CC BY
38
Заключение. Результаты исследований свидетельствуют, что в животноводческой отрасли Хойникского района радиологическая обстановка постепенно улучшается. Благодаря естественному распаду радионуклидов и принимаемым мерам удельное содержание Cs-137 в животноводческой продукции снижается. Количество молока, поступившего в 2009 году на молокозаводы Хойникского района с активностью Cs-137 менее 100 Бк/кг, как из общественного, так и из частного секторов, достигло 100 %. Наблюдается прирост производства молока и мяса, одновременно производство свинины и говядины в районе остается убыточным, а молока - рентабельным.
ЛИТЕРАТУРА
1. Аверин, В. С. Основные принципы, цели и задачи концепции реабилитации населения и территорий, пострадавших в результате катастрофы на Чернобыльской АЭС / В. С. Аверин // 17 лет после Чернобыля; проблемы и решения: сб. науч. тр. - Минск, 2003. - С. 89-91.
2. Методика расчета экономического эффекта от внедрения в агропромышленном секторе результатов научных исследований по преодолению последствий катастрофы на Чернобыльской АЭС / В. С. Аверин [и др.]. - Гомель, РНИУП «Институт радиологии», 2008. - 34 с.
3. Анненков, Б. Н. Ведение сельского хозяйства в районах радиоактивного загрязнения (радионуклиды в продуктах питания) / Б. Н. Анненков, В. С. Аверин. - Минск: ЗАО «Пропилеи», 2003. - 110 с.
4. Богдевич, И. М. Рекомендации по ведению агропромышленного производства в условиях радиоактивного загрязнения земель Республики Беларусь / И. М. Богдевич; под ред. проф. И. М. Богдевича. - Минск, 2008. - 74 с.
5. Карпенко, А. Ф. Развитие скотоводства в загрязненных районах Гомельской области / А. Ф. Карпенко, Е. В. Дубе-жинский // Актуальные проблемы интенсивного развития животноводства: материалы ХШ Международной науч.-практ. конф., посвящ. 80-летию образования зооинженерного факультета УО БГСХА. - Горки, 2010. - С. 338-342.
6. Карпенко, А. Ф. Экономическая и радиологическая оценка эффективности производства сельскохозяйственных предприятий Брагинского района / А. Ф. Карпенко, А. Л. Мостовенко, М. В. Макарова // Аграрная экономика. - 2010. -№ 5. - С. 30-34.
7. Подоляк, А.Г. Резервы производства зерна в южных районах Гомельской области, загрязненных радионуклидами / А. Г. Подоляк, А. Ф. Карпенко, А. Л. Мостовенко, М. В. Макарова // Земляробства i ахова раслш. - 2010. - № 5. - С. 18-20.
8. Четверть века после чернобыльской катастрофы: итоги и перспективы преодоления. Национальный доклад Республики Беларусь. - Минск: Департамент по ликвидации последствий катастрофы на Чернобыльской АЭС МЧС Республики Беларусь, 2011.-90 с.
9. Научные основы реабилитации сельскохозяйственных территорий, загрязненных в результате крупных радиационных аварий / Н. Н. Цыбулько [и др.]; под общ. ред. Н. Н. Цыбулько. - Минск: Институт радиологии, 2011. - 438 с.
УДК 636.5
DEVELOPMENT OF AVIAN EMBRYO THERMOREGULATION AND ARTIFICIAL INCUBATION
M. W. LIS, J. NIEDZIOLKA
Department of Poultry and Fur Animal Breeding and Animal Hygiene, Agricultural University of Krakow, al. Mickiewicza 24/28, 30-059 Krakow
(Поступила в редакцию 07.05.2012)
Summary. Provision of optimal temperature conditions during artificial incubation is a basic condition for obtaining healthy, full-fledged Chicks. Incubation of eggs of birds is in the exchange of heat between the egg and the external environment. In the case of breeding in natural conditions the heat is supplied to the egg only on the surface which is in contact directly with skin chicken-mother hen. During artificial incubation thermal energy is supplied through the entire surface of the egg. Therefore, the best way to ensure the thermal homeostasis of the embryo during artificial incubation is the measurement of the temperature of the shell eggs, and not be guided by the temperature of the air inside the incubator. Violation of the thermal comfort of the embryo leads to violations of the progress of embryogenesis and functioning of the it systems of circulation of the blood, endocrine and immune systems. This leads to a reduction of the results of incubation and the danger of the emergence of the Chicks hidden defects during cultivation.
