Scrotal Surface Research Articles

Changes in the scrotal temperature of subjects in a sedentary posture over a heated floor

As Koreans habitually sit on the heated floor in their residential buildings, the male testis is directly exposed, and is therefore affected by the floor surface temperature. The purpose of this study was to investigate the changes in the scrotal temperature of the subjects in a sedentary posture over the heated floor. A rigid screening test was performed to select healthy subjects. Finally, six college students volunteered to participate in the experiments. Two experiments were performed in a controlled environmental chamber. Experiment I was designed for a low metabolism state, with the subjects reading a book in a sedentary posture for 50 min. The floor surface temperature (tf) was controlled by varying the temperature of water (tw) flowing into the floor coil from 15 to 50 degrees C, at 5 degrees C intervals. Experiment I revealed that the final scrotal surface temperature was 32.27, 32.62, 33.51, 33.34, 34.14, 34.28, 34.34 and 35.04 degrees C at the tw 15 degrees C (tf 17.0 degrees C), 20 degrees C (tf 20.8 degrees C), 25 degrees C (tf 24.1 degrees C), 30 degrees C (tf 27.8 degrees C), 35 degrees C (tf 31.7 degrees C), 40 degrees C (tf 35.9 degrees C), 45 degrees C (tf 38.6 degrees C) and 50 degrees C (tf 42.2 degrees C), respectively. At tf 17.0 and 20.8 degrees C, the scrotal temperature exhibited a declining pattern and a low temperature for spermatogenesis. At tf 24.1, 27.8 and 31.7 degrees C, however, the thermal regulatory system of the scrotum and testis was activated appropriately. On the contrary, scrotal temperature ascended at tf 35.9, 38.6 and 42.2 degrees C. Of the six subjects, two subjects demonstrated scrotal temperatures above 35 degrees C at tf 38.6 degrees C and four subjects exhibited scrotal temperatures above 35 degrees C at tf 42.2 degrees C. Experiment II was designed for a high metabolism state, with the subjects playing a card game in a sedentary posture for 180 min. The tf was controlled by varying the tw from 30 to 40 degrees C, at 5 degrees C intervals. Experiment II revealed that the final scrotal temperature was 33.43, 34.78 and 35.61 degrees C, and the difference between the initial and final scrotal temperatures was +0.34, +1.06 and +2.24 degrees C, at tw 30 degrees C (tf 27.8 degrees C), 35 degrees C (tf 31.7 degrees C) and tw 40 degrees C (tf 35.9 degrees C), respectively. The scrotal temperature was affected by the floor surface temperature and by the rate of metabolism of the subject in a sedentary posture. As derived from regression analysis, the recommended surface temperature of a heated floor is within 23-33 degrees C under the assumption that scrotal and consecutively testicular temperature above 35 degrees C impairs spermatogenesis.

Testicular thermoregulation in Bos indicus, crossbred and Bos taurus bulls: relationship with scrotal, testicular vascular cone and testicular morphology, and effects on semen quality and sperm production

