A proposal to apply operative temperature for the evaluation of thermal conditions in the broiler living zone

Transkript

1 Arch.Geflügelk., 76 (1). S , 12, ISSN Verlag Eugen Ulmer, Stuttgart A proposal to apply operative temperature for the evaluation of thermal conditions in the broiler living zone Ein Vorschlag zur Verwendung der fühlbaren Temperatur zur Bewertung der Temperaturbedingungen in der mittelbaren Haltungsumwelt von Broilern G. Nawalany Manuscript received 12 October 10, accepted 18 December 10 Introduction The research carried out in the years in real operating conditions of a mass scale broiler chicken production revealed the dominating influence of litter on temperature and humidity parameters inside a broiler house. It has been concluded that the temperature of litter (Θ L ) during the first 5 days of the winter production cycle was lower by even 14 K from the optimal temperature required at this stage of the rearing process (Θ opt ); whilst in the last 25 days of the summer cycle, Θ L was higher from Θ opt by as much as 15 K (BIEDA and KOŹBIAŁ, 1999; BIEDA et al., 03; NAWALANY et al., 04). The consequence of such thermal conditions was poor broiler production results (HERBUT et al., 1993). Outcomes of numerous studies clearly point out the need to ensure proper temperature and humidity of litter the only partition that comes in direct contact with birds (BESSEI, 06; REITER, 06; NAWALANY et al., 10). In poultry breeding, thermal conditions inside broiler houses are most frequently evaluated on the basis of indoor temperature and air humidity, whilst the temperature of litter surface is not usually measured. With the temperature of litter surface being unknown, it is practically impossible to optimize thermal conditions in the broiler living zone, particularly to limit the possibility of thermal discomfort and stress. The aim of the article is to introduce the concept of operative temperature (Θ 0 ), commonly used to asses indoor thermal comfort of people, as a criterion helping to evaluate thermal conditions in the broiler living zone (EN77: 05). The value of Θ 0 is established based on indoor air temperature in the broiler living zone (Θ i ) and litter temperature (Θ L ). Materials and Methods The research was carried out in one of 10 broiler houses, each with the capacity of,000 chickens, on a broiler Dept. of Rural Building, University of Agriculture in Kraków, Poland farm in the village of Ujazd (south of Poland). The broiler house was a typical building with the production hall of 1,000 m 2 (12 84 m). It was equipped with forced air heating, vertical mechanical ventilation and a fogging system all controlled automatically. The autumn production cycle started with 18,500 Ross chickens bred on a half of the production hall covered with a 10-centimetre layer of litter from long straw (barley and wheat). 7 days later, broilers were spread out across the entire production hall. Production results in the researched production cycle ( ) are presented in Table % of chickens died, most frequently during the 1 st week of the production cycle. Until week 3, the chickens were fed with DKA starter (protein 2 g kg 1, AME N 12.6 MJ kg 1 ) birdseed, in the weeks 4 and 5 DKA grower (protein 5 g kg 1, AME N 13.1 MJ kg 1 ), and in week 6 DKA finisher (protein 195 g kg 1, AME N 13.2 MJ kg 1 ). Throughout the entire rearing cycle the birds had free access to water bowls. No bacterial or viral diseases were observed. This particular production cycle was selected for research due to its particular planning and organization, which involved the extension of the cycle to 49 days, as earlier transport for slaughter was impossible, and one earlier population reduction on day 42. The temperature of litter surface was measured with the help of two PT-100 sensors, with the accuracy of ± 0.1 C, placed at the span of 1 metre on the surface of 18 m 2, located in the centre area of production facility (strip 3 m width, 6 m long). The temperature of indoor air was measured with the help of a PT-100 sensor located at the height of m above the litter within the measurement field. Air and litter temperatures were recorded every 1 minute and the results were registered by a multichannel HP data logger. Moreover, the breed was under daily monitoring (deaths, production reductions) and weekly check of chicken weight gain. The average weight of 1 bird was calculated as average weight of randomly selected birds and then multiplied by the total number of broilers. The research had been preceded by trial studies ( ), which had involved electronic measurement of air movement at the height of m above the floor level, with mechanical ventilation turned on. The trial phase revealed that the velocity of air flux did not exceed 0.1 m s 1. The study also involved an electronic measurement of relative air humidity, which thanks to the fogging system remained within the range 55 and 70%. In order to evaluate thermal conditions in the broiler living zone, the concept of operative temperature (Θ 0 ) was proposed. Operative temperature Θ 0 can be calculated by

