Nutrition of the Ewe Flock
Table of Contents
Nutritional Management is the one of the most important management items the shepherd should be concerned about. Ewes that are fed well balanced diets are more fertile, milk better and wean more lambs that grow faster. Not only do well fed ewes wean more pounds of lamb per year, but they are healthier and more resistant to infections and disease than ewes that are under Nutritional Stress. If you are in the sheep business to make money, the Nutrition Management of the ewe flock should be your number one concern.
Feed costs on the average sheep farm in Ontario accounts for approximately 80% of the Direct Farm Expenses. From the l986 Enterprise Analysis Project, the average ewe (from 30 farmers, 5070 ewes), cost $62.48 to feed for a year. This represented 82% of the Direct Farm Expenses and 50% of the Total Farm Expense. Feed costs are the single largest expense on sheep farms in Ontario Therefore, it is imperative that the flock owner evaluates the feed resources he or she has and manage the feed resource to maintain good ewe nutrition and generate a reasonable profit per ewe.
The most damaging disease in sheep flocks in Ontario is "Empty Gut Disease". If "Empty Gut Disease" hits your flock it will reduce profits to zero or lower. The cause of Empty Gut Disease is inadequate intake of nutrients by the ewe. There are five nutrients we supply to the flock they are: water, energy, protein, vitamins and minerals. Most often, the limiting nutrient on most farms is energy. Energy is supplied in the ration through the hay and grain mix. Most cases of Empty Gut Disease occur when inadequate amounts of concentrate (grain mix) is supplied to the flock. Empty Gut Disease results from an inadequate evaluation of feed resources and when body condition scoring is not performed. Empty Gut Disease is the main reason for low profits in the sheep business.
How does the shepherd avoid Empty Gut Disease?
The shepherd must identify the resources available.
Forages: The hay (roughage) is the most variable feed source on the farm. It is very difficult to access its quality without detailed analysis. Hay quality depends on a number of things, species composition (% grass, % legume), time of cutting (June or August) and soil fertility.
Timothy will range in crude protein content (% C.P.) from 17% to 7.8% and in total digestible nutrients (% T.D.N.) from 65% to 50% depending on the time of cutting. Alfalfa will range from 20 to 12% C.P. and 66 to 59% T.D.N. from the late vegetative to the mature stage of growth. The stage of growth has a great effect on % Crude Protein and to a lesser extent on % T.D.N. in the forage sample. The species content will also have some effect.
For example: Hay cut mid-bloom
75% Alfalfa 25% Timothy = % C.P. = 15%
Sample # 2
25% Alfalfa 75% Timothy = % C.P. = 11%
Since a wide variation in forage quality is present, the forage should be analysed. At the minimum, forages should be tested for the following nutrients: crude protein, acid detergent fibre (ADF), calcium, phosphorus, magnesium, potassium and possibly the trace elements (copper, manganese and zinc).
In order to manage sheep easily, and according to their needs, it is critical to know where in their production cycle, any given group of ewes is at any given time, so they can be separated and managed accordingly. Regardless of the production system a producer is in (accelerated or once-a-year), the key to profitability is feeding to production (and knowing what stage of production the ewes you are feeding are in), and minimizing feed costs by avoiding unnecessary extra feeding.
In a ewe's production cycle, we generally consider that there are six (6) important stages of production: maintenance, flushing, breeding, early gestation, late gestation, and early lactation. Management in general, and nutritional management specifically, must change for each of these stages if a producer is to have a successful lamb crop and, more importantly, good returns for lambs sent to market.
In terms of nutrition, requirements are least during maintenance and early gestation; and greatest during late gestation and lactation (especially for ewes carrying multiple fetuses and nursing twins or more). The diagram below gives a good indication as to the changes in nutrient requirements as a ewe goes through the various stages of production.
Figure 1. Approximate daily digestible energy (DE) requirements of 65 to 70 kg breeding ewes at various production stages.
By this, we mean that the animal's only nutritional needs are those to maintain desired body weight. No form of production is occurring (i.e. the animal is not lactating, or pregnant). Requirements for all other stages, therefore, must always be higher than that for maintenance. Duration is dependant on production system; being next to zero days in some accelerated lambing programs, and up to 16 weeks in once a year lambing situations. Because ewes are not only maintaining their weight, no grain feeding is required during this period.
The practice of increasing nutrient intake and condition prior to and during breeding is called flushing. Its purpose is to increase the rate of ovulation and, hence, lambing rate. The response to flushing is affected by the age of the ewe (mature ewes show a greater response than yearlings), its breed, body condition, and the stage of the breeding season. The greatest response is seen early and late in the breeding season; with flushing during the seasonal peak being least effective in increasing lambing percentage. Flushing is especially beneficial for thin ewes that have not recovered from previous lactation stress.
Flushing is generally accomplished by providing ewes with fresh pasture, supplemental harvested forage, or up to one pound of grain per ewe daily, depending on environmental stress (time of year), availability of forage, and body condition of the ewes. Special feeding usually begins around two weeks prior to breeding and continues at least 2 to 4 weeks into the breeding season. This ensures good embryo attachment to the uterus wall, reducing early embryonic death. Flushing should not be continued too long, because an extended period of high feeding is unnecessarily costly, and overconditioning during pregnancy should be avoided, as should be drastic or severe decreases in the level of nutrition. Typical grain feeding would be in the range of ½ to 1 pound of mixed grain per ewe per day.
