Adjusted 200-day scrotal size as a predictor of 365-day scrotal circumference

Data collected from 264 bulls of 13 beef breeds at the Michigan Bull Test Station was evaluated to determine if scrotal circumference (SC) adjusted to 200 d of age could be used to predict scrotal circumference at 1 yr of age. Scrotal circumference of each bull was recorded on arrival at the test station and at the time of breeding soundness examination (BSE) and was adjusted to 200 and 365 d of age, respectively. Bulls with adjusted SC>34.0 cm by 365 d of age averaged a larger SC at 200 d (P < 0.0001) and faster scrotal growth (P < 0.0001) than bulls with a 365 d adjusted SC /= 23.0 cm had a 95% probability of achieving SC > 34.0 cm by one year of age. Calves measuring < 23 cm at 200 d had a 54% probability of achieving > 34.0 cm scrotal size by one year. This information can contribute to the selection of breeding bulls that will achieve desirable scrotal size by one year of age.     

Phenotypic relationships of scrotal circumference to frame size and body weight in performance-tested bulls

The objective of this study was to determine if frame size (height) is related to scrotal circumference. A total of 695 bulls (425 Angus, 65 Hereford, 70 Charolais, 135 Simmentals) were tested for postweaning gain in five stations over a period of 1 to 3 years. Variables examined included hip height, weight and scrotal circumference at beginning and completion of a 140-d feeding period. Correlations among these traits, adjusted for age (7 to 10 months at entry), year, station and management were estimated for each breed. Both height and weight were correlated positively with scrotal circumference at the start and the end of the test period in all four breeds. When height and scrotal circumference were adjusted for weight, correlations were negligible, with the exception of end-of-test values for Charolais bulls (-0.26). Negative correlations were obtained between the scrotal circumference at the start of the test and the change in height during the test after adjustment for weight in Angus bulls (-0.18) and in Charolais bulls (-0.15). These small negative phenotypic relationships indicate that a bull's fertility is not seriously reduced by large frame size at the completion of a feedlot performance test. For maximum fertility in bulls, scrotal circumference needs to be evaluated independently of frame size.     

Relationships between growth parameters and scrotal circumference in young beef bulls

Scrotal circumferences of 119 young bulls of four distinct breeding groups were measured at the end of a feedlot performance test and at the beginning of the breeding season when the bulls were approximately 14 months old, to study the relationships of weight and growth parameters with testes size. Scrotal circumference was positively correlated with body weight at the end of feedlot test in the four breeding groups. The association between scrotal circumference and body weight was much stronger in the breeding group which had been selected for low yeariing weight than in the other three breeding groups which had been selected for high growth rate. The relationships between scrotal circumference and preweaning and postweaning gain differed among the four breeding groups. Preweaning gain was the most important factor in the association between body weight and scrotal circumference among the three beef breeding groups. The results indicated that the preweaning stage was a critical period for testicular development and that the probability of finding beef bulls with smaller than average testes among the bulls selected for weaning weight would be relatively small. Scrotal circumference was reduced $\text{(2.5–11\%)}$ from the end of feedlot test until the beginning of the breeding season.     

Scrotal circumference of two-year-old bulls of several beef breeds

Scrotal circumference (SC) was measured on 7,918 2-yr-old Angus, Charolais, horned and polled Herefords, Limousin, Shorthorn, and Simmental bulls presented to culling committees at six show/sales between 1977 and 1983. Only SC data from bulls within the age range of 24 +/- 4 mo were used. Scrotal circumference data were corrected across breeds for the effects of location-year and sire and were adjusted to a common bull age of 730 d. The adjusted mean SC (+/- SE) for 2-yr-old beef bulls was Simmental, 38.8 +/- 0.10 cm (n = 540); Aberdeen Angus, 37.2 +/- 0.09 cm (n = 629); Charolais, 36.3 +/- 0.09 cm (n = 499); horned Hereford, 36.1 +/- 0.03 cm (n = 3,769); polled Hereford, 35.6 +/- 0.04 cm (n = 2,170); Shorthorn, 34.9 +/- 0.11 cm (n = 231); and Limousin, 32.2 +/- 0.18 cm (n = 80). The authors' recommendations of minimum acceptable SC for 2-yr-old beef bulls are Simmental, 36.0 cm; Angus and Charolais, 35.0 cm; horned and polled Herefords and Shorthorn, 34.0 cm; and Limousin, 33.0 cm.     

