Impact of ruminally pulse-dosed calcium acetate, butyrate, their combination, or limestone on milk composition

Authors: Hall, Mary Beth

Submitted to: Ruminant Physiology International Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Unlike other carbohydrates, increasing sugar in dairy cattle diets often increases milkfat yield. Sugar ferments rapidly in the rumen, essentially pulse-dosing acetate (Ac), propionate, and butyrate (Bu). Both Ac and Bu are lipogenic. To explore the basis for sugar’s milkfat effect, we ruminally dosed calcium (Ca) salts of Ac and Bu commensurate with what could be produced from dietary sugar in cows with high dry matter intakes (DMI). In a 4 x 4 Latin square design with four treatments (TRT) in four 1-wk periods, ruminally-cannulated lactating Holstein cows (12) on a common diet were dosed ruminally with CaAc (Ac; 240 g), CaBu (Bu; 160 g), CaAc+CaBu (Ac+Bu; 240 g + 160 g), or ground CaCO3 (112 g; CON) at 2 and 6 h post-0700 feeding; doses were made iso-Ca with added CaCO3. Milk samples from each cow at each milking (0330, 1030, 1830) the day of dosing and the day before and after, were analyzed for fat, protein, and lactose. Component yield (g) for summed 1030 + 1830 milkings were compared by TRT by subtracting values for the day before dosing from the day of dosing. Data were analyzed with the MIXED procedure of SAS with TRT and period as fixed variables, cow as a random variable, and parity, days in milk (<60 d, >60 d), and 3-d average DMI as covariates. A priori contrasts compared TRT with CON. Significance was declared at P = 0.05. Relative to CON, fat yield increased with Ac+Bu; protein yield increased with Bu. For milkfat, we hypothesize that Bu and Ac in excess of basal requirements were both essential for starting and elongating de novo fatty acids to increase fat yield.