Effects of Oat Hay Content in Diets on Nutrient Metabolism and the Rumen Microflora in Sheep

SIMPLE SUMMARY: Providing high-quality forage for the animal husbandry to improve the quality of animal husbandry products and meet the needs of the public is one of the focuses of the current animal husbandry development. Oats have high nutritional value, and the planting area in our country is increasing year by year. It has become the new favorite of the breeding industry, and its development prospects are very broad. At present, there are few domestic research reports on the best addition of oat hay in ruminant diets, ruminant digestion and metabolism, and ruminant flora. Therefore, the purpose of this study is to add different proportions of oat hay to sheep feed to study its effect on sheep digestion and metabolism and rumen microflora. The experimentally obtained data showed that, with the increase in the content of oat hay in the diet, the appearance of sheep dry matter (DM), organic matter (OM), acid detergent fiber (ADF), and neutral detergent fiber (NDF) digestibility, as well as the diversity and abundance of rumen microbes, showed an upward trend. All presented data provide a theoretical basis for the scientific application of oat hay in sheep breeding. ABSTRACT: Oats have the characteristics of drought tolerance, cold resistance, strong adaptability, high forage yield, and high nutritional value. However, there are few reports on the most appropriate amount of oat hay in ruminant diets, the digestion and metabolism of ruminants, and the rumen microflora. To study the effects of oat hay content in diets on nutrient digestion and metabolism and the rumen microflora in sheep, 9 German Merino and Mongolian crossbred rams of similar body condition and weight with permanent fistulas were selected. The 3 × 3 Latin square design was used to randomly divide the rams into 3 groups, with 3 animals in each group. The three groups were fed different kinds of roughage: whole-plant corn silage only (corn silage group, CSG), oat hay mixed with whole-plant corn silage (1:1) (mixed group, MG), and oat hay only (oat hay group, OHG). The nutrient digestion and metabolism of each group were measured, and the pH and rumen microflora were examined after feeding for different durations. Dynamic changes in microbial communities were detected. The nutrient digestion and metabolism results showed that, with an increase in the content of oat hay in the diet, the intake and apparent digestibility of dry matter (DM) and organic matter (OM) showed an increasing trend, and the intake, digestion, and stability of acid detergent fiber (ADF) and neutral detergent fiber (NDF) increased in the OHG. The apparent digestibility, dietary nitrogen, deposited nitrogen, and nitrogen retention rate in this group were significantly higher than those in the CSG (p < 0.05). The rumen pH and sequencing results showed that the rumen fluid pH of the CSG was significantly lower than that of the OHG at 1 and 5 h (p < 0.05). The main microbial in the rumen of the three groups of sheep were Bacteroides, Sclerotium, and Proteus. The dominant taxon in the CSG was Prevotella, followed by Vibrio syringae, and the dominant taxon in the MG and OHG was Prevotella, followed by Rikenellaceae. Redundancy analysis showed that ADF and NDF in the feed had an effect on the abundance of Fibrobacteres, Ruminococcaceae, and Prevotella. Our findings indicate that the use of oat hay roughage in the diet significantly improves the apparent digestibility of NDF and ADF and helps maintain the stable state of the sheep’s rumen internal environment and the growth of rumen microorganisms.