Genetic parameters and relationships between growth traits and scrotal circumference measured at different ages in Nellore cattle

Records from 106,212 Nellore animals, born between 1998 and 2006, were used to estimate (co)variance components and genetic parameters for birth weight (BW), average weight gains from birth to weaning (GBW), average weight gains from weaning to after yearling (GWAY), weaning hip height (WHH), postweaning hip height (PHH) and scrotal circumferences at 9 (SC9), 12 (SC12) and 15 (SC15) months of age. (Co)variance components were estimated by an animal model using multi-trait analysis. Heritability estimates for BW, GBW, GWAY, WHH, PHH, SC9, SC12 and SC15 were 0.31 ± 0.01; 0.25 ± 0.02; 0.30 ± 0.04; 0.51 ± 0.04; 0.54 ± 0.04; 0.39 ± 0.01; 0.41 ± 0.01 and 0.44 ± 0.02, respectively. Genetic correlations between growth traits ranged from 0.09 ± 0.01 to 0.88 ± 0.01, thereby implying that, at any age, selection to increase average weight gains will also increase stature. Genetic correlations between BW and average weight gains with scrotal circumferences were all positive and moderate (0.15 ± 0.03 to 0.38 ± 0.01). On the other hand, positive and low genetic associations were estimated between hip height and scrotal circumference at different ages (0.09 ± 0.01 to 0.17 ± 0.02). The results of this study pointed out that selection to larger scrotal circumferences in males will promote changes in average weight gains. In order to obtain Nellore cattle with the stature and size suitable for the production system, both weight gain and hip height should be included in a selection index.     

Relationship of scrotal circumference to age, body weight and onset of spermatogenesis in goats

Scrotal circumference (SC) and body weight (BW) measurements were obtained from 122 crossbred (Saanen x Loca; Jumnapari x Local) bucks, ranging in age from 3 to 28 months. Spermatogenesis and semeniferous tubule diameters were studied from testicular biopsies in 24 bucks. The results showed that SC increased curvilinearly and was significantly correlated with age (P < 0.05). Scrotal circumference correlated more significantly with BW (P < 0.001). Spermatogenesis was completed at 6-7 months with a sudden increase in tubular diameter at the same time. Since SC is an indirect measurement of testicular size, a marked increase in testicular size indicated the onset of active spermatogenesis and, hence, the possibility of using bucks for breeding at an earlier age than normally recommended. Further, SC norms obtained in this study may become useful in the evaluation of bucks for breeding soundness.     

Determination of minimum weaning scrotal circumference in Santa Gertrudis bulls fed a low energy ration

The scrotal circumference (SC) of 374 Santa Gertrudis bulls was measured prior to and following a period of low energy feed intake. A step by step regression was performed to formulate prediction equations in which the future SC of young bulls could be determined. These equations accounted for only 30 to 50% of the variation. Analysis of variance was used to determine the minimum SC at 7, 8 and 10 mo of age needed to obtain a 30-cm SC by 1 yr of age. At 7 mo, the bulls with the largest final SC, were those with an SC larger than 18 cm (P < 0.01). As the 8-mo SC increased so did the 13-mo SC (P < 0.01). As the 10-mo SC increased, the 15-mo SC also increased but bulls with less than a 21-cm SC were smaller (P < 0.01). Differences were also found between the 7 and 8-mo old weights of bulls and the initial SC (P < 0.01). As the initial testicle size increased, the 7, 8 and 10-mo ages and the 10-mo weight tended to increase. Few differences were found in initial SC measurements between the bulls that reached a 30-cm SC and those that did not at the end of one year regarding weight and age within each SC. These findings indicate that the SC at the beginning of a low energy feed period can be useful in determining the minimum SC outcome by the end of the test period.     

