The effects of fermented cassava pulp with yeast waste and different roughage-to-concentrate ratios on ruminal fermentation, nutrient digestibility, and milk production in lactating cows.

The study's goal was to evaluate the impact of concentrate diets containing fermented cassava pulp with yeast waste (CSYW) with various roughage to concentrate ratios (R:C) on ruminal fermentation, nutritional digestibility, milk production, and milk composition in lactating cows. Four mid-lactation Thai crossbred dairy cows were randomly assigned a 2 × 2 factorial arrangement in a 4 × 4 Latin square design, weighing 440 ± 60.0 kg (75% Holstein Friesian and 25% Thai native breed), and having 90 days-in-milk (DIM). The different dietary treatments consisted of the following: factor A: soybean meal (SBM) and replacing SBM with CSYW at 100% dry matter (DM) in the concentrate diet, whereas factor B consisted of varying the R:C ratio from 60:40 to 50:50. An interaction effect between protein source and R:C ratio on intake was not observed (P > 0.05). The CSYW-diet did not affect the intake of concentrate and rice straw. However, when the R:C ratio was changed to 50:50, there was a significant increase in the apparent digestibility of neutral detergent fiber and acid detergent fiber (P < 0.05). There was no evidence of an interaction effect between CSYW and the R:C ratio on the parameters of the rumen, the microorganisms in the rumen, or blood urea-nitrogen. The concentration of ammonia-nitrogen in the rumen, however, significantly increased (P < 0.05) when animals were given a concentrated diet containing CSYW. Total VFA, C2:C3 ratios, acetic acid (C2), propionic acid (C3), butyric acid (C4), and methane levels were unaffected by the replacement of SBM with CSYW in concentrate diets or the R:C ratio given to lactating cows (P > 0.05). There was no evidence of an interaction between CSYW and the R:C ratio across any and all milk-related parameters (P > 0.05). The R:C ratio had no effect on milk production or composition (P > 0.05). With the exception of milk protein (P < 0.05), milk yield and milk composition were not affected by replacing SBM with CSYW in concentrate diets (P > 0.05). The concentration of protein in milk produced by animals fed a CSYW-diet increased from 3.05 to 3.25%. On the basis of this research, it is recommended that CSYW be used as a protein source in a concentrate diet in place of SBM with a R:C ratio of 60:40 or 50:50.