2 50 Nawalany: Evaluation of thermal conditions in the broiler living zone Table 1. Characteristics of rearing cycle ( ) Kenndaten des Mastdurchgangs ( ) Day of cycle Number of chicken Weight (kg) Stock (birds per m 2 ) (kg m 2 ) 1 * ** ,2 18,4 3, ,5 18,3 8, ,0 18,2 16, ,5 18,1 27, , , ,4 17,9 43,0 42 *** ,4 13,9 33,4 49 **** ,7 13,9 35,3 * chickens in half of production hall ** chickens in production hall *** production reduction by 4,000 chickens **** end of production cycle means of a modified formula found in the EN77 standard 05: in which: Θ L litter surface temperature, [ C], Θ i air temperature at the level of birds' heads, [ C]. The formula can be used in the following conditions: v 0.1 m.s 1 and RH = 50 70%. The symbols and units of measured and calculated physical quantities are described in Table 2. Results Θ Θ L + Θ i O = [ C] 2 Results of Θ Loc, Θ Lf and Θ i measurements as well as the required air temperature Θ opt and the calculated Θ 0f and Θ 0oc are presented in a chart (Figure 1). The Θ Loc curve reflects daily maximum temperatures of litter surface regarded as litter temperature beneath a resting bird, whilst the Θ Lf curve shows minimal temperatures of litter Table 2. Symbols and units Symbole und Einheiten Symbol Parameter Unit Θ L ; Θ L1 ; Θ L2 temperature of litter surface C Θ Loc temperature of litter surface beneath bird C Θ Lf temperature of litter surface not occupied C by birds Θ 0 operative temperature C Θ 0oc operative temperature of resting birds C Θ 0f operative temperature of birds in C movement Θ i real indoor air temperature at the level of C birds heads Θ opt required indoor air temperature at the level birds heads C surface which correspond to temperatures of litter not occupied by birds or occupied by birds in movement. The characteristic feature of curve Θ Lf was that from the beginning of the breeding cycle it ran closely to curve Θ i ; then in weeks 3 and 4 both temperatures were the same, which means that from week 4 on birds were able to find a spot whose thermal conditions approximated their thermal comfort. From week 4 on, Θ Lf was in a constant rise reaching the level of C, which can be accounted for by a systematic weight gain of chickens. The production reduction by 4,000 chickens on the 42 nd day of the production cycle mostly influenced Θ Lf, which fell by over 7 K. The values of Θ 0f and Θ 0oc also gradually decreased. Θ 0oc fell from approx. 35 to approx. C and Θ 0f from approx. to approx. C. Θ L1, Θ L2 and Θ i values in selected weeks presented in Figures 2a h reveal an increasing tendency and the dominance of Θ L1 and Θ L2 from week 4 of the rearing cycle until the day of production reduction (day 42). All these temperatures featured wide amplitudes in the period between week 3 and 5 of the rearing cycle. Day of the rearing cycle was notable for a significant rise of litter temperature Θ Lf (see Figure 1), which was a result of population increase to 43 kg m 2 (17.9 birds per m 2 ). If there had not been the partial population reduction on day 42, one would expect the temperatures Θ Loc and Θ Lf to become the same around day 48 of the cycle. After that stocking density decreased to 33.4 kg m 2 (13.9 birds per m 2 ), which was accompanied by a significant drop of Θ L1 and Θ L2 (see Figure 2h) caused by a decrease of heat flow from resting birds and reduction of biothermal processes in the litter (BIEDA and NAWALANY, 06). It has been observed that the unoccupied area of the production hall, left by birds delivered for slaughter (including the measurement field A), was very quickly covered by the remaining birds. As a result, Θ Lf started to rise again (see Figure 1). Resting time of chickens as well as litter surface temperature changes in the measurement field are presented in the chart in Figure 3. According to the curve Θ L, it was about 11 minutes and ended when the litter under the bird reached the same temperature as the bird s body. After 9.5 minutes, litter surface temperature under a resting broiler chicken increased by 10.7 K, and within 27 minutes from the moment the bird left the litter, it decreased by 9.8 K.