Influence of age and scrotal circumference on breeding soundness examination of range rams

Breeding soundness examinations (BSE) were conducted on 3,167 range rams on New Mexico sheep ranches during 1982, 1983 and 1984. Age and scrotal circumference (SC) were recorded for each ram and based on SC, rams were further classified as small (<30.8 cm), medium (31-37 cm) or large (>37.8 cm). Scrotal circumference increased with age (P < 0.05) up to 7 yr of age. Rams rated as satisfactory by BSE had a large (P < 0.05) SC, averaging 34.4 cm for all ages combined. Most rams classed as small (P < 0.01) were also rated unsatisfactory. There was no difference (P > 0.10) in BSE rating of rams classified by SC as medium or large. Results of this study suggest that SC is influenced by age, and this trait should be considered within age groups. Rams with an SC of <30 cm are more likely (P < 0.05) to be rated unsatisfactory by BSE.     

Correlation of scrotal circumference and age in American Brahman bulls

Scrotal circumference (SC) measurements were taken of 921 American Brahman bulls located on two ranches in southcentral Texas. Measurements were taken at various seasons of the year over an 11-yr time span. Body condition scores, as reflected by fat cover, and a subjective estimate of overall nutritional status were 4 or better, based upon a 1 to 9 scoring system, with 5 representing an animal with an average amount of body fat. Associated body weights were not measured and semen evaluations were not performed. Ages were calculated from exact birthdates and rounded to the nearest whole month. Ages from 8 mo to more than 36 mo were reported. SC measurements ranged from 16.0 cm to 42.5 cm. The relationship of SC and age was positively correlated (r=0.74) (P<0.0001) and could be predicted using the equation y=0.525x + 18.702 where y=SC in centimeters and x=age in months. These data provide evidence that the relationship of scrotal circumference and age of American Brahman bulls is similar to that of other cattle breeds.     

The relationship between scrotal circumference and quantitative testicular traits in yearling beef bulls

A study was designed to investigate relationships between testicle size and histological, sperm production and endocrinological traits in yearling beef bulls at the end of performance test. Twenty-five beef bulls, (Hereford, n=16; Angus, n=4; and Charolais, n=5), with scrotal circumference (SC) measurements ranging from 28.5 to 36.0 cm, were used. Just prior to slaughter at 15 mo of age, SC measurements were taken, semen was collected, and a GnRH response test was conducted. Testicles were processed for daily sperm production (DSP), epididymal sperm reserves (ESR), seminiferous epithelial area (SEA), and degree of germinal epithelial loss (DGEL). There were significant positive correlations between SC and testicular weight (P<0.05), DSP/g (P<0.02), and DSP/bull (P<0.01) and ESR (P<0.01); however, the correlation between SC and SEA was not significant (P=0.4). Scrotal circumference was negatively correlated with DGEL (P<0.05). Degree of germinal epithelial loss was also negatively correlated with DSP/g, DSP/bull and ESR (P<0.01). Morphological characteristics of spermatozoa were diversely related to sperm production traits, and the percentage of normal spermatozoa was positively related to SC (P<0.02) and negatively related to DGEL (P<0.001). Gonadotropin releasing hormone stimulation did not reveal evidence of gonadotropin deficiency in any of the bulls. However, peak testosterone levels were lower in bulls with SC below 31 cm (P<0.05) than those with SC measurements above 31 cm.     

Relationship of scrotal circumference and testicular volume to age and body weight in the swamp buffalo (Bubalus bubalis)

Scrotal circumference (SC) and testicular volume (TV) were measured in 65 swamp buffalo bulls ranging in age from 7 to 60 months and weighing 130 kg to 560 kg. Ages and body weight (BW) were recorded for each male at the time of measurement to find out if they correlated with SC and TV. SC and TV increased linearly and correlated significantly with age and BW (SC vs age: r = 0.74, p<0.01; SC vs BW: r = 0.88, p<0.01; TV vs BW: r = 0.82, p<0.01). SC measurements ranged from 15.1 +/- 1.1 cm to 24.0 +/- 0.4 cm for ages ranging from 10.0 +/- 0.6 to 48.5 +/- 6.3 months, revealing that testicular size in swamp buffaloes was very much smaller than domestic cattle. The SC norms distributed with age would be useful in the evaluation of swamp buffalo males for breeding soundness.     

