| | Finishing lambs for slaughter is typically done with grain. However, the roughage component can vary. Pasture finishing can be successful depending on the grass species used, but likely requires a period of grain feeding for the lambs to reach optimum market condition. Generally speaking, lighter lambs below 30 kg will not fatten off grass alone, as by the end of October, grass supplies will be dwindling. These light lambs should be finished in the lot or on forage crops. Alfalfa or grass mixed hay is popular to finish lambs, but annual cereal silage can be an excellent alternative.
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Silage is capable of maintaining live weight gains of 0.1 kg/day. Lambs given silage as their sole food generally either lose weight or have only limited gains (Fitzgerald, 1986). The target live weight gain for feeder lambs is 0.4 kg/day, therefore supplementary concentrates must be fed to reach the target. It is important to introduce grain gradually to lambs on grass, increasing up to 0.45 kg/day over a 3-4 week period prior to moving lambs into the finishing lot.
Higher lamb performance will be achieved on high dry matter chopped silage, that is, over 30% DM. Finishing lambs will consume up to 2.5 to 3 kg silage/day. In a study feeding Finnish Landrace ewes either hay or silage made from timothy and meadow fescue, the growth of the weaned lambs was higher on the grass silage diets compared to diets of the same material in dry hay form (Sormunen-Christian and Jauhiainen, 2001). Lambs in the UK fed red clover silage had a feed conversion efficiency (FCE) of approximately 8.0 kg feed/kg gain whereas, those fed grass silage had FCE of over 10 kg feed/kg gain (Speigers et al. 2005). Performance from the different types of silages will vary, but intake is generally improved over feeding dry hay.
Ration composition
Common early weaned lamb rations consist of 80% concentrate and 20% roughage. Whereas feeder lamb rations, or those lambs coming off pasture to be finished, would consist of approximately 40 to 50% concentrate with the balance in roughages to start, followed by a finishing ration of 80% grain, 20% roughages.
Lambs have been finished on grain and silage in Alberta feedlots. Receiving weights of lambs are generally around 30 kg. The starter ration typically consists of 20% grain and 78% silage and hay, and the balance with minerals, vitamins and supplements. The finisher ration consists of 75% grain and 23% silage. Lambs are on feed for approximately 100 days with a final weight averaging 50 kg. On the finishing rations, feeder lambs averaged 0.3 kg/day ADG. Feed consumption per day averaged 2.5 kg as fed.
In other research, silage intake of Suffolk cross lambs significantly decreased as the level of barley in the ration was increased (Chestnutt, 1992). Lambs were put on the silage rations at 33 kg live weight and slaughtered prior to reaching 43 kg. The lambs had free choice silage with limited levels of barley varying from 0.23 to 0.68 kg.
Carcass characteristics
Carcass weights and rate of gain of lambs on silage-based rations increased with increasing levels of barley (from 0.23 to 0.68 kg). In addition, measurements of carcass fat depth taken on the cut surface between the 6th and 7th ribs and at the loin were averaged to show an increase in fat depth at higher levels of barley (Chestnutt, 1992). In eastern Canada, Romanov x Dorset and Romanov x Suffolk lambs fed only silage had higher percentages of carcass with poorer muscling compared to lambs fed silage supplemented with concentrate (Petit and Castonguay, 1994). The same would hold true for lambs fed only forage based diets like hay or pasture. It is important to supplement with the correct levels of protein and energy.
Feeding behavior
Observations of lambs’ behavior in the feedlot suggest they are more content and remain full on silage rations compared to lambs that are fed on dry hay rations. Lambs did not pile up at the feed bunk at feeding times. They appeared quiet and satisfied when fed twice per day (in the morning and late afternoon). Silage is a bulkier feed with a higher moisture content giving the lambs a fuller feeling throughout the day.
With the inclusion of silage there was no observed significant sorting of the ration by the lambs. Sorting allows lambs to choose certain ingredients from the ration over others. By not being able to sort through the ration, the lambs consistently receive the balanced ration that was designed for their growing needs. This also decreases the incidence of lambs going off feed or having erratic consumption or problems with acidosis.
Listeriosis
In most areas of Alberta, silage is produced to address concerns with long term feed storage, weeds and extended harvest periods. The risk of listeriosis is the biggest concern with poorly ensiled or spoiled silage. Listeriosis is caused by a bacteria, Listeria monocytogenes. Clinical symptoms include: depression, inactivity, weakness, paralysis of the tongue and jaw, blindness and drooling. Animals lack co-ordination, lose their appetite, walk in circles and push their heads against fences and other objects. Death sometimes occurs before any, or all of the other symptoms are apparent. The incubation period is approximately 3 weeks after ingestion of the feed containing listeria bacteria. It is important to remember that when an outbreak occurs, the silage which caused the problem was probably fed 3 weeks previous.
The bacteria will not survive in the silage if the pH is below 5.2. The bacteria will survive in pockets of spoiled silage especially any punctures in the plastic that allow air in. Any old silage left over in the bunk can contaminate good quality silage, perpetuating the problem. Make sure you wait at least 3 weeks for cereal silage to properly ensile before feeding it, and longer for legume or miscellaneous crops.
Bunk management must follow slick bunks to avoid listeriosis contamination. In addition, using the clean face of the silage and feeding twice per day ensures the silage is freshest.
Economics
The economics of silage versus hay rations would vary year to year. Since silage typically costs between $25 and $35/ tonne and has 60% moisture, the equivalent price for average to good quality mixed hay at 15% moisture would be $65/tonne. When hay is priced much above $65/tonne, silage may be a better option if it is well ensiled, available and still priced in the range above.
References
Chestnutt, D.M.B. 1992. Supplementation of silage based diets for finishing lambs. Animal Production. 55:137-145.
Fitzgerald, J.J. 1986. Finishing of store lambs on silage based diets. 3. Effects of formic acid with and without formaldehyde as silage additives and barley supplementation on silage intake and lamb performance. Irish Journal of Agricultural Research v. 25:363-377.
Petit, H.V. and E. Castonguay. 1994. Growth and carcass quality of prolific crossbred lambs fed silage with fish meal or concentrate. Journal of Animal Science. ASAS July v.72 (7):1849-1856.
Sormunen-Christian, R. and L. Jauhiainen. 2001. Comparison of hay and silage for pregnant and lactating Finnish Landrace ewes. Small Ruminant Research, Amsterdam. Elsevier. January v.39 (1): 47-57.
Speijers, M.H.M., M.D. Fraser, V.J. Theobald and W. Haresign. 2005. Effects of ensiled forage legumes on performance of store finishing lambs. Animal Feed Science and Technology v.120 (3-4): 203-216.
Prepared by:
Dr. Susan Markus
Ruminant Nutritionist, A&F
Ag Info Center 310-FARM (3276) |
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