ECOLOGICAL TRENDS AT ANIMAL HUSBANDRY NITROGEN UTILIZATION

The aim of current work was a part of study for animal husbandry effects on emissions of greenhouse gases and some mitigation strategies between the end of XX and the beginning of XXI century. It’s emphasized on nitrogen (N) balance and its fluctuated values, as well as brings forward attendant factors. As a result, we deducted strong correlation models (R> 0.89, 0.85, 0.99), as an estimator of the N2O emissions (Gg.CO2), generated by manure management in relation to animal population (monogastric, ruminant, total) among the investigated middle-term periods throughout 1989 – 2011 y for the Bulgarian realities.


Introduction
The microclimate pooled physical (temperature, humidity, air flow), chemical (toxic gases) and biological (bacteria, viruses, fungi) factors.It's influenced animal health status, e.g.animal performance and could be assumed as an important livestock stressor (Morgan and Tromborg, 2006).The productive systems and technologies determined limiting factors as breeding and nutrition strategies, environmental conditions, production need, etc. to be taken into account.In this regards must be promoted the following role "hygiene = health = efficiency = profitability".
Thereby, the common air gases pollutants are ammonia, carbon dioxide, hydrosulphide and methane.The atmospheric ammonia concentrations developed animal response in terms of health problems and reduced performance.Thus, we emphasized on a number of worldwide and local mitigation strategies (genetic, nutritional, herd, technological, etc.) and some ecological aspects of ammonia.
The ammonia is a strongly alkaline, colourless, soluble in water and with irritant odour gas.Its molecular weight (17.03), absolute (0.771) and relative to air (0.5967 g.l -1 ) density under pressure liquidified at ammonium hydroxide.The main concentrations of atmospheric ammonia are generated from animal manure as excreted fecal protein-N and urinary urea-N.These amounts are bio-transformed by bacterial urease enzymes at high temperature (49 o C) and alkaline optimum (7.7 -8.0 units).
The manure management could be used as a beneficial tool for a sustainable farming system with environmental-friendly practices (Van Passel et al., 2007) maintaining the European Common Agricultural Policy.As a support of this, the manure ammonia losses from different livestock species and categories within the barn, we could depicted the situation with, as a percent of total manure N content, summarized on following graph -fig.2: The diets, provided for productive animals are formulated to maintain higher productivity based on economic limits and ecological restrictions.Likewise, the dietary protein inputs affected total tract protein digestibility and modified the ratio fecal-N/urinary-Noutput (N f /N e ) (Accioly et al., 2002;Yossifov and Kozelov, 2011;Yossifov and Kozelov, 2011a;Yossifov, 2014a) as brings forward attendant factors for the middle-term period throughout 1989 -2011.Also, we underlined on a number of worldwide and local mitigation strategies (genetic, nutritional, herd, technological, etc.) and some ecological aspects of ammonia.

Materials and Methods
We conducted our study based on following items, contributed to the ammonia losses, associated with livestock farming management: 2. Dietary protein supply -content, subfractions, etc.; 3. Species, categories, individuals, etc.; 4. Farm building management; 5. Manure management -content, storage, conditions, etc.; 6. Manure N content -fractions, spreading, etc.All obtained data were equalized by NISTC ( 2014).The values were interpreted and correlated by Statistical Package of MS, 2007.

