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Abstract SUMMARY This experiment was carried out on rabbits of three breeds raised in the experimental farm of the Faculty of Agriculture at Moshtohor during the period from October 1980 to September 1981. A respective total nuniliersof 121, 194 and 100 progeny weaned from 13,21 and 10 does of Giza White, Bauscat and Grey Flander were utilized to study the heat tolerance traits (body tempera.ture and respiration rate) and their effects on some productive traits. Depending upon the available numbers of females within each breed 4, 4 and 3 sire groupS were formed from Giza White, Bauscat and Grey Flander, respec~ively. Mating of related animales was avoided to prevent inbreeding depression. Single pair mating design was used to estimate heritability and to evaluate the genetic and the phenotypic correlation coefficients between the studied traits. R€:sul ts obtained can be summarized as follows: A. Heat tolerance traits in does: 1) Both Giza White and Grey Flander doe8 recorded nearly the aame body temperature (about 39-.00C) and ’>88piration rate (145.9 per minute), while the respective measurements in Bauscat doel!!J were about 40.00C and 150.3 per minute. 92 2) Both morning body temperatufe (39.23°0.) and rel!lpirationrate (144.7 per minute) were relatively l~~er than the respective afternoon values (39.38°C and 149.9 per minute). 3) Both winter body temperature (39.03°C) and respiration rate (129.4 per minute) were significantly lower than the respeotive summer values (39.640C and 168.9 per minute). 4)Weight of doe had no significant effect on both body temperature and respiration rate either in.the morning or ~ the afternoon. 5) Both body temperature and respiration rate were slightly decreased with advanc1ng age, though d1.fferences in each trait were significant in only B~~uscat does. 6) Neither pregnancy nor suckling status had s:tgnificant effects on both body temperature and rE~spiration rate in Giza White and Grey Flander dnas. However, suckling status had significant e~rfecton both traits of heat tolerance in BaUl!lcat 93’ B. Heat tolerance traits in offspring: 1) Both Giza ~hite and Bauscat rabbits were nearly of the eame body temperature and respiration rate, while Grtey Flander recorded slight lower va.lues in most comparable ages. 2) Both morning body temperature (39.l8°C) and respiration rate (163.7 per minute) w,ere lower than the respeotive afternoon values (39.34°0 and 186.7 per minute). 3) Both males and females of all breeds had similar body temperature (39.27°C) and respiration rate(175.1 per minute). 4) Both body temperature and respiration rate were s:l.gnifieantly increased by increasing air temperature a1: most ages. 5) Both winter bodY’ temperat~e (39.26°0) and rElspirat10n rate (170.0 per minute) were significantly lower than the respect,ive summervalues (39.28°0 and 1131.7 per minute) • .” 6) Individual body weight had non-s1gJlifieant effects on each of body temperature and respiration ~~~-~-~._-----~--~------~---------~----_/ 94 c. Effect of heat tolerance reactions on productive traits: 1) Each of body temperature and respiration rate of does had no significant effect on both litter size and litter weight at birth in the three breeds studied. 2) Each of body temperature and respiration rate of rabbits had no significant effects on their body weight at most studied ages. D~ Genetic parameters: 1) Heritability estimates of bdoy temperature in Giza White were relatively higher than those of BaUBcat rabbits either in the morning or in the afternoon. 2) Nearly heritability values of respiration rate were estimated for Giza \fhite and Bau8cat rabbits in the morning, while the afternoon estimates were almost negative. 3) Body temperature at a given time of measurement WB.S possitively associated with respiration rate at that time. 4) No consistent trend for the association between body weight and each of heat tolerance traits at all ages was detected. 95 ACKNOWLEDGMENT The author wishes to express his deep warm gratitude, obligation and full appreciation to Prof. Dr. E.A. Afifi Professor of Animal Br.eeding and Head of Animal Production Department and to Dr. M.S. Hanafi Associate Professor of Animal production, Faculty of Agriculture at Moehtohor, Zagazig University, Banha branch for suggesting the problem, planning this work, effective guidance, supervision, valuable help, critical cristicism, considerable interest and effective enoouragement during the haJ:”dtime and throughout the life span of this work. ------------------~~---------------_./ |