19 Apr 2021
Phil Elkins
Job Title
Image © CeliLeGall / Pixabay
Calving is an integral part of the production cycle in both dairy and beef cattle. Obviously, a calving is necessary to produce the primary outputs from both of these systems – milk and calves – but is also critical in ensuring health and welfare throughout the production cycle.
In dairy production, on average 75% of disease is related to the transition period – that is, the preparation for calving and production, and the period immediately after calving1. This represents a significant opportunity for veterinary involvement to improve health, welfare and productivity.
Planning for a successful calving period encompasses two key provisions – provision for optimum disease and production management, and provision for where things go wrong. As more emphasis gets placed on the first, less emphasis will be needed on the second. Similarly, provision for optimum production management will reduce the opportunity for disease to happen.
Before we can discuss optimum management, we need to consider what are the factors of a successful transition? These are summarised in Panel 1, and apply equally to both dairy and suckler cows.
A cow is deemed to have successfully transitioned if she has:
Five main categories of failure are associated with transition:
The best managed farms in the world (with good records) only achieve successful transition 70% of the time. High variability exists between farms in performance, and often within farms over time, although often the top and bottom operators show consistency.
Infectious disease control is essential throughout the production cycle with livestock. Certain diseases exist for which pre-parturition and post-parturition offer the best opportunity for control due to timing of disease. For most diseases, balance exists between challenge and immunity.
If we look at an overly simplified example of mastitis related to transition, the challenge relates to environmental conditions in the pre-calving and post-calving environments, whereas the immunity relates to nutritional competency, milking machine interactions and the physical seal at the teat end. It is clear to see how the cleanliness of the pre-calving and post-calving, and calf accommodations are integral to reducing the disease challenge to cows and calves.
Assuming cows are calving indoors, building design, stoking density, bedding choice, storage and quality, frequency of cleaning up scrape passageways and frequency of mucking out all influence the cleanliness of accommodation. On a day-to-day basis, vets can influence those factors later on the list easier than those earlier on the list, but sometimes hard conversations need to be had about building design and stocking density.
For a set stocking density, bedding material and quality, an optimum period for mucking out for any building ensures disease control. Encouraging farmers to stick to that frequency will pay dividends. If in doubt, mucking out every two weeks is often a safe starting point.
Pharmaceutical products play an important role in shifting the challenge:immunity balance. They do this through improving the local or systemic immunity, and by reducing the infectious disease load in the herd. It is important before you use these products to make sure they are appropriate and used in the right way – appropriate use of diagnostics and well-prepared protocols are the key to successful interventions.
Consider a vaccine given to reduce the incidence of calf scour when the causal agent is Cryptosporidium parvum, or, if the main issue is Rotavirus, if the vaccine is given 10 days prior to calving and, as such, insufficient time is available to boost colostral antibodies. In both of these situations, the vaccine will not provide the full benefit, yet both of these situations have occurred in the author’s experience.
Vaccines around calving time can have two main aims – boosting colostral antibodies and boosting dam immunity. If the aim is to boost colostral antibodies – which is a recognised technique for improvement in both calf scour and pneumonia – it is essential calves then assimilate those antibodies. For this to occur, the cow must be fed the right ration to produce suitable colostrum, and then that colostrum must get into the calf quick enough.
Many articles cover how to successfully ensure sufficient passive transfer of immunity to calves – needless to say this is just as important to overall calf health as it is to vaccine benefit. Useful methodology for consideration of vaccination is described by the author2 and applies suitably here, too.
Around calving, cows undergo multiple metabolic changes related to the change from maintenance and gestation to lactation and involution. These changes involve upregulation and downregulation of many biological processes involving multiple organs.
These complex interactions involving the metabolism of both calcium and energy leave opportunity for failures in transition. This can manifest in many ways, as the biological pathways are all interlinked. As such, increases in one transition disease often occur concurrently with other diseases, and considering them as transition success versus failure rather than individual disease may be useful.
In many situations, the predisposition to disease is determined before calving, whereas the disease manifestations often occur after calving. Cows that develop metritis post-calving show significant reductions in levels of dry matter intake up to nearly two weeks before calving3. In many situations, pre-calving dry matter intake can accurately predict milk yields in the following lactations. Therefore, it naturally follows that maximising dry matter intake in the run-up to calving may reduce the rate of clinical disease afterwards.
