The objective of this research was to evaluate the effect of feeding fresh cassava root (CR) along with a feed block containing high was to sulfur (FBS) on feed intake, digestibility, rumen fermentation, and blood thiocyanate concentration in Thai native beef cattle. Four Thai male native beef cattle, initial body weight (BW) of 130 + 20.0 kg, were used in this study. The experiments were randomly assigned according to a 2 × 2 factorial arrangement in a 4 × 4 Latin square design. The main factors were supplemented fresh CR levels (1.0 and 1.5% BW) and across to a feed block supplemented with sulfur added 2% (FBS-2) and 4% (FBS-4). Intakes of rice straw, concentrate diets, and FBS were not affected by treatments. Intakes of CR, sulfur, and total intake were significantly altered by the FBS treatment. The apparent dry matter and organic matter digestibility coefficient were significantly higher in animals fed FBS-4 than in those fed FBS-2. The ruminal ammonia nitrogen concentration was not affected by treatment and ranged from 15.6 to 17.6 mg/dl. Populations of protozoa and fungal zoospores were similar across treatments, whereas the bacterial population was significantly different between sulfur levels in the feed block. Feeding CR with FBS did not change total volatile fatty acid (VFA) concentrations and VFA profiles except for the propionic acid concentration, which was higher in the group with CR supplementation at 1.5% BW. Cattle fed CR with FBS showed similar blood urea nitrogen concentration at various feeding times and overall. In contrast, CR supplementation at 1.5% BW with FBS-2 increased blood thiocyanate concentrations. Therefore, supplementation of FBS-2 was beneficial to Thai native beef cattle fed with 1.5% BW fresh CR as it improved digestibility and rumen fermentation presumed, because HCN from fresh cassava root was converted into thiocyanate, which is nontoxic to farm animals.

The influence of sulfur included in fermented total mixed ration (FTMR) containing fresh cassava root on rumen characteristics, microbial protein synthesis, and blood metabolites in cattle was evaluated. Four Thai native beef cattle were randomly assigned according to a 2 × 2 factorial in a 4 × 4 Latin square design, and dietary treatments were as follows: factor A included a level of sulfur at 1% and 2% in total mixed ration, and factor B featured ensiling times at zero and 7 days. Digestibility of dry matter was increased when FTMR was supplemented with 2% sulfur. Blood thiocyanate increased by 69.5% when ensiling time was 7 days compared to no ensiling (p < 0.01). Bacterial populations were significantly different in the FTMR containing sulfur at 2% and 7 days of ensiling. Furthermore, microbial crude protein and efficiency of microbial protein synthesis were higher in the FTMR containing 2% sulfur and 7 days of ensiling (p < 0.01). Thus, high levels of hydrocyanic acid from fresh cassava root could be detoxified by a sulfur addition with an ensiling process to become nontoxic to cattle.

The aim of the present research was to determine the influence of sulfur and urea combined with fresh cassava root in fermented total mixed ration (FTMR) on digestibility, fermentation in the rumen, blood metabolite, milk yield, and milk quality in tropical lactating dairy cows. Four mid-lactation Thai Holstein–Friesian crossbred cows were studied. Pre-experiment milk yield was 12.7 ± 0.30 kg/day, and the body weight was 495 ± 40.0 kg. Animals were evaluated in a 2 × 2 factorial in a 4 × 4 Latin square design to receive diets followed by: factor A, which was a dose of sulfur inclusion at 1.0% and 2.0%, and factor B, which was level of urea inclusion at 1.25% and 2.5% DM in FTMR. The hydrogen cyanide (HCN) concentrations reduced 99.3% to 99.4% compared with fresh cassava root when FTMR was supplemented with 1.0% and 2.0% sulfur, respectively. Intake of crude protein was increased based on urea level addition (p < 0.05). Blood thiocyanate concentration was increased by 21.6% when sulfur was supplemented at 2.0% compared to 1.0% (p < 0.05). There was no difference in protozoal concentration, whereas bacterial populations at 4 h after feeding were significantly greater by 6.1% with the FTMR supplemented with 2.0% sulfur and 2.5% urea (p < 0.01). Allantoin concentrations, excretion, absorption, and microbial crude protein showed significant interactions between sulfur levels and urea levels in cows fed diets supplemented with 2.0% sulfur and 2.5% urea (p < 0.05). The molar ratios of the volatile fatty acid (VFA) profile were affected by dietary FTMR (p < 0.01). Furthermore, propionic acid increased by 4.6% when diets were supplemented by 2.5% sulfur (p < 0.01). Milk fat and total solids increased when feed was supplemented with 2.0% sulfur and 2.5% urea (p < 0.05). The diets supplemented with 2.0% sulfur levels resulted in greater concentrations of milk thiocyanate (p < 0.05). The somatic cell count was significantly reduced throughout the experiment with increasing sulfur supplementation (p < 0.05). Animals fed diets supplemented with 2.0% sulfur exhibited a decreased somatic cell count by 18.3% compared with those fed diets supplemented with 1.0% sulfur. Thus, inclusion of 2.0% sulfur with 2.5% urea in FTMR containing fresh cassava root improved digestibility, ruminal fermentation, microbial crude protein synthesis, and milk qualities in dairy cows.

