VITAMINS ▶▶▶
Animals are ca- pable of synthe- sizing Vitamin B compounds through the mi- crobial action taking place in the rumen.
lowered, the number of protozoa begins to decrease, with a decrease in the number of normal gram-negative bacteria. These changes cause the impairment of B vitamin synthesis. It was also stated that Streptococci, which are rapidly over- grown in rumen acidosis, consume thiamine, which may be a factor in the development of subsequent neurological signs.
Dietary cobalt Cobalt is the primary dietary precursor of cobalamin in rumi- nants. On average, 104 micrograms of cobalamin per 100 grams of dry rumen contents were found in cobalt-fed ani- mals, compared to 15 micrograms in cobalt-deficient animals. Although the dietary cobalt of confined livestock is usually adequate, cobalt and secondary cobalamin deficiency is a significant problem for grazing livestock in many parts of the world. The concentration of cobalt in the grazed forage is af- fected by three factors: Soil properties: Plants grown on soil containing 15 ppm co- balt with neutral or slightly acid pH can contain more cobalt than plants grown with 40 ppm cobalt and an alkaline pH. Climatic conditions: Heavy rainfall tends to leach cobalt from the topsoil. This problem is often aggravated by the rap- id growth of forage crops during the rainy season, further di- luting the cobalt content of the diet. Plant species: Plants have varying degrees of affinity for co- balt, some being able to concentrate the element much more than others. Legumes, for example, generally have a greater ability to concentrate cobalt than do grasses.
Other factors affecting vitamin B synthesis Parity: In one study, the concentrations of biotin and cobala- min in rumen fluid were greater in primiparous than in mul- tiparous cows (39.7 vs 33.9 and 5.6 vs 3.2 ng/ml, respectively). This difference was attributed here to the significant differ- ence in dry matter intake (approximately 5 kg per day). The
32 ▶ ALL ABOUT FEED | Volume 29, No. 2, 2021
rumen concentrations of the other B vitamins, however, re- mained unchanged. Type of forage: Heifers fed silage had 1.4-2.7x more cobal- amin in the rumen content than those fed chopped or pelleted hay. Preservation and stage of plant maturity: Synthesis of B vitamins can be improved by feeding fresh rather than pre- served forages. Also, feeding forages at an early stage of ma- turity favors the synthesis of greater amounts of B vitamins compared to those fed at later stages. Medication: The use of chlortetracycline or oxytetracycline for the treatment of infected wounds inhibits rumen synthe- sis of all B vitamins except for cobalamin. In other studies, however, the use of such medicines did not affect the synthe- sis of B vitamins, but they have adversely affected the digesti- bility of feed nutrients, with the dietary fibres being the most affected.
Points to consider Whether to supplement B vitamins is often seen as debatable due to the general misconception that they are produced in sufficient quantity within the rumen by rumen microbes. Re- cent researchers, however, have reported that major cellulo- lytic organisms in the rumen had specific requirements for certain B vitamins. Apart from the requirements of the rumen microbes, high-producing cattle also require a higher amount of vitamins to maintain their productivity and protect them against metabolic disorders and/or health problems such as polyneuritis and paralysis. The same holds true for very young animals, where sufficient amounts of dietary vitamin B should be provided until they reach 3-4 months of age and start to have the vitamin synthesised through the changes in the mi- crobial profile and fermentation activities in the rumen.
References are available from the author upon request
PHOTO: RUUD PLOEG
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