The objective of this study was to determine the effect of supplementing Kluyveromyces marxianus CPY1, K. marxianus RSY5 and Pichia kudriavzevii YSY2 isolated from ruminal fluid of dairy cows on transfer of aflatoxin B₁ (AFB₁) from feed into aflatoxin M₁ (AFM₁) in milk, DMI, milk production and nutrient digestibility. Four multiparous Holsteins in mid-lactation were used in a 4 × 4 Latin square design trial consisting of 14 days in each experimental period for sample collection. Between each period, 14 clearance days prior to the next treatment were allowed to minimize carryover effects. In each treatment, subsequent supplementation of isolated yeast was compared, i.e., (1) control (without yeast supplementation), (2) K. marxianus CPY1 (K1Y), (3) K. marxianus RSY5 (K2Y) and (4) P. kudriavzevii YSY2 (PY). All diets contained 22.28 µg of AFB₁/kg. Treatments were individually fed at the rate of 2 g/day (1 × 10⁹ CFU/g) of yeast biomass or corn meal in the control group. Concentrations of AFM₁ in milk was reduced with yeast and averaged 1.54, 0.36, 0.43 and 0.51 µg/L for control, K1Y, K2Y and PY, respectively (p < 0.01). The transfer of AFB₁ from feed into AFM₁ in milk was higher in control compared with K1Y, K2Y and PY (7.26% vs. 1.18%, 1.44% and 1.69% respectively, p < 0.01). Supplementation of yeast also improved DMI and milk compositions, but no differences were observed in nutrient digestibility or milk yield among treatments. Concentration and yield of milk protein, fat, lactose, solid-not-fat (SNF) and total solids were greater in cows fed yeast compared with the control (p < 0.01). These results indicate that K. marxianus CPY1, RSY5 and P. kudriavzevii YSY2 shows promise as a dietary supplementation to detoxify AFB₁ and improve DMI and yield of milk components.

Ruminal organic acid production, especially lactic acid, can be modified by feeding cattle highly concentrated diets, which have been shown to adversely affect dairy cattle health. Therefore, the use of lactic acid-utilizing organisms is considered to be a potential method for controlling lactic acid levels. This study was conducted to isolate and identify lactic acid-utilizing yeasts from the ruminal fluid of dairy cattle and to determine the specific growth rate and generation time when using lactic acid as a carbon source instead of glucose. Seventeen yeast isolates were examined in this study. Yeasts isolated from dairy cattle that were fed a high cassava pulp diet (HCP) had higher specific growth rates and shorter generation times than yeasts isolated from dairy cattle that were fed a high-concentrate diet (HC) and a mixed diet (M). The three most effective yeasts in terms of specific growth rate and generation time were Pichia kudriavzevii, Candida rugosa and Kodamaea ohmeri, with 99, 100 and 99% nucleotide identities, respectively. These three isolates could be used as potential probiotics in dairy cattle diets. Significance and Impact of the Study This study demonstrates that yeasts isolated from the ruminal fluid of dairy cattle can utilize lactic acid as a carbon and energy source for growth. The isolated yeasts can be used as probiotic supplements for dairy cattle that are fed highly concentrated diets to reduce ruminal lactic acid production.

The objective of this study was to determine the effect of feeding two fermented total mixed ration (FTMR) on methane production in dairy heifers. Four Holstein Friesian dairy heifers with mean body weight (BW) of 301.1 ± 42.2 kg were used in a simple cross-over design trial. Treatments consisted of 2 FTMR formulated to yield either low (LMD) or high CH4 production (HMD). No differences were observed in dry matter intake (DMI; 6.49 and 6.19 kg/d), BW change (-3.37 and -7.25 kg), or DM digestibility (50.64 and 46.99%) between diets. Ruminal pH, total volatile fatty acids (TVFA) and molar proportions of acetate, propionate and butyrate were not different among diets. Concentrations of blood glucose were higher (P=0.05) for HMD compared with LMD at 2 h post feeding; however, blood urea nitrogen was not different. Methane emissions were 236.32 L/d for LMD and 273.70 L/d for HMD and not different. Feeding the FTMR differing in CH4 potential did not affect DMI, digestibility, ruminal TVFA production or molar proportions of VFAs in dairy heifers.

This experiment aimed to determine the effectiveness of physically effective neutral detergent fibre as peNDF1.18 mm and the moisture levels of fermented total mixed rations (FTMR) in lactating cow performance. Eight crossbred Holstein cows with 430±17.1 kg BW in mid-lactation were used in a 4 × 4 replicated Latin square design (LSD). The treatments consisted of 20 and 25% physically effective neutral detergent fibre (peNDF) and 30 and 60% moisture contents. The results showed that DMI, and DMI of %BW0.75 were increased in 20 and 25% of peNDF with 30% moisture content. CP, EE, NDF, ADF and NFC digestibility was increased on 25% peNDF with 60% moisture content in FTMR. Acetate was increased in 25% peNDF (P<0.05), but propionate was higher in 20% peNDF compared to 25% peNDF. Milk fat percentage was increased in 25% peNDF. No differences were observed in blood glucose and BUN. Consequently, 20 and 25% peNDF1.18 mm with 60% moisture content in FTMR were the optimum levels for lactating cows.