Results and Discussion
The flows and cycling of biogenic nutrients -i.e.nitrogen (N), carbon (C), potassium (K), phosphorus (P), and their excessive levels are preconditions to generate ecological problems.Also, the cumulative capacity of N-(NH 3 , N x O x , NO 3 -), С-(СО 2 , CH 4 ), P-containing (P x O x ), and К + derivatives in atmosphere lead to disproportion and imbalance, resulting in disturbed ecosystem stability.But, the productive systems affecting environment in different order (Steinfeld et al., 2006).Thus, the main emissions of gases in ruminant sectors are related to N, as limiting factor (Bouwman et al., 1997).Near ½ of greenhouse gases emissions from agriculture (5 %) in EC 28 are generated by enteric fermentation and manure management (Freibauer, 2003;European Environment Agency, 2013).Also, Bulgarian values are near to EC 28 means (near 10 and 5 % for gases emissions from agriculture and total amounts from enteric fermentation (near 1/3 of emissions from agriculture) and manure management (near 1/6 of emissions from agriculture), respectively).
The leading negative effects of animal husbandry and agriculture could be summarized as a source of different atmospheric pollutants by various naturechemical, physical, biological, etc. (Foer, 2009).The feed lot and dairy industries excreted 27.1 кg CO 2 Eq /кg feed intake and 39.3 кg from total gases emissions (Hamerschlag and Venkat, 2011).Likewise, the animal husbandry sector is common environmental pollutant, e.g.source of ecological risks (Steinfeld et al., 2006).Therefore, we awaited harmer scenarios with deeper problems, because the future prognosis indicated food production (meat and milk) to be increased at twice till 2050 s (www.fao.org).The total amount of greenhouse gases emissions, estimated as СО 2 Еq, are near 18 %, and 4.6 billion t СО 2 Еq are generated in ЕС 28 (European Environment Agency, 2013).Also, the 4 th Assessment Report of the Intergovernmental Panel of Climate Change (AR4) generalized the atmospheric concentrations increment: CH 4 -doubled, CO 2 -by 35%, N 2 O -by 18%, compared with the pre-industrial era (IPCC, 2007).Thus, in terms of Common Agricultural Policy (CAP, 2014(CAP, -2020) ) and under the limitations and requirements of Nitrate Directive (1991), and Bulgarian Regulation N44-20/04/2006 (2014) farmers must to control their N flows and cycling (ЕС, 1991;COM, 2006).Otherwise, the environmental pollution with agricultural N becomes from imbalanced cycling at input/output criteria.The N excretion, as a function of input/output ratio, is related with breeding and nutritional systems, physiological status, environmental conditions, etc.So, the manipulation of these factors could modify animal production systems by increasing N utilization and decreasing N pollution.
The N levels, at Earth layers, are established as 4х10 21 g.The reactive form (reactive N), as N-fixing organisms, is calculated under 1 % (Mackenzie, 1998).Simultaneously, the total amounts of excreted N in animal husbandry, is estimated on 75 Тg.y - (Smil, 1999).So, the ammonia values, as a part of undesirable atmospheric components, are affected by N utilization in farming sector (Bussink and Oenema, 1998;James et al., 1999).The low N efficacy is based on higher input levels of crude protein in ruminant diets, e.g. higher output values of excreted N as fecal-N and urinary-N.It's proved by evidence that increased dietary protein per 1 % was followed by 2.8g.d -1 and 35.7g.d -1 acceleration in milk N and excreted urinary and fecal N (Hristov and Huhtanen, 2008).This confirmed the models from last 50 s y at the XX s century.So, dairy nutrition provided dietary N/milk N ratio near 2 at the ends of the 40 s , and increased up to 7 at the end of the period (Ketelaars and Van de Ven, 1992;Rotz, 2004).The leading role in this process was a result of intensification in animal husbandry and farming sector, e.g.constantly increased consumer requirements to achieve unreal levels of animal performance and productivity in short-term periods.
The excessive dietary protein supply in ruminant nutrition with higher N excretion resulted in subsequent ammonization of run-off water, atmospheric ammonia and nitrate contamination, and ecosystem acidulation and eutrophication (Galloway and Cowling, 2002).Simultaneously, the N 2 O and NО 3 -concentrations correlated positively with the level and rate of N fertilization, and fertilizer' N amounts (Tamminga, 2003).
The main decisions must be made for more effective and profitable productive systems, based on precision and balanced feeding (Avery, 2010).As we mentioned above, farming systems (feedlot and dairy) are ineffective N consumer.This misbalancing employment of N, as a result of disturbed input/output ratio, related to amount of retained N (milk and meat) and N costs for expensive protein forages and excessive N fertilization (Yossifov, 2013c).Environmental pollution related to enormous N losses inside the cycling units and between the nutrient flows, based on poor manure management, accelerated N excretion, etc.The goals of the nutritionists' exerted efforts will be to balance livestock diets' by cheapest N sources (Yossifov, 2013c) with digestibility surpassed traditional ones (Kozelov and Yossifov, 2013).These efforts will gain higher N retention (milk, meat) or lower N excretion either (Yossifov, 2012a;Yossifov, 2014a).The potential benefits with better utilization of dietary N will modified both ecological and economic effects (Oenema and Pietrzak, 2002).Also, the N biotransformation must be expected at N fixation (N compounds), ammonification (air NH 3 ), nitrification (water NО 3 -) and denitrification (N x O x ) processes.
Our database shown that an overall emission reduction in the agriculture amounted to 70 % in the period 1989 -2011, and 2011 the sector contributed 9 % to the total of the Bulgaria' GHG s .The downward trends were driven by livestock population and arable land reduction (table 2).The most important agricultural categories as well as the contribution to the total GHG emissions 1989 -2011 are agricultural soils (58 %), enteric fermentation (21 %), manure management (19 %).A good parity between investigated parameters was observed among the deducted correlation models.The regressive analysis shows that estimated N 2 O values (Gg.CO 2 -eq ), as emissions generated by manure management (у) are manifested by close relationship with animal population (х) among the investigated middle-term periods throughout 1989 -2011 y.The smooth diversion rate among the investigated parameters allows being comparable with strong correlation (R 2 > 0.85 -0.99).

Conclusion
The N excretion, as a function of input/output ratio, is related with breeding and nutritional systems, physiological status, environmental conditions, etc.So, the manipulation of these factors could modify animal production systems by increasing N utilization and decreasing N pollution.The main decisions must be made for more effective and profitable productive systems, based on precision and balanced feeding.In regards to deducted correlation models, as an estimator of the N 2 O emissions (Gg.CO 2 -eq ), generated by manure management (у), are manifested by close relationship with animal population (х) among the investigated middleterm periods throughout 1989 -2011 y for the Bulgarian realities.

Figure 2 .
Figure 2. Different forms of manure ammonia losses from different livestock species and categories within the barn (% of total nitrogen content of the manure, STANK 1999)

Table 1 . Optimal microclimate standards in animal vitality zone -ammonia*
. An admitted pollutant values for ammonia are summarized in table below (Bulgarian Regulation N44, 2014):