Low reproduction continues to be a challenge in dairy production systems despite the advancement in genetic gain through breeding and selection for milk production.
The reason for low reproduction is multifaceted, but mainly 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.
Two nutrition-related factors are body condition and negative energy balance, both of which have significant impact on the reproductive performance of dairy cows.
Body condition and energy balance are closely linked.
A cow with good energy balance is likely to be in good body condition. Other factors that affect reproduction are not discussed in this article.
Around four weeks before and after calving (transition period), dairy cows’ energy requirements dramatically increase due to the increasing demand from the developing fetus 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 a physiological condition called negative energy balance.
While negative energy balance is a natural process, its severity can have a negative impact on cow health by increasing the risk of metabolic disorders, reduce immune function and fertility.
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 can ovulate.
Energy is a major limiting nutrient in dairy cows and inadequate intake of energy can have detrimental effect on reproduction.
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 estrous.
A cow must ovulate to have a chance to become pregnant.
Increasing energy intake (or dry matter intake) can improve energy status of dairy cows and therefore, reproductive performance.
There is also strong evidence to suggest that inadequate intake of nutrients pre-calving can predispose dairy cows to impaired immune function; and, subsequently, increased risk for uterine diseases that negatively affect reproduction.
Some of these nutrients are important in various metabolic processes responsible for protein and glucose (energy) synthesis in the liver.
Example of such nutrients are B vitamins, which play significant roles in energy and protein metabolism in the liver and immune modulation.
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 one).
Supplementation with B vitamins also reduced metabolic disorders and subsequently improved fertility.
Genomic research also showed that certain genes responsible for follicle growth and development, resumption of estrus 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.
Poor (skinny cow) and excessive (fatty cow) body condition are equally undesirable; both pose a high risk of low feed intake, increased metabolic disorders, and the subsequently low reproductive performance in dairy cows.
Although negative energy balance is a physiological adaption during transition and can have significant negative impact on reproduction of dairy cows, good nutrition in terms of adequate intake of energy and other essential nutrients such as B vitamins, can help to reduce the impact of negative energy balance.
These B vitamins play vital roles in various metabolic processes in improving energy status and reproductive performance.
It is essential that B vitamins are supplemented in the diet and in rumen protected form to be effective in dairy cows.
– Contributed by Jefo Australia