Mechanisms of testicular thermoregulation, the relationship of scrotal, testicular vascular cone (TVC), and testicular morphology with thermoregulatory capability, and their effects on semen quality and sperm production were studied in 20 Bos indicus, 28 crossbred, and 26 Bos taurus bulls. The ratio of testicular artery length and volume to testicular volume were larger ( P<0.05) in B. indicus and crossbred bulls than in B. taurus bulls (1.03 and 0.94 cm/cm 3 versus 0.48 cm/cm 3; 0.034 and 0.047 ml/cm 3 versus 0.017 ml/cm 3, respectively). Testicular artery wall thickness (average 192.5, 229.0, and 290.0 μm, respectively) and arterial–venous blood distance in the TVC (average 330.5, 373.7, and 609.4 μm, respectively) were smallest in B. indicus, intermediary in crossbred, and greatest in B. taurus bulls ( P<0.05); the proximity between arterial and venous blood was consistent with the estimated decrease in arterial blood temperature after passage through the TVC (5.9, 5.0, and 2.9 °C, in B. indicus, crossbred, and B. taurus bulls, respectively). In crossbred and B. taurus bulls, there was a positive top-to-bottom scrotal temperature gradient and a negative testicular subtunic temperature gradient. However, in B. indicus bulls, both scrotal and testicular subtunic temperatures gradients were positive. Differences in the vascular arrangement, characteristics of the artery (e.g. wall thickness) or thickness of the tunica albuginea may have affected the testicular arterial blood and subtunic temperatures in B. indicus bulls. Better testicular thermoregulatory capability was associated with increased scrotal shape (pendulosity), testicular artery length and volume, and top-to-bottom gradient of the distance between the artery wall and the veins in the TVC. Increased semen quality was associated with increased testicular volume and scrotal subcutaneous (SQT) temperature gradient, and with decreased scrotal surface and testicular temperatures. Increased sperm production was associated with increased testicular artery volume, testicular volume, and SQT temperature gradient, and with decreased testicular artery wall thickness, scrotal circumference (SC), and scrotal surface, testicular subtunic, and epididymal temperatures. In conclusion, morphology of the TVC may contribute to the greater resistance of B. indicus bulls to high ambient temperatures by conferring a better testicular blood supply and by facilitating heat transfer between the testicular artery and veins. Testicular thermoregulation was associated with opposing scrotal and testicular subtunic temperatures gradients only in crossbred and B. taurus bulls. Scrotal, TVC, and testicular morphology influence testicular thermoregulatory capability and were associated with differences in semen quality and sperm production.

Effect of age and genetic group on characteristics of the scrotum, testes and testicular vascular cones, and on sperm production and semen quality in AI bulls in Brazil

The objectives were to determine the effects of age and genetic group on characteristics of the scrotum, testes and testicular vascular cones (TVC), and on sperm production and semen quality in 107 Bos indicus, B. taurus and cross-bred bulls at three artificial insemination (AI) centers in Brazil. In addition, predictors of sperm production and semen quality were identified. In general, scrotal circumference (SC), scrotal shape score, scrotal neck perimeter, and testicular size (length, width and volume) increased ( P<0.05) with age. Although there were no significant differences among genetic groups for SC or testicular size, B. indicus bulls had the least pendulous scrotal shape, the shortest scrotal neck length, and the greatest scrotal neck perimeter ( P<0.05). Fat covering the TVC was thinner ( P<0.05) in bulls ≤36 months of age and in B. taurus bulls than in older bulls and B. indicus bulls, respectively. Age and genetic group did not affect testicular ultrasonic echotexture. B. indicus bulls tended ( P<0.1) to have the lowest average scrotal surface temperature (SST). In general, ejaculate volume, total number of spermatozoa and number of viable spermatozoa increased ( P<0.05) with age. However, there was no significant effect of age on sperm concentration, motility, major and total defects. The proportion of spermatozoa with minor defects was highest ( P<0.05) in bulls 37–60 months of age. B. indicus bulls had higher ( P<0.01) sperm concentration, total number of spermatozoa and number of viable spermatozoa than B. taurus bulls, with intermediate values for cross-bred bulls. Increased sperm production was associated with increased testicular volume, SC, TVC fat cover, and SST top-to-bottom gradient. Decreased semen quality was associated with increased SC and bottom SST, and decreased scrotal shape, scrotal neck perimeter and vascular cone diameter. In summary, age and genetic group affected the characteristics of the scrotum, testes, and TVC, sperm production and semen quality. In addition, characteristics of the scrotum, testes and TVC were associated with sperm production and semen quality in bulls and could be assessed for breeding soundness evaluation.

