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==What is Zinc?==

==What is Zinc?==

Zinc is an essential mineral and belongs to the group of nutrients called the trace elements. These are essential minerals but are designated as such because they are required in much smaller amounts than major minerals such as calcium and phosphorus. Dietary zinc exists in the divalent form (Zn²⁺) and is involved in many aspects of metabolism, mainly in enzyme-mediated reactions.

Zinc is an '''essential mineral''' and belongs to the group of nutrients called the '''trace elements'''. These are essential minerals but are designated as such because they are required in much smaller amounts than major minerals such as [[Calcium - Nutrition|calcium]] and [[Phosphorus - Nutrition|phosphorus]]. Dietary zinc exists in the divalent form (Zn²⁺) and is involved in '''many aspects of metabolism, mainly in enzyme-mediated reactions'''.

==Why is it Important?==

==Why is it Important?==

==Roles in the Body==

==Roles in the Body==

Zinc plays a crucial role in skin function and wound healing, cell replication, the structure and function of biological membranes as well as the  stabilisation of the nucleic acids. It is absorbed mainly in the small intestine, the highest rates occurring in the jejunum. Various dietary factors affect the absorption of zinc, in particular high intakes of calcium, iron and phytate, all of which reduce its availability<ref>“Zinc” In: Mineral Tolerance of Animals, 2nd Edition. (2005) National Research Council, National Academy of Sciences. The National Academies Press, Washington DC: p 414.</ref>.   

Zinc plays a '''crucial role in skin function and wound healing, cell replication, the structure and function of biological membranes as well as the  stabilisation of the nucleic acids'''. It is absorbed mainly in the [[:Category:Small Intestine - Anatomy & Physiology|small intestine]], the highest rates occurring in the jejunum. '''Various dietary factors affect the absorption of zinc, in particular high intakes of calcium, [[Iron - Nutrition|iron]] and phytate''', all of which reduce its availability<ref>“Zinc” In: Mineral Tolerance of Animals, 2nd Edition. (2005) National Research Council, National Academy of Sciences. The National Academies Press, Washington DC: p 414.</ref>.   

==Consequences of Zinc Deficiency==

==Consequences of Zinc Deficiency==

===Dog:===

===Dog:===

There are two principal sets of information on zinc deficiency in puppies and adult dogs. The first involves reports of experimentally-induced zinc deficiency. These investigations used low levels of zinc and enhanced levels of calcium, which is known to interfere with zinc absorption. Robertson and Burns<ref name="Robertson">Robertson, B, Burns, M (1963). “Zinc metabolism and the zinc-deficiency syndrome in the dog”. Am. J. Vet. Res. 24:997-1002.</ref> observed deficiency signs in puppies fed dietary zinc at 33 mg/kg with a calcium content of 1.1%, both values on a dry matter (DM) basis. No adverse effects were seen in puppies fed 33 mg/kg zinc and 0.3% calcium or 133 mg/kg zinc with 1.1% calcium. These results were corroborated by Sanecki et al.<ref name="Sanecki">Sanecki, R, Corbin, J, Forbes, R (1982). “Tissue changes in dogs fed a zinc-deficient ration”. Am. J. Vet. Res. 43:1642-1646.</ref><ref name="Sanecki 1">Sanecki, R, Corbin, J, Forbes, R (1985). “Extracutaneous histologic changes accompanying zinc deficiency in pups”. Am. J. Vet. Res. 46:2120-2123.</ref> who produced zinc deficiency in weanling pointer puppies fed up to 35 mg/kg zinc and 2.6% calcium, both on a DM basis. Control puppies fed the same dietary calcium level but 120 mg/kg zinc showed no signs of deficiency.   

There are two principal sets of information on zinc deficiency in puppies and adult dogs. The first involves reports of experimentally-induced zinc deficiency. These investigations used low levels of zinc and enhanced levels of calcium, which is known to interfere with zinc absorption. Robertson and Burns<ref name="Robertson">Robertson, B, Burns, M (1963). “Zinc metabolism and the zinc-deficiency syndrome in the dog”. Am. J. Vet. Res. 24:997-1002.</ref> observed deficiency signs in puppies fed dietary zinc at 33 mg/kg with a calcium content of 1.1%, both values on a dry matter (DM) basis. No adverse effects were seen in puppies fed 33 mg/kg zinc and 0.3% calcium or 133 mg/kg zinc with 1.1% calcium. These results were corroborated by Sanecki et al.<ref name="Sanecki">Sanecki, R, Corbin, J, Forbes, R (1982). “Tissue changes in dogs fed a zinc-deficient ration”. Am. J. Vet. Res. 43:1642-1646.</ref><ref name="Sanecki 1">Sanecki, R, Corbin, J, Forbes, R (1985). “Extracutaneous histologic changes accompanying zinc deficiency in pups”. Am. J. Vet. Res. 46:2120-2123.</ref> who produced zinc deficiency in weanling pointer puppies fed up to 35 mg/kg zinc and 2.6% calcium, both on a DM basis. Control puppies fed the same dietary calcium level but 120 mg/kg zinc showed no signs of deficiency.   