Feed space availability is critical in promoting good dry matter intakes. Targeting 90cm of feed space, or 85% occupancy where dividers are in place, will reduce limitations in dry matter intake due to availability and social concerns. Increasing stocking above these figures is associated with reduced dry matter intake, reduced milk yield and increased disease. Having assured suitable feed space, taking consideration of physical and social impediments such as dead ends and dark areas, the next area for attention should be the rationing.
The principles of a suitable pre-calving ration are very simple – encourage high levels of dry matter while providing adequate protein and preparing for a large change in calcium demands. Achieving this in practice is often far harder. It is important to remember the ration on paper needs to accurately represent the ration consumed by the cows – it must be presented to the cows exactly as rationed, with good mix qualities to prevent sorting at the feed face.
Regarding the ration itself, the “Goldilocks principle” very much applies – to maximise dry matter intakes, the energy density cannot be too high, as this promotes reduced intakes and increases over-conditioning. Equally, the ration cannot have too low an energy density, as this reduces palatability and, hence, dry matter intake. In this regard, the introduction of tub-ground straw has led to large improvements in pre-calving rations. Once straw has been appropriately ground, achieving intakes of up to 6kg per cow, per day, of straw is very much achievable.
With unchopped, or poorly chopped, straw it is often difficult to achieve intakes above 3kg without significant sorting issues, which often leads to rations that are either unpalatable or too high in energy density. Metabolisable protein in the pre-calving period can be directly linked to milk production and constituents. Benefits are seen in nulliparous animals for increasing provision of metabolsable protein up to 1,100g/day, whereas in multiparous animals, the only benefit seen once supply exceeds 800g/day is an increase in milk protein yield4. Therefore, it is important to ensure sufficient metabolisable protein supply to support future production.
The failure to control calcium metabolism is clearly seen in herds with high rates of recumbency due to hypocalcaemia.
However, due to calcium’s role in smooth muscle contractility, subclinical hypocalcaemia is also associated with many other diseases, such as mastitis, ketosis, displacement of the abomasum and retained fetal membranes.
Many tactics are available for controlling hypocalcaemia, all of which are capable of reducing the incidence of clinical cases. However, it is the author’s belief none show the positive production benefits of a full dietary cation-anion balance approach. This has been proven to reduce disease incidence while increasing milk yield in multiparous cows5.
Interestingly, while small benefit may be seen in calcium homeostasis in nulliparous cows, milk performance is either unaffected or depressed due to reduced dry matter intakes. However, only limited studies look specifically at nulliparous cows.
Failure of appropriate fetal size or presentation leads to dystocia. This occurs in 17.8% of beef calvings, with risk factors including twin calvings, nulliparous dams, Charolais-bred calves and male calves6. Excess body condition was not identified as a significant risk factor in a large study, whereas maternal underconditioning was. Prevention of dystocia, through appropriate genetic selection for direct and maternal calving ease (especially with nulliparous animals), management of body condition and control of calcium metabolism are key to limiting the requirement for intervention.
Building protocols with clients to ensure intervention is appropriate is also important. Many farmers will jump too quickly for fear of losing calves or dams, whereas they may ignore the subtle signs of early dystocia – “she looked like she was messing around two days ago”. She was, and now has a rotting calf inside of her. Choosing the right point to intervene, and the depth of that intervention before asking for help, is a balance between veterinary surgeon and client, but reviewing successes and failures is an important stage in ensuring protocols remain fit for purpose.
Some basic equipment should be considered when preparing for dystocia: a clean, well-functioning and maintained calving aid, in an accessible location; clean, washed, supple calving ropes; any appropriate medications; plenty of lube (is there ever too much?); and the telephone number of the emergency vet close to hand.
Having conversations about this in advance can prove really quite beneficial, and this includes warning a vet of potential impending issues sooner rather than later – the author would rather get told something may be a problem in an hour or so than to get there as quick as possible. He can at least then make sure he is appropriately prepared.
So, in conclusion, the calving period offers a large opportunity for us, as veterinary surgeons, to engage with our clients in a preparatory way and look to optimise health, welfare and production. This will aid in changing the rhetoric from fire brigade work and a cost, to a key part of the farm team and an investment.