Endocrine and thermal responses to GnRH treatment and prediction of sperm output and viability in Holstein-Friesian Breeding Bulls

A study was conducted to determine changes in serum LH and testosterone concentrations and in scrotal surface temperature (SST; measured with infrared thermography) following GnRH treatment and to predict the number of spermatozoa collected and the proportion that were viable. Holstein-Friesian breeding bulls (n=22, average age, 24.3 mo; range, 15 to 41 mo) were examined twice 30 d apart. Concurrently, semen was collected twice weekly with an artificial vagina. Treatment with GnRH (100 μg, im) increased (P<0.0001) serum LH and testosterone concentrations and increased (P<0.0001) SST (range 0.6 to 1.1°C; P<0.05) at the top and bottom of the scrotum. In regression models to predict the total number of spermatozoa, significant independent variables included ultrasonic echotexture of the testes (negative slope), scrotal width (positive slope) and SST at the bottom of the scrotum 45 min after GnRH treatment (positive slope). In regression models to predict the percentage of live spermatozoa, ultrasonic echotexture was a significant independent variable (negative slope). Measurement of testicular ultrasonic echotexture and SST after GnRH treatment augmented measurement of testicular size for predicting the number and percentage of live spermatozoa.

Contribution of the scrotum, testes, and testicular artery to scrotal/testicular thermoregulation in bulls at two ambient temperatures.

The objective of this study was to determine the contribution of the scrotum, testes, and the testicular artery to scrotal/testicular thermoregulation in bulls at two ambient temperatures. Crossbred beef bulls, 1.5 years of age, were placed in controlled environment chambers at ambient temperatures of 15 degrees C (n = 5) or 25 degrees C (n = 6). The distal lateral aspects and entire ventral part of the scrotum was incised under caudal epidural anaesthesia (xylazine, 0.07 mg kg-1. Both testes were withdrawn from the scrotum and then replaced and maintained by clamping the scrotal incisions with towel clamps. One testis was randomly chosen to be the exposed testis and was withdrawn prior to temperature measurements. Surface and internal temperature were measured with infrared thermography and needle thermocouples, respectively. Temperature gradients (degree C; difference in temperature from top to bottom at 15 and at 25 degrees C) were: scrotal surface (with testis), 1.5 and 1.3; scrotal surface (without testis), 2.1 and 1.6; surface of exposed testis, -0.6 and 0.0; sub-tunic of exposed testis, -2.2 and -0.6; intratesticular (covered testis), 0.0 and 0.4; and intratesticular (exposed testis), -1.3 and 0.4. The scrotum markedly affects testicular temperature but the testes have limited influence on scrotal surface temperature. The bovine scrotum and testes have opposing temperature gradients that complement one another, resulting in a relatively uniform intratesticular temperature. These temperature gradients are attributed in part to the testicular artery, which goes from the top of the testis to the bottom, divides into several branches and ramifies dorsally and laterally before entering the testicular parenchyma. Intra-arterial temperatures (measured with needle thermocouples) were lower (P < 0.05) where the artery entered the testis than at both the bottom and top of the testis for both the covered (31.7, 33.4 and 34.3 degrees C) and exposed testis (29.6, 32.0 and 32.5 degrees C) at an ambient temperature of 15 degrees C. Temperature differences were similar, but less pronounced, at 25 degrees C (covered testis, 34.8, 36.3 and 36.5 degrees C; exposed testis, 32.4, 33.5, 33.9 degrees C). Results supported the hypothesis that blood within the testicular artery has a similar temperature at the top of the testis (just ventral to the testicular vascular cone) compared with the bottom, but subsequently cools before entering the testicular parenchyma.

Relationship between scrotal infrared temperature patterns and natural-mating fertility in beef bulls.

