Christoph Wand – Beef Cattle, Sheep and Goat Nutritionist/OMAF
(Previously published on Ontario, Ministry of Agriculture, Food and Rural Affairs: August, 2014)
The purpose of market lamb feeding is to cost-effectively produce a product of marketable quality and quantity. Keeping this objective in mind will help you make good business and animal management decisions.
The rumen, the largest of the four stomach compartments in ruminant animals, is a fermentation organ, not an acidic stomach. This means digestion depends on the microbes that live inside the rumen. Maintaining the health of this environment is therefore critically important when you are finishing lambs.
Sheep and lambs need several nutrients and nutrient classes for optimum growth. They are listed below in order of importance.
- Water – The majority of a lamb’s gain comes from water. Proper hydration also improves growth. As a result, it is crucial to have clean water constantly available. Waterborne minerals may interact with dietary compounds, which may improve or inhibit the uptake of some nutrients.
- Carbohydrates – In a typical ration, energy is usually the limiting factor. This means the volume of rations the lambs will need is determined by how much energy they need. In modern farm rations, carbohydrates are the prime energy source. There are two major categories:
- Non-structural carbohydrates include starches and sugars. In a grain ration, starch is the primary source of energy and is the part of the feed that is likely to be associated with acidosis – an undesirable condition where the rumen becomes acidic.
- Structural carbohydrates include the fiber and cell walls. These are found in forages and the hull of grains. Fiber is less digestible and lower in energy than starch but is usually less expensive. Digestibility is largely determined by how mature the forage is.
- Protein – In livestock nutrition, the terms “protein” and “crude protein” (CP) are typically used interchangeably. CP is an estimate of the amount of protein in a feedstuff. CP assumes that most proteins have a similar nitrogen content. For most feedstuffs, CP = nitrogen content (%) x 6.25. In mature animals with fully functioning rumens, lower-quality protein or non-protein nitrogen (NPN) can be converted to high-quality bacterial protein. However, in young lambs under 27 kg (60 lb.) liveweight, the rumen may not be fully developed. As a result, young animals depend on higher-quality protein in the ration.
- Vitamins, minerals and additives – Good lamb diets include numerous vitamins and minerals. These are usually included in commercial mineral/vitamin packages. To improve meat quality, give lambs 50-75 IU or more of vitamin E per day and the recommended levels of minerals. Coccidiostats are recommended. Note that ionophore coccidiostats can improve feed conversion if delivered in an appropriate range. Consult your flock veterinarian and mineral supplier to ensure your needs are met.
- Fats – Fats are an alternate form of energy. Due to cost, they do not usually play an important role in lamb feeding.
Feed conversion targets (ratio of feed to liveweight gain)
- Grass-fed lambs introduced to a grain diet: 8.5-6.0:1
- Lambs that are grain-fed from post-weaning (approximately 50 days old) to market weight:
- lambs up to 36 kg (80 lb.) liveweight: 4.0-3.0:1
- lambs over 38-55 kg (85-120 lb.) liveweight: 7.0-5.0:1
Days to market (DTM) and average daily gain (ADG) targets
Table 1 outlines the DTM and ADG for different feed systems assuming a market liveweight of 43-48 kg (95-105 lb.). For grass-based systems, it assumes a May/June lambing.
Table 1. Days to market and average daily gain for different feed systems.
|Grass only||50-250 g
|150-250||Low rate of gain often under-finished for some Ontario markets without grain feeding|
|Grass and finishing||50-250 g
|150-250 (plus 3-6 weeks of grain feeding)||Required if grass lamb is under-finished poor utilization of grain compared to the grain-based system described below|
|Grain-based confinement system||325 g
|100-400||Grain-only diet from weaning to market weight 4,0:1 feed conversion risk of over-finishing if corn is the primary grain|
|Grain and hay||250 g
|100-180||6.0:1 feed conversion|
Grain Feeding Strategies for Lambs
As with all ruminant livestock, lambs require transition diets when introduced to a new ration. The transition period allows the microbe population in the rumen to adapt to the new feedstuffs.
