Біологія тварин (Mar 2023)
The effect of therapeutic feed additive on rumen fermentation in cows with ketosis
Abstract
It is known that ionophoric antibiotics regulate ruminal fermentation, improve the utilization of feed protein, and prevent the occurrence of ketosis and steatosis in ruminants. Ionophoric antibiotics and β-acids of hops have a similar spectrum of biological activity, that is, they inhibit the vital activity of most gram-positive microorganisms of the rumen. Bacteria, like other living organisms, need vitamin E as an active antioxidant for cell membranes. The toxicity of tocopherol is very low, so adding it to the diet of ruminants in larger quantities can stimulate celluloselytic rumen bacteria and compensate for the negative effect of ionophores on fiber breakdown. Since rumen bacteria break down a significant part of dietary choline, methionine and carnitine, ruminants must receive them in a protected form, so their influence on rumen fermentation is insignificant. Three groups of cows of the Ukrainian dairy black-spotted breed with milk yields of 5 or more thousand kg during the previous lactation were formed: with signs of clinical ketosis — 4 animals; with subclinical ketosis — 5 animals and clinically healthy — 5 animals. For a month, cows with ketosis were given a treatment supplement containing crushed granules of hop cones (20 g), vitamin E (3 g), and rumen protected choline (50 g), methionine (20 g) and carnitine (1 g). Clinically healthy cows were used as control. In the blood of cows with subclinical ketosis, the additive increased the concentration of glucose and decreased the concentration of β-hydroxybutyrate, these indicators were within the normal range. In cows with symptoms of clinical ketosis, using of the feed additive also reduced the concentration of β-hydroxybutyrate (P<0.01), but it was still higher than normal. In sick cows, amylolytic and lipolytic activity was lower than in healthy cows (P<0.05–0.01). Celluloselytic activity was lower only in cows with clinical ketosis. The proteolytic activity of rumen content changed in the opposite way; it was higher in sick cows (P<0.05–0.01). This is a consequence of the increase in the number and activity of hyper producing ammonia bacteria in the rumen, what is characteristic for ketosis. After treatment of cows with subclinical ketosis, the celluloselytic and amylolytic activities in the rumen fluid were equal to the corresponding indicators of healthy cows, and the proteolytic activity was even slightly lower (P<0.05) than in the control group. Treatment of cows with clinical form of ketosis was not as effective, although the general trends remained. During subclinical and clinical ketosis, a greater amount of ammonia was found in the rumen fluid (P<0.05–0.01), because of higher proteolytic activity. In both forms of ketosis, the concentration of volatile fatty acids in the rumen decreased, and the concentration of lactate increased (P<0.05–0.01). After the treatment, these indicators in cows with subclinical ketosis approached the healthy animals, while the condition of cows with clinical ketosis improved, but the concentration of ammonia continued to differ from healthy animals.
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