Test on Rumen Acidosis in Ruminants

Question 1: Subacute ruminal acidosis (SARA) results in annual economic losses ranging from 5 to 10 billion US dollars in the North American dairy industry.

A. Ano

B. Ne

Explanation: The study materials indicate that 'Previous studies have shown that in the North American dairy industry, an annual economic loss of 5–10 billion US dollars is attributed to SARA'.

Question 2: Which of the following events characterize the third phase of rumen acidosis?

A. The rumen pH drops rapidly to below 5.0.

B. There is a significant proliferation of lactate-producing bacteria such as Streptococcus bovis and Lactobacillus lactis.

C. Many bacteria die and release endotoxins like lipopolysaccharides (LPS).

D. The rumen pH falls below 5.8, and the population of amylolytic bacteria increases, while fiber-degrading bacteria decrease.

Explanation: In the third phase of rumen acidosis, when the rumen pH falls below 5.6, the acidic environment compromises most rumen microorganisms. This promotes the proliferation of lactate-producing bacteria (e.g., Streptococcus bovis and Lactobacillus lactis), leading to excessive lactate accumulation and a rapid drop in rumen pH to below 5.0. Under these conditions, many bacteria die, releasing endotoxins like lipopolysaccharides (LPS). The event described in the fourth option, where rumen pH falls below 5.8 and amylolytic bacteria increase, while fiber-degrading bacteria decrease, occurs in the second phase of rumen acidosis.

Question 3: Shifting the dietary concentrate-to-forage ratio from 2:8 to 8:2 decreased the total VFAs concentration.

A. Ano

B. Ne

Explanation: Ramos et al. demonstrated that shifting the dietary concentrate-to-forage ratio from 2:8 to 8:2 elevated total VFAs concentration from 92.39 to 154.59 mmol/L, indicating an increase, not a decrease.

Question 4: The proportion of roughage in a ruminant's diet influences its salivary secretion.

A. Ano

B. Ne

Explanation: K. Jacques and colleagues found that the proportion of roughage in the diet influences salivary secretion, noting an increase in salivary outflow when the hay content in the diet was increased from 50 to 90%. An increase in hay proportion or intake directly enhanced salivary flow.

Question 5: According to the provided study materials, which factor primarily explains why High Concentrate Diets (HCD) lead to increased VFA production in ruminants?

A. The non-structural carbohydrates in HCD boost microbial fermentation, causing VFA production to exceed clearance.

B. HCD decrease the pH, which directly stimulates VFA synthesis rates.

C. HCD cause an increase in salivary bicarbonate, which enhances VFA production.

D. HCD lead to a decrease in ruminal osmolality, promoting VFA synthesis.

Explanation: The study materials state that 'When ruminants eat HCD, the non-structural carbs boost microbial fermentation, causing VFA production to exceed clearance and leading to accumulation.' This directly links HCD's non-structural carbohydrates to increased VFA production. The other options are either incorrect or not supported as the primary reason for increased VFA production by the text.