Key words: avian embryo, thermoregulation, natural incubation, artificial incubation.
Резюме. Обеспечение оптимальных температурных условий при искусственной инкубации является основным условием для получения здоровых, полноценных птенцов. Инкубация яиц птицы заключается в теплообмене между яйцом и внешней средой. В случае гнездования в природных условиях тепло поступает к яйцу только от поверхности, которая соприкасается непосредственно с кожей курицы-наседки. Во время искусственной инкубации тепловая энергия поставляется через всю поверхность яйца. Поэтому лучшим способом обеспечения термического гомеостаза эмбриона во время искусственной инкубации является измерение температуры скорлупы яиц, а не температура воздуха внутри инкубатора. Нарушение теплового комфорта эмбриона приводит к нарушению хода эмбриогенеза и функционирования его систем кровообращения,
эндокринной и иммунной систем. Это приводит к снижению результатов инкубации и опасности появления у птенцов скрытых дефектов во время выращивания.
Ключевые слова: птичий эмбрион, терморегуляция, естественная инкубация, искусственная инкубация.
Birds, like mammals, are "homeothermic animals". The term refers to organisms capable of maintaining a stable internal body temperature regardless of fluctuations in the environment's thermal parameters. This requires the body to maintain sufficiently high metabolism while regulating heat production (endothermy), but also enables the rate of enzymatic processes to be optimized. In warm-blooded animals, disturbance of thermal homeostasis upsets the body's hormonal balance and metabolism. The main role in the neurohormonal thermoregulatory system is played by the hypothalamo-pituitary-adrenal axis (HPA), the spinal cord, and thermoreceptors [3].
Warm-blooded animals are only able to fulfil endothermic conditions during the postnatal period. In the embryonic, and often also in the neonatal period, their thermoregulatory mechanism only develops gradually. For example in the domestic hen, the hypothalamus, which is considered to be an integrator of thermal signals, already begins to differentiate together with the encephalon and the spinal cord on the second day of incubation (E2), and finishes as late as the third week after hatching [30]. For this reason, to maintain the temperature needed for normal function, warm-blooded animals have to use heat from external sources (ecto-thermy) [33, 36]. The life of these animals can therefore be divided into three phases [24]:
1) prenatal phase, during which embryo development is strictly dependent on external heat energy and the embryo's ability to lose heat is limited;
2) early postnatal phase, during which the chick/neonate gradually develops the ability to maintain constant body temperature;
3) phase of full-blown homeothermy, during which the animal maintains stable body temperature regardless of ambient temperature.
The prenatal phase in birds is popularly understood as the period of egg incubation (heating). It should be recalled that from fertilization to oviposition (or the end of cleavage) the embryo develops in a thermally stable environment inside the layer's body at approx. 40-40.5oC [6]. During approx. 20 hours, when the oocyte (yolk) moves through successive segments of the oviduct and new egg layers are formed, further cell divisions take place in the germinal disc. At oviposition, the avian embryo is in the stage of discoblastula and is built from several dozen thousand cells (blastomeres) that form two layers: the epiblast and the hypoblast. Oviposition is followed by a rapid decrease in temperature and embryo development is arrested until the beginning of incubation [4].