The second set of reports comes from naturally-occurring zinc deficiency syndromes. One occurs in northern breed dogs, typically Siberian huskies or Alaskan Malamutes, which is due to a genetic defect that interferes with zinc absorption. In one study huskies represented 76% of dogs with zinc-responsive dermatosis<ref>White, SD, Bourdeau, P, Rosychuk, RAW, Cohen, B, Bonenberger, T, Fieseler, KV, Ihrke, P, Chapman, PL, Schultheiss, P, Zur, G, Cannon, A, Outerbridge, C (2001). “Zinc-responsive dermatosis in dogs: 41 cases and literature review”. Vet. Dermatol. 12:101-109.</ref>. Treatment requires lifelong dietary supplementation with a zinc content of 150 to 200 mg/kg DM. Another syndrome has been reported in which zinc deficiency is due to feeding cereal-based pet foods containing high concentrations of substances, such as phytate, that bind zinc and reduce its availability<ref>Huber, T, Laflamme, D, Medleau, L, Comer, K, Rakich, P (1991). “Comparison of procedures for assessing adequacy of dog foods”. J. Am. Vet. Med. Assoc. 199:731-734.</ref><ref>Sousa, C, Stannard, A, Ihrke, P, Reinke, S, Schmeitzel, L (1988). “Dermatosis associated with feeding generic dog foods: 13 cases (1981 – 1982)”. J. Am. Vet. Med. Assoc. 192:676-680. </ref><ref>Van Den Broek, A, Thoday, K (1986). “Skin disease in dogs associated with zinc deficiency: A report of five cases”. J. Sm. Anim. Pract. 27:313-323.</ref>.   

The second set of reports comes from naturally-occurring zinc deficiency syndromes. One occurs in northern breed dogs, typically Siberian huskies or Alaskan Malamutes, which is due to a genetic defect that interferes with zinc absorption. In one study huskies represented 76% of dogs with zinc-responsive dermatosis<ref>White, SD, Bourdeau, P, Rosychuk, RAW, Cohen, B, Bonenberger, T, Fieseler, KV, Ihrke, P, Chapman, PL, Schultheiss, P, Zur, G, Cannon, A, Outerbridge, C (2001). “Zinc-responsive dermatosis in dogs: 41 cases and literature review”. Vet. Dermatol. 12:101-109.</ref>. Treatment requires lifelong dietary supplementation with a zinc content of 150 to 200 mg/kg DM. Another syndrome has been reported in which zinc deficiency is due to feeding cereal-based pet foods containing high concentrations of substances, such as phytate, that bind zinc and reduce its availability<ref>Huber, T, Laflamme, D, Medleau, L, Comer, K, Rakich, P (1991). “Comparison of procedures for assessing adequacy of dog foods”. J. Am. Vet. Med. Assoc. 199:731-734.</ref><ref>Sousa, C, Stannard, A, Ihrke, P, Reinke, S, Schmeitzel, L (1988). “Dermatosis associated with feeding generic dog foods: 13 cases (1981 – 1982)”. J. Am. Vet. Med. Assoc. 192:676-680. </ref><ref>Van Den Broek, A, Thoday, K (1986). “Skin disease in dogs associated with zinc deficiency: A report of five cases”. J. Sm. Anim. Pract. 27:313-323.</ref>.   

====Recognised Syndromes related to Zinc Deficiency====

====Recognised Syndromes related to Zinc Deficiency====

===Cat:===   

===Cat:===   

There is little information on zinc deficiency in kittens or adult cats; the data come primarily from a study by Kane et al.<ref>Kane, E, Morris, J, Rogers, Q, Ihrke, P Cupps, P (1981). “Zinc deficiency in the cat”. J. Nutr. 111:488-495.</ref>, as detailed below.

There is little information on zinc deficiency in kittens or adult cats; the data comes primarily from a study by Kane et al.<ref>Kane, E, Morris, J, Rogers, Q, Ihrke, P Cupps, P (1981). “Zinc deficiency in the cat”. J. Nutr. 111:488-495.</ref>, as detailed below.

====Recognised Syndromes related to Zinc Deficiency====

====Recognised Syndromes related to Zinc Deficiency====

#'''Biochemical:''' Concentrations of serum and liver zinc decreased in kittens fed dietary zinc levels of 0.7 and 4.8 mg/kg DM but were normal in kittens fed zinc at 52 mg/kg DM.

#'''Biochemical:''' Concentrations of serum and liver zinc decreased in kittens fed dietary zinc levels of 0.7 and 4.8 mg/kg DM but were normal in kittens fed zinc at 52 mg/kg DM.

