IMPROVED MILBOND-TX® “VANADIUM: KEEP IT OUT OF LAYING HEN DIETS”
FACTORS AFFECTING EGG QUALITY
This issue of Milwhite’s Journal is the first in a series of four dedicated to discussing the influence of vanadium (V) on overall egg quality and egg shell pigmentation. The importance of keeping the concentration of V as low as possible in commercial egg-type laying hen diets often needs to be reviewed because of the negative effects that V has been shown to have on egg quality. If not reviewed from time-to-time and egg quality issues arise within a poultry company, V may not be remembered or even recognized as a possible cause since there are numerous other factors that are known to cause egg quality problems and these are often blamed without considering all possibilities (i.e., V).
Age of the bird, mineral/vitamin nutrition, disease/parasites and length of egg storage and storage temperature will influence egg quality. Two major stressors that are known to negatively affect egg quality are high environmental temperature and mycotoxins in the feed. Elevated temperature will affect both normal shell formation and internal quality characteristics of eggs. Mycotoxins such as the nephrotoxin, Ochratoxin A, and the hepatotoxin, Aflatoxin B1, as well as T-2 toxin, Fumonisin, Zearalenone and Citrinin have all been shown in research studies and in the field to negatively affect egg quality. Decreased quality characteristics that are commonly associated with mycotoxins are thin and abnormally shaped egg shells, decreased albumen height and decreased yolk weight and pigmentation.
Egg quality means different things to different people since consumer acceptability and preference standards have a major influence on purchasing decisions. There are two main attributes of eggs which are associated with their quality and these are their external and internal characteristics. The shell is the external characteristic evaluated for quality and the albumen and yolk are the internal characteristics evaluated for quality. Vanadium is known to cause problems with the normal development of the characteristics associated with these two attributes. It is also important to remember that V has not only been shown to have a negative effect on the quality of egg albumen, but it is now known that V is also detrimental to the development of normal shell pigmentation of eggs from hens laying brown shelled eggs.
High quality feed-grade sources of phosphate are always expected to contain very low concentrations of V. However, when world-wide feed-grade phosphate prices increase, the cheaper inferior sources of feed-grade phosphate often find their way into the feed ingredient market. High-V phosphate sources are known to originate from any part of the world where raw rock-phosphate deposits are mined. Usually, geologic phosphate deposits have a higher V concentration than marine phosphate deposits. Concentrations as high as 6,000 mg V/kg have been reported in some rock phosphate deposits in various parts of the world. It is doubtful that a phosphate source with such a high V concentration would ever be intentionally used as a phosphorus source in any poultry diet and removal of these high V concentrations are essential before such sources could be used in any animal diet. Most marine phosphates contain approximately 120 mg/kg V whereas, geologic deposits could possibly contain from 1,000 to 2,000 ppm V or more. Good quality sources of mono-calcium phosphate, di-calcium phosphate, tri-calcium phosphate, etc. generally contribute less than 2 mg/kg V to the diet of laying hens and diets of other types of poultry.
Normally, laying hen diets contain concentrations of V that would be of no concern to nutritionists and egg producers. There are times however, when the diets of laying hens and other poultry may contain a poor quality source of phosphate that contributes a high concentration of V to the diet. In these cases, problems with albumen quality and egg shell pigmentation can be directly attributed to V. Vanadium is a “transition” element that has four valence states (+5, +4, +3 and +2) and for that reason V has strong oxidation potential and therefore promotes oxidative stress within animal cells.
Vanadium has been shown to act as a catalyst in the oxidation of certain organic compounds such as membrane phospholipids and has also been shown to inhibit the enzymatic actions of pepsin and trypsin during protein digestion in the stomach and lumen of the intestine, respectively. It is because of the high oxidation potential of V that its detrimental mechanism of action in animals is partly through inhibition of cellular enzymes and cell damage from lysis. In fact, it has been speculated that the deterioration of interior egg quality characterized by a low albumen height caused by V is mediated by muscle atrophy leading to an inhibition of motility in the magnum, which is the albumen-secreting portion of the hen’s oviduct.
Miles and Henry (2004) reviewed the effect of V on egg interior quality and reported data from their laboratory documenting the effect of time and storage conditions on interior quality of eggs from hens fed diets containing 0 or 10 mg V/kg. Hens fed V had poorer albumen quality than hens not fed V and storing collected eggs in the layer house at ambient temperature rather than in a cooler (15.5◦ C, 60% relative humidity) decreased albumen quality at a faster rate. However, these researchers reported that V had no effect on the rate of decline in either environment. Implications of this finding are of importance in countries where government regulations do not require eggs to be refrigerated. Even though consumption of V would result in poorer albumen quality the deterioration of albumen quality would not be expected to increase at a faster rate if the eggs laid by hens consuming V were stored at ambient temperature.
The maximum tolerable concentration of V for poultry is listed in many literature references as 10 mg V/kg diet. However, research data have shown that problems with albumen quality will more than likely begin to occur when the concentration of V is 5 mg V/kg diet or higher. If a decision is ever made to use high-V phosphates during a crisis situation then they should cautiously be used in diets for ruminants rather than poultry because V is better tolerated by ruminant animals. Ruminants have a maximum tolerance in the diet of 50 mg V/kg. In the next issue of Milwhite’s Journal the topic of discussion will center on the negative influence that V has been found to have on the pigmentation of brown shelled eggs.
The information presented in this issue of Milwhite’s Journal was compiled by Dr. Orlando Osuna, Director of Health Science at Milwhite, Inc. and Dr. Richard Miles, Professor Emeritus, University of Florida, Gainesville, FL, USA.
Miles, R.D. and P.R. Henry. 2004. Effect of time and storage conditions on interior quality of eggs from hens fed vanadium. J. Appl. Poultry Research. 13: 619-627.