Rebecca Thorn
- Jun 15, 2021
- 7 min read

TRAC Beef & Sheep Newsletter - Winter 2021 Edition

As consultants we are regularly questioned on what it is like elsewhere, often the answer is “it’s all relative”, relative to rainfall, stocking rates, and farming practices adopted.

In the current season, it is fair to say it’s tough across the board, from West to East in SA and to North and South in Victoria, most districts are experiencing a tight home-grown feed platform. The term “Green Drought” is being slipped into many conversations, and not to be too pessimistic the facts are that autumn follow-up rains did not come for many, day lengths are shortening and ground temperatures are beginning to decline…. a perfect storm.

Feed demands for many grazing enterprises are now on the increase and in autumn calving herds and autumn lambing flocks dry matter intakes are peaking. The articles in this newsletter are looking at some of the feed challenges we see ahead, and what to consider when winter feed is available with high protein low fibre feed on offer.

What is very evident amongst our clients is that condition scores and supplementary feeding programs through summer are now paying off. Autumn lambing ewes with pre-lambing conditions score 3-4 are holding milk, spring lambing ewes are well-positioned to manage into the final trimester where cost-efficient energy-dense diets can be implemented.

Autumn calving cows are also holding condition where BCS’s have been well managed through summer with joining programs either underway, and in some cases completed, which has required some supplementary feeding and close attention to mineral supplementation.

It is easy to get distracted and overwhelmed with the challenges ahead, plans may change but make sure the goals don’t. Now is the time to stay focused, if you require a second opinion or some assistance to evaluate where things are, our TRAC Productivity Team is only too happy to talk through your program with you, so don’t hesitate to call.

GETTING THE BEST OUT OF FAST GROWING PASTURES & CROPS

With the sun out and many areas having an early Autumn break plant growth rates are the highest they have been for years. Plants are growing a lot of lush green vegetation for the animals to eat off. The question is, Will this lush grass/ crop be a balanced ration for my animals?

We know that sheep are ruminant animals with 4 stomachs designed to digest pretty crappy dry feed into nutrients the animal can live off. What happens to this digestive system when we have a fast-growing, low dry matter, high protein very degradable, forage? Let’s have a look at a few attributes of this forage and how it will affect the performance of your animals.

Digestibility

This is a term that reflects the forage's ability to be digested by the ruminant animal. The higher the digestibility the quicker it breaks down in the rumen. Normally we would say that the quicker foodstuffs break down the better it would be for the animals, but in some cases, the food breaks down so fast, the food has left the animal as manure before the rumen bugs have had a chance to extract all the nutrition out of it.

Fast-Growing

When the plants are fast-growing the amount of structural fibre they have is low. E.g. a piece of fresh green grass leaf has very little fibre in it when compared to a bit of cereal straw after harvest. As plant matter matures the amount of neutral detergent fibre, NDF increases, and with that, the amount of time the animals have to spend breaking down the fibre before they can digest it. This can also be said about the fibre that the animals can’t digest, the more mature a plant gets the higher the indigestible proportion is.

Low Dry Matter

During the wetter winter months the plants suck up more moisture and a larger percent of the plant is water. Animal requirements are expressed as dry matter, meaning when the plants have high amounts of water in them then the animals must eat more fresh weight grass to receive enough nutrients. In some cases, the amount of water they ingest will have a negative effect on the amount they can physically eat due to the water taking up room in the rumen.

High Protein

Plants access their protein from the soil in the form of nitrates. In the winter, the plant's ability to extract more nitrogen from the ground is increased due to moisture in the soil increasing the microbial activity for the nitrogen cycle. Applying nitrogen based fertiliser e.g. Urea, Sulphate of Ammonia, or blends result in the plant sucking up more nitrogen, that is converted into protein by the plant.

These levels can quite quickly get to the excessive point with a reading higher than 30% crude protein (CP) when the animal's requirements are under 18% CP. This then poses an issue to the animal as this excessive amount of protein can be toxic. To help cleanse itself the animals use a large amount of energy transforming the excessive protein (ammonia) into urea which can then be excreted in the urine. This process uses up energy that could have been used for weight gain and or production of milk or wool.

