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Simple Summary: Dietary neutral detergent fiber (NDF) is commonly used as an indicator of the fiber content in animal diets, particularly in ruminant nutrition. NDF plays a crucial role in the digestive process of ruminant animals, as it affects feed intake, rumen fermentation, and nutrient utilization. The levels of NDF affect feeding behavior, rumen fermentation, and production performance during the period of peak lactation in dairy cows. To prove it, four Holstein dairy cows were subjected to a feeding experiment with varying NDF levels in their diets. The results indicated that increased NDF levels resulted in reduced dry matter intake, while the time spent eating and ruminating increased. Moreover, higher NDF levels led to increased pH value and acetate concentration, as well as changes in the proportions of certain bacteria in the rumen. Milk yield, protein percentage, and nitrogen efficiency decreased with increasing NDF levels, while milk fat percentage and milk urea nitrogen concentration increased. Notably, diets with 25% and 34% NDF had negative effects on feeding behavior, rumen fermentation, and production performance. However, the diet with 28% NDF was effective in enhancing the production performance compared to the one with 31% NDF. These findings offer a valuable strategy for optimizing the provision of dietary NDF to cattle, thereby enhancing their overall performance. This study investigated the impact of dietary neutral detergent fiber (NDF) levels (25.49%, 28.65%, 31.66%, and 34.65%, respectively) on the feeding behavior, rumen fermentation, cellulolytic bacteria, and production performance of dairy cows during peak lactation. A feeding experiment was conducted using four fistulated Holstein dairy cows (600 ± 25 kg) with days in milk (50 ± 15 days), employing a 4 × 4 Latin square design to assign the cows to four groups. The results demonstrated that increasing NDF levels in the diet had the following effects: (1) A linear decrease in dry matter intake (DMI), NDF intake, and physically effective NDF8.0 (peNDF8.0) intake; a linear increase in the average time spent eating and ruminating, as well as the time spent eating and ruminating per kilogram of dry matter (DM); a quadratic response in the time spent ruminating per kilogram of NDF and peNDF8.0. (2) A linear increase in average pH value, acetate concentration, and the proportions of Fibrobacter succinogenes and Ruminococcus flavefaciens among total bacteria; a linear decrease in ammonia nitrogen (NH3-N) concentration, microbial crude protein (MCP), total volatile fatty acid (TVFA), propionate, butyrate, and lactate. (3) A linear decrease in milk yield, milk protein percentage, and nitrogen efficiency of dairy cows; a linear increase in milk fat percentage and milk urea nitrogen (MUN) concentration. Based on the combined results, it was found that diets with 25% and 34% NDF had detrimental effects on the feeding behavior, rumen fermentation, and production performance of dairy cows. However, the diet with 28% NDF showed superior outcomes in production performance compared to the one with 31% NDF. Therefore, it is strongly recommended to include a diet containing 28% NDF during the critical peak lactation period for dairy cows. [ABSTRACT FROM AUTHOR]

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 (Leymus chinensis + 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; p < 0.05). Ruminal NH3-N content was higher in the AS group than in the AC and CW groups post-feeding (9 h; p < 0.05). The percentage of ruminal Oscillospira and unknown microbes was higher in the CW group than in the other groups (p < 0.05). The total rumination time and rumination time per dry matter intake of AC were significantly higher than those of the other groups (p < 0.05). Milk lactose content in the AS group was highest among the groups (p < 0.05), and milk fat content was higher in the OG group than in the CW group (all p < 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 L. chinensis 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. [ABSTRACT FROM AUTHOR]

This study investigated the effect of moderate risk level (8 µg/kg) AFB1 in diet supplemented with or without adsorbents on lactation performance, serum parameters, milk AFM1 content of healthy lactating cows and the AFM1 residue exposure risk in different human age groups. Forty late healthy lactating Holstein cows (270 ± 22 d in milk; daily milk yield 21 ± 3.1 kg/d) were randomly assigned to four treatments: control diet without AFB1 and adsorbents (CON), CON with 8 μg/kg AFB1 (dry matter basis, AF), AF + 15 g/d adsorbent 1 (AD1), AF + 15 g/d adsorbent 2 (AD2). The experiment lasted for 19 days, including an AFB1-challenge phase (day 1 to 14) and an AFB1-withdraw phase (day 15 to 19). Results showed that both AFB1 and adsorbents treatments had no significant effects on the DMI, milk yield, 3.5% FCM yield, milk components and serum parameters. Compared with the AF, AD1 and AD2 had significantly lower milk AFM1 concentrations (93 ng/L vs. 46 ng/L vs. 51 ng/L) and transfer rates of dietary AFB1 into milk AFM1 (1.16% vs. 0.57% vs. 0.63%) (p < 0.05). Children aged 2–4 years old had the highest exposure risk to AFM1 in milk in AF, with an EDI of 1.02 ng/kg bw/day and a HI of 5.11 (HI > 1 indicates a potential risk for liver cancer). Both AD1 and AD2 had obviously reductions in EDI and HI for all population groups, whereas, the EDI (≥0.25 ng/kg bw/day) and HI (≥1.23) of children aged 2–11 years old were still higher than the suggested tolerable daily intake (TDI) of 0.20 ng/kg bw/day and 1.00 (HI). In conclusion, moderate risk level AFB1 in the diet of healthy lactating cows could cause a public health hazard and adding adsorbents in the dairy diet is an effective measure to remit AFM1 residue in milk and its exposure risk for humans. [ABSTRACT FROM AUTHOR]