For the purpose of investigating the mechanism of obesity-induction/re-induction including weight-cycling in beagles, a study was conducted using commercially available dog food combined with human food to mimic at home-snacking and diet-supplementation behaviours. Adult female beagles, which had free access to water and exercise, were used (n = 9). All dogs were initially offered two times their daily calculated number of calories using a dry extruded diet plus blend of canola and soybean oils and allowed to eat ad libitum. After 3 weeks, Pecan shortbread cookies were added to the diet mixture. Obesity was induced during a 19-week period with 1875-2250 kcal/day consumed, on average, during this period. The dogs were then subjected to a weight-loss regimen while consuming 490-730 kcal/day. After weight loss, a similar degree of obesity was re-induced for 17 weeks even though dogs consumed only 1125-1250 kcal/day. Body weight, body condition scores, kcal consumption and food efficiency were recorded. Results indicated that less time and fewer kcal were required to re-induce the same degree of obesity compared with the initial obesity induction. Human snack foods appeared to stimulate appetite and thus contribute to the obese state. Food efficiency was also increased during the obesity-reinduction period compared with the induction period. This information may help pet owners better understand the need to limit table scraps and human-type food snacks in dogs prone to obesity as well as weight maintenance after weight loss.

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.

Polyunsaturated fatty acids (PUFAs) are important for neonatal growth and development in all mammalian species studied to date. Normal fetal development requires the 18carbon essential fatty acids as well as long-chain polyunsaturated fatty acids (LCPUFAs) with 20and 22-carbon–chain lengths (1). Provision of both dietary (n-3) and (n-6) PUFAs in appropriate amounts are needed to optimize development of nervous system tissue and to promote kidney, liver, and skin functions. Two LCPUFAs, arachidonic acid of the (n-6) series and docosahexaenoic acid of the (n-3) series, which are synthesized by chain elongation and desaturation of essential fatty acids, have received increasing interest recently because they are found in high concentrations in the phospholipids of normal cell membranes of the central nervous system (2). It was shown (3) that human infants who consume low LCPUFA levels also have lower LCPUFA levels in the phospholipids of the cerebral cortex. The clinical relevance of this finding is the subject of various growth and neurodevelopment studies. Because the PUFAs are transported via plasma lipoproteins (LPs), the effects of dietary fatty acids on LP metabolism may play an important role in development. In dogs, high-density lipoproteins (HDLs) are the predominant plasma LP fraction (75–85%) (4). This differs from humans, where low-density lipoproteins (LDLs) predominate. For this reason, dogs are considered to be ‘‘HDL mammals’’ (5,6) and also exhibit atherosclerosis-resistance properties (4). However, as in humans, diet can alter canine LP cholesterol distributions. For example, a study by Bauer (7) demonstrated that dogs fed a diet that is high in saturated fat (primarily from beef tallow) show an increase in both LDL and HDL fractions, and all LP fractions tend to shift toward a lower density. Dreon et. al. (8) also reported that feeding saturated fat increases both LDL and HDL concentrations in humans. Replacing saturated fat with unsaturated fat in the diet decreases LDL more than HDL in humans. Polyunsaturated fatty acids are the most potent fatty acids for reducing LDL cholesterol (9). An early study of canine LP metabolism showed that immature dogs had greater hepatic LDL receptor activity than mature dogs. This activity was undetectable by 24 mo of age. Canine liver contains two distinct LP receptors. There is an apoprotein-B,E (apo-B,E) receptor, which binds both LDL and HDL cholesterol, and an apo-E receptor, which binds only HDL cholesterol. The apo-B,E receptor is seen in immature, growing dogs, whereas only the apo-E receptor is found in adult dogs (10). This same study also revealed that feeding cholesterol can suppress apo-B,E receptors in immature dogs, whereas in mature dogs, prolonged fasting can induce expression of apo-B,E receptors. The apo-E hepatic membrane receptors remain constant in both immature and adult dogs or decrease only slightly with age (10). Thus, the possibility exists that immature dogs have greater concentrations of LDL fractions during early life, and dietary fatty acids may further modify plasma LP fractions overall. The present study was conducted to investigate plasma LP distribution changes during suckling and early adolescence of puppies born to bitches that were fed diets that varied only in fatty acid composition and were otherwise identical. 1 Presented as part of the WALTHAM International Science Symposium: Nature, Nurture, and the Case for Nutrition held in Bangkok, Thailand, October 28–31, 2003. This symposium and the publication of the symposium proceedings were sponsored by the WALTHAM Centre for Pet Nutrition, a division of Mars, Inc. Symposium proceedings were published as a supplement to The Journal of Nutrition. Guest editors for this supplement were D’Ann Finley, James G. Morris, and Quinton R. Rogers, University of California, Davis. 2 This work was supported in part by Nestle-Purina PetCare and the Mark L. Morris Professorship in Clinical Nutrition at Texas A&M University. 3 To whom correspondence should be addressed. E-mail: jbauer@cvm. tamu.edu. 4 Abbreviations used: ALA, a-linolenic acid; HDL, high-density lipoprotein; LA, linoleic acid; LCPUFA, long-chain polyunsaturated fatty acids; LDL, low-density lipoprotein; LP, lipoprotein; PUFA, polyunsaturated fatty acids.

This prospective study involved supplementing 18 normal dogs with flax seed (FLX) and sunflower seed (SUN) and evaluating their effects on skin and hair coat condition scores and serum polyunsaturated fatty acids (PUFA) concentrations. Skin and hair coat were evaluated in a double-blinded fashion using a numeric scoring system and serum PUFA concentrations were determined. Our hypothesis was that changes in serum PUFA concentrations are associated with improvements in skin and hair coat and that serum PUFA would provide an objective method for making dietary fatty acid supplement recommendations. Although a numerical improvement was found in hair coat quality in both groups, this improvement was not sustained beyond 28 days. The relative per cent of 18:3n-3 concentrations in serum phospholipids increased in the FLX treated dogs but these concentrations remained unchanged in the SUN treated dogs. Also, elevations in relative per cent of 18:2n-6 concentrations in serum phospholipids were seen in the FLX group. The ratio of serum polyunsaturated to saturated fatty acids also showed a transient increase. These increases preceded the peak skin condition score peak value by approximately 14 days. It was concluded that a 1-month supplementation with either flax seed or sunflower seed in dogs provides temporary improvement in skin and hair coat. These changes appeared to be associated with increased serum 18 carbon PUFA.