Be on the front foot to maintain ewe condition score when grazing stubbles – Assess quality, quantity, fungi and moulds
Daniel Schuppan – Nutrien Ag Solutions, Animal Production Specialist - 0477 315 931
Stubble feed value varies from year to year. The real feed value of stubbles still lies within the grain remaining after harvest and not in the dead plant (leaf and stem) material. With a wet start to harvest, and who knows if it will continue, the feed value of the stubble will change.
If rain continues after harvest this will promote germination of the spilt grain and summer weeds. If the grain germinates this will provide good quality feed but will decline as the plant matures and dies off. So the question always gets asked; do or don’t you spray this germination? I would suggest spraying to maintain feed quality if you don’t have enough sheep to keep on top off all the growth. Summer weeds such as milk thistle and prickly lettuce provide good sheep feed, but caltrop and potato weed can cause short and long term liver damage so with the current value of livestock do not graze toxic summer weeds.
While grain or palatable green feed is in stubble livestock will generally maintain or gain weight. If the remaining dry matter is below 50-55% digestible (7-8 ME), then stock will lose weight. The stem and leaf is generally high in fibre which reduces the amount of feed stock can physically eat. If the protein in the dry matter is less than 6-7% the rumen microbes have less “fuel” and are unable to digest the dry feed efficiently. The rain will stimulate microbes to start the breakdown process of the dry matter so the feed value and palatability may actually be below 50% at the start of the summer although how bulky the crop is will still have a big influence on feed quality.
The digestibility of the leaf, which generally makes up 20% of the dry matter in a stubble, is higher than the digestibility of the chaff and stem and generally ranges between 35-50% (4-7 ME) with 4-7% protein. These levels are below the maintenance requirements of a dry ewe which require feed with an energy density of 8ME and 8% protein. If a ewe was losing 100g of live weight per day you would not notice this, but over 2-3 months this is 1 condition score.
To measure the amount of grain in a stubble count the number of grains in a 0.1m2 quadrat ten or more times across a paddock. Approximately 28 wheat grains, 25 barley grains, 8 lupin grains, 5 pea grains and 2 faba bean grains in a 0.1m2 will equal 100kg of grain per hectare on the ground. GRDC Grain and Graze research found that stock would lose weight below 40kg of grain or 40kg green weeds dry matter per ha although I feel in most situations this benchmark should be closer to double those figures.
It is critical to maintain ewes in condition score 3 to 3.5 by supplementing with grain, hay or silage. Cereal stubbles are deficient in calcium so provide a calcium source via a block or loose lick. If a urea-based supplement is used this provides a non-protein nitrogen source which helps promote a healthy population of rumen microbes to increase the amount of dry feed taken in and digested.
Wet conditions can promote nasty fungi (moulds) which can produce toxins which are toxic to sheep. Monitor feed eg grains, hay stubbles and pastures for mould and also livestock for the animal health impacts of mycotoxin. Moulds and toxins can be tested and mycotoxin toxin binders may be used so make sure you discuss with your livestock advisor. After the issues with lupinosis last summer across the state when it wasn’t as wet, I would recommend not to risk grazing lupin stubbles. Once again if you decide to graze the stubbles then test for the Phomopsis fungi first. Note the fungi can also get on the seed so it is also worth testing before feeding.
The key to making the most out of stubbles is involved with grazing management. Firstly, having a good water supply is essential for performance and secondly, regularly rotating stock is important for even grazing. Graze sheep in a stubble paddock for a week as a rule of thumb and you can always come back and graze 2 or 3 times.
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