Types of incubation. Incubation is popularly understood as "warming of eggs", or providing heat energy needed for the initiation and maintenance of normal embryo development. In the case of the domestic hen, it is necessary to provide from 300 to 600 mW (1W = 1J s-1) depending on egg size and stage of embryogenesis. This value can be calculated from the formula [35]:
where Qi - instantaneous power requirement for incubation, W; n - number of eggs in a clutch; K - egg's thermal conductance, W* °C-1; Te - egg temperature, °C; Ta - ambient temperature, °C; c - fraction of the egg surface covered by the brood patch.
The egg's thermal conductance K is calculated from the formula:
where M - egg mass, kg; t - time of measurement, s; Cp - egg specific heat, J*kg-1 x0C-1.
In fact, heat exchange between the egg and its environment takes place during incubation. It occurs along the same principle as between other physical media, namely through conductance (heat flow from a hotter1 to a colder physical medium), convection (heat exchange with the gaseous medium), evaporation (vaporization of water) and radiation (thermal radiation).
The natural incubation process involves what is termed contact incubation [35], during which the incubation environment parameters are regulated by the layer in accordance with its brooding instinct [23]. The most important characteristic of this type of incubation are differences in eggshell surface temperature. This is due to the fact that heat is supplied to the egg only through that part of the surface that is in direct contact
1 A physical medium's thermal energy status is reflected in its temperature
Qi = nK x (Te-Ta) x (1-c),
(1)
K = M x Cp/t,
(2)
with the skin of the brood hen, while the other part of the shell is in contact with nest material or air (Fig. 1) [35]. From approx. 12 days of incubation, the embryo, due to circulation of blood in chorioallantoic membrane vessels, is able, to a certain extent, to make temperature uniform over the whole shell surface. The heat dissipation mechanism, based on blood flow in the chorioallantoic membrane, takes on special significance in the final week of incubation [25, 37].
brooder
incut
envir \—l r
nest
T K>T >T
incub egg envir
Fig. 1. Schematic representation of heat exchange between the egg and its environment in the case of contact incubation
The basic assumption of artificial incubation is to provide the optimum environment for normal development of the avian embryo. This is why modern incubators are enclosed climate chambers [35]. The egg is surrounded by warmed air of uniform temperature, and heat energy is supplied by the entire surface (convec-tive incubation, Fig. 2) [35]. As a result, the temperature gradient on the shell is different compared to natural incubation, and under such conditions the embryo is unable to redistribute its blood flow to optimize its own temperature [22].
T
incub
T
egg
^ Ti
incub
Fig. 2. Schematic representation of heat exchange between the egg and its environment in the case of convective incubation
Heat production by the chick embryo. Air temperature in the incubator is definitely the main factor affecting the rate of embryogenesis [22, 36]. It is assumed that optimum incubation temperature (machine temperature, MT) ranges between 36 and 38°C depending on the stage of embryo development [22]. In practice,
however, temperature is maintained between 37.6 and 37.8°C in the incubator, and between 37.0 and 37.2°C in the hatcher, with an allowance of 0.1 °C [6]. It may seem that egg temperature should not differ from air temperature in the incubator. In fact, these two values may differ considerably depending on the stage of incubation, because as embryogenesis progresses, there is an increase in embryo metabolism and thus in heat production (Fig. 3) [19].
The first signs of heat production by the chick embryo were recorded on day 3 of incubation [19]. This process significantly intensifies after the chorioallantoic membrane (CAM) adopts the function of the embryo's respiratory system [19]. In the domestic hen, this takes place on day 8 of incubation (E8), increasing oxygen consumption by the embryo 6-fold compared to E3 [39]. From this point of embryogenesis, chick embryos can respond to lower incubation temperature with a momentary intensification of metabolic processes [19]. During the period between E10 and E16, the increased activity of the HPA axis (Freire et al. 2006) is paralleled by a rapid increase in heat production by the chick embryo, from 25-30 mW to approx. 130 mW [19]. Heat production by the embryo during the period between E16 and E18 becomes stable within 137-155 mW [19], and oxygen consumption reaches approx. 570 mL/day [39]. After internal pipping (IP), the embryo assumes pulmonary respiration and as a consequence, heat production increases almost twofold [14].
