Page 500 - Small Animal Clinical Nutrition 5th Edition

516 Small Animal Clinical Nutrition

VetBooks.ir (i.e., diabetes and obesity) because of their low-insulinogenic study in healthy obese-prone dogs fed a low-fat, high-fiber, L-
carnitine-supplemented food for six months showed similar
responses (Sunvold and Bouchard, 1998).
Another study evaluated the effects of feeding the same five results (Allen et al, 1998).
carbohydrate sources on glucose and insulin responses in cats. Several studies demonstrated the effectiveness of L-carnitine
Rice had the highest postprandial insulin response and higher supplementation for overweight cats. One 18-week study of
glucose levels early in the postprandial period.This study found obese (>1.2 RBW) pet cats either supplemented with an aque-
that barley, corn and sorghum were the best carbohydrate ous source of L-carnitine or a placebo, were fed a moist, high-
sources for cats with impaired glucose control (Bouchard and protein, low-carbohydrate commercial cat food intended for
Sunvold, 2000).When considering which weight-management weight loss. Weight loss was safely achieved in study and con-
food to use in a canine or feline weight-loss program, it is trol groups; however, the L-carnitine-supplemented cats had
important to evaluate the carbohydrate sources. Based on these significantly more weight loss than the placebo group (Center
data, it is best to avoid foods based primarily on rice when et al, 2000). In a study involving obese colony-housed cats, cats
selecting weight-loss foods. Note that the earlier listing of rice receiving L-carnitine supplements lost significantly more
on a specific product’s ingredient label, the more rice the prod- weight than cats without supplements (both groups were fed a
uct contains. Arbitrarily, rice should not be one of the first three low-fat food) (Ibrahim et al, 2003). Thus, weight-loss foods
or four non-water ingredients on a weight-loss or weight-con- with supplemental L-carnitine have improved weight-loss per-
trol food’s label (Chapter 9). formance in overweight dogs and cats.
The recommended upper limit for DM carbohydrates in L-carnitine supplementation during fasting and experimen-
foods for weight loss in dogs is 40%; for prevention of weight tal induction of hepatic lipidosis may be protective (Armstrong
regain, the upper recommended limit should not exceed 55% et al, 1992; Blanchard et al, 2002).
DM. For cat foods intended for caloric-restriction weight loss, The recommended level of L-carnitine in foods intended for
the DM carbohydrate content should not exceed 35%; for pre- weight loss in dogs is at least 300 ppm (DM). For cat food
vention of weight regain, the recommended upper limit should intended for weight loss, the recommended level is at least 500
not exceed 40% (DM). ppm (DM). The recommended levels for prevention of weight
regain in dogs and cats are the same as for weight loss.
L-Carnitine
L-carnitine is a vitamin-like, amino acid compound present in Antioxidants
all animal cells. Biochemically, it is involved in a variety of func- Obesity increases oxidative stress, which may also contribute to
tions including fat metabolism and energy production (Chapter diseases associated with obesity (Tanner et al, 2006; Sonta et al,
6). In food animals during active growth, among other things, 2004; Urakawa et al, 2003). Studies also show supplemental
L-carnitine improves nitrogen balance, increases protein accre- antioxidants help blunt oxidative stress. For example, serum
tion and reduces fat deposition (Odle et al, 2000). levels of vitamin E and β-carotene were significantly lower in
The food animal industry has long been interested in nutri- obese children than for normal weight cohorts consuming sim-
ents that influence partitioning away from body fat and toward ilar amounts of these nutrients (Strauss, 1999). Obese rats
muscle deposition. L-carnitine supplementation results include receiving dietary vitamin E supplementation had lowered
improved nitrogen balance, increased protein accretion and oxidative stress biomarkers compared to those in similarly sup-
reduced body fat (Gross et al, 1998). In a 12-week study involv- plemented lean rat cohorts (Laight et al, 1999; Blakely et al,
ing obese dogs (>1.3 RBW) fed a dry, low-fat, high-fiber food 2003). Furthermore, as in other species, antioxidant combina-
with or without added L-carnitine, dogs were fed to achieve tions seem to work best because they participate in networks to
weight loss equal to 2.5% of their initial obese weight per week. regenerate and/or spare each other to extend/improve their
Food, energy and protein intakes were similar in both groups. positive effects on oxidative stress in dogs and cats (Jewell et al,
Although dogs in control and study groups lost similar 2000; Milgram et al, 2002; Devlin et al, 2001). Effective inclu-
amounts of weight, the L-carnitine-supplemented dogs main- sion levels have been studied for vitamins E and C and seleni-
tained lean body mass and had a trend towards greater body um for their antioxidant benefits in dog and cat foods.
weight loss (Gross et al, 1998). Although other sources of antioxidants are available (e.g.,
Results were similar in another controlled study of obese carotenoids, thiols and various fruits and vegetables), the fol-
dogs (42 to 43% body fat) in a 19-week weight-loss program. lowing discussion focuses on vitamins E and C and selenium as
Dogs were fed dry, low-fat, high-fiber foods with or without antioxidant key nutritional factors because: 1) they are biologi-
added L-carnitine. In the first seven-week phase of the study, cally important, 2) they act synergistically (e.g., vitamin C
both groups were fed free choice.The L-carnitine-supplement- regenerates vitamin E after reacting with free radicals), 3) they
ed dogs lost more body weight. During the last 12 weeks of the are safe and 4) information about inclusion levels in pet foods
study, the dogs’ food intake was adjusted to provide just less is usually readily available.
than 1% loss of their initial body weight per week. The L-car-
nitine-supplemented dogs tended to have a higher lean body VITAMIN E
mass percentage, lower percent fat mass and lost more weight Vitamin E is the main lipid-soluble antioxidant in plasma,
than the other group (Sunvold et al, 1998, 1999). Another erythrocytes and tissues (NRC, 2006). It functions as a chain-