Associations of scrotal circumference with semen traits in young beef bulls

Associations of percent live sperm, sperm number, sperm concentration, sperm motility, and potential breeding efficiency score with scrotal circumference were studied using data from the records of 465 Polled Hereford and 264 Simmental bulls. Data were subdivided by breed and within breed into three groups according to scrotal circumference (SC) size. Group I bulls had SC measurements <32 cm. Group II included bulls with SC measurements between 32 cm and the mean measurement of the breed (i.e., 35 cm for Polled Hereford and 38 cm for Simmentals). Group III was comprised of bulls with SC values above their respective breed averages. Age and body weight differences were also evaluated in the three groups. Average age differences among bulls in the three groups differed by not more than nine days in the two breeds. Average body weight differences among the three groups were statistically significant (P<0.05) with the maximum difference between any two groups within breed being 80 pounds. Average differences in percent live sperm and sperm number were greater (P<0.05) in Groups II and III than in Group I. For sperm concentration ratings, sperm motility ratings and potential breeding efficiency score, and for both breeds, Group I had a significantly lower (P<0.05) number of bulls classified satisfactory and a significantly greater (P<0.05) number of bulls classified unsatisfactory than did groups II and III.     

Scrotal circumference measurements in purebred Dorset, Hampshire and Suffolk lamb and yearling rams

Purebred Suffolk, Hampshire and Dorset lamb and yearling rams (n=753), underwent performance testing from 1986 to 1989. Scrotal circumference, birth date and entry weight were recorded for each ram entering the test station. Mean age in days at entry, weight (lbs), and scrotal circumference (SC; cm) were greatest for the Hampshire rams. For all rams combined (Dorset, Hampshire and Suffolk), the mean SC by month of age revealed rapid growth from 2 to 6 mo, with a 3- to 6-mo mean SC significantly (P0.05) for mean SC measurement and a less rapid increase in SC diameter. Between 12 and 13 mo a significant increase (P相似文献   

Evaluation of four mathematical functions to describe scrotal circumference maturation in Nellore bulls

Four functions to characterize scrotal circumference (SC) growth in Nellore bulls were compared to identify which was the most suitable for biological interpretation. Nellore bulls (n = 532), born between September and December of 1992 to 1994 were used in the study. Measurements were made on fixed dates in January, April, July and October of each year. At the time of SC measurements, the ages of the bulls ranged from 200 to 1300 d. The functions used to describe the data were: Brody, SC = A (1 - B exp -kt); Logistic, SC = A/(1 + B exp -kt); Gompertz, SC = A exp(-B exp -kt) and Richards SC = A (1 + B exp -kt)m, where SC is the scrotal circumference at t days of age, A is the estimated SC at maturity, B is the integration constant established by the initial values of SC and t, k is the maturity constant, which equals the ratio between the maximum rate of growth and SC at maturity; m is the inflection point parameter for Richards function, which did not converge. The Brody, Gompertz and Logistic functions fitted the data in a similar fashion, with similar values for the statistics EMS and R2, and they reached convergence with similar computational costs. The Logistic function presented the best pattern of average prediction error, and therefore, it was selected for biological interpretation. For the Logistic function, estimated SC at maturity (A) was 37.95 cm at 72 mo of age. The maturity index (k) was .11 cm, and the inflection point (time of maximum growth) was reached at 13.09 mo of age at an average SC of 18.97 cm.     

The effect of using the Breeding Soundness Evaluation as a selection criterion for Santa Gertrudis bulls on bulls in subsequent generations

Results of Breeding Soundness Evaluations (BSE) used to select Santa Gertrudis bulls over a 10-yr period were analyzed in retrospect to determine the effect on bulls in subsequent generations. Bulls were tested at three ages: 16 mo (n = 1,936), 20 mo (n = 3,111) and at maturity (≥ 24 mo, n = 3,814). Scrotal circumference (SC) and sperm motility and morphology were evaluated. Sixteen-mo-old bulls were required to have an SC ≥ 30 cm to be tested. During 1977 to 1980, 20-mo-old bulls with an SC < 30 cm were culled, and the minimum SC was increased to 32 cm during 1981 to 1986. Mature bulls during this period were required to have an SC ≥ 35 cm to be tested. A BSE < 60 was considered a failing score, and bulls were culled at this level. There was a positive correlation between SC and sperm motility and SC and sperm morphology in 16-mo-old and 20-mo-old but not in mature bulls (P < 0.0001). The percentage of bulls passing the BSE was positively correlated with SC at all ages (P < 0.0001), and the passing rate increased over the years (P < 0.0001). Scrotal circumference increased over the years in bulls that passed the BSE (P < 0.0001). This increase with years was not as apparent in the semen quality traits measured. By using the BSE and a minimum SC to select prospective herd sires, the proportion of bulls passing the BSE is expected to increase in subsequent generations. Santa Gertrudis bulls can be reliably selected for use as herd sires at 16 mo of age.     