The infrared temperature pattern (IRT) of the scrotal surface was recorded for 73 yearling beef bulls and a color video thermogram of the pattern of each bull was recorded. The average scortal surface temperature, temperature at the top and bottom of the scrotum, scortal temperature gradient, and thermal class (normal, questionable, or abnormal scortal surface thermal pattern) were recorded for each thermogram. Thirty-seven bulls had a normal temperature pattern (51%), 20 had a questionable pattern (27%), and 16 had an abnormal temperature pattern (22%). Bulls exhibiting abnormal scrotal temperature patterns had lower (P < .05) percentages of sperm exhibiting normal head and tail morphology and had a higher (P < .01) percentage of sperm with proximal droplets than did bulls with normal or questionable thermogram patterns. Thirty bulls with acceptable testis size and semen quality and representing the three thermal classes were each exposed single-sire to approximately 18 heifers during a 45-d pasture breeding period. Pregnancy rate was lower (P < .01) for bulls with abnormal scrotal temperature patterns (68 +/- 4%, n = 8) than for bulls with normal (83 +/- 4%, n = 13) and questionable temperature patterns (85 +/- 4%, n = 9), and pregnancy rate was related significantly to all four major characteristics (surface, top, and bottom temperatures and temperature gradient) of scortal thermograms. Data indicated that bulls with abnormal scortal temperature patterns exhibited a reduced ability to maintain an effective thermal gradient from top to bottom of the testes and that bulls with abnormal scrotal temperature patterns achieved reduced pregnancy rates when used for natural mating.

Effects of dietary energy on scrotal surface temperature, seminal quality, and sperm production in young beef bulls.

The objective of this study was to determine the effect of dietary energy, breed (British vs Continental x British crosses), and their interactions on scrotal surface temperature (SST), seminal quality, and sperm production in bulls. This experiment, replicated over 2 yr, included 72 Angus, Angus x Simmental, or Hereford x Simmental bulls fed either a moderate- (100% forage) or high-energy (80% grain, 20% forage) diet for 168 d after weaning. At the end of the feeding period, SST was determined by infrared thermography, seminal samples (two ejaculates) were collected by electroejaculation, and reproductive tracts were collected at slaughter. Bulls fed the high-energy diet were heavier (P < .0001; diet x time interaction), had thicker backfat (P < .05; diet x line x time interaction), and had a larger scrotal circumference (P < .05). Testicular tone decreased over time (P < .0001) with a diet x time interaction (P < .05). There was no significant effect of diet on top, bottom, or average SST. However, bulls fed the moderate-energy diet had a larger (P < .02) SST gradient (3.9 vs. 3.4 degrees C). Bulls fed the moderate-energy diet had more (P < .01) morphologically normal spermatozoa (68.8 +/- 2.1 vs 62.5 +/- 2.5%) and a higher proportion (P < .006) of progressively motile spermatozoa (53.4 +/- 2.1 vs 44.5 +/- 2.4%). No effects (P > .05) of dietary energy on epididymal sperm reserves or daily sperm production were detected. Increased dietary energy may affect scrotal or testicular thermoregulation by reducing the amount of heat that can be radiated from the scrotal neck, thereby increasing the temperature of the testes and scrotum.

Ejaculation increases scrotal surface temperature in bulls with intact epididymides

The objective of the study was to determine the effects of ejaculation on scrotal surface temperature (SST) measured with infrared thermography in bulls. In 18 Holstein bulls (18 mo old), sexual stimulation and spontaneous ejaculation (into an artificial vagina) increased SST at the bottom of the scrotum (0.9 °C; P < 0.0001). In 11 Angus bulls (1 yr old) electroejaculation increased both bottom and average SST (1.7 °C; P < 0.005 and 0.9 °C, P < 0.05), while in 12 Simmental cross bulls (2 yr old) electroejaculation significantly increased top, bottom and average SST (1.0, 1.2 and 1.1 °C, respectively). However, there was no significant increase in SST following electroejaculation in 15 Simmental cross bulls (2 yr old) with caudal epididectomies. The increase in SST was attributed to a localized increase in SST over the cauda epididymides, perhaps due to heat produced by contraction of the cauda epididymides during ejaculation. The results support the hypothesis that spontaneous ejaculation or electroejaculation increases SST and that this response is mediated by the cauda epididymides. Infrared thermography of the scrotum for evaluation of scrotal/testicular thermorégulation for clinical or research purposes should be performed before semen collection since thermography conducted soon after ejaculation may be misleading.

Contribution of the scrotum and testes to scrotal and testicular thermoregulation in bulls and rams.

