Effects of Different Forage Types on Rumen Fermentation, Microflora, and Production Performance in Peak-Lactation Dairy Cows

Forages are vital in maintaining the dietary structures of ruminants, and reducing their costs is important for improving dairy production efficiency. Thus, this study investigated the effects of dietary forage types on dry matter intake, production, rumen fermentation, and the microbial profile in peak-lactating cows. Eight cows (600 ± 25 kg) with days in milk (60 ± 10 days) were assigned to four groups using a replicated 4 × 4 Latin square design: OG (oat hay + alfalfa hay + corn silage + concentrate), CW (<i>Leymus chinensis</i> + alfalfa hay + corn silage + concentrate), AS (alfalfa silage + oat hay + corn silage + concentrate), and AC (alkali-treated corn straw + alfalfa hay + corn silage + concentrate). The ruminal butyrate acid concentration was lower in the OG group than in the AS and AC groups post-feeding (12 h; <i>p</i> < 0.05). Ruminal NH3-N content was higher in the AS group than in the AC and CW groups post-feeding (9 h; <i>p</i> < 0.05). The percentage of ruminal <i>Oscillospira</i> and unknown microbes was higher in the CW group than in the other groups (<i>p</i> < 0.05). The total rumination time and rumination time per dry matter intake of AC were significantly higher than those of the other groups (<i>p</i> < 0.05). Milk lactose content in the AS group was highest among the groups (<i>p</i> < 0.05), and milk fat content was higher in the OG group than in the CW group (all <i>p</i> < 0.05). Overall, our results suggested that the butyrate acid content of forage from oat hay in rumen fermentation was significantly lower than that of calcium oxide and alfalfa silage sources when the dietary nutrition level was similar. The diet derived from <i>L. chinensis</i> increased the number of fibrillation helices related to fiber-decomposing bacteria and simultaneously increased unknown strains. Forage derived from alfalfa silage tended to increase milk protein levels. Alkali-treated corn straw could significantly increase the total rumination time and unit dry matter rumination time of dairy cows, which plays an important role in maintaining rumen health. The rational use of low-quality forage has broad prospects in China.