The reproductive performance of your herd is greatly influenced by the difference between energy inputs (nutrition – energy, protein, fibre etc) and energy outputs (milk production, walking, inflammation etc) during the mating period.
Getting a cow to cycle (have a heat) and for the resultant egg to get fertilised (conception) is only part of the picture which may be easier for the cow to do than getting them to hold and maintain a pregnancy.
Approximately 12 days after a successful insemination, the developing embryo must implant or ‘stick’ onto the uterine wall for the pregnancy to continue. Once implanted the placenta develops and within this structure the embryo develops into a foetus. Without implantation the pregnancy will not hold. There are other factors that will influence this process such as transition management, feeding prior to mating etc, but a major factor is feed management over the mating period.
This implantation process is all occurring at a time when cows are reaching or at peak lactation. During this period if the herds’ feed inputs are dropping or the feed quality is deteriorating, as pastures go into a reproductive stage, there is a mismatch between energy output and energy input – more is going out than is coming in. This difference can be greater for higher producing cows, timid/young cows that can’t compete and with cows suffering some disease or inflammatory process. Any time a cow experiences a negative energy balance reproduction can suffer.
Any day during mating that milk production drops, cows that were mated 12 to 14 days prior have a higher risk of not holding their pregnancy as the implantation process is affected. This may seem like a ‘conception’ problem when analysing your mating results, but fertilisation of the egg may have happened, the resultant embryo just did not implant onto the side of the uterus. Maintaining feed levels and feed quality to minimise production drops is therefore an important influencer of the herd’s reproductive performance.
A strategy we can implement to get some of the way around the problem of declining feed quality as mating progresses is to try and mate as many cows as possible over the first few weeks of the mating period and to feed them well for the following few weeks until implantation occurs.
Using reproductive hormonal programs can help to get non-cycling cows to cycle (a CIDR synchrony program) and cycling cows to show heat earlier than expected (a double Why Wait with two rounds of PG or a standard Why Wait program). Not only does this help with improving 6-week in-calf rates (a marker of a herd’s profitability) but it also gives cows as many chances as possible to get mated over a set mating period. If reproductive spend is limited, then the first cows to look at are the higher value cows – high producing cows and higher genetic merit younger cows.
Another strategy we can use to improve reproductive outcomes is to use early pregnancy testing as a tool to deal with phantom cows. That is those cows that have been inseminated but do not have a return insemination within 35 days post insemination but are found to be not pregnant by ultrasound scan.
What is required is pregnancy testing cows near the end of AB period of those cows that were mated 28 days or more ago which have not had a return mating in the meantime. Any resultant empty cow can then be hormonally treated (often just a 3ml injection of prostaglandin) and AB mated to a following heat. Just one more extra chance of getting in-calf over the AB mating period.
If you require more information or advice, please contact us.