Grain-based feeding system
If lambs have been creep-fed and are weaned at approximately 50 days and 18-27 kg (40-60 lb.) liveweight without having consumed appreciable amounts of forage, the following recommendations can apply:
- Continue feeding a creep diet for 2 weeks after weaning, where the creep and “receiving” or “starter” rations are the same: 17% CP, 85% total digestible nutrient (TDN)
- Use a growing/finishing ration for lambs that are over 27 kg (60 lb.): 15%-16% CP, 80%-85% TDN
- Use a separate ration for animals over 40-45 kg (90-100 lb.): 13%-14% CP, 75%-85% TDN
As animals make the transition from one level in the grain feeding program to another, blend the new diet into the previous one at increasing rates for 3-7 days (Table 2).
Table 2. Example of a transition diet
|Day||Old Diet||New Diet|
|1 and 2||75%||25%|
|3 and 4||50%||50%|
|5 and 6||25%||75%|
Grass (forage)-based system
If lambs are coming off an all-grass or forage program and need additional finishing, the transition period required is much longer. In this case, the following recommendations can apply:
- Have a “receiving diet” that is at least 90% forage (less than 0.25 kg [0.5 lb.] grain per head per day). If possible, use the same forage the lambs have been eating, or a similar one.
- Provide the receiving diet for 1 week.
- Assuming the desired finishing diet is 80% or more concentrate, allow at least 3 weeks (or preferably 4 weeks) to switch the lambs from the receiving diet to the new diet. Gradually increase the proportion of concentrate over this time.
Free-choice versus restricted feeding
Regardless of what equipment is used, there are typically two strategies for feeding grain. One is free-choice feeding (also known as ad libitum, ad lib or full feeding). The other is restricted feeding (or limit feeding). Each has benefits and drawbacks, and the producer must decide which strategy is most appropriate based on his or her equipment and management ability.
Free-choice feeding often uses a hopper-type feeder, where a continuous supply of feed ensures the hopper is never empty. This allows for constant storage and frees producers from making or delivering feed on a frequent basis. However, there is a risk that lambs will eat more of one diet component and less of another, and there is no control over intake patterns. This makes lambs on free-choice feeding programs more susceptible to overeating, irregular intake and acidosis. For this system, allow 10 cm (4 in.) of feeder space per lamb, and ensure feeders do not go empty.
This strategy is a powerful animal management tool because it allows producers to dictate when and how much feed animals receive. It allows more control over intake, more equal consumption of various diet components (e.g., grains vs. pellets) and frequent assessment of feed intake and conversions. Its major drawbacks are the increased labor required to deliver feed at least twice per day and the need for additional bunk space to allow all animals to eat at one time. To avoid trampling during feeding, allow 12-25 cm (5-10 in.) of feeder space per lamb, and watch the animals diligently.
Restricting feeding to 90%-95% of the ad lib intake improves feed efficiency. This is known as “slick bunk management,” “23-hour feeding” or “target feeding,” and is a strategy that is gaining popularity in the beef feedlot industry.
Textured Diets versus Pelleted Diets
Once the decision to feed grain is made, a ration type must be chosen. Both textured and pelleted diets have advantages and disadvantages in terms of what feeds can be utilized, equipment requirements, cost and convenience.
- allow the use of commodities, such as whole-shelled corn, soybean meal (SBM), etc.
- allow for the use of molasses in dry rations to:
- stimulate intake
- prevent sorting
- ensures that minerals and medications and other powders bind to larger feed particles
- may be purchased or home-made
- allow the possibility of total mixed rations using silages and commodities
- may cause serious handling issues
Pelleted supplement + grain
In this diet, small grains and corn comprise 70%-90% of the total grain, while pelleted supplements comprise 30%-10% of the total grain diet.
- all vitamins, minerals and additives are properly included
- according to research, intake may be lower on pellets
- sorting of ingredients may occur
- because this diet includes purchased materials, feed costs may be higher
“Processing” means milling or rolling grain. It is also referred to as cracking, grinding and hammer-milling. Pelleted diets use grains that have been processed before pelleting. Generally, processing adds about $10 per ton to the diet cost, due to labor, power use and machinery upkeep.
Sheep are ruminant animals. They can utilize forages, fermenting them in the rumen. Unlike our acidic stomachs, a sheep rumen uses bacterial fermentation and requires a neutral pH (a balance between acidity and alkalinity). Sheep secrete bicarbonate from the salivary glands while chewing. Thus, cud-chewing (rumination) promotes saliva production and rumen health.
In most cases, coarser grains are better because this promotes rumination and extends the amount of starch that is available for digestion over a longer period. This helps prevent acidosis.
