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

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.

Keywords: 16S rRNA; microorganisms; oat hay; sheep.

Figure 1

The dynamic changes of the sheep rumen liquid pH value over time. Different lowercase letters in the same industry indicate significant differences (p < 0.05), and different uppercase letters indicate extremely significant differences (p < 0.01).

Figure 2

Community composition of bacteria at the tax level of phylum in different times. (A) CSG. (B) MG. (C) OHG.

Figure 3

Community composition of bacteria at the tax level of genus in different times. (A) CSG. (B) MG. (C) OHG.

Figure 4

Community composition of bacteria in different groups. The tax level of phylum (A), the tax level of genus (B).

Figure 5

The effect of oat hay on the beta diversity of rumen microbes in sheep.

Figure 6

Linear discriminant analysis of effect size (LEfSe) was used to identify significant differences between bacterial groups in the same group at different times.

Figure 7

Bacterial taxa significantly differentiated between samples padded different groups identified by linear discriminant analysis effect size (LEfSe).

Figure 8

Bi-plot from the redundancy analysis (RDA) that shows the relationships between the bacterial community composition at the genus level and the environmental variables for all samples.