==Effects of High Zinc Intakes==

==Effects of High Zinc Intakes==

===Dog:===   

===Dog:===   

Zinc is of relatively low toxicity in dogs. In fact some studies have shown beneficial effects of zinc at concentrations higher than the accepted nutritional requirement. Marsh et al.<ref>Marsh, KA, Ruedisueli, FL, Coe, SL, Watson, TDG (2000). “Effects of zinc and linoleic acid supplementation on the skin and coat quality of dogs receiving a complete and balanced diet”. Vet. Dermatol. 11:277-284.</ref> reported that feeding a complete and balanced diet containing higher than normal levels of zinc (400 mg/kg DM) and linoleic acid (6% DM) to black Labrador retrievers for 9 weeks was associated with significant improvements in coat condition. Dogs fed the high zinc level on its own showed a significant decrease in transepidermal water loss.  

'''Zinc is of relatively low toxicity in dogs'''. In fact some studies have shown beneficial effects of zinc at concentrations higher than the accepted nutritional requirement. Marsh et al.<ref>Marsh, KA, Ruedisueli, FL, Coe, SL, Watson, TDG (2000). “Effects of zinc and linoleic acid supplementation on the skin and coat quality of dogs receiving a complete and balanced diet”. Vet. Dermatol. 11:277-284.</ref> reported that feeding a complete and balanced diet containing higher than normal levels of zinc (400 mg/kg DM) and linoleic acid (6% DM) to black Labrador retrievers for 9 weeks was associated with significant improvements in coat condition. Dogs fed the high zinc level on its own showed a significant decrease in transepidermal water loss.  

Therapeutic doses of zinc of about 20 mg/kg bodyweight/day (equivalent to a dietary zinc concentration of approximately 1100 mg/kg DM for a Bedlington terrier weighing 9 kg), have been given to certain dog breeds such as the Bedlington terrier, Labrador retriever, West Highland white terrier and Dobermann pinscher, which have an inherited defect that results in toxic excesses of copper in the liver, causing hepatitis and cirrhosis. Zinc supplementation is continued for 2 to 3 months, followed by halving the dose thereafter to block copper absorption and decrease copper accumulation in the liver<ref>Brewer, G, Dick, R, Schall, W, Yuzbasiyan-Gurkan, V, Mullaney, T, Pace, C, Lindgren, J, Thomas, M, Padgett, G (1992). “Use of zinc acetate to treat copper toxicosis in dogs”. J. Am. Vet. Med. Assoc.  210:564-568.</ref><ref>Hoffmann, G, Jones, PG, Biourge, V, van den Ingh, TSGAM, Mesu, SJ, Bode, P, Rothuizen, J (2009). “Dietary management of hepatic copper accumulation in Labrador retrievers”. J. Vet. Int. Med. 23:957-963.</ref> [WikiVet Link to Copper].

Therapeutic doses of zinc of about 20 mg/kg bodyweight/day (equivalent to a dietary zinc concentration of approximately 1100 mg/kg DM for a Bedlington terrier weighing 9 kg), have been given to certain dog breeds such as the Bedlington terrier, Labrador retriever, West Highland white terrier and Dobermann pinscher, which have an inherited defect that results in toxic excesses of copper in the liver, causing hepatitis and cirrhosis. Zinc supplementation is continued for 2 to 3 months, followed by halving the dose thereafter to block copper absorption and decrease copper accumulation in the liver<ref>Brewer, G, Dick, R, Schall, W, Yuzbasiyan-Gurkan, V, Mullaney, T, Pace, C, Lindgren, J, Thomas, M, Padgett, G (1992). “Use of zinc acetate to treat copper toxicosis in dogs”. J. Am. Vet. Med. Assoc.  210:564-568.</ref><ref>Hoffmann, G, Jones, PG, Biourge, V, van den Ingh, TSGAM, Mesu, SJ, Bode, P, Rothuizen, J (2009). “Dietary management of hepatic copper accumulation in Labrador retrievers”. J. Vet. Int. Med. 23:957-963.</ref> [WikiVet Link to Copper].

===Cat:===   

===Cat:===   

Sterman et al.<ref>Sterman, M, Shouse, M, Fairchild, M, Belsito, O (1986). “Kindled seizure induction alters and is altered by zinc absorption”. Brain Res. 383:382-386.</ref> fed adult cats a dietary zinc content of 600 mg/kg DM for 6 weeks with no apparent adverse effects, although the blood zinc concentration increased compared with control cats fed a zinc level of 100 mg/kg DM. This suggests that, like the dog, cats can tolerate zinc concentrations well above the nutritional requirement.

Sterman et al.<ref>Sterman, M, Shouse, M, Fairchild, M, Belsito, O (1986). “Kindled seizure induction alters and is altered by zinc absorption”. Brain Res. 383:382-386.</ref> fed adult cats a dietary zinc content of 600 mg/kg DM for 6 weeks with no apparent adverse effects, although the blood zinc concentration increased compared with control cats fed a zinc level of 100 mg/kg DM. '''This suggests that, like the dog, cats can tolerate zinc concentrations well above the nutritional requirement'''.

==Dietary Sources==

==Dietary Sources==