In sheep, whole grains are large enough to be ruminated and chewed and do not require processing, except in young lambs (creep feed). Processing grains creates smaller particles that are more palatable to lambs, thus increasing intake. General processing guidelines are:
- For lambs less than 9 kg (20 lb.) liveweight, process all grains.
- For lambs less than 22-27 kg (50-60 lb.), corn should be processed.
- For lambs over 27 kg (60 lb.), all grains can be fed whole, reaping the benefits of whole grain without compromising intake.
Avoid processing unless required. In most cases, this means only processing young lamb rations. A whole grain diet produces better rumen health in lambs compared to processed feeds. Improved rumen health means improved performance. However, in some cases, the handling benefits of all-pelleted diets may outweigh their biological drawbacks.
Lamb Feeding Systems for Finishing
Many producers consider mixing their own finishing rations when their lambs reach a size they feel might justify it. To determine if mixing lamb rations on-farm is economical, consider the following points:
- Calculate the cost of a farm-made diet, based on ingredients alone. Determine the cost of the commercial alternative. If the difference between the two indicates that on-farm mixing may be economical, estimate the tonnage that could be mixed per year.
- Calculate the cost of all necessary mixing/delivery equipment that are above and beyond what is needed for purchased, complete feeds. This could include commodity storage bins, augers, complete diet bins, feed carts and the mill. Possible systems include:
- Total Mixed Ration (TMR) – With TMR systems, silages, hay and grain are fed at the same time. Stationary and mobile mixers are available. TMR mixers use a batch-mixing approach. They require specialized feeding arrangements (drive-through feeders for mobile units, conveyor belts or wagons for stationary units). Daily time requirements include loading, mixing and dispensing.
- Tractor-drawn mix-mills – These are large-batch mixers, which can grind dry hay into concentrate rations. They are run off PTO power and have their own dispensing auger. These allow bins to be filled at one or more locations. Daily time requirements include loading, mixing and dispensing.
- Stationary volumetric mills (for example Farmatic™, Modern Mill™, etc.) – These use feed proportioners and overhead gravity flow bins to deliver feed into the four to six compartments on the top of the mill. These compartments can be “mini-bins” serviced by augers. Stationary volumetric mills control ingredient flow rate and produce a steady flow of one desired ration. However, they require calibration when a new load of the same ingredient is received or the diet is re-formulated, and they can only be used for concentrate. That said, stationary volumetric mills are cost-effective, and pre-owned systems are readily available. A schematic for set-up is given in Figure 1.
- Automated, continuous mini-batch mixers (for example, Precision™) – Although it appears to perform the same function as stationary volumetric mills, this system (Figure 2) offers a huge advantage. Instead of volumes, this system uses ingredient and ration weights in batches of approximately 30 kg, so re-calibration is not required for each lot of ingredient. It can be programmed to build several rations at one time in sequence, without re-calibration. For example, one Precision™ system can feed up to four rations to four different delivery auger systems at all times. It creates complete feed logs in the programmable control center. If there are any problems with intake, ingredient levels or power supply, it sends a pager alert. These are primarily used in hog barns that use the puck-style conveyer to drop feed, so it is easily converted to flex augers. The cost to install this system is about $15,000.
- Blending boxes – Like stationary mills, blending boxes use the volumetric principle. Unlike stationary mills, they have no motorized parts. They are based on flow rates through slides. Blending boxes are less accurate and have no potential for rolling or grinding.
- Decide on an appropriate amortization period for the extra equipment. It should reflect the lifetime of the machinery (typically about 5-10 years).
- Calculate any additional costs of feeding equipment. For example, a TMR feeding system needs enough bunk space, which may be limited if you are using an all-grain system fed in hoppers. Two hopper types are pictured in Figures 3a and 3b.
- Multiply the differential calculated in step 1 by the tonnage over the amortization period to see if it covers the entire cost related to farm mixing. (Note: Remember to factor in additional labor needs.)
In certain situations, specialized feeding programs for market lambs are ideal. These include situations where extra value can be gained by investing in the additional feed and labor. The producer must moderate his or her expectations according to the flock production system. Various aspects of diet preparation must be considered to optimize the delivery of nutrients and to ensure lamb health. Producers are encouraged to implement market feeding programs in consultation with nutrition providers and veterinarians to ensure all aspects and information are taken into account.