How green is your pasture?

What colour is your pasture?  Satellites and drones now track pasture quality, using colour.  Pasture dead matter content determines quality, so the browner your pasture, the poorer the quality.  Pasture quality is what limits animal performance during summer and autumn.  And if it’s drying off, pasture supply is yet another challenge at this time of year.

Pasture quality is a function of the ratio of plant cell contents (juicy, sugary, containing highly digestible soluble protein) to cell walls (fibrous and structural) and the digestibility of these cell walls by micro-organisms in the rumen of sheep, goats, cattle, deer or forestomachs of alpacas and llamas.  As pasture plants age and switch from leaf to stem growth, dead matter builds, dropping both energy and protein content.

Using Waikato dairy pastures in an average (no drought) year as an example, dead matter increases from a low of 10% between August and October to 40% in April/ May.  Late summer/autumn ranges in metabolisable energy (ME) of 9-11 MJ ME/kg dry matter (DM) and crude protein (CP) of 15-22% DM CP are normal.  Once autumn rains arrive, a green tinge closely follows.  But looking closely you will see the brown thatch at the base that first has to rot down, initially causing negative pasture growth, before those early leaves can take hold.

Pasture energy is usually the key parameter
Because NZ pastures usually exceed animal protein requirements, the pasture energy is usually the key parameter, with a linear relationship between energy content and intake when pasture supply is unlimited.  The more your livestock eat, the more they will grow or produce.  But to maximise intake in summer and autumn, once pasture protein drops below about 18% (or low protein maize silage or grain supplements are fed), protein supplements are vital.  Quality protein is crucial for milk, meat and fibre production, reproduction and immunity.

Lucerne – the Queen of forages
Quality protein supplements are the expensive part of any ration.  Lucerne (alfalfa) is called “Queen of forages” in the USA, due to its outstanding protein content and well-balanced amino acid profile, comparing favourably with soybean, yet much cheaper.  Added bonuses of feeding lucerne are more energy, minerals (mainly calcium, but also magnesium, potassium, sulphur, iron, cobalt, manganese, and zinc) and vitamins (beta-carotene) than other fodders.  Fiber Fresh Feeds are all lucerne or lucerne-based, to boost growth, health and production.

In dry conditions, total intake can be increased by including a palatable, moist, chopped forage as part of the ration.  Research in dairy cattle fed total mixed rations (TMR) based on chopped ensiled forages and concentrates has shown cows will eat 15-50% more TMR than pasture of the same energy content because the TMR is chopped, has a higher DM density and a lower structural carbohydrate concentration.

Other dangers
At this time of year, it’s also possible for two pastures with the same energy and adequate protein levels to have very different intakes, due to the presence of mycotoxins, other secondary compounds or toxins, parasite larvae and other nutrient imbalances, for example.  Consumption of mycotoxins, including endophytes, produced by fungi in pasture usually in late summer and autumn cause diseases such as facial eczema, ryegrass staggers, fescue foot and zearalenone toxicity.  They also affect reproduction.  These fungi thrive on pasture dead matter and stems, particularly in hot, humid weather.

Preventing stock from grazing affected pastures, feeding forage supplements or alternative forages to reduce toxin intake are the most common management techniques to minimise mycotoxicoses.  In these cases, high quality forages and/or balanced supplements are required and the dietary transition must be carefully managed to avoid production losses.

The bottom line
In summary, from now until rains have replenished soil moisture levels and temperatures have dropped below levels supporting fungal growth, supplements to or instead of pasture are key. Investing in the best quality forage supplements to base or balance the ration and maximise intake is essential, settling for anything less is false economy.  Focus on highly digestible, high protein, palatable forage of consistent quality that is preferably chopped, conserved moist, stores well and can be fed so wastage is minimised.  For growing, pregnant or lactating animals and those facing an immune challenge, particularly internal parasites, protein is paramount.  There are simply no forage supplements produced that outclass those of Fiber Fresh Feeds, so get to know their range now!