Seawater incubation experiments were conducted in June and October 1992 to examine bacterial utilization of labile dissolved organic matter (DOM) in open ocean surface waters of the eastern North Pacific. Natural plankton extract-DOM (PE-DOM) and selected model compounds were added to seawater samples to evaluate bacterial utilization and respiration rates relative to bacterial carbon production rates for the various amendments. PE-DOM always stimulated bactelial production and DOM utilization, and the primary nitrogen source supporting this bacterial production was dissolved organic nitrogen (DON). Utilization of DON during exponential growth was balanced by the production of ammonium for samples amended with PE-DOM. Bacterial growth efficiencies for samples amended with PE-DOM ranged between 3.4 and 8.8", and generally were slightly higher in June than in October Of the model compounds tested, net bacterial biomass production was observed only in samples amended with glucose, glucose plus ammonium (glucose+NH,t), and dissolved free amino acids (DFAA). Bacterial growth efficienc~es for these amendments were 0.8, 1.9, and and 9.3.%, respectively. Bacterial production at in sjtu DOM concentrations was observed in June but not in October Using the bacterial dissolved organic carbon (DOC) utilization rates observed in this study together with other detailed information pertaining to bulk DOC at our study site, we estimate that the turnover time for labile DOC in these surface waters ranges from approximately 2 to 6 d depending on the lability of the standing stock of DOC. On the basis of (a) the exclusive use of DON as a nitrogen source in PE-DOM amendments, (b) the stimulation of ammonium utilization in the glucose+NH,+ amendment, and (c) the higher growth efficiencies observed for samples amended with either PE-DOM or DFAA, we suggest that bacterioplankton biomass production in eastern North Pacific surface waters is primarily energy limited As a result of this energy hlitation, bacterial production appears to be additionally constrained by the quality of the nutrients available for assimilation. Thus, the quality of the DOM substrate, specifically the D0C:DON ratio, can be a major determinant of bacterial production in pelagic marine systems.

It is generally believed that diets containing increased amounts of polyunsaturated fatty acids (PUFA) result in improved canine skin and hair coat (SHC). However, the extent to which dietary fat amount and type play a role remains to be systematically investigated. The objective of this study was to investigate the role of both increased dietary fat amount and type on SHC assessments of dogs. Improvements of SHC conditions were investigated after feeding three diets containing increased total dietary fat (i.e. 13% total fat) for 12 weeks in relation to a lower fat acclimation diet (i.e. 9% total fat). The higher fat diets varied in polyunsaturated and saturated fat types and amounts but total fat was kept constant. Skin and hair coat assessments were performed at selected intervals by a trained group of veterinarians and graduate students. In addition, hair lipids were fractionated by thin layer chromatography after extraction of plucked hair samples. Significant improvements were found in hair coat glossiness and softness in all dogs fed the higher fat diets in relation to the acclimation diet. Improvements as a result of fat type were also seen but only at 12 weeks. A parallel finding was a marked increase in hair cholesteryl ester content determined at the end of the study at which time SHC scores were significantly improved. Skin and hair coat condition improvements may thus be related to increased cholesteryl ester deposited on the hair shaft surface when high fat diets are fed. Whereas this finding is preliminary, hair lipid analysis may be a useful, non-invasive technique with which to help assess dietary effects on canine SHC.

The fatty acid (FA) patterns of plasma/serum triglycerides (TG), phospholipids (PL) and cholesteryl esters (CE) of captive and free-ranging black rhinoceroses (Diceros bicornis) were investigated. Free-ranging animals (n = 28) stemmed from four different regions. Captive animals sampled included specimens from North American (n = 11) and three different European facilities (n = 6). The European animals were tested on 1-4 different diets, resulting in a total of 15 blood samples. Regardless of differences between the free-ranging animals from different regions, differences between captive and free-ranging animals were relatively uniform: captive animals had higher overall proportions of polyunsaturated fatty acid (PUFA), due to levels of linoleic acid (LA, 18:2n6) that were drastically increased as compared to free-ranging animals. In contrast, levels of alpha-linolenic acid (ALA, 18:3n3) were consistently lower on conventional zoo diets. n6/n3 ratios for TG, PL and CE were 1.6, 10 and 8 in samples from free-ranging animals, respectively, as compared to 4.1-16.3, 16-148 and 40-277 in samples from captive animals. There was a distinct correlation between the proportion of grain-based products (commercial concentrates, plain grains and bread) in the diets of the European animals and the measured levels of n6 PUFA. An animal from a facility with a very low proportion of grain products in the diet nevertheless had high LA readings, most probably due to the use of sunflower oil as 2% (dry matter basis) of its diet. One animal that received a high proportion of grass meal pellets due to an oral disease had increased ALA contents after the diet change. These results allow conclusions on the suitability of diets fed in captivity: the black rhinoceros is prone to several uncommon diseases that have been suspected to be linked to oxidative damage, possibly due to the disposition of this species to excessive iron storage. An unnatural dietary loading with PUFAs would exacerbate this problem. Additionally, n6 FAs are known as precursors of pro-inflammatory mediators, and their overrepresentation could therefore exacerbate any inflammatory processes. Therefore, the current practice of using grain-based feeds as major ingredients in captive rhinoceros diets is discouraged. Diet items containing ALA (a precursor of anti-inflammatory mediators) such as, fresh grass, fresh browse, the respective silages should be included at higher levels in diets for captive black rhinoceroses. Grass meal pellets, although a good source of ALA and linked with high levels of ALA in an animal of this study, must be chosen with care for black rhinoceroses due to their particular proneness for high iron contents. SummaryThe fatty acid (FA) patterns of plasma/serum triglycerides (TG), phospholipids (PL) and cholesteryl esters (CE) of captive and free-ranging black rhinoceroses (Diceros bicornis) were investigated. Free-ranging animals (n=28) stemmed from four different regions. Captive animals sampled included specimens from North American...

