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Biomedical subjects

C J Thwaites

Publications and source records attributed to C J Thwaites.

At least 19 recordsLinked to original sources
PubMed1999

Effects of treadmill exercise on sweating in three breeds of goats.

OBJECTIVE: To compare the sweating responses of three breeds of goats to exercise at 30 degrees C. DESIGN: Factorial experiment with two goats of each of three breeds exercised for 60 min at 3 km/h and 30 degrees C on 6 days. PROCEDURE: Two mature females of the Anglo-Nubian, Saanen and Toggenburg breeds were used. Rectal temperature, respiration rate and sweating rate at three sites were recorded every 20 min during six replicates of exercise at 48 h intervals on a treadmill. RESULTS: Respiration rate varied with time and breed (P < 0.01) and increased from 20 +/- 2 breaths/min to 135, 195 and 260/min after 60 min exercise in Anglo-Nubian, Saanen and Tottenburg goats, respectively. Bread differences in rectal temperature were small but significant (P < 0.001), and mean values increased from 38.9 degrees C before exercise to 39.7 degrees C after 1 h exercise. The breed x sites interaction for sweating was significant (P < 0.01). On the rump breed differences in sweating rate were not significant. On the loin, Toggenburg goats started to sweat most rapidly and reached maximal values of 80.2 +/- 10.6 g/m2/h after 20 min and then decreased to 70.0 +/- 4.3 g/m2/h at 60 min. Sweating rate on the ear was highest in Toggenburg goats, followed by those of Saanen and Anglo-Nubian goats (P < 0.05), but the differences were small (7 g/m2/h); peak values of 67.3 to 76.1 g/m2/h were recorded after 20 min. CONCLUSION: Respiration and sweating rates increased significantly during exercise in all three breeds of goats, but breed differences were marked only for respiration rate. The goats sweated more on the rump than on the loin on ear, with peak values after 40 min of exercise.

Analysis of Variance↗
PubMed1993

Evaluation of ram semen motility by a swim-up technique.

The turbidity formed as ram spermatozoa swam up into a clear medium was measured using a colorimeter and this was used as an objective index of sperm motility. Wavelengths of 470-475 nm yielded higher optical densities (OD) than did 520-640 nm. The recommended distance between the light beam and semen-medium interface, and operation temperature were 5 mm and 30-37 degrees C, respectively. Of seven media tested, Tris-glucose was preferred on the basis of results, availability and cost. Diluting semen before testing reduced OD, whereas increasing semen concentration (0.6 to 2.4 x 10(9) spermatozoa ml-1) and the total number of spermatozoa used increased OD. OD gradually increased with time in all experiments (P < 0.001). High positive correlations between OD and known percentages of motile spermatozoa (0.82-0.91 at from 5 to 20 min, all P < 0.001) suggest that this swim-up technique, which is objective and inexpensive, is valid for measurement of sperm motility in rams.

Animals↗
PubMed1992

Relationships between the results of a modified sperm penetration test and a swim-up technique and the fertility of ram semen.

Two relatively simple techniques for the objective measurement of semen quality, and which are easy to apply in the field or laboratory, have been developed: a modified sperm penetration test read by the naked eye and a colorimeter-based swim-up technique. Both the modified sperm penetration and swim-up methods produced promising results in prediction of ram fertility; the modified sperm penetration test was correlated (P<0.05) with a 48-day nonreturn rate and a 60-day conception rate; the correlation between a swim-up velocity and the 60-day conception rate approached significance (r=0.483; 0.1>P>0.05).

Journal Article↗
PubMed1992

Comparison of a swim-up technique with the Hamilton Thorn Motility Analyser for measurement of sperm velocity and motility.

A colorimeter-based swim-up (SU) technique was developed and compared with a Hamilton Thorn Motility Analyser (HTM) for the evaluation of ram semen. SU parameters (sperm velocity in microns s-1, proportion of rapidly moving spermatozoa, and motility index) were significantly correlated (r from 0.47 to 0.98, P from < 0.05 to < 0.001) with most HTM parameters in semen containing known proportions of motile and immotile spermatozoa and in semen that was cold shocked, aged, diluted-stored and frozen-thawed. There were, however, no significant correlations between sperm velocity and HTM parameters in the fresh semen studied, possibly because of the small number of observations (n = 21) and narrow range of semen quality (83 +/- 2% subjectively scored motility) available. It is concluded that the swim-up technique is a simple, cheap, objective and reliable means of measuring sperm velocity and motility in ram semen.