Heritability estimates and adjustment factors for the effects of bull age and age of dam on yearling testicular size in breeds of bulls

Scrotal circumference, testicular length and body weight were measured in 3,090 yearling bulls of 12 breed groups finishing growth performance tests during a 5 yr period. Breeds were Limousin, Hereford, Charolais, Angus, Red Poll, Simmental, Pinzgauer, Brown Swiss, Gelbvieh and three crossbred breed groups. All bulls were born during a 60-d calving season starting in late March of each year and were subjected to similar management and environmental influences during the study. The bulls were the progeny of 307 sires averaging approximately 26 sires per breed group and 10 sons per sire. Breed group, sire within breed group, year and age-of-dam effects were important (P<0.01) for all testicular traits at both a constant age (354 d) and constant body weight (418 kg). Paternal half-sib estimates of heritability were 0.41 +/- 0.06 for ageconstant scrotal circumference, 0.34 +/- 0.06 for testicular length and 0.37 +/- 0.06 for calculated paired testicular volume, respectively. Age-constant genetic correlations between yearling body weight and testicular traits were small, indicating that testicular growth and body growth rates are largely independent, regardless of breed. Testicular size of bulls from 2-yr-old dams was smaller than that of bulls from older dams. Most of these age-of-dam effects on testicular size were removed when testicular size was adjusted for the effects of body weight, suggesting that age-of-dam effects on testicular size are primarily the result of age-of-dam effects on body weight. Age adjustment factors for yearling scrotal circumference did not differ (P>0.20) among breed groups and averaged 0.032 cm per day of age. Adjustment factors for age of dam were +1.3, +0.8, +0.4, and +0.0 cm for sons of 2-, 3-, 4- and 5-yr-old dams, respectively.     

Relationships among fertility, scrotal circumference, seminal quality, and libido in Santa Gertrudis bulls

Forty Santa Gertrudis bulls were used to examine relationships among scrotal circumference, seminal quality, libido, and fertility [assessed as the percent pregnant of estrous females (PE rate) and the percent pregnant of females mated (PM rate)]. These bulls were selected from 220 two year old bulls to represent variations in scrotal circumference and seminal quality. Each of the 40 bulls were exposed to 100 cyclic Santa Gertrudis heifers for a 4-day (96 hr) breeding period. The number of estrous females available to each bull varied from 12 to 27. A breeding soundness examination (BSE) was conducted on each bull approximately 45 days prior to the 4-day breeding period and immediately after the 4-day breeding period. The three components of the BSE scroe (scrotal circumference, spermatozoal abnormalities and spermatozoal motility) were not significantly correlated with PE rate or PM rate at either evaluation. There was no significant correlation between PM rate and scrotal circumference; however, each of the 4 bulls having a scrotal circumference less than 30 cm had a PM rate below 31%. Relationships between seminal quality and PM rate were unclear and differed between the two evaluations. There was a trend for bulls having poor seminal quality at the first evaluation to improve by the second evaluation. Consequently, fluctuations in seminal quality between evaluations is one possible explanation for low correlations between seminal parameters and PM rate. Libido (number mated/number in estrus x 100) was positively correlated (r = 0.44) with PE rate. Using a stepwise regression procedure, the independent variables accounting for the most variation in PE rate (dependent variable) included libido, secondary spermatozoal abnormalities, and BSE score (r(2) = 0.44). Results of this study indicate that current methods of fertility evaluation did not accurately predict the fertility of individual Santa Gertrudis bulls as measured by PE rate and PM rate during a 4 day breeding period.     

