Feature: The key to sound nutrition

FEATURE

The key to sound nutrition

Knowing what’s in your pasture is key for sound nutrition. DAVID NASH, Director of Nutrition Technology at Kentucky Equine Research, explains why.

Pasture often contributes up to 100 per cent of your horse’s daily nutrition, so we should know its nutritional composition before making dietary recommendations and, just as important, know whether it’s suitable for your horse. What’s acceptable for a rapidly growing or lactating mare may be completely unsuitable and dangerous for a metabolic affected horse.

The quality and quantity of pasture can change dramatically between seasons, areas and plant species, so it’s important to be aware of what your pasture is doing.

Where to test?

paddocks to test can be daunting, but a simple method is to assess which paddocks are similar in pasture type, soil type and structure, and perhaps stocking density. Grouping these together may give a sufficient representative sample of your paddocks. When sampling, keep away from areas like gateways, stock camps and trees, as generally animals defecate around these to give non representative results.

When to test?

Many large commercial studs have pasture sampling dating back decades with additional information such as fertiliser, herbicide and sowing records. Generally, they will take samples through each season. This gives a true picture of what the pasture is contributing to the horse’s diet throughout the year, allowing for adjustment to the diet if required - especially through summer and spring when pasture nutrient concentration is extremely different.

How to take samples

Taking samples correctly gives a sound representation of what your horse is eating. To take pasture samples you will need a clean labeled bag, scissors, a clean bucket and a ruler.

Step 1: Label the bag with the date, property and paddock name so you know which pasture you’re testing. Remember, paddocks may be quite different in their nutrient content.

Step 2: Determine your horse’s pasture grazing height by measuring the height of the pasture before and after grazing. For example, if the height of un-grazed areas is 20cm and the height of the grazed areas is 10cm, then the length of the grazed pasture is between 20cm and 10cm. Thus, pasture samples should be between 10 and 20cm in length as this is a representative sample of what the horse is consuming.

Step 3: With scissors or pasture shears, take 12 to 20 pasture samples at grazing height across the paddock. Some people like to do that randomly, while others walk a ‘J’ pattern across the paddock. Clip pasture samples into 2-5cm pieces and place in a clean bucket.

Step 4: When sampling is completed, mix the samples thoroughly. Place in the labeled sample bag. Continue the process for other paddocks you wish to sample.

Step 5: Try to deliver you samples to the laboratory the same day. If it’s warm, put them in a cooler to reduce fermentation. If you can’t get them to the laboratory within one to two days, freeze them overnight and express post to the laboratory the next day. If this is not possible, especially given mail delivery times during the pandemic, drying the pasture before sending will help maintain its integrity. To do this, weigh the pasture sample first, then place in a microwave safe container and microwave for 3-5 minutes or until dry to the touch. Remove from the microwave and weigh the sample again. Record both these results on the laboratory submission forms as it helps laboratory staff establish the pasture’s moisture content as it stands in the paddock. The dry matter results are important, which we’ll explain below.

What to look for

On your lab report, you will most likely see results in dry matter and ‘as fed’. ‘As fed’ is how pasture is eaten by the horse, while dry matter calculates nutrients with the moisture taken out. In the same sample, dry matter results will be a lot higher than ‘as fed’. As a rule of thumb, you would expect to see grains, formulated textured feeds, and pellets at around 8-12% moisture. The same may apply for hay and some dry pasture, with haylage at around 20-30%, and fresh pasture with up to 80% moisture. So when comparing various ingredients, it’s important to compare the product at the same moisture level. ‘As fed’ pasture may appear less nutrient dense than a specific grass hay, but once you compare them on a dry matter basis, you’ll see that the pasture is actually quite nutrient rich – giving you a better idea as to its suitabilty for your horse.

Crude Protein: refers to the hay or pasture’s protein content. Calculated by multiplying the amount of Nitrogen present by 6.25, it’s a rather crude way of assessing protein content, but it does give some idea. Some laboratories offer testing for lysine and other amino acids to help assess the quality of the protein. Higher levels of essential amino acids such as lysine and methionine indicate higher quality. Protein in forage can vary greatly from low single figures in dry cereal straw to a high 20% range for legume hays such as lucerne, or highly productive ryegrass pastures. These results can vary greatly throughout the season, so monitor carefully and make adjustments to the whole diet.

Crude Fat: gives an estimate of the forage’s fat content. Fat analysis results are obtained using near-infrared spectrophotometry (NIR) analysis, or wet chemistry (a process using acid hydrolysis or ether extract techniques). These may give varied results so for consistency, always ask for the same technique to be used.

