With the global population currently sitting at 7.8 billion and a further two billion expected by 2050 according to a 2018 United Nations report, milk production has almost doubled in the past 50 years to help meet demand.And we will likely see even higher production levels in the future.But as the production level rises, reproduction in dairy herds remains a significant challenge for producers.Conception rates in the average Australian herd offer challenges with an average first service conception rate of 38 per cent and pregnancy rate as low as 11 per cent.
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Moreover, days open range from 154 to 127 for lower and higher production level herds respectively. This difference of 27 days will have a significant economic impact as each day open will cost about $4 to $5, which means an annual cost of $108 per cow or $10 800 yearly for a herd of 100 cows.Although reproductive problems may look like they occur suddenly, research demonstrates reproductive challenges are the result of health, nutrition or management issues that may have occurred months earlier.Several factors will impact the reproductive performance of cows, such as health around calving, cow comfort, heat stress, loss of body condition before calving and in early lactation.In addition, it is essential to properly feed the cow before calving to ensure follicle development and a functional ovarian activity very early in lactation.A delayed ovulation will only result in fewer cows pregnant early. In fact, only 45 per cent of cows will be pregnant at 150 days in milk when their first ovulation occurs after 50 DIM, compared to 75 per cent pregnant when they ovulate earlier.There are two major periods impacting the reproductive performance of dairy cows and they are transition period and early lactation.During the transition period, the combination of reduced dry matter intake and sudden increase of requirements for milk production, create a negative energy balance.
Maintaining dry matter intake during the week(s) before calving with an increase after calving is crucial to reduce the extent of negative energy balance and to improve the metabolic health of transition cows.In early lactation, an excessive loss of body condition due an insufficient DMI to meet the need for energy (glucose) and other important nutrients will exacerbate the already dysfunctional immune response.
All of these will have a negative effect on reproductive performance including higher early embryonic loss.Nutritional composition of feed, including energy, protein (amino acids), minerals, vitamins A, D3 and E, as well as other essential nutrients such as B vitamins, play a key role in the reproductive performance of dairy cows.Some specific B vitamins are involved as enzyme cofactors at the cell level for energy (glucose, fat), protein and other important synthesis. More specifically, folic acid plays an important role in embryo cellular development in cattle.
Many researchers are showing dairy cows are responding positively to the supplementation of protected B vitamins in the diet, meaning those specific protected B vitamins blends promote an enhanced reproduction in dairy cows.
