There has been a great deal of talk regarding the proper diet for feeding ducks. Lots of talk about protein percentages and calcium levels make feeding ducks way too hard. Unless you're formulating your own feeds, most any poultry feed will be fine. Instead, all the "do this..." don't do that..." causes people to be far too concerned about WHICH feed to use. The best feed is a commercially mixed diet formulated for ducks. Next best is a commercially mixed poultry feed. The most effective and efficient diet is in pelleted form rather than mash because the structure of a duck's bill. Most mashes have a tendency to stick in the lamellae which affects the ability of the tongue to move food to the back of the throat (Scott and Dean 1991).

Generally, birds feed to meet their energy requirements. There are instances when birds will foraging on unusually food sources to meet a severe deficiency, usually minerals. When food is ingested, it is partioned in several ways to determine the amount of nutrients actually used by the animal. The total amount of  nutrients, such as energy, in a food item are called gross energy. Once it's eaten, it's termed ingested energy. Ingested energy can be partitioned into metabolizable energy and fecal energy. Metabolizable energy is the amount which actually is absorbed by the bird.  Metabolizable energy is measured by feeding captive birds a known amount of food (gross energy intake) and the fecal production collected and energy content measured using bomb calorimetry. The difference is termed apparent metabolizable energy (AME). It differs from true ME (TME) by including endogenous energy loss in the measure resulting in an underestimation of ME. One can attempt to correct AME to TME by keeping a bird without food for 24 hour and collecting the feces to determine the amount of endogenous loss. The critical assumption with this measure is that gut activity is the same with and without food, an assumption I personally am skeptical is met. The energy which actually enters the the bird's body is further partitioned into maintenance and production energy. Maintenance, as the name would suggest, is to maintain the body. Production energy is used for either reproduction or growth. The first priority is to maintenance, and additional energy can be used for production. Birds fed high energy diets deposit more fat than birds fed low energy diets (Whittow 1976). In chickens, body mass and percent body fat is lower in birds fed 2 hr/day rathyer than birds fed ad lib, but lipogenesis is greater (Whittow 1976). During laying, twenty percent of the production energy is directed to egg production, which occurs as a result of a reduction in fat storage (Whittow 1976).

Should one use a 28% protein feed? No. But the difference between 16 and 20% is meaningless, and probably wrong. Have you ever noticed that the label on the feed bag says "guaranteed not less than..." meaning that an "18% protein diet" may actually be 20%. Without actually testing each bag, the only thing you know is that the feed isn't less than X% protein. What test to use to measure protein content is also a concern, most use the Kjeldahl method which measures the nitrogen content and multiplies that by 6.25 to estimate the protein content rather than a direct measure of protein. Regardless, a concern is the amino acid composition of the protein. There are 4 essential amino acids, methionine, cystine, lysine, and tryptophan. Because the bird cannot synthesize these amino acids they must be provided in the diet. Recommended percentages of dietary protein for these 4 are 2.0, 1.5, 5, and 1.0, respectively (Scott 1978). The amount of protein doesn't equate to quality of the protein because quality is based upon the amount of essential, digestible amino acids (Holsheimer 1978). The first limiting amino acid (except if the diet is high in legumes) is usually lysine.  This is the real nutritional weakness of corn because it's very low in lysine (around 0.2% compared with wheat which is 0.4%). To calculate the amount of protein which can be used, calculate the grams of protein per 100 grams of product, divide by 5 and multiply by 100 to get the percent protein which can be used (Holsheimer 1978).  

Most feeds are formulated on a ME:P level and they tend to be far too similar to worry about, particularly to cause someone to worry about feeding the feed over the weekend until the feed store opens. Most feeds are in the 2,500 –2,750 kcal ME/kg range (Scott 1978). Heck, even feeding a bag of 28% protein diet for a week isn't going to damage a duck. If a feed is listed as 16% protein and compared with one listed as 20%, generally the 16% feed will have a lower ME value to assure the birds ingest more feed to allow adequate protein intake. Often, people mention "cutting the protein content" by adding a whole grain, such as oats, to reduce the protein content. I'd caution against doing this without taking the time to calculate the new ME:P ratio that you've created. Oats are approximately 10% protein, and around 1165 kcal ME/pound (Scott et. al. 1976). If I am mixing 20 pounds of feed consisting of a  22% protein diet with a ME level of 1300 kcal/lb with an equal amount of oats, the resulting diet would have 3.2 lbs of protein and 24,650 kcal, giving a resulting diet of 16% protein and 1232.5 kcal/lb. If a bird is eating 400 kcal/day, then it's ingesting 4.96 oz of feed/day and 1.12 oz of protein. To consume a similar ME of the mixed diet, the bird would ingest 5.12 oz of feed/day and 0.83 oz of protein.

