To determine the relationship between plasma and tissue a-tocopherol concentrations during vitamin E depletion, weaned lambs were placed on a vitamin E-deficient diet for 0, 1, 2, 4, 8 and 12 weeks. aTocopherol was measured in plasma, erythrocytes, liver, adrenal, adipose tissue, three different skeletal muscles and heart muscle. The a-tocopherol concentration in plasma fell at the same rate as the atocopherol concentration in skeletal muscles, heart muscle, adrenal and adipose tissue. The a-tocopherol concentration in liver and erythrocytes fell at a faster rate than that of plasma and all muscle tissues. There were significant correlations between a-tocopherol concentration in plasma and a-tocopherol concentrations in all the tissues measured. Different skeletal muscles had significantly different concentrations of a-tocopherol which may relate to their differing susceptibility to nutritional myopathy. The increase in malondialdehyde in oxidatively-stressed muscle tissue and the correlation with atocopherol concentration in most muscle tissues indicated that the muscles had reduced antioxidant capacity in vitro as a result of vitamin E depletion. It was concluded that during vitamin E depletion in sheep a-tocopherol concentration in plasma was a good index of vitamin E status under the experimental conditions employed. a-Tocopherol : Vitamin E : Nutritional myopathy : Sheep
Dry senesced pastures available during the summer and autumn period in Western Australia and other areas with a Mediterranean climate are low in vitamin E. The use of expensive and labour-intensive supplements to prevent nutritional myopathy induced by vitamin E deficiency in weaner sheep is common. Low vitamin E concentrations in the muscle preslaughter can also reduce the shelf life of meat. There is growing interest in incorporating saltbush into farming systems in Western Australia. The potential for saltbush to boost the vitamin E status of sheep and improve the shelf life of meat was investigated. Fifty (2 × 25) 18-month-old Merino hogget wethers (average liveweight 48 kg) were grazed on either a saltbush-dominant saline pasture or on a ‘control’ dry pasture, stubble plot for 14 weeks. At the start of the experiment, all animals were orally supplemented with 2500 IU of dl-α-tocopherol acetate in 6.25 mL solution. The α-tocopherol content in saltbush was 139 and 116 mg/kg dry matter for old man and river saltbush, respectively. Concentrations of α-tocopherol were measured in plasma at Weeks 0, 4, 8, and 12 and in muscle and liver samples taken at slaughter. Grazing on saltbush significantly elevated α-tocopherol concentrations in the liver and muscle compared with grazing on dry pasture, well above the threshold for vitamin E inadequacy (P < 0.001). Plasma α-tocopherol concentrations in sheep fed saltbush increased up to Week 8 and then decreased until the end of the experiment as availability of saltbush declined (P < 0.05). Plasma α-tocopherol in sheep fed dry pasture increased in the first 4 weeks due to the initial vitamin E treatment but declined thereafter, indicating that the pasture was low in vitamin E. The high muscle concentrations of α-tocopherol in sheep fed saltbush also improved colour stability and may have had an influence on drip and cooking loss. The meat from the saltbush-grazed sheep was moister but drip and cooking loss was the same as from the drier meat of the control sheep. In conclusion, this study demonstrates that saltbush is a potential vitamin E source for sheep.
Vitamin E and selenium have been reported to improve immune function across a range of species. Ewes lambing on poor-quality dry pasture in autumn in Western Australia are at risk of being deficient in vitamin E and selenium at lambing thus predisposing their lambs to deficiencies and increasing the risk of infection and disease. This study tested the hypotheses that (i) supplementation of autumn-lambing ewes with vitamin E plus selenium in late gestation will increase the concentrations of vitamin E and selenium in plasma in the ewe and lamb and (ii) that the increased concentrations of vitamin E and selenium in plasma in the lambs will improve their innate and adaptive immune responses and thus survival. Pregnant Merino ewes were divided into a control group (n=58) which received no supplementation or a group supplemented with vitamin E plus selenium (n=55). On days 111, 125 and 140 of pregnancy ewes in the vitamin E plus selenium group were given 4 g all-rac-α-tocopherol acetate orally. On day 111 the ewes were also given 60 mg of selenium as barium selenate by subcutaneous injection. The concentrations of α-tocopherol and selenium were measured in ewes and/or lambs from day 111 of pregnancy to 14 weeks of age±10 days (weaning). Immune function of the lamb was assessed by analysing the numbers and phagocytic capacities of monocytes and polymorphonuclear leucocytes and plasma IgG and anti-tetanus toxoid antibody concentrations between birth and 14 weeks of age±10 days. Maternal supplementation with vitamin E plus selenium increased the concentration of α-tocopherol in plasma (1.13 v. 0.67 mg/l; P<0.001) and selenium in whole blood (0.12 v. 0.07 mg/l; P<0.01) of the ewes at lambing compared with controls. Supplementation also increased the concentration of α-tocopherol (0.14 v. 0.08 mg/l; P<0.001) and selenium (0.08 v. 0.05 mg/l; P<0.01) in lambs at birth compared with controls. There was no significant effect of supplementation on immune function or survival in the lambs.
The aim of this experiment was to compare the effects of electrical stimulation and lamb age on the retail colour stability of lamb meat. Poll Dorset Merino crossbred lambs that were 5 months (‘suckers’, SU) and 12 months (‘carryovers’, CO) finished on the same green annual pasture were slaughtered at a commercial abattoir. Half of the carcasses in each age group (10) were either electrically stimulated (ES) or not stimulated (NES) post-dressing with a commercial high voltage electrical stimulation system. Luminescence (L), hue angle (indication of redness), chroma (intensity), and oxy/met (a measure of browning) values were measured at 0 h (0 days), 21 h (0.86 days), 93 h (3.88 days), and 166 h (6.91 days) after meat had been cut 1 day after slaughter, over wrapped, and put under simulated retail display conditions. Three muscles, m. longissimus thoracis et lumborum (LL), m. gluteus medias (GM), and m. rectus femoris (RF), were measured in this way. A linear mixed model was used to fit a repeated-measurements model to the light measurements of L, hue angle, chroma, and oxy/met. Oxy/met rate of change was compared by fitting splines to predict the time required for oxy/met to reach an arbitrary benchmark value of 3. Colour and rate of colour change during display were affected by both age class and electrical stimulation but these effects depended on the muscle. The LL was the darkest (lowest L) and reddest (lowest hue angle), whilst RF was the most stable in colour (lowest rate of change for oxy/met) of the 3 muscles tested. Age class had a greater effect on oxy/met rate of change for the LL and GM compared with RF. Oxy/met of LL changed more rapidly for CO than SU lambs. ES increased the time for oxy/met to reach 3 in RF and GM for SU only but did so for both age groups in LL. ES decreased this time in RF and GM for CO. CO meat contained a higher concentration of myoglobin than SU meat. Negative effects of electrical stimulation on colour stability are more likely to occur in older lambs and in the GM and RF rather than in the LL.
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