B. J. Leury

Aromatase-deficient (ArKO) mice accumulate excess adipose tissue.

Aromatase is the enzyme which catalyses the conversion of C19 steroids into C18 estrogens. We have generated a mouse model wherein the Cyp19 gene, which encodes aromatase, has been disrupted, and hence, the aromatase knockout (ArKO) mouse cannot synthesise endogenous estrogens. We examined the consequences of estrogen deficiency on accumulation of adipose depots in male and female ArKO mice, observing that these animals progressively accrue significantly more intra-abdominal adipose tissue than their wildtype (WT) litter mates, reflected in increased adipocyte volume and number. This increased adiposity was not due to hyperphagia or reduced resting energy expenditure, but was associated with reduced spontaneous physical activity levels, reduced glucose oxidation, and a decrease in lean body mass. Elevated circulating levels of leptin and cholesterol were present in 1-year-old ArKO mice compared to WT controls, as were elevated insulin levels, although blood glucose was unchanged. Associated with these changes, the livers of ArKO animals were characterised by a striking accumulation of lipid droplets. Our findings demonstrate an important role for estrogen in the maintenance of lipid homeostasis in both males and females.

Conjugated linoleic acid decreases fat accretion in pigs: evaluation by dual-energy X-ray absorptiometry

Thirty female Large White x Landrace pigs (average weight 57.2 (sd 1.9) kg) were allocated to one of six dietary treatments containing 0, 1.25, 2.5, 5.0, 7.5 or 10.0 g 55 % conjugated linoleic acids (CLA) isomers (CLA-55)/kg diet and fed for 8 weeks. Each pig was scanned at 0, 28 and 56 d and again at post slaughter using dual-energy X-ray absorptiometry (DXA) to determine the temporal pattern of body composition responses. Values determined by DXA were adjusted using regression equations generated from validation experiments between chemically and DXA-predicted values. Overall, there was a significant linear reduction in fat content with the increasing levels of CLA in the diet (P=0.007, P=0.011, P=0.008 at week 4, week 8 and for the carcass, respectively). The greatest improvement was recorded at the early stages of CLA supplementation and for the highest dose of CLA (week 4, -19.2 % compared with week 8, -13.7 %). In the first 4 weeks of feeding CLA, pigs receiving 10 g CLA-55/kg diet deposited 93 g less fat/d than pigs fed basal diets (P=0.002) compared with only 6 g less fat than control animals in the final 4 weeks. Lean content and lean deposition rate were maximised at 5 and 2.5 g CLA-55/kg diet for the first 4 weeks (P=0.016) and the final 4 weeks of treatment respectively. DXA estimates of bone mineral content and bone mineral density were not affected by CLA supplementation throughout the experiment. These data demonstrate that dietary CLA decreases body fat in a dose-dependent manner and that the response is greatest over the initial 4 weeks of treatment.

Accuracy of dual energy X-ray absorptiometry (DXA), weight and P2 back fat to predict whole body and carcass composition in pigs within and across experiments

Abstract An Hologic QDR4500 dual energy X-ray absorptiometer (DXA) was used to measure body composition in 151 pigs ranging from 10 to 120 kg live weight. Large White×Landrace pigs of mixed sexes were selected from five different experiments to evaluate DXA accuracy within and across experiments. Values predicted by DXA including total tissue mass, fat tissue mass, lean tissue mass and bone mineral content, for the live animal, carcass and half carcass were evaluated by comparison with chemically-determined values. Relationships between chemically-determined values and measurements of weight and backfat at the P2 site were also evaluated. Chemically-determined values were strongly related with DXA-derived values, more so than with weight and P2 or a combination of both, particularly in the measurement of fat composition. In contrast to estimates derived from weight and P2, DXA-derived estimates remained accurate when between experiment variation was included. Incorporation of subregions into a whole body software analysis influenced DXA’s ability to predict fat tissue mass with the most accurate measurements achieved by placing the entire scan image in the left arm region of the regional analysis grid. These results demonstrate the efficacy of DXA as a nondestructive method for determining body composition in the live animal and carcass, and its greater accuracy than current routinely used methods.

An analysis of the nutritive value of heat processed legume seeds for animal production using the DVE/OEB model : a review

Recently obtained information on structural and compositional effects of processing of legume seeds is reviewed, in relation to legume seed characteristics affecting digestive behavior and nutrient utilization. The emphasis is on (1) manipulation of digestive behavior by heat processing methods, particularly on protein and/or starch components of legume seeds, (2) prediction of changes of potential nutrient supply to ruminants from legume seeds after heat processing, using the newly developed DVE/OEB model, and (3) obtaining information on optimal processing conditions of legume seeds as intestinal protein source in term of protein DVE and OEB values (to achieve target values for potential high net absorbable protein in the small intestine while holding any N loss in the rumen to a low level), using the protein evaluation DVE/OEB model. The information described in this paper may give better insight in the mechanisms involved and the changes occurring upon processing of legume seeds. A focus of the review is on evaluation of the models and new approaches to establishment of a protein evaluation system that more accurately accounts for digestive processes in the ruminant on a quantitative basis.

