Plasma and tissue α-tocopherol concentrations and meat colour stability in sheep grazing saltbush (Atriplex spp.)

Abstract

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.

Short term supplementation rates to optimise vitamin E concentration for retail colour stability of Australian lamb meat

“…In Western Australia vitamin E deficiency causes nutritional myopathy in grazing lambs due to a lack of green pasture in the summer season. Coincidentally meat retailers observe a decline in colour stability of meat during this period (Pearce, Masters, Smith, Jacob & Pethick, 2005), with meat appearing brown before the retail shelf life bench mark of 48 hours is reached (a benchmark commonly used in Australian retail).…”

Salt intake and reproductive function in sheep

“…In addition to high amounts of NaCl, saltbush also contains high levels of other minerals such as potassium (3.6%), magnesium (0.8%) and sulfur (0.4%). Despite these factors, saltbush can be grazed and has the potential to be a valuable source of protein (18% crude protein (CP)) and vitamin E, both beneficial for sheep (Norman et al, 2004;Pearce et al, 2005). The complex composition of saltbush makes the interpretation of results somewhat difficult when the plant is fed to sheep.…”

Production factors influence fresh lamb longissimus colour more than muscle traits such as myoglobin concentration and pH

“…Ripoll (2008) reported different housing and feeding production systems changed mean meat L*, a*, b* and chroma by 2.0, 2.1, 1.3 and 2.3 units. Dietary Vitamin E intake influences the fresh colour of lamb meat (Pearce, Masters, Smith, Jacob, & Pethick, 2005) in addition to delaying browning during meat display (Jose, Pethick, Gardner, & Jacob, 2008), however these studies reported the effects of vitamin E using spectrophotometric measures that are not directly comparable with colourimetric measures.…”