R. E. Newman

Dietary n-3 and n-6 fatty acids alter avian metabolism: metabolism and abdominal fat deposition

The effects of dietary saturated fatty acids and polyunsaturated fatty acids (PUFA) of the n-3 and n-6 series on weight gain, body composition and substrate oxidation were investigated in broiler chickens. At 3 weeks of age three groups of chickens (n 30; ten birds per group) were fed the fat-enriched experimental diets for 5 weeks. These diets were isonitrogenous, isoenergetic and contained 208 g protein/kg and 80 g edible tallow, fish oil or sunflower oil/kg; the dietary fatty acid profiles were thus dominated by saturated fatty acids, n-3 PUFA or n-6 PUFA respectively. Resting RQ was measured in five birds from each treatment group during weeks 4 and 5 of the experiment. There were no significant differences between treatments in total feed intake or final body mass. Birds fed the PUFA diets had lower RQ and significantly reduced abdominal fat pad weights (P<0.01) compared with those fed tallow. The dietary lipid profile changes resulted in significantly greater partitioning of energy into lean tissue than into fat tissue (calculated as breast lean tissue weight:abdominal fat mass) in the PUFA groups compared with the saturated fat group (P<0.01; with no difference between the n-3 and n-6 PUFA groups). In addition, the PUFA-rich diets lowered plasma concentrations of serum triacylglycerols and cholesterol. The findings indicate that dietary fatty acid profile influences nutrient partitioning in broiler chickens.

Dietary n-3 and n-6 fatty acids alter avian metabolism: molecular-species composition of breast-muscle phospholipids

The effects of diets high in n-3 polyunsaturated fatty acids (PUFA; provided by fish oil), n-6 PUFA (sunflower oil) or in more-saturated fatty acids (tallow) on the distribution of subclasses of choline phospholipids (PC) and ethanolamine phospholipids (PE) from the breast muscle of broiler chickens were examined. Supplementation with the different fatty acids had no effect on the distribution of phospholipid subclasses. Feeding sunflower oil or tallow gave a molecular-species profile similar in both fatty acid subtype and proportion. In the diacyl PC phospholipids, 16 : 0-18 : 1n-9 and 16 : 0-18 : 2n-6 accounted for approximately 60 % of the total molecular species, whereas for the alkylenyl PC the predominant species were 16 : 0-18 : 1n-9 and 16 : 0-20 : 4n-6. Of the diacyl PE the dominant species was 18 : 0-20 : 4n-6 which accounted for 50 % of the molecular species, and of the alkylenyl PE the dominant species were 16 : 0-18 : 1n-9, 16 : 0-20 : 4n-6 and 18 : 0-20 : 4n-6. Supplementation with fish oil significantly increased levels of both eicosapentaenoic acid (20 : 5n-3) and docosahexaenoic acid (22 : 6n-3) in PC and PE when compared with either sunflower oil or tallow supplementation. The increase in the n-3 PUFA incorporation was associated with a corresponding decrease in the proportion of arachidonic acid (20 : 4n-6) in both PC and PE. Different dietary fats induce different patterns of fatty acid incorporation and substitution in the sn-2 position of the diacyl and alkylenyl PC and PE of avian breast muscle, and this finding is indicative of selective acyl remodelling in these two phospholipids.

Ghrelin secretion is more closely aligned to energy balance than with feeding behaviour in the grower pig

Secretory characteristics of the ghrelin profile for the pig are still unknown. Our objective was to clarify the mechanisms that influence ghrelin secretion during differing feeding patterns. Pigs were initially fed a commercial pelleted diet offered ad libitum and blood samples collected for 24 h at intervals of 1 h. The pigs were then entrained for 17 days to a twice daily interval feeding regimen (0900-1000 and 1600-1700 h) and blood samples were collected for 12 h (0800-2000 h). This was followed by a similar interval feeding and blood sampling regimen with the 0900-1000 h feeding period being replaced by a sham feed where pigs were shown their usual feed but none offered. During the ad libitum feeding regimen, there was no preprandial rise or postprandial fall in circulating plasma total ghrelin concentration, which remained constant throughout the sampling period. In addition, no preprandial rise or postprandial fall in ghrelin concentrations was observed when pigs were fed either twice or once daily; however, plasma ghrelin concentration rose gradually over the 12-h sampling period during the twice daily feeding regimen and increased further when pigs were fed once per day. This increase in ghrelin levels coincided with an increase in plasma GH and non-esterified fatty acid concentrations and was not associated with either plasma glucose or insulin concentrations. These results suggest that circulating total plasma ghrelin concentrations in the pig appear to be influenced by chronic changes in energy balance rather than the feeding pattern per se.