A novel model was used to determine the role of the scrotum and testes in scrotal/testicular thermoregulation in bulls and rams. Eleven yearling bulls and 12 yearling rams were used at an ambient temperature of 15 degrees C. The distal lateral aspects and entire ventral part of the scrotum were incised under caudal epidural analgesia (xylazine, 0.07 mg ml-1). Both testes were withdrawn from the scrotum, the vaginal tunic was removed and one testis was replaced in the scrotum. Surface and internal temperatures were measured with infrared thermography and needle thermocouples, respectively. Temperature gradients (difference in temperature from top to bottom; degree C) for bulls and rams, respectively, were: scrotal surface (with replaced testis) 2.1 and 3.5; scrotal surface (without testis) 2.5 and 3.6; scrotal subcutaneous (with replaced testis) 1.0 and 0.7; testicular subtunic (without scrotum) -0.7 and -0.3; deep intratesticular (with scrotum) -0.2 and -0.6; and deep intratesticular (without scrotum) -0.5 and -0.5. Results supported the hypotheses that the scrotum has a positive temperature gradient (warmer at the top than the bottom) and that the testis has a negative temperature gradient (warmer at the bottom than the top). These opposing gradients apparently complement one another, resulting in a relatively uniform intratesticular temperature, below body core temperature, that is essential for normal sperm production. The scrotum substantially increased intratesticular temperature, but scrotal surface temperature was not significantly affected by the presence of a testis.

Insulating the scrotal neck affects semen quality and scrotal/testicular temperatures in the bull

Nine Simmental X Angus bulls (2-yr of age) were used in 2 experiments. In Experiment 1, the scrotal neck was insulated (from Day 1 to Day 8) in 5 bulls, and semen was collected from all 9 bulls by electroejaculation approximately every 3 d until Day 35. Bulls with insulated scrotal necks had lower percentages of normal spermatozoa (P < 0.08) and higher percentages of spermatozoa with head defects (P < 0.06) or droplets (P < 0.08) than the untreated bulls. There was a time-by-treatment interaction (P < 0.04) for midpiece defects; the incidence was higher (P < 0.05) in the insulated than noninsulated bulls from Day 5 to Day 32. Spermatozoa within the epididymis or at the acrosome phase during insulation appeared to be the most affected. Compared with the noninsulated bulls, the insulated bulls had twice as many (P < 0.02) spermatozoa with midpiece defects and 4 times as many (not significant) with droplets on Day 5, fewer (P < 0.04) normal spermatozoa and 3 times as many with midpiece defects (P < 0.05) and with droplets (not significant) on Day 8, fewer (P < 0.02) normal spermatozoa on Days 15 and 18, and more sperm cells (P < 0.05) with head defects on Days 18 and 21. In Experiment 2, scrotal subcutaneous temperature (SQT; °C, mean ± SE) prior to and after the scrotal neck had been insulated for 48 h in all 9 bulls was 30.4 ± 0.7 and 32.4 ± 0.6 (P < 0.01) at the top, 30.3 ± 0.7 and 31.8 ± 0.6 (P < 0.03) at the middle, and 30.2 ± 0.8 and 30.7 ± 0.6 (P < 0.05) at the bottom of the scrotum. Concurrently, there was an increase (0.9 °C) in intratesticular temperature (ITT) at the top (P < 0.07), middle (P < 0.04), and bottom (P < 0.04) of the testes. Scrotal surface temperature (SST) prior to and after the scrotal neck had been insulated for 24 h was 29.2 ± 0.7 and 28.2 ± 0.4 (P < 0.05) at the top of the scrotum and 24.7 ± 0.6 and 25.3 ± 0.7 (not significant) at the bottom, resulting in SST gradients of 4.6 ± 0.6 and 2.9 ± 0.5, respectively (P < 0.05). However, after the scrotal neck had been insulated for 48 h, none of the SST end points were significantly different from those prior to insulation. It appears that compensatory thermoregulatory mechanisms restored SST but were not able to restore SQT and ITT. Insulation of the scrotal neck affected SST, SQT, ITT and semen quality, emphasizing the importance of the scrotal neck in scrotal/testicular thermoregulation.

