Appropriate Trace Mineral Supplementation
Can Improve Conception Rates

Well, its mating time again! When I was in dairy practice twenty years ago, the main indicator of this seasonal occurrence was that sales of tail paint and stock iodine took a sudden hike in volume. (Adding stock iodine to the water has long been an attempt to improve conception rates of cows by supposedly meeting a greater need for iodine around mating time.)

As vets, we didn’t really get involved with planning and the necessary support for reproduction until problems became evident, such as non-cycling cows and repeat breeders. We mainly addressed problems only after they arose, checking ovaries, jabbing cows with hormone, or doing whatever, in those days, was considered best to try and get the cows back in calf again. Although it was well recognised that efficient and effective reproductive performance was closely linked to providing good nutrition, we did little more than grumble that cows often weren’t getting enough to eat to enable them to produce milk and also cycle promptly.

How different it is today! The importance of good nutrition to efficient reproductive performance is still paramount, but we realise that certain specific nutritional requirements of cows should be addressed well before mating time, not just a month or so before we expect them to cycle.

Reproductive performance is influenced by many factors. The plane of nutrition is important, but factors like rate of weight gain, level of stress, and level of milk production, all have large effects on reproduction. And all these are influenced by various trace minerals, particularly copper, selenium, zinc, cobalt, iodine and manganese.

Deficient levels of all these trace minerals can be associated with suppression of oestrus, early embryonic death, and/or reduced conception rate. We used to think that as long as we maintained these minerals at an adequate level, (compared to the reference ranges established that delineate deficient, marginal, or adequate levels), then we had done our best for the animals and their reproductive needs..

But more recent research conducted throughout the world, including New Zealand, has shown that not only the time period, but both the amount and the form in which these minerals are provided, can have a significant effect on reproductive performance. Rather than just maintain “adequate” levels of these minerals, we are better to try and provide levels that are “optimum” for the needs of any particular herd of cows, and to provide them over a prolonged period of time.

Providing “optimal” mineral supplementation to help influence conception rates is best commenced several weeks before calving. This is because some of the factors around calving time that can effect later conception, such as retained membranes, lowered immune status, mastitis, and metabolic disorders, can be minimised if trace mineral levels have been optimised. Several trials have demonstrated that conception rates are significantly better in cows fed appropriate trace minerals from several weeks before calving, than those only starting supplementation after calving.

As well, the form of minerals supplemented can have an influence, especially those minerals that are subject to poor absorption or utilisation due to antagonists in the diet. Most research has compared reproductive performance in cows supplemented with organic amino acid complexed minerals, to cows supplemented with inorganic minerals such as sulphates, or non-supplemented controls. Consistently, animals supplemented with the organic complexes of copper, zinc, cobalt and manganese, have shown better conception rates than the controls or those on inorganic minerals.

The benefit of any trace mineral supplementation programme is usually measured by production responses such as milk yield, milk quality, or weight gain. But there is well documented evidence that appropriate trace mineral supplementation can have a significant effect on reproductive performance.

Ideally, nutritional supplementation to optimise reproductive performance should begin before calving, but it is never too late to bolster the nutritional needs of cattle, including trace minerals, to help get them back in calf in timely fashion.