Insulin secretion, body composition and pig performance are altered by feeding pattern

Three studies investigated the effect of feeding strategy on production performance and endocrine status of growing pigs. For Experiment 1, 20 entire male pigs (70.0 ± 4.6 kg) were allocated randomly to individual pens in one of four climate-controlled rooms. Pigs were fed for 23 days either ad libitum or entrained to feed bi-phasically for two 90-min periods. For Experiment 2, 20 entire male pigs (41.2 ± 3.5 kg) were housed as per Experiment 1. Pigs were fed for 49 days either ad libitum or fed bi-phasically for two 60-min periods. For Experiment 3, 100 female pigs (66.1 ± 3.5 kg) were randomly allocated to individual pens within a commercial piggery and fed for 42 days either ad libitum or bi-phasically for two 60-min periods. Ear vein catheters were inserted into 10 pigs from each group and hourly blood samples were collected for 24 h in Experiments 1 and 2 and for 11 h in Experiment 3. Plasma insulin, non-esterified fatty acid and glucose concentrations were determined in Experiments 1 and 2, and glucose and insulin concentrations in Experiment 3. Feed intake and performance were recorded in all experiments and carcass composition was assessed by computed tomography for Experiment 2. There were no differences in final liveweight between the two treatment groups for all experiments. Pigs fed for two 90-min periods (Experiment 1) showed no difference in feed intake when compared with feeding ad libitum. Pigs in Experiment 2 fed for two 60-min intervals consumed 2.49 kg/pig.day compared with those fed ad libitum that consumed 2.68 kg/day (P = 0.057). In Experiment 3, pigs fed twice daily consumed 2.82 kg/pig.day compared with 2.91 kg/pig.day in ad libitum-fed pigs (P = 0.051). Bi-phasic fed pigs in Experiment 2 had improved (P < 0.05) feed conversion efficiency compared with pigs fed ad libitum. For all experiments, there was no difference in plasma glucose concentrations between the two treatments. In all three experiments, the circulating insulin concentrations for pigs fed ad libitum remained at a constant level throughout the sampling period. However, plasma insulin concentrations for the bi-phasic fed pigs significantly increased ~1 h after both feeding periods during all three experiments. Insulin secretion of pigs fed for two 90-min periods differed from that of pigs fed for two 60-min periods. Plasma insulin concentration increased five-fold following feeding for 60 min, compared with that in pigs fed for 90 min, which increased two-fold. Bi-phasic-fed pigs from Experiment 2 had reduced (P < 0.05) total carcass fat and significantly increased muscle when compared with pigs fed ad libitum. The data showed that feeding pigs at two succinct periods aligned insulin secretion to the time of feeding. Pigs fed for 60 min, unlike those fed for 90-min intervals, had reduced feed intake in comparison to those fed ad libitum. This may suggest that the duration of the feeding bout is important for this response and this may in turn influence both energy balance and the way energy is partitioned.

Dietary fatty acids affect the growth, body composition and performance of post-weaning gilt progeny