300
200
.a £
100
10 mW
25 mW
130 mW
E16
160 mW
E10
Day of incubation
1 mW
0
E3
E6
Fig. 3. Heat production by the egg in successive stages of embryogenesis (based on Lourens et al. 2006)
It is of note that a positive correlation is observed between egg size and heat production, which is probably associated with a greater proportion of yolk in these eggs. This means that eggs from older flocks will produce more heat than eggs from young flocks [11, 19, 27]. At the same time, because of lower fertilization success and higher embryo mortality in the case of eggs from point-of-lay and end-of-lay flocks (below 35 and above 50 weeks of age), total heat production by the embryos in the incubator can be lower compared to the set of eggs from the peak of production (35-50 weeks of age) [42].
Temperature of shell surface area as an indicator of embryogenesis. For reasons mentioned above, it appears that internal egg temperature (IET) would be a better indicator for monitoring the course of incubation than air temperature in the incubator [15]. However, it would be difficult to perform such measurements in practice because this would involve damaging the shell and inserting a probe into the egg. This carries the risk of embryo damage and/or infection. One solution is to replace IET measurement with measurement of eggshell temperature (EST), which indicates the exchange of heat between the egg and the environment [21]. The difference between IET and EST is small and ranges between 0.1 and 0.2 °C [10, 18]. EST measurements can be performed using a thermistor [18], a pyrometer [15] or a contactless thermovision camera [1, 2, 17]. EST monitoring devices are increasingly fitted to incubators of the new type.
It seems that the highest hatchability and quality of chicks is found when EST is between 37.5 and 37.8 °C [16, 18, 20]. This is not possible when a constant temperature of approx. 37.8 °C is used in the incubator [12, 13, 22]. Under such conditions, EST value in the first week of incubation, when CAM blood vessels are not fully developed, is lower than air temperature in the incubator. As metabolic processes increase in the second week of incubation, EST is higher by 0.2 °C than incubation temperature on day 10 of incubation (E10) and by as much as 2 °C at E20 (Fig. 4) [2, 15, 19].
day of incubation
o Egg shell temperature Temperatu re of incubation
Fig. 4. Changes in (broiler) chicken eggshell temperature during incubation with a constant temperature of 37.8°C in the incubator and 37.2°C in the hatcher. Thermovision camera measurements (based on Lis et al. 2011)
This means that only embryos in the middle period of incubation can maintain optimum EST temperature. EST will be too low for embryos in the initial stage of incubation and too high in the final stage. This is particularly dangerous in the latter case as it may cause hyperthermia in embryos [13]. For this reason, during artificial incubation, thermal conditions should be controlled according to the stage of embryogenesis to ensure normal embryo development. Three parameters can be adjusted: temperature, motion, and degree of air saturation with water vapour.
To reach and maintain EST at the recommended level of 37.5-38.0 °C in the first week of incubation, air temperature in the incubator should exceed this values. From approx. 9 days of incubation, embryo heat production exceeds the amount of heat lost through evaporation of water from the egg, and from this moment incubation temperature should be gradually decreased [18, 19, 23].
The degree of air saturation with water vapour (relative humidity, RH) is a major factor influencing the exchange of heat between the egg and its environment. Humid air has a greater heat capacity than dry air, and an increase in relative humidity is paralleled by a decrease in the rate of evaporation. Therefore, when beginning incubation, it is recommended to close the dampers to increase humidity in the incubator to ap-prox. 80% as a result of water evaporating from eggs (Fig. 5).