Environmental factors affecting measurement of bovine scrotal surface temperature with infrared thermography

Abstract The objective was to determine the effect of time of day (diurnal variation), interval after feeding, prolonged recumbency, moisture on the scrotum, and ambient temperature on scrotal surface temperature (SST) in bulls as measured by infrared thermography. There was no significant effect of diurnal variation on SST. Within 30 min after the start of feeding, SST at the bottom of the testes and average SST increased, and slowly declined thereafter. In bulls that were lying down for at least 1 h, SST remained relatively constant after rising at an ambient temperature of 15°C, but increased after rising at ambient temperatures of 5 and 25°C. Ambient temperature had a large effect on bottom SST, a small effect on top SST and an intermediate effect on average SST. The SST gradient (difference between top and bottom SST) was greatest at 5°C and least at 25°C. When ambient temperatures changed rapidly, there was an apparent overcompensation in SST (measured 3 h after ambient temperature stabilisation), followed by a normalisation of the temperature (measured 24 h after temperature stabilisation). Moisture on the scrotum decreased SST and following drying returned to normal in approximately 30 min. Therefore, for representative SST measurement, scrotal infrared thermography can be performed at any time of the day, but should not be done within several hours of feeding or until 1 h after rising, and the scrotum should be dry. Measurement of SST can be conducted over a wide range of ambient temperatures, although abrupt changes in ambient temperature may result in artifacts due to overcompensation.

Scrotal surface, subcutaneous, intratesticular, and intraepididymal temperatures in bulls

Sixteen 2-yr-old beef bulls were used in the study. Under caudal epidural analgesia (xylazine HCl, 40 mg), infrared thermography was used to determine scrotal surface temperature (SST) and needle thermistors were used to determine scrotal subcutaneous (SQT) and intratesticular (ITT) temperatures at 3 locations on the posterior aspect of the scrotum: 3 cm from the top of the testis, 3 cm from the bottom of the testis, and at the midpoint of the testis. Average temperatures (°C) at the top, middle and bottom locations were 30.4 ± 0.4, 29.8 ± 0.6 and 28.8 ± 0.8 (SST); 33.3 ± 0.2, 33.0 ± 0.2 and 32.9 ± 0.3 (SQT); and 34.3 ± 0.1, 34.3 ± 0.1 and 34.5 ± 0.1 (ITT). Correlation coefficients between SST and SQT were moderate to high, those between SQT and ITT were low to moderate, and those between SST and ITT were low. Therefore, caution must be exercised when making inferences about ITT based on measurement of SST. The temperature gradient from top to bottom was most pronounced for SST (1.6 °C), smaller for SQT (0.4 °C), and slightly negative (relative to the surface) for ITT (−0.1 °C). These gradients may be due to the arrangement of the vasculature; the scrotum is apparently vascularized from the dorsal pole of the testis to the ventral pole, while the testicular artery ramifies dorsally from the bottom of the testis to the top. Intraepididymal temperatures (IET) of the head, body and tail of the epididymis averaged 35.6 ± 0.2, 34.6 ± 0.1 and 33.1 ± 0.3 °C. The head of the epididymis was warmer than the testicular parenchyma, but the tail, an important storage site for spermatozoa, was cooler.

The testicular vascular cone, scrotal thermoregulation, and their relationship to sperm production and seminal quality in beef bulls

