Ruminal pH is an important physiological parameter that regulates microbe activity; optimizing ruminal pH may improve rumen fermentation and milk production. The purpose of this experiment was to determine the effect of sodium bicarbonate (NaHCO3) or selenium (Se) in mineral salt block (MSB) supplementation on ruminal pH, rumen fermentation, milk yield and composition in Holstein Friesian crossbred dairy cows. Four crossbred dairy cows with an initial weight of 456 ± 6 kg in mid-lactation were assigned at random using a 4 × 4 Latin square design. The experiments were divided into four periods, each lasting 21 days. Each cow was fed a basal diet supplemented with a different type of mineral salt block: a control with no MSB supplementation, and MSB groups with MSB containing NaHCO3 (MSB-Na), MSB containing Se (MSB-Se), and conventional commercial MSB (MSB-Com). MSB-Na contained NaHCO3 (500 g/kg) to prevent acidosis, MSB-Se contained organic Se (15 mg/kg) as an antioxidant, and MSB-Com was a positive control mineral salt block. The results show that there was no significant difference in feed intake between treatments, but there was a significant difference in mineral salt intake between treatments (p < 0.05). Supplementing mineral blocks had no effect on nutrient intake or apparent digestibility (p > 0.05). Ruminal pH was not different between treatments at 0 and 1 h post-feeding, but at 2 and 4 h post-feeding, ruminal pH in cows fed MSB-Na and MSB-Se was significantly higher (p < 0.05) than it was in cows fed MSB-Com and the control. Total volatile fatty acid (VFA), acetic, propionic, butyric, and ammonia nitrogen and blood urea nitrogen were not influenced by mineral blocks supplementation. Milk yield, milk composition and energy-corrected milk (ECM) were not affected by supplementing mineral blocks. However, compared with the control, the somatic cell count (SCC) in the milk was reduced (p < 0.05) by supplementation with the mineral salt block. Based on the results of the experiments, it was concluded that MSB-Na or MSB-Se supplementation improved ruminal pH while having no effect on feed intake, rumen fermentation, milk yield, or composition, though it did reduce SCC in milk. However, additional research should be conducted to investigate the effect of MSB on rumen ecology and milk production in dairy cows fed a high-concentrate diet.

The investigation aimed to study the effect of vegetable oil sources on feed intake, nutrient digestibility and biohydrogenation bacterial population in Thai Friesian dairy cows. Three fistula Thai Friesian cows with mean body weight (BW) of 600±100 kg were assigned to receive three vegetable oil sources i.e. palm oil (PO), soybean oil (SBO) and sunflower oil (SFO) included at 4 %DM in commercial concentrate. All cows were fed on different diets that contained concentrate of 1 %BW and rice straw of 1 %BW according to a 3×3 latin square design (LSD). The results revealed that dry matter digestibility (DMD) and organic matter digestibility (OMD) tended to be higher in cows fed on SBO and SFO (P=0.06). Moreover, the DNA copy numbers (copies/ml) of biohydrogenation bacteria (Ruminococcus albus) and cellulolytic bacteria (Ruminococcus flavefaciens and Prevotella ruminicola) were higher in cows fed on SBO (P less than 0.05). In summary, supplementation of SBO in diet resulted in a higher nutrient digestibility and rumen biohydrogenation bacteria population.

This study was conducted to investigate the effect of vegetable oil and yeast fermented cassava pulp (YFCP) supplementation on feed intake, nutrient digestibility and rumen fermentation in Thai Friesian dairy cows (Thai native x Holstein Friesian). Eight Thai Friesian dairy cows (447±44 kg.BW) were assigned to 4×4 double latin square design (DLSD) with two sources of oil i.e. palm oil (PO) or soybean oil (SBO) and four levels of YFCP (0, 5, 10 and 20%DM) in the dietary treatments. All cows received total mixed ration (TMR) comprised of rice straw to concentrate at a ratio of 40:60. The results showed that supplementation of SBO had lowered feed intake, nutrients digestibility, metabolize energy intake (MEI), total digestible nutrient (TDN) and methane emission than PO treatment. However, cows received SBO had greater total volatile fatty acid (TVFA), propionic acid (C3), butyric acid (C4) than cows received on PO (P less than 0.05). In addition, supplementation of YFCP at 10%DM in the diet as an optimum level in dairy cow diets (P greater than 0.05). Finally, the interaction between the addition of SBO and YFCP at 10%DM (SBO+YFCP) had a positive effect on enhancing ether extract intake (EEI) in dairy cows.