There has been a decreased in the proportion of lactating dairy cows on commercial farms that become pregnant at the first insemination over the last 25 - 30 years.
There are many reasons being offered as to why there is a decline in reproductive efficiency such as increase in postpartum disease, increase in herd size which makes management more difficult and so on. Although the average milk production per lactation has increased tremendously over the years, it is not an accurate predictor of the chance for pregnancy.
Some of the factors that have been identified may contribute to lower fertility. What are some management tips to help promote reproductive efficiency?
Fat supplementation and reproduction introduction
There has been many studies on influence of nutrient intake on reproductive performance including feeding supplemental fat.
It make sense to supplement fat as milk production is a very energy intensive process.
Moderate supplementation of fats often stimulates milk production and improve reproductive efficiency.
However, which fats are most effective or how these fats work are important effects on fat supplementation that are worth looking into.
Fats defined
There are many types of supplemental fats in the market with each source having different mix of fatty acids.
There are fats such as animal tallow or yellow grease which mainly composed of oleic acid (around 40%) or dry fats with high palmitic acid.
A variety of vegetable oils can also be fed as free oil or in the seed form.
Canola oil is high in oleic acid while cottonseed, sunflower oil and soybean are high in linoleic acid. Flaxseed on the other hand is high in linolenic acid.
Linoleic acid and linolenic acid are essential fatty acids for the cow as the the cow is unable to synthesise them. Hence, it is important to ensure the cow has sufficient fatty acids by supplementing fats.
Dietary fats are modified in the rumen by bacteria
The ruminal microbes will convert unsaturated fats to saturated fats.
It is unclear why this is the case but scientists speculated that this is an attempt from the bacteria to protect themselves as unsaturated fats can be toxic to the bacteria.
Most of the consumed unsaturated essential fatty acids, linoleic and linolenic acids will be converted by the bacteria to stearic acid.
During this process known as biohydrogenation of unsaturated fats in the rumen, several intermediate forms of fatty acids - trans fatty acids will be formed.
It is known that some of these trans fatty acids will influence the cow's metabolism and cause depressing milk fat synthesis.
Hence, it is important to take note the type of supplemental fat fed to the cows.