Livestock production is the predominant industry in Tibet Autonomous Region (TAR), with significant numbers of yaks, cattle, horses, sheep and goats raised under various production systems. Little was known about the mineral and trace element status of these animals, although it was suspected that they were at risk from iodine and selenium deficiency. The investigation was intended provide a comprehensive assessment of the mineral and trace element status of livestock and identify any of these nutrients that may limit livestock productivity in TAR. The study involved scientists from the Tibet Academy of Agricultural and Animal Sciences (TAAAS), the Institute of Animal Science, Chinese Academy of Agricultural Sciences (CAAS) and Australia. They investigated the mineral and trace element status of yaks, cattle, sheep and horses in Tibet and determined the mineral and trace element content of herbage and of crop residues fed to livestock. They also sought new diagnostic tests to assess vitamin B12 and iodine status of livestock.
The project team investigated the mineral nutrition of livestock at 40 households in seven important livestock producing counties of the TAR. The livestock included in the survey were sheep and yaks in Damxiong, Lizhou and Naqu, sheep in Gangba, yaks in Jiali and cattle in Bailang and Jiangzi. At the time of the investigation (late autumn-early winter and late winter-early spring) livestock available for testing were pregnant ewes and lactating cattle and yaks. Blood and faeces from all species, urine and milk from cattle and yaks, and pasture and feed supplements were collected for laboratory testing. Of the wide range of feed supplements offered to livestock the more common supplements were cereal hay and straw and barley meal.
In general, livestock were in moderate to poor condition and pastures were of poor quality (indicated by low protein content). The team identified that the low levels of some major and trace minerals may limit livestock productivity. The risk from sodium and phosphorus deficiencies appears to be widespread, particularly in sheep and yaks, and a number of sheep groups were at risk from calcium deficiency. Sheep in Damxiong and cattle and yaks in all counties were at risk from copper deficiency, and sheep in all counties except in Gangba and yaks in Damxiong, Jiali and Linzhou were at risk from selenium deficiency. There was little evidence of a risk from iodine deficiency, although in sheep the utilisation of iodine may have been impaired by a low selenium status.
In view of the range of mineral deficiencies that may be limiting livestock productivity the team recommended that it would be of value to the livestock industry for Tibetan scientists to undertake a training program in the detection and correction of mineral disorders. Experiments were needed to determine the magnitude of the response to mineral supplementation, measured by increases in milk or wool production or body weight gain, and to determine the most cost-effective method of providing these mineral supplements.
The team recommended that assessment of the mineral nutrition of livestock be extended to include other important livestock-producing counties and that surveys be undertaken in the warmer wetter months when livestock productivity may not be limited by energy and protein intake. With increased levels of production marginal, mineral deficiencies can become more severe and previously unsuspected mineral deficiencies may emerge.