Preventing facial eczema
Pastoral nutritional deficiencies
Cow mineral deficiencies in maize silage
As we move towards summer, the fire risk boards are being joined by another warning chart – facial eczema (FE) risk. The combination of humid and rainy weather conditions and high night-time temperatures.
FE occurs when animals (the disease is not limited to dairy cows) eat spores of the fungus Pithomyces chartarum, which are mainly found in the base of pasture. These spores release a type of mycotoxin (sporidesmin), which damages the liver. The liver is such an important organ in production animals that the economic effect of this disease is huge. It is sometimes not seen at the time of the damage, only appearing when the cow is stressed and the liver has to respond to the extra workload,e.g. during calving.
Despite its name, FE is not a skin disease. Not all animals will show skin lesions but their damaged liver will lead to reduced milk production, weight loss and reproduction issues. Faull (1991) looked at 565,000 dairy cows and found that whilst only 6% of them had skin lesions, 38% of cows had damage to their livers.
As the saying goes, “prevention is better than cure”; this is true of FE. An action plan should be developed for your property and put in place prior to spore counts rising. Actions could include:
• Applying fungicides
• Trough treatment with zinc
• Inter-ruminal boluses
• Identifying high-risk and low-risk paddocks
• Addition of zinc to feed
Zinc mops up the sporidesmin toxin, meaning it cannot cause as much cell damage. Higher levels of zinc than a cow’s maintenance requirements are needed to prevent FE. Care must be taken to use products registered with ACVM (Agricultural Compounds & Veterinary Medicines) to ensure no adverse effects, especially from heavy metal contaminants, and dosage must be at the correct level for the size of cows in the herd.
Under-dosing could mean not enough zinc is present in the system to mop up the toxin and so cows still suffer from FE; over-dosing risks zinc toxicity. When adding zinc to feed, it needs to be included accurately and spread evenly throughout the feed. If using blends, take care to ensure the zinc does not separate out from the bulk raw materials during transport. Palatability enhancers should be used in water treatments so the bitter taste of the zinc is masked and cows still drink the water.
Zincmax+ is an ACVM-registered product, for use with in-line dispensers or trough dispensers, that has a peppermint taste and contains additional organic copper. Long periods of dosing at high zinc levels could deplete copper levels; Zincmax+ is designed to maintain healthy copper levels in the herd.
Signs that cows are affected by FE start with a reduction in milk solids. As cows become increasingly impaired, their sensitivity to the sun causes them to seek shade and they can be restless. Care should also be taken when spore counts are low. The sporidesmin toxin has a cumulative effect – one week of low ingestion can have the same effect as one day of high intakes.
In summary, be prepared. Monitor both spore counts and weather conditions. Ensure grazing rotations are sufficient to prevent the build-up of dead matter but offer enough in the risk period to avoid cows grazing to low pasture levels, as this is where spores are higher in number.
Faull, B (1991). Prevalence and costs of facial eczema on dairy
When stock graze pasture or eat supplementary feed, they get more than just the plant matter you feed them. They inevitably ingest a few insects, a few billion bacteria and a range of other, less obvious substances, including mycotoxins. Of all these ‘extras’, it’s the mycotoxins that can cause the most trouble.
The prefix ‘myco-‘ means fungus, so mycotoxins are toxins produced by fungi. Fungi are found everywhere – including in pastures and in bought-in feed. That means that mycotoxins can also be found in pastures and feed. Mycotoxins can have beneficial effects: some of them provide plants with protection against insect attack. However, some mycotoxins have the side effect of causing animal health issues.
In ryegrass-based pastures, troublesome mycotoxins can build up in leaf sheaths and flower stalks. They are produced by the endophyte Neotyphodium lolii, a fungus that grows inside ryegrass plants. This endophyte produces two mycotoxins – lolitrem B and ergovaline. Lolitrem B causes the characteristic tremors seen in ryegrass staggers, while ergovaline reduces the heat tolerance of animals.
Animals affected by endophyte mycotoxins eat less, so milk production suffers. Stock can also become more temperamental and may be more inclined to kick off the cups while in the shed.
The endophyte grows mainly in the seed, seed head, tillers and leaf sheaths, rather than in the actual leaf blade. This means that stock are more at risk of developing problems if they graze hard into the base of the pasture, or graze seed-heavy pasture. In addition, the risk increases when there is a long, hot period of weather followed by rain.
