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The application of n-alkane as markers to estimate herbage intake, apparent digestibility and species composition of diet consumed by grazing sheep were studied. Six local Mongolian sheep were used to determine dry matter (DM) intake, apparent DM digestibility and species composition of diet during summer, autumn and winter. Animals were orally dosed twice daily with n-alkane gelatin capsules containing 60 mg C32-alkane as an external marker. Diet composition was estimated by comparing the odd-chain n-alkanes pattern profile (C27-C31) of the consumed plant species with the n-alkanes fecal concentrations of grazing animals, using a non-negative least squares algorithm called 〝EATWHAT〞software package. The alkane pair C32:C33 and C33 alkane were used to estimate DM intake and diet apparent DM digestibility, respectively. The results showed that daily dry matter intake of the sheep were 1.77, 1.61 and 1.18 kg d-1 in summer, autumn and winter, respectively. Apparent DM digestibility, CP, ME and NDF intake of diet consumed by sheep decreased significantly (P＜0.01) from summer to winter, with no evident changes in ADF and ADL intake. Diet composition indicated Artemisia frigida Willd was the most dominant diet component, contributed 79.68, 68.12 and 86.26% of sheep's diets in summer, autumn and winter, respectively. Cleistogenes songorica Ohwi and Convolvulus ammannii Desr were the important components of the diet. Although Stipa breviflora Griseb is one of the main plant species in the study area, the sheep rarely choosed it. The study indicated that CP and ME in diet consumed by sheep were deficient in winter. Therefore, appropriate supplementation strategies should be indispensable during this period.

the shortening of photoperiod and were higher in the implanted groups than in the non-implanted groups, and there was a strong interaction between SDPP and MT implantation; prolactin, insulin like growth factor I and leptin showed the opposite results to MT and INS. This study provides evidence that MT and photoperiod can be used to regulate nitrogen partitioning, modulate cashmere goat body composition and improve cashmere production in practice. The technique can be extended to Inner Mongolia and other cashmere goat raising areas in China.

The traditional scientific system of animal nutrition has existed for over 100 years, but substantial changes are yet to take place. With the lapse of time, limitations of this traditional scientific system have been more and more evident and such a system should be dramatically revised with innovations. Beginning in the late 1980s, our group started to use system-science principles and approaches in animal nutrition research. The author published a book entitled "An Introduction to Systems-Nutrition of Animals", which marked the birth of a new scientific system in animal nutrition to stimulate further development of this discipline. System-nutrition is defined as a branch of biological sciences that concerns system-level studies of the integrative picture of flux, metabolism, utilization and regulation of nutrients (e.g., proteins and amino acids) from dietary and endogenous origin in the whole animal system at organism, organs, tissues, cells and molecules levels to achieve such goals as nutritional manipulation and prediction, as well as optimum feeding decision and optimum nutritional engineering programs for animal feeding.