Forage Analysis for a Successful Lambing.

With lambing time approaching for many, we have started to see a couple of cases of twin lamb disease in early lambers which has prompted a more in-depth nutrition review on these farms.

Forage analysis is vital to ensure your stock are receiving adequate energy and protein, as well as trace elements. Knowing your forage energy and protein levels allows you or your vet to calculate how much concentrates, if any, are required in late gestation.

Trace element content of your forage is a good indicator as to whether to supplement ewes, and if home-grown, allows you to build up a picture of the trace element status of each field on the farm.

Collecting Forage Samples

Use a bale corer to collect samples 20-30cm deep from 6-10 large bales, (repair holes in wrapped bales with silage tape to avoid spoilage) or 12-20 small bales from each field. Approximately 200-300g of forage is required but check with your vet. Thoroughly mix the samples in a bag then squeeze the air out, seal and send to your vets or feed laboratory for analysis, ensure the bag is labelled appropriately.

If possible, take a selection of bales to a weighbridge to get an average bale weight to help calculate a more accurate feed plan.

If sampling fresh grass, use scissors to cut a couple of handfuls of grass 2cm above the ground, from 6-10 sites in a field, using a W pattern to choose site locations, avoiding hedgerows, gateways, and troughs.

Feeding the ewe

Sheep nutrition aims to feed the rumen microbes (bugs) the right balance of energy, fibre, and protein. These microbes then produce nutrients for the animal. Rumen microbes need a near neutral pH of 5.5-6.5 to function and survive, a high energy diet lowers the pH, destroying the microbes. A high fibre diet can help neutralise the pH thanks to saliva produced during chewing.

To maintain a steady pH avoid feeding over 500 grams of concentrate per head in one feed, as this will upset the pH, split the feed into two or three times daily to avoid this. 

Energy Requirements

To work out the requirements of the ewe, the dry matter intake (DMI) needs to be calculated. The maximum total DMI of a dry ewe is 1.5% of her bodyweight, this increases to 2-2.5% for late-pregnancy and 3-3.5% during lactation. For example: 70kg ewe will eat 1.6kg in late pregnancy. DMI is affected by many factors, including the type and quality of forage, and stage of production. Allow 15cm of feed space at per ewe for best forage intakes.

Metabolisable energy (ME) is the energy available to an animal from the diet. To work out how much ME in megajoules (MJ)/day, a ewe is getting, multiply DMI for that forage by the ME of your forage. For example: 70kg ewe on average hay 2 weeks pre-lambing will eat 1.5kg of hay at 8.5ME giving 12.75ME. This ewe needs 15.3ME though so falls short. The deficit is ME required minus ME provided from the forage: 15.3ME – 12.75ME = 2.6ME. Check with your concentrate provider what the ME is, it is usually around 12.5ME/kg fresh weight. Therefor we divide the deficit ME by the concentrate ME/kg fresh to see how many kg of concentrate to feed each ewe: 2.6ME/12.5ME = 0.2kg.

A more detailed look at protein and energy requirements can be found in AHDB Feeding the Ewe.

Protein

The protein available to the ewe comes from protein made by the rumen microbes and protein that passes through the rumen unchanged. Calculating protein intakes is complex, consult your vet for tailored protein analysis.

Supplementing forage

Feeding concentrates ensures each ewe gets the extra energy and protein they need. Allow 45cm per ewe of trough space when feeding concentrates. Ask your feed supplier for the energy and protein content of your feed, sometimes buying a higher quality feed works out cheaper per ME. Poor protein intakes in the 4-6 weeks pre-lambing will result in poor colostrum. Consider feeding all ewes some concentrate in the last three weeks of pregnancy, especially if planning to adopt lambs onto your singles.

Topping up energy requirement with energy buckets can be expensive and ineffective. It tends to be that a third of animals use them a lot, a third use them sometimes, and a third never use them. The cost per ME/MJ can also be three times more than that of concentrates.

Checking your diet

Ask your vet to perform metabolic profiles on five ewes per management group at three to four weeks pre-lambing. These blood samples will check ketones (BOHB) to assess energy levels for warning of twin-lamb disease, and urea and albumin to check protein intakes for colostrum quality.

Twin lamb disease

Twin lamb disease can affect thin ewes as they have no bodily reserves and aren’t receiving enough energy in the diet. Fat ewes are also at risk, as they have lower feed intakes due to less space in the abdomen from excess fat. Checking ketone levels is a good indication for at-risk ewes. The clinical signs are weakness, depression, blindness, recumbent.

Successful treatment relies upon catching the disease quickly and providing a good quality energy source as well as non-steroidal anti-inflammatory injection. Supplementing calcium also is useful as hypocalcaemia can show similar signs. Use a good oral drench with propylene glycol, glycerol, and calcium to give your ewe some go!