The objectives of the present study were to determine changes with age and relationships among characteristics of the testicular artery, scrotal surface temperature, scrotal circumference, testicular consistency, seminal quality and sperm production. Beef bulls aged 6 mo (n=12), 1 yr (n=12), 2 yr (n=11), and 3 yr (n=12) were used in this study. The mean length of the testicular artery as well as the length, width, and surface area of a latex cast of the testicular artery all increased between 6 mo and 1 yr of age (P<0.01). Wall thickness of the testicular artery and testicular arterial-venous distance in the spermatic cord decreased with age and with proximity to the testicle (P<0.01). Distance from the testicular vascular cone to the inner surface of the skin at the top of the scrotal neck (primarily fat) increased between 1 and 3 yr of age (P<0.01), and was associated with an increased top scrotal surface temperature (P<0.09). Increased epididymal sperm reserves were associated with an increase in testicular consistency, scrotal circumference and scrotal surface temperature gradient, and with a decrease in testicular arterial wall thickness and testicular vascular cone to skin distance. A decrease in sperm defects was associated with an increase in testicular consistency and with a decrease in the average scrotal surface temperature. Increased sperm motility was associated with increased scrotal circumference and a decreased top testicular vascular cone to skin distance. These findings emphasize the importance of thermoregulation to sperm production and seminal quality.

Elevation of Intratesticular and Scrotal Skin Surface Temperature in Men with Varicocele

A possible mechanism of varicocele-induced infertility is believed to be elevation of testicular temperature. Sensitive needle thermistors were used to measure directly intratesticular and bilateral scrotal surface temperatures simultaneously in anesthetized infertile men with varicocele and control subjects. We found that intratesticular temperature is elevated significantly in humans with varicocele. In addition, we have shown that scrotal skin surface temperature is elevated in men with varicocele. Furthermore, we demonstrate that unilateral varicocele is associated with bilateral elevation of scrotal surface temperature. These findings confirm the results of animal studies revealing elevation of intratesticular temperature associated with varicocele and suggest bilateral elevation in unilateral varicocele.

Relationship of scrotal surface temperature measured by infrared thermography to subcutaneous and deep testicular temperature in the ram.

The right testis of 9 anaesthetized rams was removed from the parietal tunica vaginalis and replaced by a surrogate testis (water-filled balloon) through which water of known temperature was circulated. Thermistors were inserted in the surrogate testis, between the scrotal skin and parietal tunica vaginalis on the right side, and deep within the intact left testis. Scrotal surface temperatures over the surrogate and intact testes were measured by infrared thermography. Scrotal surface temperature was correlated (P less than 0.01) with both subcutaneous (r = 0.95) and surrogate (r = 0.91) testicular temperature. The temperature differential between scrotal surface (30.1 +/- 0.1 degrees C) and deep testicular temperature over the intact side (34.9 +/- 0.09 degrees C) was 4.8 degrees C at an ambient temperature between 24.0 and 26.6 degrees C. Contact with the scrotal skin is not required to measure scrotal surface temperature by infrared thermography. This, coupled with the close association between scrotal surface temperature and that of underlying structures, will enhance our ability to understand better testicular temperature regulation and scrotal/testicular function.

Heat induced infertility of boars: The inter-relationship between depressed sperm output and fertility and an estimation of the critical air temperature above which sperm output is impaired

Eight groups of Large-White gilts were each inseminated with different numbers of normal motile sperm, in the range 0.28–7.0 × 10 9. A significant ( P < 0.05) relationship between conception rate and the number of motile sperm inseminated was shown. This relationship can be used to equate output of motile sperm with levels of fertility of boars. The optimal number of motile sperm for conception following intra-cervical insemination was near 5 × 10 9 and the threshold number, below which animals did not conceive, was c. 4 × 10 8. In a second experiment, three Large-White boars were subjected to graded thermal treatment (air temperature was increased by 1°C per day for 20 days, from a basal level of 20°C to a maximal level of 40°C) and responses of ejaculate and other physiological characteristics were monitored. Scrotal surface temperature, respiration rate and rectal temperature increased ( P < 0.05) beyond basal levels at air temperatures of 30°C, 33°C and 35°C, respectively. Motility of sperm in ejaculates decreased when air temperature reached 30°C and this response was presumed to reflect hyperthermia in epididymal tissues, consistent with increasing scrotal surface temperature at this same air temperature. Motility fell below a pre-treatment level of about 93%, to 19% ( P < 0.05), 3 weeks after heating. Volumes of seminal plasma and gel in ejaculates were also lower ( P < 0.05) following heating. Changes in daily sperm production were minor and, as a result, daily motile sperm production levels paralleled changes in motility. Proportions of abnormal types of sperm increased ( P < 0.05) to maximal levels in the last week of heating and all returned to pretreatment values 5 weeks later. High proportions of sperm with kinoplasmic droplets appeared in ejaculates collected after heating ( P < 0.05), evidence that epididymal cell types in the boar are sensitive to heat. As a result of heat treatment, normal motile sperm production decreased from control levels (1.28 × 10 10·day −1) to 0.15 × 10 10·day −1, 3 weeks after heating ceased. However, the results suggest that normal sperm output by Large-White boars can be maintained at air temperatures as high as 29°C. By relating the results of both experiments, it is concluded that fertility of the boars in the second experiment (if mated once daily) would be depressed for about 5 weeks after heat treatment ceased. The findings support many field reports which indicate a contribution of boars to lower conception rates of sows during and immediately following summer and the results can be used in formulating strategies to circumvent this widespread problem.

