The Development of resistance to cooling in baby rabbits

Abstract

The studies were carried out on baby rabbits born in autumn or spring in cages kept in an open shed. The air temperautre in the shed varied from 2 to 25°C but the nest temperature was almost independent of these changes and in the coldest part of nest amounted to 20-26°C. The normal body temperature of baby rabbits 1 hr after birth was equal to 34.2°C. During the first day it rose to approximately 37°C but then the increase was more slow and after 1 month it reached the normal temperature of adult rabbits (39.6°C). New-born rabbits kept separately are not able to maintain a constant body temperature even at relatively high ambient temperatures. The resistance to cooling, however, develops rather quickly. In 20°C 6-day-old rabbits retain constant body temperature and in 8°C 12-day-old specimens. The rate of body cooling of baby rabbits exposed to cold decreases with the age and this decrease is faster than the reduction of the relative body surface area (cm 2 /g). The increase of resistance to cooling in baby rabbits during first 8 days after birth may be partly explained by the improvement in the mechanism of vasomotor regulation of the heat losses and probably also by the augmented rate of heat production. From the eighth day after birth the hair cover plays more important role in thermal economy of baby rabbits.

Impact of rearing mangement on health in domestic rabbits: a review

“…During the first 10-12 postnatal days, the kits have only a limited capacity for independent thermoregulation (Poczopko, 1969;Hull, 1973 and typically huddle together and actively cover themselves with the nest material by crawling under it (Hudson and Distel, 1982;Bautista et al, 2008). On about postnatal day 17-20, the kits emerge from their breeding burrow and start to explore the environment (Broekhuizen et al, 1986).…”

Changes in thermogenesis and its hormonal regulators during the postnatal development of rabbits and guinea pigs

“…Hence the body temperature of newborn rabbits decreases rapidly even at relatively high ambient temperatures, e.g. at 20 or even 30 C (Daves & Mestyän, 1963;Hull, 1965;Poczopko, 1969), whereas in newborn guinea pigs hvpothermy is not observed even after the animals have remained an hour in a temperature of 8°C (B a r i ö, 1953; Daves & Mestyän, 1963;Brück & Wünnenberg, 1965a).…”

“…During measurements the animals were kept under resting metabolism conditions, that is, in a state of complete physical rest and at thermoneutrality but were not fasted before measuring. Choice of neutral ambient temperature for young rabbits of different age was made on the basis of the study by Hull (1965) and Poczopko (1969) and for guinea pigs on the study by Brück & Wünnenberg (1965a The animals were taken out from their mothers and placed in a respiration chamber. After equilibrium had been established (20-30 minutes) measurements of O, intake and C0 2 emission were begun, which lasted about 40 minutes.…”

Heat economy and the energy cost of growth in the bank vole during the first month of postnatal life

“…Barnett, 1956;Lagerspetz, 1962), ra ts (e.g. Capek et al, 1956; Poczopko, 1961) a n d dom estic an im als: pigs (Mount, 1968), ra b b its (Poczopko, 1969).…”

“…BODY TEM PERATURE AND RESISTANCE TO COOLING I t is n o t easy to d e te rm in e th e body te m p e ra tu re of n e s tlin g voles, as m e a su re m e n ts o u tsid e th e n e st cause u n d e re stim a tio n , a n d d a ta on n e st te m p e r a tu re can n o t be id e n tifie d w ith th e body te m p e r a tu re of th e y o u n g liv in g in it (Barnett, 1956;Poczopko, 1969;McManus, 1971). T h e re fo re on ly d ire c t m e a su re m e n t of th e a n im a ls' body te m p e r a tu r e s can in d ic a te th e th e rm a l conditions d u rin g th e ir d ev e lo p m e n t in th e n est.…”