3 Nawalany: Evaluation of thermal conditions in the broiler living zone ΘLoc Θ0oc ΘLf Θ0f Θopt Production cycle (days) 49 Figure 1. Extreme temperatures of litter surface (Θ Lf and Θ Loc ), real indoor air temperature (Θ i ), optimal air temperature (Θ opt ) and calculated operative temperatures (Θ 0f and Θ 0oc ) Verlauf der Extremtemperatur der Einstreuoberfläche (Θ Lf und Θ Loc ), der tatsächlichen Innenlufttemperatur (Θ i ), der optimalen Lufttemperatur (Θ opt ) und der berechneten, fühlbaren Temperatur (Θ 0f und Θ 0oc ) a b c d 3:00 3:15 3: 3:45 11:00 11:15 11: 11:45 13:00 13:15 13: 13:45 Time (hours:minutes) 14:00 14:15 14: 14:45 e f g h 9:00 9:15 9: 9:45 12:00 12:15 12: 12:45 2:00 2:15 2: 2:45 13:00 13:15 13: Time (hours:minutes) Serie2 ΘL1 Serie4 ΘL2 Serie1 13:45 Figure 2.Temperature of litter surface (Θ L1 and Θ L2 ) and indoor air temperature (Θ i ): a 7 th day of life, b 14 th day of life, c 21 st day of life, d th day of life, e 35 th day of life, f 41 st day of life, g 42 nd day of life (2:00 3:00), h 42 nd day of life (13:00 14:00) Verlauf der Temperatur der Einstreuoberfläche (Θ L1 und Θ L2 ) sowie der Innenlufttemperatur (Θ i ): a 7. Lebenstag, b 14. Lebenstag, c 21. Lebenstag, d. Lebenstag, e 35. Lebenstag, f 41. Lebenstag, g 42. Lebenstag (2:00 3:00), h 42. Lebenstag (13:00 14:00)

4 52 Nawalany: Evaluation of thermal conditions in the broiler living zone ΘL Θ0f Θ0oc Θ0f 8: 8:45 8:50 8:55 9:00 9:05 9:10 9:15 9: 9:25 9: The 35. day of production cycle (hours:minutes) Θ0 Figure 3.Temperatures of litter Θ L, indoor air temperatures Θ i and operative temperatures for resting bird Θ 0oc and bird in movement Θ 0f in 35 th day of breeding cycle 8: 9:) Verlauf der Einstreutemperatur Θ L, der Innenlufttemperatur Θ i und der fühlbaren Temperatur für die ruhenden (Θ 0oc ) und die sich bewegenden (Θ 0f ) Broiler am 35. Lebenstag (8: 9:) 42 39ºC ΘL 5: 5:35 Θo 5: 5:45 5:50 5:55 6:00 6:05 6:10 6:15 6: The 42. day of production cycle (hours:minutes) 6:25 6: Figure 4. Real temperatures of litter surface Θ L, indoor air temperatures Θ i and operative temperatures Θ o in 42 nd day of rearing (5: 6:) Verlauf der tatsächlichen Temperatur der Einstreuoberfläche Θ L, der Innenlufttemperatur Θ i und der fühlbaren Temperatur Θ o am 42. Masttag (5: 6:) The second process took more time because the heat transferred to the litter by a resting bird generated a biothermal process in the litter and accompanying heat emission, which prolonged the cooling period. Discussion Short resting times of broilers (Figure 3) make it necessary to increase their physical activity, which may positively influence bone and brain growth (REITER and BESSEI, 09). Nevertheless it is still unclear how such short resting times affect bird welfare and productivity. Unfavourable thermal conditions of resting birds are presented in Figure 4 which shows temperature distribution 1 hour before the bird population was partly reduced. At times, the values of Θ L1 exceeded the temperature of birds' bodies (approx. 39 C) and for example at 6:11 it was about 41 C. At the same time, Θ 0 reached almost C, which is the level of thermal stress. After the population was reduced by 4,000 birds, Θ Lf and Θ 0f fell suddenly (see Figure 1) reaching the level close to thermal comfort. According to previous research (BIEDA and NAWALANY, 06), 2 or 3 population reductions starting from week 5 had a positive influence on Θ L. When reduction is not possible during the production cycle, a litter cooling system is recommended (NAWALANY et al., 10). Other solutions include subfloor ventilation or floor grating (BESSEI, 06). Studies conducted with various birds species in mass scale production farms confirm that controlling litter quality, its temperature and humidity were more important than population reductions (DAWKINS et al., 04). Previous multiannual observations of production cycles conducted by the author in various seasons of the year