Diagram 1:

Moisture % Hay Hay Pasture Pasture

As Fed Dry Matter As Fed Dry Matter

10.0 – 80.0 –

Dry Matter % 90.0 – 20.0 –

DE, Mcal/lb 0.79 0.88 0.23 1.15

Crude Protein % 8.1 9.0 4.2 21.0

Calcium % 0.45 0.5 0.16 0.8

ABOVE: Protein in forage can vary from single figures in dry cereal straw to a high 20% range for legume hays.

Fibre content in forage is extremely important for all horses, more so for horses with metabolic issues. Key fibre fractions to look for are neutral detergent fibre (NDF) and acid detergent fibre (ADF). NDF, which is more digestible for horses, consists of cellulose, hemicellulose and lignin but not pectin, while ADF is comprised of cellulose and lignin. When assessing its suitability, forage with an NDF of between 40-50% and an ADF of 30-35% is considered ideal for performance horses, young stock and broodmares with no metabolic or growth issues. Mature or sedentary horses in little to no work and easy keepers may benefit from forage with slightly higher values.

Forage with NDF levels greater than 65% and ADF levels in excess of 45% will have little nutritional value, but may be an excellent choice for horses with metabolic issues and obesity, as it provides fewer calories but has the fibre content that helps maintain gastric health. Always remember, horses evolved eating low quality roughage in small frequent meals.

Carbohydrate Levels: are extremely important in assessing forage suitability, and if not carefully attended to can cause major issues for your horse. Several key factors are non-structural carbohydrates (NSC), starch, water soluble carbohydrates (WSC), ethanol soluble carbohydrates (ESC) and fructans, which you may be familiar with, especially if you have an EMS, obese or laminitic horse.

NSCs are a combination of starch and WSCs. Starches are complex carbohydrates or sugar molecules bonded together in long chains. Starch levels in pasture are generally a lot lower than those found in cereals. WSCs are classed as a combination of simple sugars and fructans. Simple sugars can be digested enzymatically in the horse’s small intestine and fructans are fermented in the hind gut. You will also commonly see ESC, a subset of WSC, which represents the simple sugar content of the forage. While fructan levels may not appear on the analysis, you can calculate these by subtracting ESC from WSC.

Sugar levels can vary between pasture species, with the highly bred cultivars of ryegrass and fescues at the top of the list, cocksfoot and phalaris in the middle, and native grasses such as kangaroo and wallaby at the lower end.

As plants rely of photosynthesis to generate and grow, the forage’s sugar content will depend on the amount and duration of sunlight exposure. WSC levels in pasture can double from winter to spring, and from 6:00am to 6:00pm. To limit your horse’s sugar intake, late at night and early mornings are when pasture

ABOVE: Pasture acceptable for a lactating mare may be completely unsuitable for a metabolically affected horse.

sugar levels may be at their lowest. This is also dependent on your pasture: if you have highly productive pasture even the lower levels of pasture sugar content may be too high for your horse.

Mineral Content: is quite important to ensure your horse’s total diet is balanced. Many laboratories offer macro and micromineral analysis for minerals such as calcium, phosphorous, magnesium, potassium, copper, zinc and manganese. It’s important to specifically request a chemical analysis for minerals, as NIR analysis does not give reliable results.

There are many aspects to consider when assessing pasture suitability for your horse. Australian agricultural departments have well trained staff to assist you, and many rural stores have a trained agronomist on staff. At Kentucky Equine Research we have several technical team members who can explain how to take pasture samples and read the results, and can offer potential pasture improvement solutions for your farm and horses. For more information on pasture quality testing, please visit www.ker.com, or talk to your local agronomist, or a Department of Agriculture field officer.

Diagram 2: WSC content of pasture throughout the day (Langland, 2007).

250

WSC Content (g/kg DM) 200

150

100

50

0

6:00am 9:00am 11:00am 6:00pm 11:00pm

1

ALL THINGS COUNTRY

Indulge yourself in some good 'ol country comfort

2

3 4

6 5

1. JUST COUNTRY Sunbody Alex, Natural/Chocolate Bound Edge, HG45ALEX – $119.95. 2. ARIAT Women’s Cruiser, Glitter Antique Brown, 10035877 – $179.95. 3. EQUESTRIAN HUB Bates Kimberley Swinging Fender 17" (Medium). Poley knee pads for a secure seat, traditional stock stirrup bar, long double girth points, swinging fender that moulds around your leg and moves with you and your horse, easy change gullet, CAIR panels – $2200. 4. ARIAT Men’s Rebar M5, Slim DuraStretch Edge Stackable Straight Leg – $129.95. 5. EQUESTRIAN HUB Woven stretch belt, One size, available in 35 colours – $25.00, Members price $21.25. 6. EQUESTRIAN HUB Dolan Jackeroo 17″. Dolan Jackaroo 17”. An all-leather, Australian made saddle, felt lined, 3” rigging dee’s for girth points, comes with a girth, suit ASH/TB type horses, SQHB, is a ‘full rough-out seat’ – $1995. Stockist info page 108.