Improving small ruminant productivity in Western China through the management of diet digestibility and feed use efficiency

Abstract

Increasing the productivity of mixed forage and livestock farming systems is an important pathway for the improvement of rural livelihoods in developing economies, however production is limited by seasonal fluctuations in feed quantity and quality. In the Loess Plateau of north-western China, regular feed deficits often occur during winter and early spring, despite government programmes aiming to increase the area of lucerne grown as high-quality feed. This thesis explores how changes in the provisioning of lucerne can increase the productivity of sheep in the Loess Plateau, in accordance with the administrative aims of the region. Feeding practices and their consequences for animal production were reviewed, revealing that livestock producers who grow lucerne typically offer it in greater proportions during the growing season but seldom conserve any for use during winter. Instead, protein deficient grain-crop residues are relied upon for feeding animals during winter, resulting in severe production losses. A review of previous research into feeding practices typical in the region found that negative protein balance is a factor in digestibility decline during underfeeding. Given that lucerne is available, protein-rich and presently underutilised, it was hypothesised that animal performance in these systems could be improved by modifying the timing with which lucerne is incorporated into rations. The benefits of storing enough lucerne to meet the minimum nitrogen requirements for rumen function during winter deficits were explored with a series of investigations in Qingyang Prefecture, Gansu Province, People's Republic of China. First, Tan weaner sheep (mean weight 15.4 kg) were fed corn straw, corn grain and lucerne hay in respective ratios of 80:20:0 (metabolisable energy = 7.4 MJ/kg dry matter, crude protein = 40 g/kg dry matter; "S1") or 55:20:25 (metabolisable energy = 8.2 MJ/kg dry matter, crude protein = 65 g/kg dry matter; "S2"). Rations were offered daily in a constant quantity supplying approximately 80% maintenance energy requirements estimated at the start of the experiment. Sheep fed S2 retained more weight on average than those fed S1 after 20 days of experimental conditions. Sheep fed S1 experienced a sustained decrease in ration digestibility and metabolisable energy intake per kg dry matter ingested. The mean dry matter digestibility and metabolisable energy observed in S2 fed animals remained stable, with no statistically significant differences between starting and finishing values. The results indicate that the capability for underfed Tan weaner sheep to absorb energy from low protein rations typical of winter rapidly decreases and that the lucerne hay in the diet prevented this decrease.

Date of Award	2017
Original language	English