There are a few simple strategies that can help reduce the chance of stock being affected by ryegrass mycotoxins:
Young stock are particularly susceptible to the effects of mycotoxins, so extra care should be taken with their grazing set-up.
Mycotoxins can also be found in supplementary feed, and are produced by different fungi to those found in ryegrass. Any conditions that promote the growth of fungi in the feed will increase the chance of mycotoxins being present. Warm, humid storage conditions are most likely to increase fungal growth.
Any type of supplementary feed can be affected: blended feed, pellets, cereals, silage and baleage. Feed can be affected if it is bought from vendors or made on farm. Reputable vendors of supplementary feed ensure that their product is well managed throughout its life: from growing, through harvesting, processing and storage. The same precautions should be taken for feed produced on farm.
Good storage conditions are essential: protect the product from damp and use it as soon as possible.
If you suspect stock have been affected by mycotoxins, move them onto safe pastures (e.g. tall fescue, lucerne, chicory) and/or feed high-quality supplement. Leave them undisturbed as much as possible, and separate them from the main herd. If milking, reduce the frequency to once a day.
Pastoral Nutritional Deficiencies
Macronutrients and micronutrients are essential for a healthy productive animal. As grass is the basis for feeding cows in New Zealand, analysis of the grass for macro and micro nutrients is critical to help balance the cow's diet.
Working with Hill Laboratories, Ballance Agri-Nutrients and SealesWinslow have compiled a large database of results showcasing the difference between a cow’s mineral requirements and what a region's pasture actually contains. The database shows each region of New Zealand has a unique set of deficiencies that limits animal performance.
Dairy Pasture Optimum - red line
Dairy Cow Requirements - dotted line
Maize Silage Deficiencies
Maize silage is a high quality forage but it can be lacking in a number of minerals essential to cattle.
Maize silage has many valuable benefits as a supplement for pasture-fed dairy cows – it is relatively low in crude protein and high in starch, complementing pasture’s typically high protein and low soluble sugar content through spring and autumn. The relatively high yield potential of maize and its long storage life as silage makes it one of the most popular supplementary feeds in New Zealand dairy systems.
Maize silage is useful in early spring when pasture availability limits dry matter intake (DMI); later it helps to boost peak milk production levels by balancing the protein and starch content of the pasture to better meet the cow’s requirements. Through autumn and winter, feeding maize silage helps to lift cow condition scores and to extend milk production through the late lactation phase. During this time, a diet of pasture alone is likely to limit what can be achieved in terms of milk production and cow condition.
When you’re feeding maize silage to cows, it’s important to look at the nutritional requirements of your stock, and see how that is being met by the composition of the feed – the silage, the pasture and any other feeds being offered. The table below shows the typical analysis of maize silage and autumn grass, and the requirements of lactating dairy cows.
*Data taken from AgFact 251 (AgResearch)
Maize silage has relatively low levels of several minerals – most notably calcium, magnesium and sodium. Low dietary intake of these key minerals can cause stock health issues (mainly in spring), but they can also reduce the productivity of the cows.
If your goal of providing supplementary feed in autumn is to help extend lactation, then you want to make sure that the feed supports productivity. When it comes to maize, there’s an easy way to achieve this, simply use a mineral additive, which can be added to the maize silage prior to feeding out. This will boost the levels of calcium, magnesium and sodium so that the cow receives the dose of minerals that she requires for health and productivity.
Balancing the Rumen Diet
The production potential of any animal is influenced by a range of factors, including its genetics, its disease burden, water availability and of course, its feed. And when it comes to feed, there are two main considerations: is there enough feed for the animal, and does the quality of that feed meet animal requirements?
In New Zealand, because we’re pasture based, we typically estimate feed quality by the metabolisable energy [ME] level. But that doesn’t tell the whole story.
ME is a measure of the gross energy in a feed minus the estimated losses that occur as the animal processes that feed – the energy that is lost in dung, urine and as gaseous by-products of the fermentation process (mostly methane and carbon dioxide).
ME certainly has its place when you’re calculating the value of feed, but it’s not the only part of the story. If we’re concerned about optimising production or animal growth, then we need to focus on creating a balanced diet that contains all of the components needed to achieve our goal. To do that, we need to consider quality as well as quantity.
