EFFECT OF GRADED LEVELS OF DIETARY OXALIC ACID ON GROWTH PERFORMANCE, PHYSIOLOGICAL RESPONSES AND HISTOLOGICAL ALTERATIONS IN New Zeland White RABBITS

A total of 50 NZW rabbits (25 males + 25 females) of 2 months old were used to study the toxic effect of the mycotoxin oxalic acid (OA) on rabbits.  The animals  were fed on graded levels of OA (0-30% of the diet) for 2 months.  Feed intake and conversion, retained OA in different animal tissues, and blood picture were determined. 
                The  bodyweight  gain  of  the  treated  animals  proportionally decreased according to the dietary levels of OA.  The decrease was significant beginning at 10% OA and more.  The feed intake, generally, decreased by increasing the dietary level of OA.  The decrease was significant,  also, beginning from the level  of  10% OA and more.  The feed conversion tended to be bad proportionally with the OA- level in the diets, particularly (and significantly) at the highest 2 levels of OA.  Increasing its dietary level increased OA intake.  There were significant increases in kidney and liver weights and decreases in the carcass weights by feeding OA.  There were significant increases in transaminases activity and cholesterol, creatinine, uric acid, and OA concentrations; and decreases in blood total protein levels.  OA accumulation in the animal organs took the following-descending order: muscles, liver, and kidney. Male animals contained more OA than females.  The histological examination confirmed that all alterations were happened only in the animals group fed on 30% OA.  Their livers suffered from a mild congestion of the portal vein in the portal tract.  The kidney showed a degeneration of the glomeruli, polymorphonuclear leucocytes infiltration, interstitial nephritis, and oxalate deposition.
                The animals treated with the highest 2 levels (30  and  20%  OA)  reflected  lower appetence for feed from the 3^rd week of the contaminated feeding.  These animals showed also stress symptoms.  These symptoms tended to be severer by elongation of the feeding period, particularly at the highest level of the toxin.  Therefore, the animals of this group fed on 30% OA died at the 6^th week, whereas those fed on 20% OA died at the 7^th week.  The animals fed on 10% OA showed stress syndromes and bodyweight loss at the 8^th week.  The post-mortem (P.M.) test for the animals fed on 20% OA revealed presence of inflammation and congestion along the digestive system; blue spots on the esophagus, stomach and intestine; haemorrhagic patches on the stomach, intestine, liver, lungs and kidneys; pale lungs; enlarged-dark kidneys and liver; and whity crystalline precipitations (gout) in the stomach.  The animals group fed on 30% OA reflected the same previous P.M. picture, but severer, with bleeding of the digestive system.  The other animal groups were normal.
                Results obtained of the present study refer to the toxicity signs of OA and therefore it is a must to avoid feeding small and mono-gastric animals on OA-rich plants.