Obesity in dogs and cats have been increasingly recognized in recent years. Because obesity underlies various diseases, pet owners and veterinarians have an important responsibility to help animals lose weight and maintain their health. Diet therapy, however, is typically based on limited calorie intake and animals may suffer stress from hunger and this is also a concern to animal owners. For this reason, many clients drop out of weight control programmes. In the present study, we focused on dietary diacylglycerol (DAG) as a potentially effective ingredient for canine weight control without caloric restriction. We replaced a portion of the fat in dog food with either DAG or triacylglycerol (TAG), referred to as DAG or TAG diets here, and fed overweight beagle dogs (body condition score of 4 or higher) with either the DAG or TAG diet for a 6-week period. Results indicated that, even though the food composition other than fat type were identical, dogs fed the DAG diet showed a statistically significant reduction in body weight averaging a 2.3% reduction within 6 weeks while the TAG-fed dogs maintained their obese body weights. In addition, the DAG group also showed a reduction in body fat content, serum triglyceride and total cholesterol concentrations. These results suggest the possibility of developing a pet food using DAG to control weight and serum lipid levels without compromising caloric intake.

The objective of the study was to test the hypothesis that food‐allergen‐sensitized dogs would produce higher levels of IgE antibodies to soy after challenge with an intact soy diet, compared with egg‐based (elimination diet), hydrolyzed soy‐ and corn‐based diets. Eight dogs were sensitized with six food allergens by subcutaneous injections. Seven dogs were used as nonsensitized controls. All dogs were fed an elimination diet containing egg and Brewer’s rice (to neither of which any dog had been sensitized) for six weeks. Serum samples were collected, frozen (−20°C), and submitted to Greer Laboratories® for ELISA analysis. The 15 dogs were randomly assigned into three groups and fed a pelleted diet consisting of hydrolyzed soy/corn starch, intact soy/corn starch or intact corn diet using a crossover design. After a three‐week challenge, serum samples were collected. All dogs were placed on the elimination diet during the 6‐week washout periods. ELISA results were expressed as relative values (%R) compared with pooled canine sera. There was a statistically significant difference between sensitized and control dogs for all diets including the elimination diet (SASS®). While there was a modest %R increase when intact soy was fed, no statistically significant differences in serum IgE to soy were found for any of the diets. We were unable to reject the null hypothesis (P < 0.05).  Sponsored by a research grant through Nestle Purina Pet Care Company.

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Racing dogs are often fed raw meat. Raw meat may become oxidized because it contains no preservatives but few studies have examined the effect of feeding oxidized food to dogs. This study was originally designed to determine the effect of different concentrations of dietary fat on greyhound performance. After the experiment had been completed, however, it was discovered that the peroxide values (PV) of both diets were elevated indicating that fat oxidation had been present. This study was considered to have value, therefore, because it compared performance and blood parameters in eight trained Greyhounds fed either a high fat moderately oxidized (HFMO) diet (43%ME fat with PV of 44 mEq/kg) or a medium fat highly oxidized (MFHO) diet (31%ME fat with PV of 211 mEq/kg) for 8 weeks per diet in a randomized cross‐over design. Dogs were raced over 500 m twice weekly. Race times over the last 4 weeks of each diet period and blood parameters before racing during the last week of each diet period were compared. Dogs fed the MFHO food ran 0.04 m/s slower (p = 0.06) and serum alkaline phosphatase concentrations were higher (149 vs. 56 U/L; p < 0.0001) than in dogs fed the HFMO diet. Further evaluation is needed to determine whether lower dietary fat or increased oxidation was responsible for the altered performance but oxidation of the food should be considered as one possible explanation for an increase in serum alkaline phosphatase during a diet trial.