There are times of year when heifer performance becomes a key concern. The period prior to mating heifers is one of those times. While many factors affect heifer fertility, trace element evaluation is a critical area to consider.
Replacement heifers carry the genetic future of the herd and are vital to any farm, whether they are dairy or beef suckler enterprises. Achieving high conception rates in the first breeding season increases productivity. Economic returns are also enhanced when heifers conceive well in their second mating season, which can be a challenging time. The length of time from calving to the resumption of cycling is longer in first-calving heifers than in adult cows. Many herds calve first-calving heifers earlier than cows to give them the extra time they need to return to oestrous and be cycling with the rest of the herd at the start of the next breeding season1 .
Once puberty is reached, nutrition must be at a level that allows the heifer to continue cycling, ovulate a viable oocyte (egg), and hold the pregnancy. Nutritional demands of heifers, including trace elements, during pregnancy can exceed that of mature cows because the heifer is partitioning nutrients; for her continuing growth, for foetal development and in the second breeding season for the additional requirement of lactation8. Deficiency of energy or protein for extended periods of time during the first 2.5 years of life will have a negative impact on foetal development, calf viability, milk production, and rebreeding for the next pregnancy1. Dairy heifers on target to calve at the optimum 24 months4a have been shown more fertile, (higher % conception to first service) and also to have similar improvements in fertility in the second breeding season compared to those calving at >26 months. As these heifers are significantly more likely to survive in the herd beyond a third calving, they also spend significantly more days in milk, producing improved lifetime yields4a,7. For beef heifers the optimum age at first calving is also 2 years; for spring-calving, grass-based suckler systems, delaying age at first calving from 24 to 36 months of age, is proven to reduce net margin per hectare by 50%4b. Therefore, it is important that heifers reach their weaning, bulling and calving weight targets at the right age each season. Nutrition has crucial influence on achieving these targets4a. (Please see AHDB website for recommended targets4ab.)
Trace minerals are an essential component of a nutritional program for heifers and cows. Trace elements are required in small amounts on a daily basis for healthy, productive heifers and cows. Copper is important for growth and in enzymes responsible for fertility and thrive. Selenium is required for growth, immunity and fertility. Cobalt is used by the rumen microbes to make vitamin B12, which is required in growth. Iodine is fundamental for thyroid hormones which are involved in metabolism and foetal development3.
There is a well-defined relationship between liver copper storage and the amount of copper absorbed from the diet. If the diet also contains significant levels of molybdenum, sulphur or iron there will be reduced copper available for the cattle to absorb, as these elements bind to the copper and prevent copper-dependant enzymes from functioning (‘thiomolybdate toxicity’). Copper-dependant enzymes are important for oestrus and energy metabolism8. Feed/ forage analysis is essential to identify the relative concentrations of these antagonists.
Trace Element Boluses
Beware of over supplementing as there is a risk of causing toxicity with some trace elements. Deficiency should be diagnosed by a vet using blood and liver analyses to effectively confirm diagnoses. Blood and liver analyses can also be used by your vet to monitor the efficacy of a feeding program. If deficiencies are diagnosed, then it is essential to find a suitable way of rectifying the imbalance. One option is to consider an oral trace element bolus which delivers multiple trace elements over extended periods. Boluses are recognised as a prudent form of supplementation because of their slow-release formulation8. However, every herd requires an individual approach to address each unique situation on-farm.
The Bimeda Cosecure Cattle Bolus, is the only multiple trace element bolus available in the UK which is a licensed medicine (‘POM-VPS’) and could be an appropriate option for providing trace element supplementation. The Cosecure Cattle Bolus supplies ionic copper, ionic cobalt and selenium at a constant rate, for up to six months. Many cattle also suffer from iodine deficiency. Bimeda also manufactures an iodine-containing bolus, CoseIcure. Like its sister product Cosecure, CoseIcure lasts for up to six months and delivers ionic copper, ionic cobalt and selenium, as well as iodine.
In a published trial, Cosecure cattle boluses were used in cows which had previously experienced low conception rates and poor cycling. Some had shown clinical signs associated with copper deficiency and thiomolybdate toxicity, such as ‘spectacles eyes’ and poor coat colour. Cattle which were treated with Cosecure Cattle boluses benefitted from increased fertility compared to the control group. The Cosecure group had significantly fewer inseminations to become pregnant than non-bolused animals and had a significantly shorter calving interval when compared to non-bolused animals5.
In another published trial, dairy cows were given one of three treatments; subcutaneous injections of copper and selenium, matrix boluses or Cosecure boluses. Combined data from 406 cows on three farms demonstrated there was a significant difference between the conception rates of the three groups. It was found that the conception rate in cows treated with the Cosecure bolus was 1.8 times higher than those treated with injections; and 1.5 times higher than those treated with the matrix bolus6..