Context Feeding of fresh cassava root in ruminants is limited because it contains a high level of hydrocyanic acid (HCN), which is responsible for poisoning. Aims The objective of the present study was to evaluate the effect of sulfur levels supplementation in the fermented total mixed ration (FTMR) containing fresh cassava root as an energy source on the gas kinetics, ruminal fermentation, reduction of HCN concentration and nutrient digestibility in the in vitro gas production. Methods The experimental design was a 3 × 4 factorial in a completely randomised design. Dietary treatments contained factor A, which was three levels of sulfur supplementation at 0, 1 and 2% in FTMR, and factor B was ensiling time at 0, 7, 14 and 21 days respectively. Key results Concentration of HCN in FTMR was significantly reduced (P &lt; 0.05) by 73.7% when sulfur was supplemented in FTMR at 2%. The levels of HCN in FTMR were 2.89, 0.61, 0.61 and 0.49 ppm, for ensiling time of 0, 7, 14 and 21 days, respectively (P &lt; 0.01). HCN was reduced when ensiling started at 7 days. Gas production from soluble fractions (a) ranged from –1.2 to –2.4 and was not significant (P &gt; 0.05). Furthermore, gas production from the insoluble fraction (b) ranged from 48.8 to 53.9, and gas production rate constants for the insoluble fraction (c) ranged from 0.1 to 0.2. The potential extent of gas production (a + b) was also unchanged when the concentration of sulfur increased (P &gt; 0.05). In addition, there were no interactions between sulfur levels and ensiling times on all parameters (P &gt; 0.05). In contrast, cumulative gas production (at 96 h of incubation) was significantly different when sulfur increased at 2% (P &lt; 0.05), while ensiling times did not affect cumulative gas production. Ruminal pH was affected by FTMR and decreased with an ensiling time of 21 days, ranging from 6.0 to 6.1 after ensiling. Ensiling time did not affect ruminal ammonia-nitrogen concentration (P &gt; 0.05) among dietary treatments which ranged from 21.2 to 24.0 mg%. FTMR ensiled for 21 days had the highest in in vitro dry matter digestibility, an in vitro neutral detergent fibre and in vitro acid detergent fibre digestibility which were 61.0–62.5, 35.1–43.1 and 22.3–25.9% dry matter (DM) respectively. Regarding the concentration of total volatile fatty acid (VFA), acetic acid, propionic acid and butyric acid, ranges from 94.7 to 113.6 mmol/L, 59.3 to 67.4, 20.2 to 25.9 and 11.3 to 13.8 mol/100 mol, respectively, were observed and did not differ among treatments (P &gt; 0.05). The concentration of total VFA relative to the sulfur level and ensiling time had no effect on ruminal VFA concentrations. However, exceedingly high percentages of sulfur (2% of the DM) in the diet tend to increase total VFA concentration. Conclusions Using of 2% sulfur supplementation in TMR containing fresh cassava root fermented could improve the kinetics of gas and nutrient digestibility while maintaining ruminal fermentation parameters and the rate of HCN disappearance. Implications These findings should be examined in further in vivo experiments in order to increase animal performance.

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