Zebu, Jersey, and Zebu x Jersey crossbred heifers were subjected to a rising temperature regime over the range 65 to 105°F. Sweating rates, respiration rates, skin temperatures, and rectal temperatures were measured. All breeds showed similar responses in skin temperature and rectal temperature to increase in air temperature. The increase in skin temperature was approximately linear with rise in air temperature. Rectal temperature did not commence to rise until an air temperature of 90°F and a skin temperature of 98° was reached. Breed differences in sweating and respiratory rates with increase in air and skin temperature were observed. The Jersey heifers showed an early and almost linear increase in sweating rate with rise in air and skin temperature, whereas the sweating rate of the Zebu heifers did not increase until air temperature had risen to at least 85°F and skin temperature to 95°. Two crossbreds began to increase their sweating rates at temperatures intermediate between those recorded for Zebus arid Jerseys. The remaining two behaved similarly to Jerseys. All three breeds showed similar maximum sweating rates in response to this rising temperature regime. The respiratory rate of' the Jerseys was higher than that of the Zebus at all temperatures, and particularly at high temperatures. Crossbreds respired at rates comparable to the Jerseys until an air temperature of 90°F and a skin temperature of 97°F were exceeded, when their respiration rates became intermediate between the other two breeds. The significance of these differences is discussed.
(1) The distributions of living and dead sperm in the oviducts of hens a t various time intervals after artificial insemination were determined by using sperm labelled with 32P and assaying the radioactivity of serial sections of the oviduct. Appropriate. tests of the method showed it to be valid and reasonably accurate for short-term experiments. (2) The number of sperm reaching the site of fertilization at the upper end of the oviduct (the infundibulum) was dependent primarily on where in the lower genital tract the sperm were deposited. Following intravaginal insemination with 2 X 108 sperm, from 7 X 103 to 70 X 103 sperm were detected in the infundibula of different hens up to 1 hr after insemination. After intra-uterine insemination with a like number, from 137 X 103 to 2642 X 10103 sperm were detected. (3) The junction of the vagina and uterus (or shell gland) proved to be a barrier to sperm progress, as was shown by the greater efficiency of sperm utilization above the junction than below it. (4) Dead sperm inseminated intravaginally did not pass into the uterus but those inseminated into the uterus reached the infundibulum in as great numbers as a similar sample of living sperm. This suggested that the mechanism of sperm transport differs on either side of the uterovaginal junction. (5) From the speed of transport of sperm and the passage up the oviduct of sperm-free fluid injected into the uterus, it is suggested that the spasmodic contraction of muscle investing the wall of the upper vagina and lower uterus induced as a response to tactile stimuli is mainly responsible for sperm movement from the uterovaginal junction to the infundibulum. (6) Motility of sperm is necessary only to traverse the vagina and perhaps to penetrate the vitelline membrane of the egg during the process of fertilization. At other stages of movement between the vagina and the egg, sperm play a passive role in their own transport.
SUMMARYMoisture content of the coats of cattle, expressed as the percentage of the dry weight of hair, has been measured in a wide variety of environmental conditions in summer, springand winter. Strips of coat were clipped from 25 Jersey, 15 Zebu x Jersey crossbred and 9 Hereford heifers in a shed, in a climate room under warm, hot dry and hot humid conditions and outdoors both in sun and shade. Moisture content, weight of coat per unit area, depth of coat, skin and rectal temperatures, sweating and respiratory rates, air temperatures and vapour pressures were measured.The mean moisture content of the coats varied in the different environments from 5·8 to 27·5 % and mean sweating rates from 28 to 438 g m-2 h-1. Moisturein summer coats out of doors in the sun averaged 11·2% and was about the same as that outof doors in the shade. In the shed, coat moisture was also low (average 11·8%) and amounted to less than half of the moisture content of clipped hair in equilibrium with a near saturated atmosphere. Herefords that had been fed a low plane ration from winter to summer, retained their long winter coats and these, in summer, had only half the moisture content of the short coats of normally fed Herefords. In the hot room, the moisture content of summer coats was usually higher than out of doors and varied around 18%.The inner part of the coat had more moisture than the outer part and estimates of moisture gradients were made. Calculation of the contribution of sweating to total moisture in indoor environments showed that, at rapid rates of sweating, it was about 8% and was higher in winter andspring coats than in summer coats (Fig. 3). It was estimated that sun and wind reduced the moisture content of summer coats by about 3% in outdoor summer environments. The effect of sun and wind on moisture content of winter coats in the same environment was estimated at nearly 9%.The results suggest that the site of evaporation was at the skin except in very hot humid indoor environments when some free moisture may have been present in the hair.
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