Day of incubation
Dry bulb temperature during i ncubation Relative humidity during i ncubation
Fig. 5. Changes in incubation parameters: temperature and degree of air saturation with water vapour in the incubator in accordance with the incubation programme that accounts for the development of the chick embryo's thermoregulatory system (M. Lis, based on the author's own measurements)
Its purpose is to make the environmental conditions inside the incubator uniform and to improve heat transfer to eggs (make eggs warmer). However, RH should not be increased by mist spraying, because drops of water settling on the shell will evaporate, thus cooling the egg. Frequent delays in the development of embryos hatched in incubators near sprayers are caused by this phenomenon [22]. It should be noted at this point that maintaining high humidity (in excess of 50%) after the end of the first week of incubation is inad-
visable because it disturbs gas exchange and hinders evaporation [7]. Under optimum thermal and humidity conditions of an incubator, evaporation (evaporative water loss) uses approx. 20 mW of energy regardless of incubation stage [32] and is therefore an important component of embryo thermoregulation.
Sufficient air motion in the incubator is particularly important during the first days of incubation when the embryo must be intensively warmed, and also after 12 days of incubation when heat production by the embryo increases rapidly and it has to be removed. When air motion in the incubator is too weak, eggs located in the bottom trays are cooled less intensively than those in the upper trays. This will cause differences in the rate of embryo development, resulting in hatching asynchrony and discrepancy in hatching results depending on the location of egg tray in the incubator. It is therefore recommended that air motion should be strong, because it increases heat dissipation from the entire egg area and reduces EST [9]. By way of example, air moving in the incubator at 2.8 m/s results in dissipation of approx. 280 mW of heat and reduces shell surface temperature by as much as 2.9 °C [38].
Thermal stress during incubation. Because the thermoregulatory system develops parallel to the increase in embryo metabolism and the associated heat production [10], there is a clear correlation between the strain on this system during embryogenesis and postnatal body function [3, 7, 40]. For this reason, improper incubation parameters, fluctuations in incubation temperature and technical problems with the incubator disturb the normal course of embryogenesis. It is believed that over successive days of development, embryos become less sensitive to hypothermia and more sensitive to hyperthermia [31].
Hyperthermia. Embryonic hyperthermia is the most frequent error made during artificial incubation [8]. The tolerance limit of hyperthermia depends on temperature, stage of embryogenesis and time of exposure. For example, 13-day-old embryos exposed to 55 °C completely survived up to 30 minutes and all died within the next half hour [31]. During the first week of incubation, embryos show considerable tolerance to elevated incubation temperature. However, this causes a non-physiological acceleration of the rate of embryogenesis, which is conducive to developmental anomalies. A ten-hour exposure of eggs to a temperature exceeding 38.5 °C during the first 12-36 hours of incubation may lead to increased embryo mortality between E2 and E4, and in the hatchery waste to head deformations such as celosomia, mandibular development or absence of mandible, crooked beak, anophthalmia [8, 31].
Later on, hyperthermia results in decreased hatchability, which is due, among others, to embryo malpositions (most often head between legs or head over wing). Blood vessels are dilated and sensitive to damage [31], and the heart is markedly smaller than in healthy chicks [28, 31]. In addition, long-term hyperthermia causes a decrease in the body weight of chicks, dehydration and accelerated pipping, which leads to disturbed yolk sac retraction, yolk sac coagulation as well as navel defects [16, 18, 20].
In breeding and veterinary practice, hyperthermia most often occurs in the perihatching period. A common mistake made in poultry hatcheries is the sudden change in parameters of the incubation milieu following transfer of eggs, namely no microclimate synchronization between the incubator and the hatcher. As a consequence, the quality of hatched chicks decreases as a result, among others, of damaged allantoic vessels, cardiac muscle and umbilical vessel, which leads to omphalitis [26]. In addition, air quality and thermal and humidity conditions in the hatcher gradually deteriorate as new chicks hatch. Under such conditions, heat dissipation is more difficult, especially since the greater the hatcher capacity, the easier the overproduction of heat. Hyperthermia results in the increased embryo/chick blood levels of corticosterone, glucose, protein and fatty acids, with a decrease in the concentration of thyroid hormones [29]. This serves to secure energy sources for the heart, skeletal muscles and the nervous system [40]. Chronic embryonic hyperthermia in the perihatching period also lowers the body weight of broiler chickens during the first three weeks of fattening, one reason being the use of proteins as a source of energy [22].