Ok, so now we have an understanding of the attributes of pasture and crop specy's current growth stage, how can we utilise it better.

We can slow the rate of passage through the rumen down by adding some slow fermenting feeds like hay and straw. These feeds will provide the animal with structural fibre that will float in the rumen and form a raft that will trap fast fermenting foodstuffs in the rumen longer, allowing the bugs more time to access the energy and protein. In the deep dark coldness of winter, feeding small amounts of fibre can also help the animal feel warmer. You see when a ruminant animal digests fibre it takes a lot of bug activity to break the fibre down into simple sugars the bugs can use. All these bugs create heat when they are digesting the fibre, so a little fibre can help the animal create more warmth for itself.
Feeding free choice stock salt will help the animals with osmotic balance. This means all the extra water that the animals are ingesting can easily move out of the body to create balance. Salt and particularly sodium help the animal at cellular levels to transport energy, amino acids and minerals such as calcium, phosphate and potassium. It can also help more efficient utilisation of protein and energy. Animals have no ability to store sodium, so it needs to be consumed by the animal daily.
We can’t change the grass and the protein load that our animals have to eat, but we can help the animals balance the energy and protein. By feeding a concentrated source of energy e.g. cereal grains, we replenish the animal’s energy reserves that are being used to excrete the excessive protein in many pastures and crops.

Whilst these are a few pointers on helping your sheep get the best out of fast-growing pasture this season. A more targeted approach may be needed on a farm-by-farm basis. Talk to one of our consulting nutritionists to get a specialised program for your animals.

GRASS TETANY

Autumn is coming to a gentle close as we prepare for winter, hopefully bringing more rain and with that, more feed. Hand-feeding is usually still on the task list for a little while to come, until the feed-gap closes, and pastures and cereals have enough dry matter cover to be a substantial feed for grazing cattle and sheep. New growth of any type typically has low NDF, high water content, and high protein which leads to rapid digestion. Manure pats get loose, and bums begin to dirty. New growth, especially fertilised, generally has high potassium as well. To help slow passage rate, absorb more nutrients, and reduce wasted energy, waiting until a good gumboot height is available of feed or supplying some roughage that will also help in the reduced chance of grass tetany.

Grass tetany occurs when an animal’s magnesium intake/absorption drops below the animal’s critical needs, otherwise known as hypomagnesemia. As the majority of magnesium is stored in the animal’s skeleton it is hard for them to quickly access, especially in older animals. Ruminant animals absorb magnesium through the rumen wall, and this can be affected by rate of passage in the rumen and levels of potassium in the diet.

Signs of cows that are affected by low magnesium can be that they are aggressive in nature and show signs of muscle tremors and in some cases, it can lead to death. The condition progresses quickly and therefore many animals are just found dead.

Older animals (over five years) are at the greatest risk, as are animals that are on fast-growing pasture or crop that have had high levels of nitrogen or potassium fertilisers applied.

Perennial ryegrass toxicity PRGT can sometimes be mistaken for grass tetany as animals in both cases have muscle tremors and difficulty standing. They are both vastly different issues with PRGT coming from toxins in the ryegrass that act as the plants defence system, whereas grass tetany as previously described occurs from low blood magnesium.

Best practice based on current knowledge is to provide the animals with a high magnesium supplement, some people try to dust pasture or hay with magnesium, but this is labour restrictive. Using a high-quality loose lick mineral, with a high magnesium content will allow animals daily access to meet their nutritional requirements. Feeding high-risk cattle hay will slow the rate of rumen passage down allowing the animal to absorb more magnesium out of the feedstuff.

To help manage this year’s Grass tetany season:

Graze grass at 2.5 plus leaf stage as the plant will have more fibre and less potassium;
Minimise sudden changes in diet - if your cows are in confinement make the change to pasture over 10 - 14 days to allow the animals digestive system time to adapt;
Reduce stress events like yarding or long-distance movements; and
Provide your animals with a high-quality loose lick with added magnesium like the ones from the TPM range.