| A deficiency of manganese in the diet of young growing chickens is one of the causes of perosis and of thin-shelled eggs and poor hatchability (see also
calcium and phosphorus imbalances,
Calcium and Phosphorus Imbalances, and vitamin d deficiency,
Vitamin D3 Deficiency). It may also cause chondrodystrophy. |
|
Perosis, which occurs in young chicks, is characterized by enlargement and malformation of the tibiometatarsal joint, twisting and bending of the distal end of the tibia and the proximal end of the tarsometatarsus, thickening and shortening of the leg bones, and slippage of the gastrocnemius or Achilles tendon from its condyles. Higher intakes of calcium or phosphorus will aggravate the condition due to reduced absorption of
magnesium by precipitated calcium phosphate in the intestinal tract. In laying hens, reduced egg production, markedly reduced hatchability, and eggshell thinning are often noted. |
| A manganese-deficient breeder diet can result in chondrodystrophy in chick embryos. This condition is characterized by shortened and thickened legs, shortened wings, a “parrot beak” brought about by a disproportionate shortening of the lower mandible, globular contour of the head due to anterior bulging of the skull, edema usually occurring just above the atlas joint of the neck and extending posteriorly, protruding abdomen (apparently due to a relatively large amount of
unassimilated yolk), and retarded growth of down and feathers. In the young chick, nervous signs may also be noted, which are characterized by a “star-gazing” posture similar to that observed in cases of thiamine deficiency. This posture is a result of defective or absent otoliths in the inner ear. |
| Prevention of perosis requires a diet adequate in all necessary nutrients, especially manganese, choline, niacin, biotin, and folic acid. Deformities cannot be corrected by feeding more manganese. Effects of manganese deficiency on egg production are fully corrected by a diet that contains manganese at 30-40 mg/kg, provided that the diet does not contain excess calcium and phosphorus. Calcium intake may be excessive if calcium supplements are provided free-choice. When meat meal is
used as the principal source of protein, the feed may contain excess phosphorus. |