The effect of handling pre-slaughter and carcass processing rate post-slaughter on pork quality

Forty-eight male crossbred (Large White-Landrace) pigs were used in a 2×2 factorial design to determine the effect of pre-slaughter handling (minimal and negative handling prior to slaughter) and the rate of carcass processing post-slaughter [normal rate (45min) and delayed rate (70min) from time of exsanguination to carcass entering the chiller] on muscle glycolysis and pork quality. Pigs negatively (using an electric goad) handled at the abattoir just prior to slaughter had lower muscle glycogen concentrations in the Longissimus thoracis (LT) and the Biceps femoris (BF) at all times post-slaughter and lower lactic acid at 5, 45 and 70min post-slaughter compared to pigs minimally (no use of electric goads) handled prior to slaughter. Negative handling of pigs just prior to slaughter also resulted in pork which had higher surface exudate and a higher incidence of PSE compared with pigs minimally handled prior to slaughter. A prolonged rate of carcass processing resulted in reduced muscle glycogen in the LT and BF at all times post-slaughter. Delays in carcass processing rate also affected pork quality, as the meat was paler in comparison with pig carcasses that were processed without any delays. The results from this experiment have indicated that the use of electric goads to move pigs at the abattoir, and delays in carcass processing post-slaughter, can have a detrimental influence on ultimate pork quality.

Comparison of different dietary magnesium supplements on pork quality

Forty-eight crossbred (Large White×Landrace) boars were used to compare the effect of dietary magnesium aspartate (MgAsp), magnesium sulphate (MgSO(4)) and magnesium chloride (MgCl(2)) on muscle glycogenolysis and pork quality. The pigs were fed finisher feed supplemented with either MgAsp, MgSO(4) and MgCl(2) for 5 days prior to slaughter. At the abattoir, all pigs received 15 electric shocks from an electric goad 5min prior to slaughter. Pigs fed the diet supplemented with MgSO(4) had the highest plasma Mg concentrations at slaughter in comparison with pigs fed the MgAsp and MgCl(2) supplemented diets. There were no differences in plasma adrenaline and noradrenaline concentrations at slaughter between the different diets. Pigs fed the Mg diets had higher muscle glycogen concentrations in the Longissimus thoracis (LT) muscle at 5min and at 40min (except MgCl(2)) post-slaughter compared to pigs fed the control diet. Also pigs fed the Mg diets had lower muscle lactic acid concentrations in the LT at 5min post-slaughter and lower drip loss at 24hr post-slaughter compared to pigs fed the control diet. These results indicate that cheaper magnesium sources, MgSO(4) and MgCl(2), are as efficacious as MgAsp in reducing drip loss and improving pork quality.

Comparison of the color stability and lipid oxidative stability of fresh and vacuum packaged lamb muscle containing elevated omega-3 and omega-6 fatty acid levels from dietary manipulation

A series of three experiments were conducted with second cross ([Merino×Border Leicester]×Poll Dorset) wether lambs to evaluate the effects of dietary treatments on manipulation of muscle long-chain (LC) omega-3 fatty acids (FA) on the color stability and oxidative stability of fresh and vacuum packaged lamb. At the end of 7-, 6- and 6-week experimental periods for experiments (Exp.) 1-3 respectively, lambs were slaughtered at a commercial abattoir. At 24 h post-mortem, muscle longissimus lumborum (LL) and longissimus thoracis (LT) were removed and evaluated for color and lipid oxidative stability under specified commercial storage and display condition. Of the dietary supplements used, fish meal and fish oil moderately (P<0.01) and markedly (P<0.001) increased muscle omega-3 FA content, while both protected canola seed (P<0.001) and protected sunflower meal protein significantly (P<0.02) increased muscle omega-6 FA content or ratio of omega-6/omega-3 of the longissimus muscle. In all experiments, the substantial increase (P<0.001) in muscle LC omega-3 and omega-6 FA had no consistent significant effect on color values (redness (a*), yellowness (b*) and lightness (L*)) for fresh and vacuum packaged lamb over a 6-day display period. Lipid oxidation, determined by the levels of thiobarbituric acid reactive substances (TBARS) indicated the enrichment of muscle polyunsaturated fatty acid (PUFA) levels in lambs did not produce significant differences resulting either from main treatment effects or for treatment×day×type interactions (where type was fresh and vacuum packaged). Present results demonstrated the color and lipid oxidative stability of lamb longissimus muscle during refrigerated display was not affected by enhanced levels of omega-3 and omega-6 FA due to dietary treatments.

Effects of undernutrition and exercise during late pregnancy on uterine, fetal and uteroplacental metabolism in the ewe.

