The Flushing Effect


The Flushing Effect

When cattle are in good order and heifers are well grown using a timed AI program should give excellent conception rates.  Last year a particularly exceptional result was achieved by one of HCH Genetic’s clients who used a synchronised breeding program and managed nutrition to generate what is commonly referred to as the “flushing effect”.  There has been much anecdotal evidence over the years that this effect is real, but why it works has only recently been understood.

The flushing effect is created when cattle are fed well above maintenance about three weeks prior to joining.  In the past, research focused on the effects of increased nutrition on gonadotropins (Gonadotropin Releasing Hormone (GnRH)), LH (Luteinising Hormone) and FSH (Follicle Stimulating Hormone).  No relationship could be found.

More recently, scientists such as JG Gong in the UK have been investigating the effect of “flushing” at the ovarian level.  They have found a marked effect on the growth of small follicles from increased nutrition.  Increased nutrition causes increased levels of insulin IGF 1 and bGH.  The effect of these metabolites in the blood does not seem to affect GnRH, LH or FSH, but actually have a direct effect on the follicles within the ovaries.

This research has been well accepted by the scientific community and a great deal of work has been done on the metabolic pathways involved.  It is now accepted that insulin in the blood has a direct effect at the follicular level.

The science is very impressive and convincing, but how can this be applied to practical farming?   The effect that total nutrition has on fertility is complex, but the main effects discovered in this research have been ENERGY dependent.  Therefore diets three weeks prior to joining should increase the total energy of the diet while ensuring that water, protein, fibre, vitamins and minerals are not limiting and soluble nitrogen sources such as nitrates and urea are not too high.  (Some lush rapidly growing pastures can present this problem).

It is relatively easy to formulate a diet to increase energy and achieve the flushing effect.   If pasture is the only option, then limiting intake for about a month to three weeks and then allowing access to as much as the cattle can eat may create this effect as long as nitrates in lush pasture do not interfere.

A diet that produces high levels of propionic acid in the rumen gives higher levels of insulin in the blood.  As we now know, high insulin levels in the blood increase the number of small follicles in the ovary, boosting fertility.  Supplementing with (correctly buffered) cereal grains three weeks prior to joining will increase the energy levels consumed by cattle.  Cereal grains are known to produce higher levels of propionic acid in the rumen and should therefore; more reliably cause the flushing effect.

Feeding cereal grains may present a problem if farms are not set up to handle concentrated supplements.  If the set up is there, then buffered cracked grain mixes or pellets, even whole oats are a great option.  Increased grain levels in a TMR is an ideal option for those who have the infrastructure. Stock “cubes” with a high grain content can work well if feed troughs are not an option.   There are many ways to incorporate grains in to the diet.

Feel free to give us a call at HCH Genetics if you need assistance in this area.