Gilt progeny are born lighter, have lower weaning weights and require more medication throughout their life time than do sow progeny. Therefore, strategies to improve their post-weaning performance are of importance to pork producers. Dietary fatty acids have been shown to be potent modulators of physiological processes. Studies in other species have reported that dietary fatty acids affect in utero development, cognitive behaviour, immune system function, carcass composition as well as feed efficiency of offspring. However, little information is available that details their use in gilt progeny and when fed throughout their lifetime. In the present study, two experiments were conducted to investigate the effects of feeding three different types of fat to gilts and their progeny on the growth, body composition and performance post-weaning. Diets were enriched with either saturated fatty acids (SFA; tallow), or n-3 (fish-oil extracts) or n-6 (safflower oil) polyunsaturated fatty acids (PUFA) and were fed to gilts through gestation and to their progeny post-weaning. In Experiment 2, half of the female progeny from n-3 and n-6 PUFA litters were fed SFA post-weaning. For both studies, there was no significant difference in weaning bodyweights. However, in Experiment 1, pigs fed n-6 PUFA diets post-weaning were significantly lighter 7 days post-weaning than were pigs fed SFA- and n-3 PUFA-enriched diets. Despite feed intake of n-6 PUFA-fed pigs becoming comparable to that of the other groups during the finisher period, bodyweight for this group remained significantly lower than that of the other groups at the conclusion of the experiment. No effect of dietary fatty acid type on the carcass composition of finisher pigs, as determined by computed tomography, was found. The results of Experiment 2 showed that feeding pigs n-6 PUFA diets post-weaning through to slaughter significantly compromised their growth, being in agreement with those from Experiment 1. Feed consumption for this group was significantly less during the post-weaning and the finisher periods. However, pigs from n-6 PUFA litters that were fed SFA diets post-weaning showed no compromise in growth and performance and were comparable to pigs from the other treatment groups. During the grower and finisher periods, pigs fed n-6 PUFA diets had a significantly higher rate of mortality that was as much as 13 times that of pigs fed SFA diets. Pigs from n-6 PUFA litters that were fed SFA diets post-weaning were not affected in this manner. The results of the current study showed that feeding diets enriched with n-6 PUFA to pigs significantly compromised their growth and performance and that this fatty acid type may also have negative health effects with prolonged consumption. The data suggested that the type of fatty acid used in pig diets may be an important consideration for nutritionists when formulating diets to optimise post-weaning growth and performance.

Dietary n-3 and n-6 Fatty Acids Alter Avian Pituitary Sensitivity

Abstract The effects of dietary saturated and polyunsaturated fatty acids (PUFAs) of the n-3 and n-6 series on avian pituitary sensitivity were investigated by infusing human growth hormone (GH) releasing hormone--fragment 1-29--and chicken luteinising hormone releasing hormone (LHRH) into catheterized broiler chickens. At 3 weeks of age three groups (n=18; six birds per group) were fed for 6 weeks isonitrogenous and isoenergetic experimental diets containing 80 g/kg of edible tallow (saturated fatty acids), fish oil (n-3 PUFAs) or sunflower oil (n-6 PUFAs). Jugular catheterisation was performed under general anaesthesia during week four of the dietary treatments and the birds allowed 7 days post surgery to recover. A bolus of LHRH (20 μg/bird) and a GH releasing hormone (12.5 μg/kg) infusion was given on different days to each chicken and serial blood samples taken over a 1 h period. Plasma luteinising hormone and GH concentrations were measured by radioimmunoassay. Pre-infusion GH concentrations were similar for the tallow, fish and sunflower oil dietary groups (5.2±3.9, 5.2±1.0 and 6.1±3.1 ng/ml, respectively), however, GH concentration in response to the GH releasing hormone infusion was elevated in the sunflower oil group (44.7±5.7 ng/ml) when compared to chicken fed tallow (33.7±9.7 ng/ml) or fish oil (21.3±5.0 ng/ml). There was a significant decrease (P<0.05) in the clearance rate of plasma GH for the birds fed the fish oil compared with those fed sunflower oil with an intermediate value being observed in the tallow fed group. Pre-infusion plasma luteinising hormone concentrations for the birds fed tallow (3.2±0.7 ng/ml) were significantly elevated (P<0.05) when compared to birds fed either the sunflower oil (0.84±0.25 ng/ml) or fish oil (0.93±0.22 ng/ml) diets. There were no significant differences between the dietary groups in either the maximal plasma luteinising concentration or its disappearance rate following the LHRH infusion. The data demonstrate that dietary fatty acids alter avian pituitary sensitivity and this modulation is determined by the nature of the dietary fat rather than the degree of saturation per se. In addition, this study also shows that dietary fats have a differential effect on pituitary cell activity and are specific to certain pituitary cell types.