Hypothermia. Domestic fowl embryos may be at risk of hypothermia in case of incubator failure or improperly executed technical procedures such as egg candling or transfer. It is believed that maintaining hatching eggs for a dozen or so minutes at hatching room temperature (approx. 25 °C, air humidity 6570 %), as provided by hatching technology, has no adverse effect on further development [15]. It seems that the embryo's response to hypothermia depends on the degree to which thermoregulatory mechanisms have been developed. This is confirmed by the observations of Lis et al. [17], who used thermographic registration (Gig. 6) to observe the rate of heat loss from eggs left at T = 22.4 °C for 30 min in a hatching room. The mean decrease in the surface temperature of eggs after they remained outside the incubator at T = 22.4 °C for 30 min was 4-6 °C, but the first 15 min of cooling had the greatest effect on EST value. Over the next 15 min when the eggs were held outside the incubator (between 15 and 30 min of hypothermia), EST value decreased by an average of 2 °C regardless of the stage of embryogenesis, with differences between particular days of incubation not exceeding 0.8 °C [17]. The authors cited above distinguished 5 stages of
incubation depending on the rate of heat loss by the egg. The first stage is confined to the first dozen or so hours of incubation, during which egg content reaches proper temperature for activation of embryo development. The second stage covers the period between 2 and 6 days of incubation and is characterized by a rapid decrease in EST by approx. 3.5 °C after 15-minute hypothermia and by approx. 6 °C after 30-minute hypothermia. Termination of growth by CAM, which grows to cover the inner shell and acts as the embryo's proper respiratory organ, seems to be the reason for a lower decrease in AEST value during the period between 7 and 12 days of incubation (stage 3) compared to the preceding period. During this stage, heat production by the embryo is still inadequate to influence the rate of heart loss by the embryo. The next stage (stage 4) can be set between 13 and 17 days of incubation. The decrease in EST by 4.2 °C after 15-miute hypothermia, observed during this period, may suggest that the embryo is highly sensitive to disturbances in thermal parameters. Meanwhile, the small decrease in EST value by only 0.8 °C (down to 36.2 °C) in perihatching stage 5 (E18-E19) indicates that some elements of the thermoregulatory mechanism begin to function in the embryo at this stage of embryogenesis. It should be noted at this point that EST value in E19 decreased by 2.2 °C after further 30 minutes of hypothermia, i.e. by a similar value as for eggs during the earlier stages of embryogenesis [17]. One interpretation is that from E17, the embryo's thermoregulatory mechanism is able to maintain constant body temperature for a short period of time [19, 24, 36].
Many laboratory studies investigated the embryo's response to long-term hypothermia. Tazawa and Rahn (1986) observed that after temperature was decreased to 8 °C, 6-day embryos survived up to 26 hours and 20-day embryos up to 8 hours. M. E. Suarez et al. found that embryos held at 24 °C between 8 and 18 days of incubation die within 48 hours [34]. Nevertheless, even short hypothermia may contribute to developmental deformities [31]. Under hypothermic conditions, the efficiency of respiratory processes is decreased and the function of the embryo's circulatory system is disturbed, as evidenced by slowed heart rate, decreased blood pressure and alkalization of blood. Underheating eggs by 0.5-1.0 °C for most of the incubation period slows embryogenesis processes, extends hatching by one to two days, and considerably reduces the body weight of embryos/chicks. In the anatomopathological picture, hypothermic embryos and newly hatched chicks show the characteristics of extended incubation. In such a case, the yolk sac is enlarged, green or olive striped, with incomplete retraction. The intestine, in particular the cloaca, are distended and filled with white-green faeces. Deposits of uric acid salts accumulate in the pericloacal area. In addition, considerable enlargement of the heart, oedema and sometimes deformation of lower legs are obsrved [28, 31]. Because decreased incubator temperature increases relative air humidity and decreases evaporation efficiency, dead embryos have higher amounts of the amniotic fluid.
