Question

If NDF levels don’t meet the daily requirements of a cow, the rumen pH will fall bellow 5.7 and this significantly reduces the dry feed intake levels. The pH level decreases when cellulolytic bacteria, which are responsible for digesting fibers isn’t enough, and Amy lotic bacteria, which are responsible for breaking down starches and sugars, are in excess. NDF is essential in stimulating saliva secretion to buffer the rumen and increase the pH level. If NDF levels are low, Cows will not chew the bolus, which is formed, during rumination long enough to stimulate saliva secretion and therefore buffer the rumen. This means there is inadequate saliva secretion, as the cow must chew the bolus a certain amount of time to stimulate more saliva to keep pH level within the normal range. As I mentioned before, this low pH wont allow the cow to digest fiber and the cows an therefore cows feed intake will be reduced. If the pH level continues to be low for an extended period of time, Amy lotic bacteria can inhibit the growth of cellulolytic bacteria and trigger the bacteria that generate high amounts of lactic acid, which could lead to acute acidosis.

Could You please check if my answer for the question that says what is the effect of low NDF levels on cows is correct or not?

Answer 1

Low NDF levels on cows is not correct because of the following reasons,

1. Low NDF cause decrease in pH. Low pH level causecause acute acidosis, that means decreased in blood pH and bicarbonate, caused by overproduction of ruminal D-lactate. It will appear when animals ingest excessive amount of nonstructural carbohydrates with low neutral detergent fiber.Acute acidosis, often resulting in death, is most commonly seen in 'barley beef' animals where cattle have obtained access to excess feed. NDF is essential in stimulating saliva secretion to buffer the rumen and increase the pH level.

2. Decreasing NDF gave linear increases in BW gain, yield of milk, protein, true protein, lactose, and SNF, and milk/DM intake and milk N/N intake, and linear decreases in milk urea.

3. NDF levels are low, Cows will not chew the bolus, which is formed, during rumination long enough to stimulate saliva secretion and therefore buffer the rumen.

The physical effects of NDF on chewing, salivation and rumina! buffering are confounded with metabolic effects due to different chemical composition which alters the amount and type of fermentation products produced. In addition, cows in mid- and late-lactation have typically been used in these studies as their milk composition is more sensitive to changes in ration composition. However, the physiological state of these cows is much different than cows in early lactation. Energy intake of cows in early lactation is below energy requirements and it is impossible to balance rations to meet requirements for both fiber and energy. As rations with inadequate fiber content upset rumen function, decrease energy intake and may result in health problems such as acidosis, displaced abomasums, and lameness, it is necessary to balance rations considering the effects on rumina! pH more directly. Meeting energy requirements without compromising rumina! function and animal health is much less difficult for cows in mid- and late-lactation; hepatic lipidosis, ketosis and displaced abomasums due to post-calving difficulties are reduced or eliminated and energy intake generally exceeds energy expenditure for maintenance and milk production.