The Effects of Dietary Minerals and Electrolytes on the Growth and Physiology of the Young Chick

Abstract

The effects of the mineral elements, calcium and available phosphorus (aP), and the electrolytes, sodium, potassium and chloride in the diet on the growth and physiology of male broiler-type chickens were investigated. The concepts of total dietary cation-anion and electrolyte (Na + K - Cl, meq/kg) balance were compared for their ability to describe observed growth and various parameters to 42 d of age. There were 12 dietary treatments; each was given to four replicates of 32 birds housed in a deep-litter, environmentally controlled shed. Diets were nutritionally adequate and were based on practical ingredients. Total cation-anion balance was varied from 327 to 700 meq/kg and electrolyte balance, from -29 to 553 meq/kg. Results showed that total dietary cation-anion balance did not describe the growth of chickens as well as electrolyte balance. Low (<180 meq/kg) or high (>300 meq/kg) electrolyte balance in a diet led to depressed liveweight at 42 d of age. There was an optimum electrolyte balance from 250 to 300 meq/kg. The extent of liveweight depression from feeding diets with an electrolyte balance greater than 300 meq/kg depended on the type of cation added to the diet (Na or K): the range of the Na:K ratio for optimum growth was 0.5–1.8. Acid-base balance was influenced mainly by a diet with a low electrolyte balance (-29 meq/kg). Plasma ion levels (Ca, inorganic P, Mg, Na, K, Cl) were unaffected by dietary treatment, except that high dietary calcium reduced plasma inorganic P levels. Increasing calcium from 1.30 to 1.74% reduced liveweight at 42 d of age by 5%, but subsequent increases up to 2.30% Ca had relatively minor effects. Liveweight tended to be lower for birds fed a diet containing 1.30% Ca and 0.81% aP compared to 0.45% aP with 1.30% Ca. Total cation-anion balance cannot be used in preference to dietary electrolyte balance to describe growth of broiler chickens. However, even though there was a good relationship between growth and dietary electrolyte balance, there were specific cation effects (Na and K) independent of electrolyte balance.