38 9-C - 33
4 • i
i - 36
ll feh - ¡j^Hj - 34
- 32
M ^__ ^_ • *
- 30
m 9. •à Jt
m > - 28
A It l i 26 2DC
Fig. 6. Thermal image of hatching tray with eggs on day 10 of incubation. Air cell of the eggs visible as a dark area of lower temperature (Photo Jacek Augustyn)
Thermal conditioning of embryos. In light of the above information concerning sensitivity of chick embryos to disturbances in the body's thermal homeostasis, attempts to improve tolerance of the chick during the postembryonic period by a temporary increase or decrease in incubation temperature are of interest. Research completed to date has shown that exposure to high temperature (39.5 °C and RH = 65 %) for 12 h/d from E7 to E16 stimulates the development of chorioallantoic blood vessels and the hypothalamic-pituitary-thyroid axis, which accelerates the development of the thermoregulatory mechanism in the embryo/chick. As
a consequence, chickens improve their thermotolerance to high rearing temperature. Exposure to high temperature (39.5 °C and RH = 65 %) for 2 h/d from E5 to E12 increases the expression of genes responsible for angiogenesis (development of blood vessels), stimulates the development of chorioallantoic blood vessels (higher density) and improves embryo thermotolerance during incubation [29, 41]. Exposure to low temperature (25 °C) for 30 min/d from E18 to E19 improves chickens' tolerance to low temperature during rearing and reduces the probability of ascites in chickens [41].
In summary, ensuring optimum thermal conditions during incubation is the primary prerequisite for producing healthy chicks of good quality. Disturbances to the embryo's thermal comfort, caused by incubator failure or improperly executed technical procedures may interfere with embryogenesis and function of the circulatory, hormonal and immune systems. This negatively affects hatching results and may expose "hidden" defects in chicks during rearing. It appears that the best way of ensuring the embryo's thermal homeo-stasis during incubation is to measure eggshell temperature rather than relying on air temperature within the incubator.
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УДК 636.2.053.2.087.7
ЭФФЕКТИВНОСТЬ ПРИМЕНЕНИЯ ПРЕМИКСОВ С РАЗЛИЧНЫМ УРОВНЕМ МИНЕРАЛЬНЫХ ВЕЩЕСТВ И ВИТАМИНОВ В КОРМЛЕНИИ ПЛЕМЕННЫХ БЫЧКОВ
В МОЛОЧНЫЙ ПЕРИОД
И. И. ГОРЯЧЕВ, М. М. КАРПЕНЯ
УО «Витебская ордена Знак Почета государственная академия ветеринарной медицины»
г. Витебск, Республика Беларусь, 210026
А. А. НЕВАР
РУП «НПЦ НАН Беларуси по животноводству» г. Жодино, Республика Беларусь, 222160
(Поступила в редакцию 11.05.2012)
Резюме. Использование премиксов с более высокими уровнями витаминов и микроэлементов в рационах племенных бычков оказывает положительное влияние на их рост и усвоение питательных веществ. Наивысший среднесуточный прирост составил 920 г, что на 7,9 % выше по сравнению с контролем. Затраты кормов на 1 кг прироста сократились до 4,56 к. ед., или на 6,1 %. Установлено также, что включение витаминно-минерального премикса № 2 в рацион животных способствует повышению усвоения организмом азота на 5 %, кальция - на 9,9, фосфора - на 11,3 %.
Ключевые слова: племенные бычки, премикс, микроэлементы, витамины, молочный период, живая масса, кровь.
Summary. Use of premixes with higher levels of vitamins and trace elements in diets of breeding bull calves has a favourable effect on their growth and nutrient digestion. The highest average daily weight gain was 920 g which is 7.9 % more as compared to the control. Food intake per1kg of gain was reduced to 4.56 calorie units, or by 6.1 %. It has also been established that inclusion of
