Influence of grassland composition and climate conditions on the productivity of Aberdeen-angus calves
The research has been conducted in 2017 in Pesaka area at Yosifova Montana village in the herd of “TRACE ANGUS FARM” LLC from May to October (grazing period). A group of 10 Aberdeen Angus calves equaled by gender (male), age (weaned in April) and live weight. The animals remained outdoors during the entire experimental period (grazing), they have been fed only with grass, and in the second experimental period have been fed only with 1.5 kg of corn mash. The weight development of calves during the pasture period (average live weight and average daily growth by months) has been studied. Climate factors, air temperature (T0C) and rainfall (mm/m2) have been reported. Dry mass yield (kg) is determined by mowing the area from each point. Botanical changes in grasslands (%) are determined by weight through an analysis of grass samples, taken immediately before mowing, and a percentage of the main botanical groups has been established: wheat grasses, legumes, motley grasses. The main chemical composition of dry biomass of cell walls has been analyzed: Crude Protein, Crude Fats, Crude Fibers, Ashes, Calcium, Phosphorus, Non-nitrogenous Feed Extracts. Fiber components: Neutral Detergent Fibers, Acid-Detergent Fibers, Acid-Detergent Lignin, Hemicellulose and Cellulose and have been determined as a percentage of the dry substance. The quantity of Neutral and Acidic Detergent Fibers, as well as the Hemicellulose is higher in grassland during October. During the autumn period the dry fodder mass has a 109,7% higher content of Cellulose in comparison to the spring period. The potential energy nutrition value of fodder has been assessed by the Bulgarian system as Feed Units for Milk and Feed Unit for Growth.
The research results show that grassland formed during May has a higher content of Crude Fibers, Crude Fats, Mineral Substances, Calcium and Phosphorus, but a low level of Crude Protein (102,35gkg-1) and Non-saturated Extract Substances (325,23 gkg-1). The higher productivity of fresh and dry mass of grassland, studied during May (1 7800.00 kg of fresh and 684,23 kg of dry mass) is a prerequisite for satisfying animal needs with sufficient food amounts, containing the necessary nutrients. The average daily growth of calves in the group has been lower during May, June and July, but varies from 0.487 kg to 0.597 kg. The additional feeding with corn mash allowed for a significant higher growth (1200 g – 1680 g) in the observed group during August, September and October.
In quality meadows and pastures, the wheat grasses occupy 50 to 80% of grassland, which is due to their high durability and sustainability in unfavorable climate and soil conditions, as well as to their better competitiveness compared to species from other botanical families. Legumes have the highest nutrition value, but due to their rigor to environmental conditions and lower durability, their participation in the natural grassland is 5 to 10% (rarely 20 to 30%). In the motley grasses group plants with nutritional value, which depends on the state of development at the time of using, are included. Their relative share varies from 5 – 10% to 50 – 60%. The highest level of diversity of species from this group can be found in mountain meadows and alpine pastures, in highly humid meadows, as well as in dry hilly pastures.
According to the data for botanical composition of natural pastures in the Montana region used by the Aberdeen Angus meat breed, wheat grasses predominate and define the shape of grassland during May and October. Unlike wheat grasses, the participation of legumes is limited, both in spring and autumn grasslands. This influences the protein content and nutritional value of the fodder mass.
Meteorological conditions, temperatures and rainfall affect the grassland condition in an experimental pasture. The rainfall quantity during May, June and July is 2.7 (mm/m2). August has the lowest humidity rate (1.4 mm/m2). The highest rainfall quantities have been registered in the month of October – 3.6 (mm/m2). The average monthly air temperature is highest in the months of July (21,50C) and August (21.70C), and lowest in October (10.80C), which varies from 4.90C to 16.70C. During May and June the average measured temperatures are lower in comparison to those in July and August, combined with a higher quantity of rainfall. The temperature and rainfall combination during the various months of the studied period defines the productivity of the pasture.
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