5 Nawalany: Evaluation of thermal conditions in the broiler living zone 53 confirmed that litter significantly influences thermal conditions in the broiler living zone. Bird observations reveal that in the second half of the production cycle, when the temperature of the broiler living zone is mostly influenced by litter, chickens prefer cooler areas. Just after the procedure of population reduction has been finished, the emptied and cooled litter area is quickly occupied by the remaining birds, with crowd density temporarily larger than it had been before the population reduction. In the researched production cycle, Θ Loc >39 C was noted for 3 minutes in all, reaching the maximum value of 41.1 C. The longest periods of Θ Loc > 39 C were observed on day 33 and 42 and lasted 49 and 44 minutes, respectively. The analysis of Θ i reveals that for the most part of the production cycle this temperature was at a slightly higher level than Θ opt. In week 3, Θ i > Θ opt lies by approx. 3 K, and in weeks 4 to 6 by approx. 4.5 K, which contributed to the growth of Θ 0. The differences between Θ i and Θ opt can quite easily be reduced by means of a ventilation system, maybe except for extreme heat waves in summer. Thermal conditions in the broiler living zone are also significantly affected by population reduction around the th day of rearing. This did not only prevent sudden Θ Lf rise, but did also contribute to the cooling of litter across the area left by birds. The reaction of birds was movement into the cooled area of the production hall with new crowd density exceeding the state before population had been reduced. This emphasises the significance of Θ L for thermal conditions in the living zone occupied by broilers. Thus, BESSEI (06) was right in stating that high stocking density limits heat movement from litter, whose temperature increases. Also, the results of multiannual research conducted by the author confirm with all certainty that broiler stocking density contributes to Θ L growth (BIEDA and NAWALANY, 06). It is then advisable to follow BESSEI s (06) recommendations, like keeping birds on a floor grating or litter with subfloor ventilation, which successfully reduce unfavourable influence of high stocking density on bird growth rate. The evaluation of thermal conditions conducted on the basis of temporary or momentary physical parameters may be to some extent erroneous. Yet, the application of the proposed method of thermal conditions evaluation, based upon the monitoring of significant parameters, is more suitable for the decision-making process, e.g. regarding the size of bird population, partial population reduction, or modernization of the ventilation system. The suggestion to apply Θ 0 for the evaluation of thermal conditions inside the broiler house seems to be grounded for at least a few reasons. Firstly, it extends the monitoring scope of physical parameters of Θ L, which most significantly influences thermal conditions inside the broiler house from week 4 on. Secondly, knowing the value of Θ 0 and its trends makes it possible to counteract thermal stress and discomfort at every stage of rearing (for example by improving litter quality, adjusting Θ i to Θ opt, reducing the population, or cooling the litter). Moreover, combined with the knowledge of thermal preferences and thermal tolerance of birds, it enables optimal adjustment of thermal conditions for particular breeds and genetic lines. Θ 0 is a complex physical value, which in the conditions of air movement (v < 0.1 m s 1 ) in the broiler living provides reliable information on the current thermal condition of birds. Taking into consideration birds physical activity, Θ L should be measured in a constant manner with the help of electronic sensors with a logger, equipped with a display, which makes it possible to interpret Θ i, Θ L and Θ 0 trends. It seems reasonable to include continuous Θ L measurements into the system of thermal conditions monitoring inside a broiler house. In the future, it will be easier to determine Θ 0 after the introduction of coefficients which take into consideration the process of heat exchange through radiation, convection and heat transfer between a resting bird and the litter in real