A high-quality diet has several characteristics. It provides a high yield of nutrients per kg of dry matter (DM); it has an ideal ratio of all of the various components required to achieve the production or growth goals; and it allows the animal to eat a high volume of the feeds.
The feed intake of stock is critical. We know that animals regulate their feed intake and we think there are two key reasons they stop eating – one, when they have met their energy or nutrient requirements, and two, when continuing to eat causes them more discomfort than not eating.
If an animal has a bulky, low-energy feed, then it can only eat so much before the rumen is full and the animal feels discomfort. It might still be hungry, but the discomfort from the rumen outweighs the discomfort from not having consumed enough energy, so the animal stops eating, even though it has a nutritional shortfall.
When we look at creating a high-quality diet for farmers to feed their stock, we’re trying to minimise the discomfort factors that will stop an animal eating. Our focus is on getting the animal to voluntarily eat as much as we need it to.
Feedstuffs that are rapidly digested help to maximise the voluntary intake of stock, because the rumen takes longer to reach fullness. One of the keys to this is readily degradable structural fibre – the more quickly fibre can be broken into small pieces, the more quickly it will move though the digestive tract, so the less likely the animal is to stop eating. The diet also needs to have high concentrations of readily fermentable carbohydrates (sugars, starch, pectin), protein that is slow to degrade in the rumen, and sufficient macro- and micro-nutrients to meet the animal’s needs.
At some times of the year, pasture quantity is actually the limiting factor in an animal’s diet. In early spring, for instance, pasture growth rates can struggle to keep up with animal demands – which can be quite problematic at a time when we’re trying to drive up production and growth rates. At other times, it’s pasture quality that limits the overall feed quality. The season, management practices, pasture species and fertiliser strategies will all influence the nutrient composition of pasture, and the only way to know what you’re feeding your stock is to get your pasture analysed.
Use pasture as the base of your animal’s diet, but supplement that as needed to create a diet that will drive production. That might be additional pasture, forage, mineral supplementation or specialist feeds.
Feed Quality for Animal Performance
Few would argue that for any animal, whether a good working dog, a thoroughbred racehorse, growing steers, high producing cows or ewes producing high fleece yields, a high quality diet is essential for top production or performance.
Pasture Quality, Feed Quality or Diet Quality are terms used regularly on-farm by farmers, consultants and researchers as desirable for lifting animal performance - but what, specifically, is a high quality diet?
For grazing animals, digestion is based on a healthy rumen acting as a fermentation vat to breakdown the diet into nutrients the animal can absorb into its body for productive uses – maintenance, growth, warmth, lactation, fleece growth.
In New Zealand's grazing based farming systems, pasture and feed quality is most commonly gauged by estimated metabolisable energy (ME) contents - but does this describe the whole picture?
For high animal performance, a high quality diet has several key characteristics:
As diet quality is directly related to animal performance - feeding a diet which does not meet any one of the key characteristics above will result in lowered productive performance – for example offering a rank pasture to young, growing lambs gives a diet that is unpalatable to the lambs (they won’t eat much), has a low yield of nutrients (the lambs are unable to extract very much from the feed), and does not necessarily offer the correct mix of nutrients (low in protein, too high in fibre, possibly limiting in minerals). The end results then will be disappointing growth rates (or possibly even weight loss).
Considering this then, a high quality diet provides:
To maximise animal productivity also requires ad-libitum access to this feed. While this may seem obvious, the best possible feed will not generate good animal growth or productivity if insufficient is available to the animal. The first limiting nutrient in an animal’s diet is often insufficient quantity – particularly through the early spring period when pasture growth rates can be struggling to keep up with animal demands.
Well managed pastures can generally meet the requirements to be considered a high quality diet for most stock classes. However, seasonality, management practices, grass species and fertiliser policies can dramatically affect the nutrient composition of most pastures.
To help optimise animal performance then, information about the composition as well as the quantity of the pasture available is a valuable place to start. Identifying the component that is most limiting in a diet allows focus on boosting animal performance in the most cost effective way – be that simply additional quantity of pasture, or mineral supplementation if macro or trace elements are deficient, or if specific nutrients are limiting animal performance (such as very low starch content of spring pastures).
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