As for calcium, unless a bird is laying 40+ eggs, they don't need supplemental calcium. Will it hurt them, not unless the Ca:P ratio is way off, again not something that will happen with a commercial diet. Optimal Ca:P ratio is 2:1 with the ratio being AVAILABLE P. P from animal sources is considered to be 100% available, while P from plant sources is considered to only be 30% available (Scott et al. 1976). Just because calcium is in the diet, it doesn't mean they absorb it. Gut absorption is regulated by the hormonal state of the bird. A laying bird will absorb more and a non-layer or drake won't absorb very much. Additionally, large excesses of  either Ca or P will result in precipitation of the other in the intestine, resulting in a deficiency (Scott et al. 1976). Ca requirements are thought to be relatively constant (Robbins 1983), yet studies have reported a correlation between Ca requirements and temperature. These results have probably been confounded by changes of intake because intake is correlated with temperature (Robbins 1983).  

Vitamins are divided into 2 categories, the fat-soluble vitamins are vitamins A, D, E, and K. These vitamins are absorbed with lipids in the intestine and stored in the body fat (lipid reserves). Because these vitamins are easily stored in the body, it's easier to develop toxic levels in the body. Excess vitamins A and D are can be toxic to animals (Robbins 1983). Yellow corn is an important source for provitamin A (Robbins 1983). The water soluble vitamins are thiamin, riboflavin, niacin, pyridoxine, pantothenic acid, biotin, folic acid, cyanocobalamin, choline,ascorbic acid, and myo-inositol. The water-soluble vitamins are not stored in the body and any excess excreted (Robbins 1983).  

Most waterfowl propagators are aware of the higher niacin requirement for ducks compared with other poultry. There are a couple of reasons for this, including differing physiology which limits niacin biosynthesis from tryptophan and poor niacin availability in many feedstuffs. Experiments with alfafa meal, distillers dried solubles, and wheat standard middlings increased the niacin content of the diet, but failed to decrease leg weakness in pekins, suggesting it was unavailable to the bird. (Heuser and Scott 1953).  Heuser and Scott had to supplement the diet with pure niacin to eleiment leg weakness. Niacin deficiency is exacerbated by the use of amprollium, suggesting that if chick starter with amprollium is used, niacin supplementation is necessary. Supplementation can either be through addition of Brewer's yeast or pure niacin tables (11 mg/kg diet).  

A concern in feeding any animal is the effects temperature has. Many people suppliment feeds during cold temperatures, yet ignore changing dietary needs during high temperatures. Generally food intake changes by 1.5% for each 1oC change from an ambient temperature of 20 oC (68oF), meaning a bird will eat proportionally more in colder temperatures and proportionally less in higher temperatures (Austic 1985).  These values apply to average daily temperature, large amplitude changes depress consumption and decrease effeciency. This is particularly true at higher temperatures. At high temperatures, the feed needs to have minimal protein levels with optimal amino acid balance because of the specific dynamic effect (heat of digestion) is greater for protein than for fats. The best way to increase energy density of the diet is by using fats. Because most birds bolt during the times with high temps, it's critical that the diet have adequate lysine. Also, with high temperatures, more thiamin is required (probably best if one's NOT feeding amprollium at high temperatures), and increased potassium (Austic 1985). During molt, metabolic requirements increase from 26% (ortolan buntings) to 45% (chickens) further making feeding birds in warm climates difficult (Whittow 1976).  

While there's alot of information presented, it barely scratches the surface of what is known about avian nutrition. It should point out how much effort has went into developing the commercial diets available, and why it's better to feed a commercial diet than trying to mix and match and add vitamin premixes in hopes of mimicing these diets. In the long run, it cheaper for you and healthier for the birds.  

References

Austic, R. E. 1985. Feeding poultry in hot and cold climates. Pp. 123-136 In M. K. Yousef (ed.).

Stress physiology in Livestock, vol. III. CRC Press, Boca Raton, FL.

Heusner, G. F. And M. L. Scott. Studies in duck nutrition 5. Bowed legs in ducks, a nutritional disorder. Poultry Science 32:137-143.

Holsheimer, I. J. P. 1978. A. C. Risser, Jr., L. F. Baptista, S. R. Wylie, and N. B. Gale, (eds.).

Proceedings of the First International Birds in Captivity Symposium. International Foundation for the Conservation of Birds, Seattle, Wash.

Robbins, C. T. 1983. Wildlife feeding and nutrition. Academic Press, New York, NY.

Scott, M. L., M. C. Nesheim, and R. J. Young. 1976. Nutrition of the chicken. M. L. Scott & Associates, Ithaca, NY.

Scott, M. L.1978. Avian nutrition. Pp A. C. Risser, Jr., L. F. Baptista, S. R. Wylie, and N. B.

Gale, (eds.). Proceedings of the First International Birds in Captivity Symposium. International Foundation for the Conservation of Birds, Seattle, Wash.

Scott, M. L. and  W. F. Dean. 1991. Nutrition and management of ducks. M. L. Scott of Ithaca, Ithaca, NY. 177pp.

Whittow, G. C. 1976. Energy metabolism. Pp. 174-184 IN P. D. Sturkie, ed. Avian Physiology, 3rd edition. Springer-Verlag, New York, NY.    

Back To Links