Evaluation of Dietary Phytochemicals as Rumen Modifiers in Lactating Dairy Cows

Phytochemicals such as tannins included in dairy cow nutritional programs, as a natural feed additive, promise to improve rumen bypass protein and consequently reduce the feeding cost by decreasing the amount of CP needed in the ration. Additionally, if tannins are fed along with high quality protein sources, this could improve the AA profile reaching the small intestine and potentially improving health and performance of dairy cows. The black pepper, specifically its alkaloid piperine, is a nontoxic, natural dietary compound with a broad range of physiological activity. Lactating dairy cows ingesting these phytochemicals (tannin extracts and black pepper) will potentially benefit by increasing feed efficiency, protein reaching the duodenum, oxidative stress, and immunity. Objectives of this study were to evaluate the effects of phytochemicals in the ration of lactating dairy cows by assessing feed intake and efficiency, rumen fermentation, milk yield and composition, and blood metabolites and biomarkers. We hypothesized that diets containing phytochemicals would increase milk and component yields, benefit rumen fermentation, and improve feed efficiency and nutrient utilization as well as prevent oxidative stress. Sixteen Holstein cows (14 multiparous and 2 primiparous; DIM =114 ± 20) were used in a crossover design experiment with an adaptation period. Cows were randomly assigned to a treatment sequence according to DIM, lactation number, prior milk yield averages, and body weight. Treatments included: 1) basal diet with soybean meal pellets at 3.37% of DM (CON), 2) basal diet with soybean meal pellets fed at 3.37% of DM containing phytochemicals at 4.4% concentration (TRT). The experiment lasted a total of 56 d and consisted of a 14-d adaptation (covariate) period and two 21-d treatment periods. All milk weights were recorded daily, and milk samples were collected during the last 3 d of each period in both milkings. Rumen fluid, body condition scores (BCS), and body weights were collected on day 19 and 20 of each period. Blood samples were collected from the coccygeal vein on d 13 and 20 during the adaptation and treatment periods, respectively. Data were analyzed using MIXED procedures of SAS. Dry matter intake was similar among treatments. Milk yield as well as fat and protein yield decreased in TRT cows in comparison to CON. Propionate proportion in VFA was lower in TRT cows. Greater apparent total-tract digestibility was observed in DM, OM, and CP when feeding TRT diets. Similarly, glucose concentrations were lower in TRT cows in comparison to CON. Albumin and the antioxidant activity measured by SOD was increased in TRT cows. The concomitant decrease in propionate proportion and blood glucose could partially explain the decrease in milk yield in TRT cows. Although the effects observed in VFA proportions and apparent total-tract digestibility of nutrients are indicatives that these phytochemicals act as rumen modifiers, further research is needed to optimize their dosage for an effective response in the rumen