In early pregnancy, fetal growth is very small, and the total feed requirement of the ewe is not significantly different from that during the mainentance period. Ewes can therefore be fed a similar ration with a slight increase in the amount offered. It is unusual that grain feeding is necessary during this time unless forage is exceptionally poor and ewes are underconditioned.
Next to lactation, this period has the greatest nutrient demands for fetal growth and the development of the potential for high milk production. Over 80 percent of fetal growth occurs in the last six weeks of pregnancy. Inadequate nutrition (especially energy) during this time will have detrimental effects on milk production of the ewe, birth weight of the lambs, and vigour (survivability) of the lambs. Ewes should be fed at least 0.75 lbs of mixed grain per ewe daily if lambing percentage is expected to be average and up to 1.5 or 1.75 lbs of mixed grain per ewe daily to ewes whose lambing percentage is expected to be above 200 percent.
Lactating ewes normally reach their peak in milk production around 3 to 4 weeks after lambing and produce 75 percent of their total milk yield during the first 8 weeks of lactation (Boylan, 1984). A ewe nursing twin lambs produces 20 to 40 percent more milk than a ewe nursing one lamb.
Because lamb growth is of primary importance, and is dependant on the milk production of the ewe, optimizing milk production is critical. Too often, we see flocks where ewes are not being fed high enough levels of feed for the number of lambs they are nursing. In most cases, this usually entails not enough grain being fed during the first 4 to 6 weeks of lactation (inadequate energy, but often not enough protein as well). Milk production in the ewe responds to nutrient intake just as it does in dairy cattle.
With average to good quality hay, ewes nursing singles will need about 1.5 lbs. of mixed grain per day; those nursing twins will require 2 to 3 lbs. per day.
The above information deals with the stages of production assuming once a year lambing, whether on grass or winter lambing. Producers who are on an accelerated program will have to keep ewes in above average body condition for it to be successful. Ewes should not be allowed to lose too much body condition during lactation if they are expected to rebreed, and perform well in terms of number of lambs born, weaned, and weight of lambs weaned.
The step to good flock nutrition that is most often over-looked is Body Condition Scoring. The shepherd must condition score the flock to determine how the ewes are responding to the nutritional package supplied to them. If this step is not completed the entire exercise of forage sampling and ration formulation is useless! The Shepherd must assess how the flock is responding to the feed provided to them. If body condition scoring is not done, good flock nutrition will not be obtained.
Adequate feeder space must be provided to the ewe flock. Sixteen to eighteen inches of feeder space must be provided per ewe if all the ewes are to eat at once. If this space is not supplied the small and more productive ewe will lose body condition and becomes less productive. Adequate feeder space will ensure that all ewes will have equal opportunity to consume their daily ration.
In many cases, water is the cheapest nutrient supplied to the ewe flock. The flock should have available to them a fresh, clean source of water, at all times. This is particularly important for lactating ewes and young lambs. Lactating ewes require a lot of water if they are going to milk well. Dry ewes require less water than lactating ewes and water for dry ewes during the winter can be supplied by snow if necessary. It is recommended that one square foot of water surface be provided for every 40 ewes.
Another important thing that must be determined before the shepherd can effectively manage the feed resources available, is the flock's reproductive status. The shepherd can not effectively supply the flock with the proper nutrition if the ewes are not at a similar stage in the production cycle. For example: it is difficult to meet the requirements of all the ewes in the flock when some ewes are going to lamb in January and other ewes are not going to lamb until April. The nutritional requirements are different depending on the stage of production. To ensure that all ewes are at the same stage of production, ram control is very important. A suggested breeding schedule could be:
Rams with the ewes in Nov. - Dec should be equipped with marking harness to determine which ewes will lamb in January
Third Breeding (if Accelerated Lambing)
This type of schedule will group your flock into lambing groups.
All the steps to improve ewe nutrition must be used together in a co-ordinated manner. One or two of the steps alone will not significantly improve flock nutrition. If some of the steps are omitted, particularly body condition scoring and allowing adequate feeder space, then the shepherd will find him or herself gradually culling the most productive ewes from the flock because of their inability to maintain body condition score. Since highly productive ewes require more feed they lose body condition score faster than the rest of the flock if they do not receive adequate nutrients.
The shepherd's biggest cost in the operation of his or her flock is feed cost. Feed cost represents approximately 80% of the total Direct Farm Expenses. To provide the flock with the proper nutrition, the shepherd must evaluate the feed resources available (feed testing); these feed resources must be compared to the flock's nutritional requirements (ration formulation); the flock must have adequate feeder and watering facilities and the flock must be body condition scored on a regular basis to access its response to the nutrition program. The shepherd must also be able to determine reproductive status of the flock; this is most effectively accomplished by proper ram management.
As a general rule the flock owner should feed hay to satisfy the flock's appetite; feed grain to obtain the desired body condition score and feed cobalt iodized salt and sheep mineral on a free choice basis. The shepherd must co-ordinate the operation necessary to obtain good flock nutrition right from feed testing through to body condition scoring and ram management, if the flock is to be productive and viable.
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