Evaluation of fecal fermentation profile and bacterial community in organically fed dairy cows consuming forage-rich diets with different particle sizes

Abstract

Organic cattle farming encourages the use of foragerich diets, and the reduction of particle size has been suggested as an approach to improve forage utilization and enhance nutrient intake of cows. However, reducing forage particle size increases passage rate, as well as the flow of potentially fermentable nutrients out of the rumen, and the consequences for hindgut fermentation have not been evaluated yet. This study evaluated the effects of decreasing dietary forage particle size on the fecal short-chain fatty acid (SCFA) profile and the bacterial community structure of dairy cows fed foragebased rations. Twenty-one organically fed lactating Holstein cows (4 primiparous and 17 multiparous; mean and standard deviation 703 ± 65 kg body weight, 135 ± 104 days in milk) were divided into 2 groups and fed 1 of 2 diets for 34 d. Diets contained 20% concentrate and 80% forage (dry matter basis), and were fed either as a control with a forage geometric mean particle size of 52 mm (CON; 11 cows) or as a diet with the forage particle size reduced to a geometric mean size of 7 mm (RED; 10 cows). Fecal samples were collected at the end of the experiment, and samples were immediately frozen at −20°C. Samples were analyzed for SCFA, and the fecal bacterial community was evaluated using 16S rRNA sequencing. Data showed that the concentration of total SCFA was not affected by treatment, but the proportion of propionate, a key glucogenic precursor in cattle, tended to be greater for RED (13.3 and 13.8 ± 0.1%, respectively). The predominant bacterial phyla, including Firmicutes (58.0 ± 0.7%), Bacteroidetes (26.9 ± 0.4%), and Verrucomicrobia (4.0 ± 0.4%), were not affected by forage particle size. Family Lachnospiraceae increased in relative abundance when the RED diet was fed (12.1 and 13.9 ± 0.5% for CON and RED, respectively), and genera Acetitomaculum (1.1 and 1.8 ± 0.2%), Turicibacter (0.7 and 0.9 ± 0.1%), and Ruminobacter (0.1 and 0.4 ± 0.1%) increased in relative abundance when RED was fed. In addition, relative abundance of some fecal bacterial taxa was correlated with major fecal SCFA and pH. Reducing the particle size of forages, from 52 to 7 mm geometric mean particle size, maintained fecal concentration of total SCFA and tended to enhance propionate concentration, without risk of dysbiosis. Thus, results suggest that reduction of forage particle size represents an effective approach to optimizing forage utilization while maintaining hindgut fermentation and fecal bacterial diversity in dairy cows fed forage-rich diets.

Dietary supplementation with calcium propionate could beneficially alter rectal microbial composition of early lactation dairy cows

“…At the genus level, similar to the study of Castillo-Lopez et al ( 49 ), we found that Ruminococcaceae_UCG-005, Ruminococcaceae_UCG-010 , and Rikenellaceae_RC9_gut_group were the most abundant genera in the fecal bacteria community of dairy cows. The relative abundance of the family Ruminococcaceae , such as the genus Ruminococcaceae_UCG-005, Ruminococcaceae_UCG-010, Ruminococcaceae_UCG-013 , and Ruminococcaceae_UCG-014 , were all higher in the calcium propionate treatment groups than the CON group.…”

Feeding dairy cows bakery by-products enhanced nutrient digestibility, but affected fecal microbial composition and pH in a dose-dependent manner

“…On the family level, Prevotellaceae and Succinivibrionaceae linearly increased with increasing BP level, which was also observed in several genera belonging to these families, such as Prevotellaceae UCG-001, Prevotella 1, as well as Ruminobacter, which might be due to their ability to grow under low pH conditions (Castillo-Lopez et al, 2020). Indeed, the abundance of Prevotellaceae UCG-001 was negatively correlated with the fecal pH.…”

Replacing concentrates with a high-quality hay in the starter feed of dairy calves: II. Effects on the development of chewing and gut fermentation, and selected systemic health variables

“…During the whole first week of life, fecal butyrate concentration was higher than propionate, suggesting an increased butyrogenesis in the gut of young calves during the first week, likely to stimulate the intestinal growth and maturation (Górka et al, 2011;Steele et al, 2016). Starting from d 7, both ruminal and fecal fermentation profile resembled that of adult cattle fecal fermentation (Castillo-Lopez et al, 2020, 2021b.…”