Drought Feeding Strategies

Excerpts from an article written by:
Ian Sawyer, Weston Animal Nutrition

It is a great article for anyone looking at their feeding strategies during drought.


Drought Feeding Strategies

The Rumen is the basis of all pasture-based agriculture. This is because cows and sheep themselves are not capable of digesting the fibrous component of pasture and forage. Fortunately they have rumens and rumen bugs that do this on their behalf!

The Rumen is a large fermentation vat filled with fluid and a vast array of microbes. It is these microbes that are the key digesters of the fibre component of forages (basically cellulose), and it is these bugs that allow our grazing creatures to eat feedstuffs that humans , poultry and other monogastric (single stomach) animals cant handle (again think cellulose) .

The array of microbes in the rumen is huge, and there are other bugs that digest starch, others for sugar etc. The principle is the same in each case however. The bugs adhere to particles of food and gradually erode or mine out the digestible bits. These digestible bits are converted to organic acids. These are good acids, which the animal can use as an energy source.

This fermentation process sounds like money for jam… but it has a cost as well. It could be said that ruminants upgrade low quality feeds, but downgrade high quality feeds! There is stuff that even the rumen bugs can’t handle. This revolves around a plant component called lignin, which is indigestible. The older and crappier your forage the more lignin it has. The more lignin it has the less digestible and lower in energy it is.

Digestibility and speed of digestion of common feeds

Product

Digestibility%

NDF%

Speed of digestion (hours)

ME-R

MJ/kg

Molasses

95

0

0.5

12

Cereals

85

10-20

12-14

12-13

Good clover

75

35

12-18

12

Good grass

70

40

18-24

11

Poor hay              

55

60

30-40

7

Straw     

40

75

45-55

6

High NDF means slow passage, low digestibility, and low energy. It means longer to take the next bite. IT MEANS LOW INTAKE AND LOTS OF ENERGY JUST FOR PROCESS OF DIGESTION.

Low NDF means fast passage, high digestibility, and higher energy. It means faster to take the next bite. IT MEANS HIGHER INTAKE AND LESS ENERGY JUST FOR PROCESS OF DIGESTION.

EQUAL WEIGHTS OF STRAW AND GRAIN OCCUPY VERY DIFFERENT VOLUMES.

This is the big issue when managing dry matter intake and energy availability. It is far more important then the actual energy decline. Cattle for example can eat 1.2% of body weight as NDF to reach gut fill. The higher the NDF of a product the less they can fit in. Couple this with a decline in energy and you start to see why stock go back ward as quality declines even if availability/volume is adequate.

The impact of maintenance on feed requirements

Maintenance is a hidden cost to most producers. No cheques are written, but it places a large burden on the producer to supply tucker that is non-productive and essentially fixed cost. Maintenance loads daily can be calculated fairly accurately. Below are quick calculations that work out the daily requirement for maintenance expressed in Megajoules/day.

Sheep Cattle

Maintenance=(1.8+ (0.1 times BW)) times 1.2 

Maintenance =((8.3+0.091 times BW) times 1.2)

50kg lamb

(1.8 + 0.1 *50) *1.2

= 8MJ/day

400kg heifer

(8.3+ 0.91 *400) *1.2

=54MJ/day

0n 8Mj/kj hay

=1kj/day for maintenance

on 8MJ/kj hay

=7kg/day for maintenance 

Note: The 1.2 is essentially a 20% allowance for activity, and in Australia our stock must walk!

It is a heap of feed, and until they fulfil that need they don’t allocate tucker towards growth and production.

Putting on weight using lower quality feeds takes about 50MJ to put on a kg of body weight. It is always more efficient to feed for gain then just for maintenance. Maintenance alone means a considerable investment for zero return. Production feeding sees a modest extra amount of feed contributing to growth after the maintenance load is paid for.

If you are going to feed, make a good fist of it. It you don’t want to feed then sell the stock up front.

Early weaning calves

You have a mob of cows and calves. The season is crook. The cows are average and slipping in condition. The calves are a pain in the backside, but you are concerned that weaning them will see the little bugger’s crash. Likewise you know that if you don’t wean them then the fertility of the cows will be compromised by poor body condition. This risks next year’s income.  What’s going on, what do you do?

Firstly, you have to manage cow condition. “Negative energy balance” is what she is experiencing. That means she putting out more energy to the calf, maintenance and exercise then she can take in feed. This occurs in beef enterprises in poor years. In a good period she can meet demands. In dairy cows that produce 40-50 litres/day it can and does occur in premium pasture and supplement with 20 kg total intake.  While a cow is in negative energy balance she is unlikely to cycle. Her whole physiology says “don’t do it…mother the little one at foot, don’t partition energy to another pregnancy”.  The biggest burden on the cow is the calf.  If you take it away, she gets into positive energy balance, she cycles and next years income is once more secure. So the first answer is YES WEAN THEM!

Weaning calves at 100-150 kg is pretty standard practice in dairy, and has been for ages. Weaning occurs commonly at 6 weeks, and can be as young as 3-4 weeks.  The secret is not to wean off milk onto crappy forage. The weaning process must move them off milk onto a high nutrient value supplement with some forage available to get rumen function happening. We have shown that low energy high NDF forages inhibit intake. Calves have a small underdeveloped rumen, so they struggle even more with these low quality forages. Give them a high energy / high protein ration however and they can consume plenty to allow them to grow without a post weaning crash.

Specifically consider your 150 kg calf:

Maintenance is 26MJ, allow 25mj for gain = total 51Mj.

You can’t do it on hay alone. They fill up the gut on 3 kg, and barely make maintenance.

Low fibre pellets take up little gut space, but contribute a lot of energy.

It can be done simply and successfully. Always Group calves if possible on weight to prevent bullying and ensure consistent intake.

Sources of supplementary feeds- The grain Vs Pellet/Nut debate

Grain Pellets
Advantages

Advantages

Price usually cheaper then compounded feeds

No further processing

High energy level , low fibre

Normally designed with buffers and safety in mind

Disadvantages Contain minerals

Wheat/triticale/barley have fast fermenting starch, a bit dangerous

Can have higher protein options

Requires some processing usually

Disadvantages

Low protein levels

Normally at premium to grain

Low mineral levels