Effect on scrotal circumference of trucking beef bulls medium and long distances

Scrotal circumference (SC) was measured both before and after 2- to 3-yr-old beef bulls were trucked either medium (138 km) or long (565 km) distances. Two SC measurement techniques were used, one recommended by the Society for Theriogenology and the “slip-off” technique. No differences (P > 0.05) were observed between pre-and post- trucking SC measurements using the Theriogenology technique when bulls were trucked either medium (n = 12; 35.9 ± 0.8 vs 35.8 ± 0.7 cm) or long (n = 16; 36.5 ± 0.5 vs 36.6 ± 0.4 cm) distances. However, when the SC of the same bulls was measured using the “slip-off” technique, there was a small, but significant (P < 0.05), reduction in SC for bulls trucked medium (38.0 ± 0.7 vs 37.5 ± 0.7 cm) and long (38.9 ± 0.4 vs 38.6 ± 0.4 cm) distances. Bulls having SC at or below the recommended minimum standard reacted no differently to the stress of trucking than did bulls having a SC well above the standard. Errors in measurement technique, severe weather conditions and testicular degeneration over an extended interval are discussed in terms of their potential contribution to the reduction in SC observed by some cattlemen. These data support the use of the SC measurement technique recommended by the Society for Theriogenology because its accuracy is not affected by trucking of bulls. The suggested implementation of an adjustment period between the trucking of beef bulls and measurement of their SC using the Theriogenology technique is not supported.     

Predicting end-of-test semen quality in bulls prior to performance testing

The first objective of this study was to determine if serum concentrations of specific hormones (testosterone, progesterone and androstenedione) in bulls at the start of performance testing could predict semen quality at the end-of-test when used in a multivariate model. The second objective was to evaluate other clinical measurements (breed, age, body weight, hip height and scrotal circumference) for predicting end-of-test semen quality. End-of-test semen quality was related to steroid concentrations and several pre-testing measurements, including age, body weight, hip height and scrotal circumference (SC). Combining the 3 steroid concentrations into a predictive test had a sensitivity of 0.6 and specificity of 0.5 at its most accurate point. The repeatability of the test result was extremely low (r(2) = 0.16; P < 0.05). In multivariate analyses, breed and start-of-test SC remained significant predictors of end-of-test semen quality (P < 0.05) while the other variables were nonsignificant (P > 0.1), suggesting that start-of-test SC was the most accurate predictor of end-of-test semen quality. Removing bulls at the start-of-test that had scrotal measurements of less than 20 cm, 24 cm, 28 cm or 32 cm resulted in sensitivities and specificities of 0.19, 0.94; 0.41, 0.81; 0.64, 0.56; and 0.94, 0.12, respectively. No cut-point had both adequate sensitivity and specificity. Because clinical tests were correlated, combining the tests to improve accuracy was not justified.     

Semen characteristics, scrotal circumference and bacterial isolates of fine wool range rams

During 1983, 887 fine wool rams were subjected to breeding soundness evaluation to determine effects of age and scrotal circumference on semen characteristics. Of rams evaluated, 94.4, 84.8, and 81.9% of young (6 yr), respectively, were rated as satis-factory. Old rams had fewer (P < 0.05) motile cells and more (P < 0.05) abnormal cells than young rams. Among older rams there was a higher percentage (P < 0.05) with testicular lesions than among young or mature rams. Scrotal circumference was positively correlated (P < 0.01) with semen volume and percentage of motile normal cells. Motility was negatively correlated (P < 0.01) with percentage of abnormal cells. Mature and old rams with large (>/=36.7 cm) testis had more (P < 0.10) abnormal cells than those in the same age groups with smaller testis. Scrotal circumference was positively correlated (P < 0.10) to volume and motility in mature and old rams, while motility was negatively correlated (P < 0.01) to percentage of abnormal cells in all age groups. Previous semen testing reduced (P < 0.05) the percentage of mature rams with leucocytes. Vaccination against epididymitis reduced (P < 0.05) the incidence of mature rams with leucocytes and testicular lesions. Brucella ovis was recovered from 54 (67.5%) of 80 ejaculates cultured. Among rams infected with B . ovis , only three (5.6%) were vaccinated against B . ovis and had their semen tested previously.