation of energy intake minus energy lost through milk – it is much more complicated. Cows prioritise energy towards milk (known as metabolic priority).
To produce milk, the mammary cells need to produce lactose. This is created using glucose. If there is insufficient glucose in the bloodstream it will be “stolen” by the udder for milk production. This causes the glucose concentration in the bloodstream to drop and insulin becomes low.
The cow then mobilises energy stores (fat reserves or lipids), causing NEFAs to rise in the blood. Massive amounts of NEFAs flood the liver, causing ketone production or fatty liver, and the cow loses weight.
To a certain extent, a cow can cope with lipid accumulation in the liver and ketone and NEFA production in the bloodstream. But glucose levels in the bloodstream can be pushed even lower if the cow is not able to eat enough owing to appetite-disturbing factors such as too high a BCS.
In this situation, DMI drops, less glucose is provided in the bloodstream to the stomach and intestines, insulin is lower and more fat is mobilised, pushing the cow into the “red zone”.
Immune cells, required to fight infection, also require a lot of glucose. This is a reason why infection can coincide with a rise in ketones.
Key take-home messages to improve fertility
- Focus on the stage pre-breeding (90 days) to ensure cows conceive, as their condition at this stage affects ovulation
- Provide cows with optimum levels of beta carotene and vitamin E during the dry period
- Calve cows in optimal condition: BCS 2.75-3
- To achieve this, focus on getting feed management right.
- Don’t overstock – every animal should be able to access feed
- Check rumen fill to ensure cows are full
- Ensure feed is palatable and always available
- Keep disease prevalence low.