Effect of three different preservative systems on the stability of extruded dog food subjected to ambient and high temperature storage.

Three different preservative treatments were applied to extruded dog food. After processing the dog foods were placed in bags and stored for 16 wk at 48.8 degrees C for 12 mo at 22.2 degrees C. The preservative treatments were as follows: 1) ethoxyquin and butylated hydroxyanisole (EX/BHA), 2) mixed tocopherols (TC/TC) and 3) ascorbyl palmitate and mixed tocopherols (ATL/TC). There were no significant differences among treatments for thiobarbituric acid values for either the high or ambient temperature tests, whereas peroxide value (PV) showed significant treatment and storage effects. For products stored at 22.2 degrees C, PV increased linearly from week 4 to week 16 in both the TC/TC and ATL/TC preservative treatments and was significantly higher than the PV for EX/BHA. In the ambient temperature test, the PV was also higher for the TC/TC and the ATL/TC treatments compared to the EX/BHA treatment after 5 and 12 mo of storage. Results of the sensory evaluations were closely associated with PV. In both the high and ambient temperature tests the dogs consumed more of the foods with the lowest PV when given a two-bowl choice. Using PV and sensory tests as criteria, we concluded that the ATL/TC and TC/TC preserved dog foods deteriorated during storage compared to the EX/BHA preserved food in both the high and ambient temperature tests.

Evaluation of nutrient utilization in the canine using the ileal cannulation technique.

Nine mature mongrel dogs were used to evaluate a surgical technique for the cannulation of the terminal ileum and used in two experiments to determine the effect of carbohydrate source on starch and dry matter digestion. Dogs (16.2 +/- 2.0 kg body weight; means +/- SD) were fitted with an ileal T-cannula constructed of polyvinyl chloride pipe. The cannula was inserted into the terminal ileum approximately 10 cm proximal to the ileocecal junction and the cannula was exteriorized through a small incision on the right flank. Dogs recovered quickly from surgery (5d). A preliminary study using Cr:EDTA in the food indicated that sampling for 12 h postprandially allowed near complete representation of digesta flow for a meal; peak flow occurred 4-to 8-h postfeeding. Two experiments were performed evaluating the effect of carbohydrate source on ileal starch and dry matter digestibility. Dogs were fed two meals daily with Cr2O3 used as a digesta marker. Diets contained 67% extruded grain (corn, rice, oats or barley) and 33% canned meat supplement on a dry matter basis. Starch digestion was complete (> 98%) within the small intestine and was unaffected by carbohydrate source. In experiment 1, prececal and total tract dry matter digestibilities were higher for rice than corn, and in experiment 2, barley was higher than oats. The ileal T-cannula allows for measurement of small intestinal nutrient disappearance without the confounding effects of colonic microflora. This method may be useful when applied to the study of other nutrients in dogs.

Gas-liquid chromatography for evaluating polysaccharide degradation by Ruminococcus flavefaciens C94 and Bacteroides succinogenes S85.

Two predominant rumen cellulolytic bacteria, Ruminococcus flavefaciens C94 and Bacteroides succinogenes S85, were incubated with ground filter paper (Whatman no. 1), cattle manure fiber, wheat straw, Kentucky bluegrass, alfalfa, and corn silage as substrates. Analyses of the initial substrate and the recovered residue after 48 h of static incubation showed that R. flavefaciens C94 was quantitatively more effective than B. succinogenes S85 in degrading total dry matter (32.3% versus 16.1%). However, B. succinogenes S85 demonstrated a qualitative advantage in degrading the hemicellulose and hemicellulosic sugars of particular substrates. R. flavefaciens degraded a mean 29.7% of the cellulose and 35.6% of the hemicellulose in the various substrates, whereas B. succinogenes degraded a mean 17.9 and 31.6% of these fractions, respectively. Gas-liquid chromatography was an important aid in characterizing the polysaccharide-degrading capabilities of these rumen species.