The Gansu alpine fine-wool sheep (GS) is the first cultivated breed of plateau type fine wool-sheep in Sunan plateau area, which is breed by means of crossbreeding and selective improvement from Xinjiang and Caucasus fine-wool sheep as male parents, and Tibetan sheep and Mongolian sheep as female parents(zhou WJ et al.2017). The Sunan plateau (Zhangye, Gansu) is known for its extreme harsh conditions,the characteristics is high altitude, low air oxygen and short forage growing season. GS grazed grassland all year round with traditional grazing management in Sunan plateau, however, long-lasting cold season and decline in nutritive value of pasture making it difficult to meet nutritional requirement for sheep, resulting in growth retardation, hypoimmunity and higher mortality rate(Deng KD et al.2018). During cold season (winter and early spring), there is a shortage of high-quality grass hay for GS, and it always struggle to maintain the normal physiological function. Previous researches demonstrated that there are positive effects of hay supplementary on sheep productive and reproductive performance, which can reduce body weight-lost, feeding costs, and increase economic efficiency(Tulu A et al.2018;Huang JQ et al.2017). Therefore, there is a big potential to improve GS performance through developing hay supplementary system in cold season.
Alfalfa has the advantages of rich nutrition and high quality, which is widely used in livestock production, and it is also praised as "the king of forage". Alfalfa hay is a good roughage resources for ruminants, which could improve nutrient digestibility, meat quality and production performance(Wang C et al.2019). There is great significance to promote animal health and improve animal production performance. Alfalfa was widely planted in Gansu Province, and Alfalfa hay, as high-quality roughage, had been well received in animal husbandry in Sunan plateau area. The diet nutritional value was affected by the feed intake, animal digestibility rate(Liu JH et al.2016). Many studies show that adding appropriate alfalfa hay to roughage could improve diet digestion, however, with the elevated proportion, the digestibility has a downward trend, which was resulting in a negative effect(Babiker EE et al.2016). Rumen was an important organ of nutrition digestion, absorption and metabolism, also a main barrier against harmful substances. The research showed that ruminal epithelium barriers was easy to be damaged by the influence of external factors, which leaded to microflora dysfunction, decrease the production performance(Fustini M et al.2016). Dietary interventions can improve production traits via changing gastrointestinal microflora abundance. The rumen microbiota is help to the host, including nutrient absorption, metabolism and developing the immune defense systems maintenance(Sun HZ et al.2016). Distinct microorganism (bacteria, archaea, fungi and protozoa) lived in the rumen with a symbiotic relationship of ruminant herbivore. These microbes could supply vitamins, protein and carbonhydtrate for host by secreting lytic enzymes available for the microbial fermentation. Additionally, rumen microorganisms improved both host organic immunity and resistance to invading pathogens(Cui ZH et al.2020).
The compositions of microbial communities of the ruminants were highly responsive to change in diet type, physiological status, and management strategy. Although several microbiome studies performed on ovine rumen, the adaption of rumen microbiome to changes in roughage was rarely reported. It is speculated that the feed rich in cellulose and hemicellulose is digested in rumen, and the nutrients are absorbed into organism through epithelium to provide energy for ruminants(Ozbayram EG et al.2017). Sheep could exhibit high dry matter, fiber digestion and efficient protein utilization when limiting by energy intake. Dietary protein and energy are often concomitantly limited in grazing GS during cold season. We questioned whether Alfalfa hay digestive rate would favor GS when offered the maintenance energy and protein intakes. Here, different levels of alfalfa hay were offered GS to simulate the supplement dietary intakes in the cold season to determine GS rumen biochemical indexes and microflora population. Collectively, our results shed new light on the effect of alfalfa hay supplement dietary on GS feeding.