Effect of clothing on scrotal temperature in normal men and patients with poor semen

Mean scrotal surface temperatures overlying the testis clothed and unclothed reaffirm a prior observation that patients with very low spermatozoa counts (⩽ 20 mil./ml.) have higher temperatures than subjects with high spermatozoa counts (% 100 mil./ml.). The insulating effect of clothing results in mean temperature rises of 1.2 to 1.5°C. over the unclothed state regardless of semen status. There were no differences in temperature rise between wearers of “jockey” versus “boxer” undershorts.

Use of exteriorized stents in vasovasostomy

Ten patients, three to fifteen years postvasectomy, underwent vasovasostomy. Using 2-0 nylon, stents were brought to the scrotal surface. Vas anastomosis was accomplished with a single transmural layer of 6-0 or 7-0 proline or chromic sutures under loupe magnification. Stents were removed in seven to ten days. After two years, a pregnancy rate of 70 per cent was achieved, comparing favorably with other more difficult operative techniques.

The influence of deep body and skin temperatures on thermoregulatory responses to heating of the scrotum in pigs.

1. The temperature on the surface of the pig's scrotum was increased by circulating water through a pad held over the scrotal surface while the animal was lightly restrained.2. At an ambient temperature of 25 degrees C there was no change in respiratory frequency even when the scrotum was heated to 42 degrees C, but peripheral blood flow did increase and body temperature fell. At 30 degrees C ambient temperature, respiratory frequency increased when the scrotum was warmed to 42 degrees C. At an ambient temperature of 32 degrees C, the frequency increased at a scrotal temperature of 40 degrees C and was even higher when the scrotum was 42 degrees C, but body temperature did not fall.3. At a constant ambient temperature the effect on respiratory frequency of heating the scrotum to a given temperature depended on the skin temperature of the trunk which was modified by means of a coat through which water was circulated.4. In a cold environment, heating the scrotum was accompanied by a fall in body temperature, the arrest of shivering and a decline in oxygen consumption.5. Cooling a thermode in the hypothalamus or over the spinal cord inhibited the increase in respiratory frequency and peripheral blood flow caused by heating the scrotum. Warming either thermode potentiates the effect of heating the scrotum.

Selecting Merino rams for ability to withstand infertility caused by heat. 1. Anatomy and functional activity of the scrotum

Merino rams selected for (Folds Plus) and against (Folds Minus) skin wrinkle have been used in a study of scrotal heat tolerance. The type selected against skin wrinkle (Folds Minus) showed a higher scrotal fluid loss and sweat gland and fibre density than the Folds Plus type. Folds Minus rams had smaller scrotal sweat glands which discharged more frequently than those of the Folds Plus rams during early periods of scrotal heating. Scrotal heat tolerance was seen to increase with increases in scrotal surface area. These findings are discussed in terms of the light they shed on the problem of identifying the features that characterize high scrotal heat tolerance in Merino rams