Background: Previous studies have demonstrated that DHA n-3 FA can reduce obesity by inhibiting adipocyte differentiation. Objective: To investigate the potential of a DHA rich supplement (fish oil; FO) over non DHA (sunflower oil; SF) to reduce weight gain in dogs, when the animals were fed increased dietary energy intakes above maintenance levels (iso-caloric in both groups). The transcriptional, metabolic and phenotypic responses in two dog breeds were assessed. Design: Six beagles and greyhounds were divided equally into two treatment groups (FO and SF). During four weeks, energy intake was increased 20-80% above maintenance level achieved by feeding basal diet (kibble), coconut fat and supplement (FO or SF). Changes to body weight gain (BWG), apparent nutrient digestibility (Dry Matter, Fat, and Gross Energy), red blood cell (RBC) FA levels, White Blood Cell (WBC) inflammatory gene expression levels (HSP90, HSP70 and IL1β) were measured twice: at days 0 and 28. A paired t-test was used to determine significance between time periods, treatments or breeds. Outcomes: BWG in beagles fed FO were significantly higher (P<0.05) than those fed SF. No significant differences in BWG in greyhounds or between breeds were shown. Differences were not seen in apparent nutrient digestibility. HSP90 gene expression was up-regulated in the beagles fed FO (P<0.05), while HSP70 gene down-regulated for both breeds fed SF (P<0.05). A significant breed difference was observed for HSP70 fed SF (P<0.05). RBC EPA levels significantly increased in both breeds fed FO (P<0.05) with no significant difference in DHA levels. Only beagles fed SF showed significant increase in LA, AA (P<0.05). Both breeds fed SF showed significant decrease in GLA (P<0.05). Significant breed differences (P<0.05) were found in RBC FA levels of EPA (FO), LA, GLA and AA (SF). Conclusion: Results from the four weeks trial do not support the potential of DHA n-3 FA to reduce BWG. However, within the same time frame, WBC inflammatory gene expression and RBC FA levels showed differences between treatments and breeds. Therefore breed differences warrant further investigation and future studies should be designed for extended periods with larger datasets.

Unexpected illness and deaths occurred in an experiment to determine the efficacy of four antibiotic feed additives in a necrotic enteritis challenge model. The experimental basal diet was based on a commercial wheatsoy formulation and contained xylanase and phytase at the recommended rates of inclusion. The starter diet in week 1 (days 0-7) was fed as a mash. Adhering to the challenge model, all birds were fed a high protein diet (50 % commercial starter, 50 % fishmeal) in the second week post-hatch (days 7-14). The fishmeal diet was fed as a short cut 5 mm pellet. All diets were mixed at the University of New England, and pelleted using a small scale 'cold' pelleter, with pellet temperatures ranging from 54°C to 81°C. The experimental antibiotics were incorporated into the diets. Challenged and unchallenged negative controls (no antibiotic) were included in the experimental design. Twelve hundred and ninety-six broiler chicks were split into 54 pens of 24 birds (1:1 sex ratio per pen). All birds were fed ad libitum and had free access to water via drinker nipples. On day 9, all birds from challenged treatments were given an oral suspension containing sporulated oocysts of 'Eimeria spp'. whilst unchallenged birds received sterile PBS. As part of the model, challenged treatments were to be inoculated with 'Clostridium perfringens' (scheduled to begin on day 14).

PUFA are important for human and animal health. To our knowledge, previous studies investigating the metabolism of PUFA in dogs have not examined breed differences. The aim of the present study was to evaluate the potential to elongate PUFA in two pure breeds of dogs. Plasma fatty acid composition (%) was measured in dogs during 3 weeks supplementation with flaxseed oil (57 % α-linolenic acid (ALA) and 17 % linolenic acid (LA)) at the rate of 100 ml/kg food following 4 months of feeding an identical standard basal diet. Plasma extracted at fasting state from five beagles and five greyhounds was analysed by GC. Plasma ALA, EPA and LA increased steadily and significantly from days 0 to 22 (P < 0·05); however, no significant breed differences were shown. Plasma DHA levels, on the other hand, showed no significant increase over time, but a significant breed difference was observed, with beagles having higher plasma level from day 0 (P = 0·002). This breed difference requires further investigation. Levels of ALA and EPA were still rising significantly between days 15 and 22, indicating that PUFA levels in plasma had not stabilised in 3 weeks. These findings together suggest that flaxseed oil could be a useful source of PUFA in dogs, especially ALA and EPA, and that breed differences may be important.

Long chain 'n'-3 fatty acids are beneficial to mammals because of their anti-inflammatory role. However, whether flaxseed oil, which is rich in short chain 'n'-3 fatty acids, has such a role, it has not been extensively examined. This study investigated the supplementation of flaxseed oil on the regulation of genes involved in inflammatory responses such as heat shock proteins ('HSP90' and 'HSP70') and interleukin ('IL1β') in the white blood cells of dogs. Five beagles and 5 greyhounds were supplemented with Melrose® flaxseed oil at the rate of 100 mL/kg food for 21 days. The blood was collected at day 0, 15, and 22 following supplementation. The expression of 3 genes was quantified using real-time polymerase chain reaction. Plasma concentrations of fatty acids such as alpha linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, and arachidonic acid were measured, and their correlations with changes in gene expression were determined. Flaxseed oil supplementation downregulated the expression of 'HSP90' and 'IL1β' in greyhounds but showed no significant effect on these genes in beagles. 'HSP70' remained unchanged in both breeds following the supplementation. Correlations of 'HSP90' and 'IL1β' expression levels with the plasma fatty acid concentrations on day 22 showed a significant negative correlation in greyhounds. Dietary flaxseed oil altered the expression of genes involved in inflammation in white blood cells. Because the expression of the genes may vary in different breeds, it will be useful to consider breed responses to dietary manipulation in canine nutrition management.

A nutritional trial aimed at flaxseed oil supplementation was performed to support a genetic project that is analysing the impact of essential fatty acids on gene expression in leucocytes. This preliminary study analyzed plasma fatty acid composition (%) following oil supplementation over time and measured the effect of breed.