operating conditions of a mass scale broiler chicken production farm. Summary The paper presents results of temperature measurements at the level of birds heads, at the level of bedding under the birds, and in areas not occupied by birds, as well as measurements of optimal air temperature and the distribution of the calculated operative temperature in the course of a production cycle conducted in real life conditions of a mass scale production. The concept of operative temperature (Θ 0 ) was used to evaluate thermal conditions in the broiler living zone. It was calculated as an arithmetic mean of indoor air and litter temperatures. The application of operative temperature for the evaluation of thermal conditions in the broiler living zone seems to be adviced as it extends the scope of physical parameters to be monitored by the temperature of litter surface and provides data necessary to monitor and regulate litter temperature or reduce stock density in order to prevent thermal stress or discomfort. Key words Broiler house, thermal conditions, operative temperature Zusammenfassung Ein Vorschlag zur Verwendung der fühlbaren Temperatur zur Bewertung der Temperaturbedingungen in der mittelbaren Haltungsumwelt von Broilern Der Beitrag präsentiert Ergebnisse von umfangreichen, kontinuierlichen Temperaturmessungen in großen, kommerziellen Broilerställen auf Kopfhöhe der Tiere, auf der Oberfläche der Einstreu unterhalb der Tiere und in Bereichen, die nicht von Tieren besetzt sind, sowie die berechneten, optimalen und durch die Tiere fühlbaren Temperaturen. Hierzu wurde das Konzept der fühlbaren Temperatur (Θ 0 ) zur Beschreibung der thermischen Bedingungen in der Umgebung der Hähnchen verwendet. Diese Temperatur wurde als arithmetisches Mittel der Innenluft- und Einstreutemperatur berechnet. Die Verwendung der operativen Temperatur zur Bewertung der thermischen Bedingungen in der Umgebung der Broiler wird als zweckmäßig angesehen, da durch die Messung der Temperatur der Einstreuoberfläche die physikalischen Regelparameter erweitert werden. Hierdurch können z.b. Entscheidungshilfen für eine Verminderung der Besatzdichte geliefert werden, die eine Beeinträchtigung des Wohlbefindens der Broiler und das Auftreten von thermischem Stress reduzieren kann. Stichworte Broiler Haus, thermischen Bedingungen, operative Temperatur

6 54 Nawalany: Evaluation of thermal conditions in the broiler living zone References BIEDA, W., M. KOŹBIAŁ, 1999: Effect of litter, floor and ground on thermal conditions of broiler house in the winter period (in polish). Roczniki Nauk Zootechnicznych, BIEDA, W., G. NAWALANY, J. RADOŃ, 03: Temperature of bedding during floor keeping of broilers. In: Scientific Network Agrorisks. IBMER, Warszawa, BIEDA, W., G. NAWALANY, 06: Effect of broiler-house stocking density on temperature of bedding and thermal conditions in the living area of birds. Annals of Animals Science 6, 1-3. BESSEI, W., 06: Welfare of broilers: a review. World s Poultry Science Journal 62, DAWKINS, M.S., S. DONELLY, T.A. JONES, 04: Chicken welfare is influenced more by housing conditions than by stocking density. Nature 427, 2-4. HERBUT, E., Z. DOBRZAŃSKI, W. BIAŁAS, 1993: Thermal conditions of the environment in broiler chicken rearing. (in polish). Biuletyn Informacyjny IZ, R. XXXI, NAWALANY, G., W. BIEDA, J. RADOŃ, 04: Thermal and moisture parameters of broiler house litter in light of research. Annals of Animals Science 1, NAWALANY, G., W. BIEDA, J. RADOŃ, 10: Effect of floor heating and cooling of bedding on thermal conditions in the living area of broiler chickens. Arch. Geflügelk. 