Animals↗
PubMed1990

The effects of elevated temperature and humidity on rectal temperature and respiration rate in the New Zealand white rabbit.

In 2 replicated factorial experiments, 7-h climate chamber exposures were used to study the responses of adult NZW rabbits to a range of elevated temperatures and humidities. At 18 mm Hg water vapour pressure, 23.8 degrees C was well tolerated, rectal temperature (RT) and respiration rate (RR) averaging 38.6 +/- 0.3 degrees C and 82.9 +/- 15.5 breaths/min, respectively. Both parameters were elevated (P less than 0.001) at 32.2 degrees, 37.8 degrees and 43.3 degrees C. RT and RR reached plateau levels of 39.5-40.1 degrees C and 410-460/min at 32.2 degrees C, which was tolerated for the full 7-h test period. Test temperatures of 37.8 degrees and 43.3 degrees C, on the other hand, could be tolerated for only 80 and 40 min respectively, before RT reached the safe upper limit of 41.7 degrees C. Final RR values at 37.8 degrees and 43.3 degrees C were 701.6 +/- 42.7 and 812 +/- 55.1/min, respectively. In a 34.5 degrees C atmosphere a humidity of 21 mm Hg water vapour pressure was classified as "dry", and was tolerated for 323 +/- 123 min. RT and RR increased by 0.6 degrees C and 316/min during the first 20 min of exposure (P less than 0.05). Thereafter both parameters increased progressively, but with no significant differences between successive recording periods, until RR reached 550.3 +/- 88.8/min at 41.7 degrees C RT. Humidities of 25, 29 and 33 mm Hg water vapour pressure were, on the other hand, classified as "wet" and were tolerated for only 92 +/- 22, 81 +/- 16 and 119 +/- 50 min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Development of sweating ability in winter- and summer-born Friesian calves aged 1 to 6 weeks.

Sweating rate, rectal and skin temperatures and respiration rate were measured at weekly intervals from 7 days of age (for 4 weeks in Experiment 1; 6 weeks in Experiment 2) in winter- and summer-born Friesian calves exposed to a temperature of 39 degrees C dry bulb and 32 degrees C wet bulb in a climate chamber. Four calves were studied in each season in both experiments. In Experiment 1, ambient temperatures were from 3 degrees to 9 degrees C higher in early summer than in late winter. During each 39 degrees C exposure, sweating rate increased from basal levels of 40-90 to plateau levels of 120-300 g/m2 per h after 90-120 min. The increase in sweating rate with age was most pronounced in winter-born calves, but summer-born calves had higher values at 1 week of age (167 +/- 52.4 vs 94.4 +/- 30.1 g/m2 per h). Seasonal differences in ambient temperature were greater in Experiment 2 (11 degrees to 17 degrees C). In this case summer-born calves had higher sweating rates at each age (plateau values of 220-320 g/m2 per h), and showed a more rapid increase in sweating rate during each 39 degrees C exposure than winter-born calves (plateau values of 100-250 g/m2 per h). The results demonstrate major changes in sweating competence during the first 4-6 weeks of life in Friesian calves, a quite pronounced effect of season (ambient temperature) on the levels of sweating achieved, and indicate that low sweating rates in newborn calves are a contributing factor in deaths due to hyperthermia in semi-arid grazing areas.

Age Factors↗
PubMed1975

Fertility and sperm transport in Merino ewes at the first oestrus following embryonic death.

The embryos of ewes were killed with colchicine on Day 17 of gestation and the ewes were mated at the subsequent oestrus. Fertility was reduced at this mating, and fewer spermatozoa were found in the uterus and oviducts than in control animals. The total number of spermatozoa in the cervix and their distribution between the lumen and walls of the cervix were not altered, but the linear distribution along the cervical walls was changed. The density of the reamining spermatozoa in the control animals after flushing the cervix showed a progressive decrease from the posterior to the anterior segments. This did not occur in the untreated ewes. It seems likely that impaired sperm transport contributed to the lowered fertility.

Analysis of Variance↗