The present study evaluated the alterations of the oxidative stress markers in adult dogs fed with high levels of PUFA from the mixture of soybean oil enriched with docosahexaenoic acid (DHA) and supplemented with a natural algae-based antioxidant (AOX). Twelve healthy adult (2 years old) Beagle dogs (6 males and 6 females, 11.20 ± 1.92 kg BW), were distributed in 2 completely randomized blocks design and fed with 4 experimental diets coated with 2 lipid sources: saturated (13% bovine tallow) or unsaturated (13% soybean oil enriched with DHA), supplemented or not with 500 mg of AOX for 4 wk, intercalated with a 4-wk adaptation period. Blood samples were collected on days 0, 15, and 30 of each block. Glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), sulfhydryl group (SH), protein carbonylation, thiobarbituric acid reactive substances (TBARS), and total reactive antioxidant potential (TRAP) were evaluated in the serum, while GSH-Px, SOD, glutathione S-transferase (GST), catalase (CAT), SH, and TBARS were measured in erythrocytes. There was no significant difference in most of the oxidative markers evaluated. In contrast, GST activity in erythrocytes was greater in the animals that consumed the diets coated with bovine tallow compared to dogs that consumed diets coated with soybean oil enriched with DHA (P < 0.05). Serum from dogs fed on diets supplemented with AOX presented greater TRAP values (P < 0.05). These data demonstrate that the concentrations of unsaturated fatty acids (UNS) used in the diets for dogs were not sufficient to cause large changes in the oxidative status. It was not possible to evaluate the efficiency of the natural antioxidant in maintaining the oxidative balance of the animals as it appears that the oxidative status of the dogs was not challenged by the unsaturated diets. Our findings also suggest that dogs, as descendants from carrion carnivores, may have some natural protection against oxidation.

-This study was conducted to determine the coefficient of total tract apparent digestibility (CTTAD) of nutrients and gross energy (GE), metabolizable energy (ME), coefficient of metabolizability of gross energy (CM of GE), and fecal characteristics of dogs fed diets with two levels of feather meal, with or without addition of an enzyme blend containing lipase and protease activity. Ten adult Beagle dogs (aged between 1 and 2 years and weighing 10.2±1.4 kg) were arranged in a 5 × 3 incomplete Latin square design with five treatments and three periods. The extruded basal diet was provided in equal amounts to all dogs (220 g/d), and 7.5 and 15% of hydrolyzed feather meal without enzymes (HFM) or HFM processed with addition of the enzyme blend (HFM EB) was added on top of the basal diet just before feeding. The contrast analysis showed that inclusion of 7.5 or 15% feather meal negatively affected CTTAD of crude protein (CP), GE, and ME of the diets with no apparent effect of the enzyme treatment. However, when both feather meal samples were evaluated, the HFM EB resulted in better CTTAD of GE and CM of GE (0.774 vs. 0.666) than HFM without enzymes (0.670 vs. 0.567), respectively. There was no effect of either feather meal on fecal score. Regression analysis showed that the enzymes added to the feathers during the digestion process increased digestible energy by 600 kcal/kg of dry matter in the diet containing HFM EB. High-performance liquid chromatography (HPLC) analysis demonstrated that feather meal had a low molecular weight, with about 95% of the molecules below 10,000 Da. Addition of enzymes during the feather hydrolysis process may improve the energy content of the feather meal when included in diets for adult dogs.

Two experiments were conducted to evaluate the effect of full-fat rice bran (FFRB) inclusion in dry diets with and without enzyme blend (EB) supplementation for adult dogs. The diets contained 0, 20, or 40% of FFRB, replacing the equivalent amount of wheat flour (WF). Experiment 1 evaluated the consumption and preference of diets using a simple choice method with 3 comparisons (0 vs. 20, 0 vs. 40, and 20 vs. 40% FFRB). Experiment 2 investigated the effect of EB supplementation on the apparent digestibility coefficients (ADC) of nutrients and GE, fecal characteristics, urinary pH, Ca and P balance, and ME of the diets. In Exp. 1, the results indicated that FFRB included in diets up to 40% did not affect the preference or consumption of food by dogs (P < 0.05). In Exp. 2, increasing levels of FFRB in the diet linearly reduced the ADC of nutrients, GE, and ME (P < 0.05). The addition of EB had no effect on any of the variables examined. Regression analysis enabled estimation of the ADC in FFRB; and ADC of DM, CP, ether extract, GE; and the apparent coefficient of ME were 60.5, 74.8, 88.4, 70.8, and 66.4%, respectively. The inclusion of 20 or 40% FFRB in the diets did not affect urinary pH but caused an imbalance in the Ca and P metabolism when included at 40% (P < 0.05), which could be one of the limitations for greater inclusion of FFRB. The ME of FFRB was estimated to be 3,443 kcal/kg DM. The FFRB appears to be palatable for adult dogs, and although ADC was reduced by 40% FFRB in the diet, this ingredient has the potential for inclusion at 20% of diets for dogs, depending on the other ingredients used to achieve adequate Ca and P balance. The inclusion greater than 20% tends to increase P in the diet and reverse the relationship between Ca and P.

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