74, REITER, K., 06: Behaviour and welfare of broiler chicken. Arch. Geflügelk.,70(5), REITER, K., W. BESSEI, 09: Effect of locomotor activity on leg disorder in fattening chicken. Berliner und Münchener Tierarztliche Wochenschrift 1, EN ISO 77, 05: Ergonomics of the thermal environment Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria. Correspondence: G. Nawalany, Katedra Budownictwa Wiejskiego, Uniwersytet Rolniczy w Krakowie, Al. Mickiewicza -, -059 Kraków, Poland: kbw@ur.krakow.pl Buchbesprechung Gänsezucht und Gänsehaltung Dr. Karl-Heinz Schneider, Gänsezucht und Gänsehaltung Das Handbuch für die Praxis; Verlag Oertel & Spörer Reutlingen, 2. überarbeitete Auflage, über 50 meistens farbige Abbildungen und mehr als 50 Tabellen, 183 Seiten, Preis 19,90 Euro, ISBN Gänse sind das am längsten domestizierte Wirtschaftsgeflügel. Sie werden wegen Ihrer Wachsamkeit, dem wärmenden Gefieder und dem wohlschmeckenden Fleisch geschätzt. Entsprechend war auch in Deutschland die Gänsehaltung zur Gewinnung von Daunen und Federn sowie zur Lieferung des Festtagsbratens zu Weihnachten bis in die Mitte des. Jahrhunderts weit verbreitet. Auch wenn heute noch in Deutschland Bettwaren mir Gänsedaunenund Gänsefedernfüllung gefragt sind und der Anteil der Bevölkerung, der zu Weihnachten einen Gänsebraten bevorzugt, zunimmt, ist die Gänsehaltung eher eine Nischenproduktion. Der Pro-Kopf-Verbrauch an Gänsefleisch liegt bei 0,3 kg/jahr und der Selbstversorgungsgrad beträgt nur rund 10%. Das heißt, dass etwa 90% des in der BRD jährlich verzehrten Gänsefleischs vor allem aus Polen und Ungarn kommen. Eine weitere Nutzung der Gänse war lange Jahre das Stopfen zur Fettleberproduktion, das aber heute in Europa nur noch in Frankreich betrieben wird. Nichtsdestotrotz kann es auch heute noch interessant sein, Gänse zur Bettfederngewinnung und zur Fleischerzeugung zu nutzen. Hier darf auch nicht die landschaftspflegerische Leistung der Gänse durch den üblichen Weidegang unterschätzt werden. Mit dem vorliegenden Buch zur Gänsehaltung, das vom Autor auch als Handbuch für die Praxis verstanden sein will, hat Dr. Karl-Heinz Schneider ein sehr interessantes Nachschlagewerk geschaffen. Dr. Karl-Heinz Schneider hat sich in seiner beruflichen Tätigkeit als wissenschaftler Mitarbeiter an der Universität Leipzig und als Leiter der Forschungseinrichtung Schlobachshof sehr intensiv mit der Gänsehaltung befasst. Diese Leidenschaft ist ihm auch in seinem Ruhestand geblieben. Nicht umsonst gilt der Autor als der Gänsespezialist in Deutschland. In seinem Buch gibt Herr Kollege Schneider zunächst einen Überblick über die Domestikations- und Nutzungsgeschichte der Gänseproduktion. Auf über Seiten werden die Wildform Graugans und die noch in Deutschland existierenden Rassen beschrieben. Neben den rassetypischen Angaben werden vor allem viele Leistungsdaten und auch Tipps und Tricks zur Haltung präsentiert. Ein weiteres Kapitel befasst sich mit den biologischen Grundlagen, wobei auch intensiv auf die Federbildung eingegangen werden. Das Kapitel Vererbung und Zucht gibt einen Einblick in die genetische Determination von Leistungsmerkmalen bei Gänsen, in die geeigneten Zuchtverfahren und in die praktische Zuchtarbeit. Informationen zur Ernährung und Fütterung fehlen ebenfalls nicht. Neben allgemeinen Grundlagen zu Nährstoffbedarf und Futtermitteln wird auch auf die praktische Fütterung der Gänse eingegangen. Ein umfassendes Kapitel widmet sich der Brut natürlich und künstlich da hier die Grundlagen für gesunde Gössel und sich gut entwickelnde Gänse gelegt wird. Das letzte größere Kapitel beschreibt die Haltungsverfahren und befasst sich auch mit der tierschutzkonformen Gewinnung von Federn sowie der Gesunderhaltung. Den Abschluss bilden das Literaturverzeichnis und das gut strukturierte Register. Das Buch selber besticht durch eine sachliche, schnörkelfreie Beschreibung der einzelnen Themenbereiche. Es ist flüssig zu lesen, leicht verständlich und doch wissenschaftlich exakt geschrieben. Die vielen Abbildungen und Tabellen sind alle aussagefähig sowie klar in der Darstellung und ergänzen den Text hervorragend. Das Buch Gänsezucht und Gänsehaltung von Dr. Karl- Heinz Schneider wird ohne Frage dem Anspruch, ein Handbuch für die Praxis zu sein ohne Einschränkungen gerecht. Die langjährige Erfahrung des Autors auf diesem Gebiet spiegelt sich in dem Werk wider. Dieses Buch kann daher allen Praktikern, aber auch Hobby-Gänsehaltern und Studierenden der Agrarwissenschaften oder Veterinärmedizin mit Interesse an Gänsen wärmstens empfohlen werden. M.A. Grashorn