Uterine, umbilical and, by difference, uteroplacental net uptakes of oxygen, glucose, lactate and 3-hydroxybutyrate (uterine uptake only) were measured in single-pregnant ewes which were either well-fed throughout, or severely undernourished for 8-20 d during late pregnancy. All animals were studied while standing at rest and then while walking on a treadmill at 0.7 m/s on a 10 degrees slope for 60 min. Undernutrition did not significantly affect fetal or placental weights at 143 d gestation but caused a 14% decrease in maternal live weight. Uterine blood flow was decreased by 32% and was associated with a significant decrease in uteroplacental oxygen uptake; neither umbilical blood flow nor fetal O2 uptake were affected by maternal plane of nutrition. Maternal and fetal hypoglycaemia in underfed ewes was accompanied by 46-63% decreases in uterine, umbilical and uteroplacental net uptakes of glucose, and similar declines in uterine and umbilical glucose/O2 quotients. Moderate maternal hyperketonaemia was associated with 2.5-fold and 3-fold increases in uterine net uptake of 3-hydroxybutyrate and 3-hydroxybutyrate/O2 quotient respectively. Exercise caused significant decreases in uterine blood flow in fed and underfed ewes but did not affect uterine or umbilical O2 uptakes; uterine net glucose uptake increased in most ewes but umbilical uptake was not significantly affected. Umbilical net uptake of lactate was significantly reduced. In underfed ewes, the extent of hyperketonaemia was significantly reduced by exercise. Contrary to earlier proposals, the ovine pregnant uterus is sensitive and adaptable to long- and short-term alterations in maternal energy balance, as achieved by chronic undernutrition and exercise respectively. Thus, the fetus and placenta significantly add to, but do not necessarily have priority over the energy demands of other tissues of the ewe.

Diet selection by sheep grazing Phalaris aquatica L. pastures of differing water-soluble carbohydrate content

A short-term shading treatment was used to create a Phalaris aquatica L. pasture with alternating strips of ‘low’ [62 mg/g dry matter (DM)] and ‘high’ (126 mg/g DM) water-soluble carbohydrate (WSC) concentration. Analyses showed that starch and all components of the WSC were reduced in concentration by shading. The shaded and unshaded pasture strips did not differ significantly in in vitro DM digestibility (84% DM), nitrogen (3.1% DM), or neutral detergent fibre concentration (42.4% DM). Synthetic alkanes were applied to the pasture strips as markers to measure the selection of the shaded and unshaded pasture by sheep. When 12–13-month-old Merino wethers were given simultaneous access to both pasture treatments, they selected 2.6-fold more unshaded (high WSC) pasture than shaded pasture. The results indicate the involvement of herbage total WSC and its components in the process of diet selection by sheep, and suggest that in future studies, more attention should be paid to reporting data for total WSC concentration.

Dietary antioxidants at supranutritional doses improve oxidative status and reduce the negative effects of heat stress in sheep

The present study was undertaken to investigate the impact of heat (thermal) stress and dietary antioxidant supplementation on the oxidative and physiological status of sheep. Twenty-four Merino × Poll Dorset crossbred ewes were housed in 1 of 2 climatic chambers (thermoneutral or heat stress) and offered either a control (10 IU vitamin E/kg DM and 0.24 mg Se/kg DM) or high antioxidant (100 IU vitamin E/kg DM and 1.20 mg Se/kg DM) diet. The sheep were exposed to 2 thermal (temperature) treatments (thermoneutral [TN]: 18-21°C and 26-30% relative humidity; and heat stress [HS]: 28-40°C and 40-50% relative humidity) for 2 wk in a single reversal design. After 1 wk of dietary treatment, animals in 1 chamber were subjected to HS for 1 wk, with the temperature being increased to 40°C between 0900 and 1700 h and then maintained at 28°C overnight. Those sheep in the TN group were maintained at 18 to 21°C. Physiological parameters were recorded 4 times a day (0900, 1300, 1700, and 2100 h) and blood samples were collected on d 1 and 7 of heat treatment. Plasma samples and red blood cell lysates were assayed for oxidative stress biomarkers. The thermal treatments were then reversed and the above measures repeated. All measured physiological parameters were elevated (P < 0.001) by thermal treatment. Respiration rate was lower during HS in sheep supplemented with antioxidants as indicated by a diet × temperature × time interaction (P = 0.010). There was 13% decline (P = 0.014) in feed intake of the unsupplemented animals during HS whereas the same was maintained in sheep supplemented with high doses of antioxidants. Plasma reactive oxygen metabolites concentrations were reduced (114 vs. 85 units/dL; P < 0.005) while biological antioxidant potential tended to be increased (3,688 vs. 3,985 μmol/L; P = 0.070) in heat stressed sheep supplemented with antioxidants. The oxidative stress index was 30% lower (P < 0.001) in supplemented sheep (2.16 ± 0.06 arbitrary units) during HS than in unsupplemented sheep (3.12 ± 0.08 arbitrary units). Plasma advanced oxidation protein products tended (P = 0.070) to decrease in antioxidant supplemented heat stressed sheep as compared to their unsupplemented counterparts. It was concluded that heat stress negatively affects the oxidative status of sheep along with the physiological responses and some of these affects can be ameliorated through dietary antioxidants supplementation at supranutritional concentrations.