Early spring diet for cows

By Gabriele Kaufler, Sustainable Agriculture Coordinator, Environment Waikato

By now everyone is looking forward to spring, which is just around the corner. Again farmers have managed through winter which for many is the toughest part of the entire season. Especially this year with the early onset of winter in May and quite severe frosts in June pasture growth rates dropped to zero unexpectedly early in the season and remained low for some time. Feeding cows well became a challenge on some farms.

What do cows need in their feed?

Strategic feeding of lactating cows, especially in early lactation is an important tool to improve animal health, milk quantity and quality. Sound feed budgeting and a lot of realistic planning for winter and spring feed demand goes a long way to protect animals and also to reduce farmers’ stress.

Safeguarding feed intake and thus body condition score by having extra feed at hand for those unexpected weather is crucial. The key is to also think about what type of feed would be necessary to meet stock requirements. Cows in early lactation need a lot of energy to produce milk – that’s what their bodies are conditioned for. If energy levels are low or digestibility of the feed is not good enough, they will milk of their backs and loose body condition quite rapidly. Whilst some condition loss is unavoidable in early lactation, cows need to get on a rising energy intake as soon as possible. This is the most important aspect to enable them to cycle well and get back into calf early.

Early spring grass is extremely high in protein. Unfortunately, at the same time it might be low in energy, as sunshine hours are low and therefore photosynthesis is not very efficient in producing those dearly needed sugars and carbohydrates. Cows require about 18-20% crude protein in their diet. Later winter and early spring pasture is often at 24-25% crude protein, and levels of up to 30% have been reported.

Any practices that lead to high nitrogen levels in the soil will invariably cause high nitrogen levels in the grass. This will increase pasture protein content as well as non-protein-nitrogen, for example nitrate. Most farmers are very aware of the associated risk of nitrogen poisoning. This occurs when the plants are unable to convert nitrogen adequately into protein resulting in toxic levels of nitrate in the feed. Nutrient management and feed quality are connected and it pays to keep that in mind.

For the second round of grazing, we have to keep in mind that most of these paddocks have been mobstocked over winter. Therefore nitrogen levels in the soil from urine and dung might be very high, ready for uptake by the pasture as soon as the soil warms up a little. Additionally many farmers apply nitrogen fertiliser to boost grass growth, following the cows around.

What is the risk of feeding cows too much protein?

How do the animals deal with the overload of nitrogen and/or protein in their diet? They have to excrete it, mainly as urea in urine but also in the dung. This process requires extra energy, creating an even higher energy deficit at this time of the year when often high protein/low energy feed is offered. Research has proven very well that this is likely to reduce milk production, not to mention the related metabolic issues.

Urine spots from cows are carrying the equivalent of 1000kg nitrogen per hectare, too much for pasture to take up. Surplus nitrogen is very likely to leach and find its way into groundwater or maybe into the farm bore – potentially affecting drinking water quality. Urine spots have been identified in many trials in New Zealand to drive nitrogen leaching especially under high rainfall conditions. Furthermore there is the risk of nitrogen run-off into surface water. Environmentally, high nitrogen levels in the soil are always a high risk scenario. Animals feeding on protein-rich pasture or crops will excrete the excess as urine and dung, thus exacerbating the issue. So, what’s the solution?

What are the opportunities to balance the diet and what’s the gain?

It’s a good start to find out what the protein levels in the feed are by taking herbage samples especially in late winter and early spring. If nitrogen fertiliser or effluent has been applied over winter and if previously mob stocked paddocks are grazed, this is an extremely important practice. The information coming back from the lab is invaluable to address any dietary deficits. Equipped with the pasture quality results farmers can then chose the right feed to balance their animals’ diet.

If pasture protein levels are well above 20%, farmers need to strategically add carbohydrates to the feed. Feeds with a high energy / low protein profile would be the obvious choices. Molasses, maize silage, grain and good quality hay would all be suitable depending on fiber demand, too. PKE is relatively high in protein at about 16 – 19% and digestibility can be an issue. Requesting a feed analysis when buying feed or feed mixes provides quality assurance.

Getting the diet right in late winter and early spring creates a win-win right through. A balanced diet will improve rumen function and reduce metabolic stress. Net feed utilisation will increase significantly, boosting production and productivity. The costs of not getting this right are numerous. They are associated to animal health risks from metabolic issues and underfed stock, although DM intakes seem to be sufficient. Additional costs occur from wasting feed energy to process and excrete the excess protein. Scouring cows are a visible indicator for all of the above risks. A well qualified animal nutritionist will be able to tailor feed supply to the specific on-farm situation. Paying for this service is money well spent.

Last but not least there is an associated environmental risk when nutrient efficiency in animals and farm systems is suboptimal. Excess nitrogen is leaching from our soils and is increasingly showing up in our groundwater and surface water bodies. New Zealand’s rural and urban communities have strongly indicated that clean water is important to them.

Applying the tools that scientists and animal nutritionists have developed to support farmers and consultants has allowed many farmers to increase productivity over the years. Proactive approaches to nutrient and feed management will create even more opportunities to finetune nutrient utilisation. This enables farmers to convert more of the nitrogen already available in the system into product and most likely it will reduce operating costs. Stock health will benefit, their longevity will increase and our waterways will benefit, too.

EW has developed resources to help farmers improve nutrient efficiency. Call 0800 800 401 for more information.