© Borgis - New Medicine 1/2011, s. 8-11
*Andrzej Tarkowski, Jerzy Truchliński
NUTRITIONAL VALUE OF VIRGINIA FANPETALS (SIDA HERMAPHRODITA RUSBY) PROTEIN IN EVALUATION OF NITROGEN FERTILIZATION EFFECT ON ENVIRONMENT
Institute of Animal Nutrition and Bromatology, University of Life Sciences in Lublin Department of Biochemistry and Toxicology
Head of Institute: Prof. dr hab. Eugeniusz Grela
Objective. The research objective was to use the Virginia fanpetals (Sida hermaphrodita Rusby) nutritional value in the evaluation of nitrogen fertilization impact on the environment.
Material and methods. The studies involved Virginia fanpetal’s forage fertilized with 100, 200 and 300 kg N/ha doses, dried and used in the biological assays performed on fistulated cows. The obtained feed material was examined to determine protein content and its biological value. In the bioassays conducted on animals protein degradation in the rumen was determined as well as its true intestinal digestibility.
Results. The optimum of 200 kg N/ha dose had a direct influence on the increasing protein content and its biological value. In consequence of this protein nutritional value formation, high rate (81%) of protein degradation and true digestibility were reported.
Conclusions. Growth of protein content in forage crops under nitrogen fertilization should be assessed by its nutritional value, availability and true digestibility in animal nutrition. This effect of nitrogen fertilization may implicate reduced nitrogen release to the human work environment and the atmosphere.
The recent decades have been marked with increasing interest in the rational management of fodder crop nutrients. It results form the need of obtaining the feed material of irrefutable superior nutritional value and the environmental protection. Among the microelement fertilizers, nitrogen modifies the content and nutritional value of feed material proteins to the highest degree. In forage plants, excessive nitrogen load increases non-protein nitrogen compounds contents. The compounds can be toxic to animals and further in the food chain – to human and natural environment (5, 11, 12).
Animal farms are known to be the major emitter of ammonia to the environment resulting in the environment acidification and eutrophication of surface and coastal waters. Therefore, the aim in the intensive animal production proves to be not only reduction of manure output but also its properties affecting the environment. In order to promote feed efficiency in animals, the tendency is to make optimal use of feed proteins in animal nutrition through the formation of its nutritional value (13).
Virginia fanpetals (Sida hermaphrodita Rusby) is a new perennial adapted for cultivation in Poland. Its multi-directional cultivation appears to be the plant advantage as well as a great capacity of adaptation to changing climate and soil conditions including chemically degraded areas (3). Virginia fanpetals is a fodder, medicinal and energy crop. Besides, the plant may be used as herbal material as its leaves and roots contain mucus in the amounts comparable to those of marshmallow (4).
Virginia fanpetals responds most strongly to nitrogen fertilization increasing the protein content to over 20% (13). Protein concentration rise is associated with concurrent changes in its nutritional value affecting digestibility and use of this component in animal nutrition. Interdependence of these changes may have a direct impact on nitrogen emission from animal manure to the internal environment of animal maintenance, as well as human and external environment.
The objective of the present study was to evaluate the use of nutritional value of Virginia fanpetals protein and its availability in animal nutrition as a measure of nitrogen fertilization effect on the environment.
MATERIAL AND METHODS
Research plant material was constituted by Virginia fanpetals forage obtained from the two-year field study. The plants were fertilized with the 100, 200 and 300 kg N/ha doses.
A protein level in the Virginia fanpetals forage was determined according to the Kjeldahl method with the use of Kjeltec kit (1). Amino acids content was established with the Beckman’s automated instrument.
Protein nutritional value was calculated using the essential amino acid index EAAI.
Dried forage from the field studies was used in the tests on milk cows fitted with a rumen and duodenal fistula.
Feeding trials studying protein availability involved Virginia fanpetals dried forage after 200 and 300 kg N/ha fertilizer doses application.
Crude protein degradation in the rumen was measured by the nylon bag technique (7).
Intestinal digestibility of protein was estimated using the mobile nylon bag technique (9).
The studied nutrients were determined separately for leaves and the whole Virginia fanpetals plant. Obtained results were analyzed statistically by STATISTICA program.
In general, varying protein contents determined in Virginia fanpetals forage was dependent on a dose of nitrogen fertilization (tab. 1).
Table 1. Influence of nitrogen fertilization on crude protein in Sida forage.
|Material Fertilization||Leaves||Whole plant|
a, b, c – differences statistically significant p < 0,0
Increasing nitrogen fertilization rate caused growth of a protein level in the Virginia fanpetals forage. In the leaves, besides primarily high protein concentration (29,9%), the effect of nitrogen fertilization on this component variation proved to be insignificant.
Nitrogen fertilization had a variable impact on the exogenous amino acid level (tab. 2). In the whole Virginia fanpetals plant, except for histidine and tyrosine, an increased content of the determined amino acids was found along with increase of nitrogen fertilization up to 200 kg N/ha dose. In the plant’s foliage, under nitrogen fertilization, the exogenous amino acid level showed similar, rising tendency, apart from tyrosine.
Table 2. Influence of N fertilization on essential amino acid content in Sida forage (%).
|Forage||N kg/ha||Exogenous amino AIDS|
|Whole plant||N 100|
The highest dose of 300 kg N/ha resulted in a decrease of exogenous amino acid content in the Virginia fanpetals forage to the content lower than at 100 kg N/ha fertilization. A marked decrease between 15 and 32% of the amino acid level was observed for lysine, leucine, isoleucine, phenylalanine and tyrosine.
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