Page 930 - Small Animal Clinical Nutrition 5th Edition

962 Small Animal Clinical Nutrition

VetBooks.ir Box 46-8. Regulatory Claims Related to Feline Urinary Foods in the United States,
Canada and the European Union.

The United States Food and Drug Administration, Center for be less than 25 mg/100 kcal, with energy content based on the
Veterinary Medicine (FDA-CVM) has issued guidelines for pet-food AAFCO-approved calculation method or an actual digestibility study.
companies to establish the following claims: “reduces urinary pH,” Analysis of multiple batches is required. The FDA-CVM does not
“low magnesium” and “improves urinary tract health.” The FDA- allow the claim of “low ash” on cat food labels. Current scientific
CVM suggests that submissions requesting permission to make information does not demonstrate that ash per se is related to the
“reduces urinary pH” or “improves urinary tract health” claims incidence of lower urinary tract disease. Ash content can only be
include supportive utility data demonstrating efficacy (i.e., the abili- included in the guaranteed analysis of the food.
ty of the food to produce appropriately acidic urine compared with The Canadian Veterinary Medical Association (CVMA) Pet Food
a non-acidifying control food) and safety data. Certification Program has established guidelines for nutrient stan-
Foods with label claims such as “helps maintain urinary tract dards for magnesium-restricted/pH-controlling cat foods. These
health” are low in magnesium and produce appropriately acidic foods must meet the following requirements:
urine. The FDA-CVM has promulgated guidelines for protocols to Magnesium levels must be no more than 0.1% and no less than
support urinary tract health claims. The guidelines focus on preven- 0.05%, dry matter basis.
tion of struvite urinary precipitates, but do not address the question Magnesium levels per 100 kilocalories (kcal) of metabolizable
of calcium oxalate precipitate formation. energy (ME) shall be no more than 20 milligrams.
Guidelines suggest safety studies for a minimum of six months. The average resting urinary pH shall be 6.5 or less, and the aver-
These studies should include physical examinations and the follow- age postprandial peak pH shall not exceed 7.0.
ing observations: food consumption, body weight measurements, In July 1995, labeling of veterinary therapeutic foods in Europe
urinalyses (including sediment examinations), serum biochemistry (termed “dietetic pet foods”) became strictly regulated (Chapter 9).
and blood gas analyses and mineral (calcium, phosphorus, magne- European regulations require only certain indications for therapeu-
sium and potassium) balance studies. Foods claiming to promote tic foods, termed “Particular Nutritional Purposes.” Indications per-
urinary tract health and reduce urinary pH must be nutritionally mitted for feline lower urinary tract disease include: 1) dissolution of
complete and balanced, as demonstrated by the Association of struvite uroliths, 2) reduction of struvite urolith recurrence, 3) reduc-
American Feed Control Officials (AAFCO) feeding protocols. It is tion of oxalate urolith formation, 4) reduction of urate urolith forma-
noteworthy that the “improves urinary tract health” claim focuses on tion and 5) reduction of cystine urolith formation. Essential nutrition-
documentation of safety, urine acidification and restricted dietary al characteristics of the corresponding foods and specific label dec-
intake of magnesium and does not in any way address the issue of larations must be met.
calcium oxalate urolith formation.
The guideline for a low-magnesium claim is a magnesium level The Bibliography for Box 46-8 can be found at
guaranteed less than 0.12% dry matter, using the maximum mag- www.markmorris.org.
nesium and maximum water guarantee. The magnesium must also

After dissolution or removal of struvite uroliths, further al, 1993). 1) Were all uroliths removed from the urinary tract at the
nutritional management is indicated to prevent recurrence. (See time of surgery or other procedure? Recurrence of uroliths follow-
Feeding Plan for Prevention of Struvite Urolithiasis and ing surgery is commonly attributed to failure of medical thera-
Urethral Plugs.) If UTI with urease-producing bacteria was the py to prevent urolith formation. However, this hypothesis is
cause of uroliths, controlling infections may prevent urolith based on the premise that all stones were completely removed
recurrence; however, most uroliths in cats are either sterile or from the urinary tract before beginning preventive measures.
cause secondary infections. It is unknown how long struvite Incomplete surgical removal of uroliths probably occurs more
preventive foods should be fed. Struvite disease is more com- frequently than recognized, even when performed by experi-
mon in young- to middle-aged cats; however, as cats age, the enced surgeons (Lulich et al, 1993a; Lulich and Osborne,
risk of calcium oxalate urolithiasis increases.Cats eating struvite 2007). 2) Did nonabsorbable suture materials left exposed in the
preventive foods should be monitored periodically for crystal- lumen of the urinary bladder during surgery provide a nidus for pre-
luria and urinary pH values. If no episodes of struvite uroliths cipitation of crystalline material? In 2005, the Minnesota Urolith
occur for several years, consider recommending a high-quality Center analyzed uroliths from more than 32,000 dogs; non-
wellness food that avoids excessive magnesium and phospho- mineral, foreign material was identified in uroliths from 96
rus, as cats get older. Cats should still be monitored periodical- dogs and 86 of these submissions contained a nidus of suture
ly for occurrence of alkaline urinary pH, struvite crystalluria material (Lulich and Osborne, 2007). Uroliths from an addi-
and urolith recurrence. tional 235 dogs contained a hollow cylindrical track consistent
Struvite uroliths may recur months to years after removal or with formation around suture material. On the basis of these
dissolution, particularly if preventive measures are not imple- findings, approximately 1% of canine uroliths would be best
mented (Osborne et al, 1990). Interpretation of recurrence of prevented by more appropriate selection and placement of
uroliths (of any mineral type) and interval until recurrence sutures. Similar data for cats have not been reported; however,
should be based on answering a number of questions (Lulich et it seems reasonable that inappropriate surgical techniques also