It is estimated that at least 60% of breeding activities occur during the Spring season. So it is very important that your herd is prepared in advance, as this is the greatest time to make an impact on your calf crop.
Management of your females forward to the time of joining is one of the most important aspects of ensuring an optimal result, be it natural mating, AI or embryo transfer.
The planning and management for your Spring AI or embryo transfer program, should begin at weaning. There are three classes of females to consider; Multiparous cows, primiparous cows, and maiden heifers. For all cows, planning and management starts with the weaning of their previous calf. For maiden heifers this begins at the time they are weaned. The focus is then on utilising the winter period to ensure pre-breeding activities such as vaccinations and genetic selection are conducted and that a focus on nutrition is paramount. For those that reside in a winter dominant rainfall area with winter dominant pastures this is a little easier than those breeders that reside in summer dominant rainfall areas.
Managing multiparous cows through the winter period for a Spring AI program is a reasonably simple approach. The aim is to ensure that cows are in at least a body condition score (BCS) 3 and ideally up to 3.5 (i.e. moderate to forward condition) at the time of calving. An assessment of the cows’ BCS when their calves are weaned is a good time to understand what is required during the winter period to ensure cows reach these BCS targets.
Generally primiparous cows that have just weaned their first calf are going to be your highest priority and the ones that will need the most attention. They tend to be lower in condition than multiparous cows given much of their nutritional intake is required for growth as well as lactation. For these reasons, they require a rising plane of nutrition sufficiently high in both protein and energy to ensure they are gaining weight rather than losing it. In summer dominant rainfall areas, winter pastures tend to have low digestibility levels and livestock will often require protein supplementation i.e. a lick, block or liquid supplement to prevent them going backwards or into negative production.
The maiden heifer, during the pre- and post- calving period, is the most challenging female to manage to ensure optimal fertility. The single biggest influence of the ability of these females to re-conceive once they have their first calf, is BCS at the time of joining. Evidence of this is clear through the FTAI results generated from the Angus Sire Benchmarking Project. A wide variation in AI pregnancy rates are observed when trying to re-join these heifers once they have had their first calf. This is almost always explained by BCS at time of joining, whereby higher BCS is usually associated with higher pregnancy rates. Heifers that have a good BCS post calving are more likely to return to cycling sooner than those in a poorer BCS.
The biggest nutritional challenge in a beef breeding female’s life occurs during the post-partum period after her first calf. The ability of cattle breeders to manage this period will determine the success of re-joining conception rates and subsequent longevity of the female in the herd. Historical management of the maiden heifer emphasised reducing the plane of nutrition pre-calving to manage dystocia. Reducing the plane of nutrition prior to calving has a negative effect on the subsequent ability of that female to produce a live calf, and also to maintain her BCS post-calving to ensure optimal fertility results for her to re-conceive. Studies by Micke et al. (2010) have in fact demonstrated that high dietary protein and energy fed during the second trimester are attributed to increased calf weight, which was correlated to a higher incidence of dystocia in cross-bred 3yo beef heifers. This highlights the importance of utilising the post- weaning period and the first trimester to reach appropriate BCS to ensure they can be maintained through to calving. Considering strategies of good genetic selection for calving ease traits and maintenance of a good BCS of the maiden heifer at calving are better strategies. This will lead to a more profitable outcome of increasing re-conception rates during their first lactation, reducing dystocia and thereby increasing the longevity of the female in the herd.
The nutritional management during the period between weaning and Spring breeding is a fundamental management tool for maximising fertility. Engaging in assisted reproduction is an investment in the genetic progression of a herd, so it is important to ensure that fundamental management procedures are optimised. Winter is therefore a good time to consider your plan for your spring assisted reproduction breeding activities.
If you are considering an AI or ET program this spring and want to discuss your plan, the Repro360 team is available to assist Angus Australia members, Call 1300 163056 or email firstname.lastname@example.org.
Dr Sophia Edwards, Vetoquinol Australia
G.C. Micke, T.M. Sullivan, P.J. Rolls, B. Hasell, R.M. Greer, S.T. Norman, V.E.A. Perry, Dystocia in 3-year-old beef heifers; Relationship to maternal nutrient intake during early- and mid-gestation, pelvic area and hormonal indicators of placental function, Animal Reproduction Science, Volume 118, Issues 2–4, 2010, Pages 163-170,