Despite the advancement in genetics and production systems, fertility is still challenging in modern dairy cows.
Although many factors may be responsible, the underlying reason for low fertility is associated with nutrition and overall management of the cow.
According to researchers from across the globe, both high and low producing cows are affected by low fertility.
So, with the right nutritional tools, it is possible to maintain high production and reproductive capacity in dairy herds. Therefore, this article will focus only on how nutrition and, in particular, B vitamins can help to improve fertility in dairy cows.
Two of the nutrition-related factors that will be discussed are body condition and negative energy balance, both of which have significant impact on the reproductive performance of dairy cows.
Why B vitamins?
First, let us briefly highlight the importance of B vitamins in dairy cows.
The B vitamins are part of various enzyme systems that facilitate different metabolic processes, for example, energy (glucose) and protein metabolisms.
They are important in immune systems and play a major role in metabolising fat and keeping the liver healthy. The liver metabolises almost all nutrients before they are used by the cow, so a healthy liver is key to a healthy and high-performing cow.
Research has shown that B vitamins in feeds are easily degraded in the rumen, between 60 per cent and 99 per cent can be lost in the rumen as a result. We also know that bacteria in the rumen synthesise B vitamins, but it is likely that a deficit may exist between an animal’s need and microbial synthesis.
Recent research evidence shows that supplementation with B vitamins improved the health, production and reproduction of dairy cows, suggesting that B vitamins may indeed be essential, and should be added to modern dairy cows’ diet.
Body condition and negative energy balance
Body condition and energy balance are closely linked. A cow with good energy balance is likely to be in good body condition.
Around four weeks before and after calving (transition period), dairy cows’ energy requirement dramatically increases due to the increasing demand from the developing foetus and milk production while intake is still low.
To meet this increasing energy demand, the dairy cow mobilises its body reserve (mainly fat), and she gets into what we call negative energy balance.
While negative energy balance is a natural process, its severity can have a negative impact on cow health and increase the risk of metabolic disorders, reduce immune function and fertility (Figure 1).
Metabolic disorders during transition can reduce fertility because affected cows are seven to 10 per cent less likely to get pregnant.
Research has shown that negative energy balance negatively affects the development of ovarian function, resulting in a decrease in the proportion of follicles that ovulate.
Cows in negative energy balance have low levels of insulin and a substance called insulin-like growth factor 1 (IGF-1), causing a delay in (or lack of) ovulation and the resumption of oestrous. A cow that does not ovulate cannot conceive; it is that simple!
Reducing negative energy balance will improve reproductive function of dairy cows. Five B vitamins, including folic acid and B12, are involved in glucose production in the liver, and their supplementation can improve energy balance and subsequently increase the number of cows that conceived to first insemination (Figure 2).
Supplementation with B vitamins also reduced metabolic disorders (Figure 3) and subsequently improved fertility.
Genomic research also showed that certain genes responsible for follicle growth and development, resumption of oestrous activity and embryo survival, were switched on when vitamins B12 and folic acid were supplemented in early lactation cows.
If cows conceive early and maintain pregnancy, they will produce more milk profitably.
While poor body condition (skinny cow) is not desired, excessive condition (fatty cow) is equally undesirable (Figure 4); both conditions pose a high risk of low feed intake, increased metabolic disorders and the subsequently low fertility.
While negative energy balance is a physiological adaption during transition, excellent nutrition — including the use of B vitamins — will help cows to achieve a positive energy balance sooner and thereby improve reproductive performance.
Cows that are in good body condition are less likely to be in severe negative energy balance, are more resilient, less likely to have post-calving disorders, and will ultimately have a high chance of getting pregnant without delay.
Providing B vitamins
Feeding rumen-protected B vitamins ensure the vitamins will be utilised effectively by the cow.
Unprotected B vitamins are readily degraded in the rumen, and it is not guaranteed that cows will get what is needed. Injectables are mainly for treatment, and not practicable and sustainable as a preventative measure.
It is more effective and easier to supplement B vitamins via supplementary feed and in a rumen-protected form. Prevention is better than treatment.
Making a difference
Maintaining optimum level of fertility in dairy cows is challenging due to the physiological changes and increased metabolic demand during transition. Improved nutrition and management using innovative technologies will help to improve reproductive performance of dairy cows.
Many of the issues affecting fertility are related to severe and prolonged negative energy balance and poor body condition. Farmers and nutritionists must ensure that nutritional solutions are aimed at reducing the severity of negative energy balance during transition period.
B vitamins play a vital role in various metabolic processes that support reproductive functions. Supplementation with B vitamins have resulted in improved fertility in a consistent manner and should be incorporated into the nutritional solutions for modern dairy cows.
Finally, B vitamins must be supplemented in rumen-protected form to ensure they are effectively used. When next you talk to your nutritionist, ask how rumen-protected B vitamins can help improve the fertility of your herd.
Razaq Balogun,
Jefo ruminant technical sales manager
Jefo is a supplier of feed additives. Its head office is in Quebec, Canada and will celebrate 40 years in 2022. Jefo Australia was established in 2005.