Quantifying the effect of seasonality on testicular function of Suffolk ram in lower latitude

Melatonin Administration Enhances Testicular Volume, Testicular Blood Flow, Semen Parameters and Antioxidant Status during the Non-Breeding Season in Bafra Rams

Our objectives were to investigate the effects of exogenous melatonin on testicular volume (TV), testicular blood flow (TBF), and semen quality in Bafra rams during the non-breeding season. One group of rams (MEL, n = 5) received a 36 mg melatonin implant twice, with 30 days in between, while the other group (CON, n = 5) served as the control. TBF, TV, and semen quality parameters were determined at three-week intervals starting three weeks before until twelve weeks after the first melatonin implant. Testicular blood flow was determined in the supratesticular (STA) and marginal testicular artery (MA) using color Doppler ultrasound. Semen was collected and evaluated, and the total oxidative status (TOS) and total antioxidative status (TAS) was determined using an ELISA. The MEL group had increased (p < 0.05) TV between the sixth and twelfth week after the start of treatment. Overall, the MEL group had lower resistance and pulsatility indexes (p < 0.05) between the third and ninth week, although there was no difference (p > 0.05) between the two groups in most semen quality parameters. However, TAS concentrations increased (p < 0.05) in the MEL group compared with the CON. The results of this study show that exogenous melatonin in the non-breeding season significantly increased both TBF and TV in Bafra rams. Therefore, giving rams implants with 36 mg melatonin twice at least one month prior to the non-breeding season is expected to improve testicular size and function and reproductive capacity.

Does Size Matter? Testicular Volume and Its Predictive Ability of Sperm Production in Rams

Over the years, testicular volume has been used to evaluate the reproductive capacity of rams and the effects of different factors related to reproductive performance. The aim of this study was to determine the most suitable tool and formula to calculate testicular volume under field conditions to guarantee a more accurate determination of sperm production. First, testicles from 25 rams (n = 50) were measured in vivo and postmortem using calipers and ultrasonography during the breeding season (BS). The accurate testicular volume (ATV) was calculated through water displacement. In addition, the sexual status of donor rams was evaluated during a period of four years in a reproduction center, and the three most crucial groups in terms of genetic value and seminal collections were studied in the second part of this experiment: ER-NBS (Elite rams during the non-breeding season), ER-BS-S (Elite rams with a standard frequency of seminal collection), and ER-BS-O (Elite rams with a high frequency of seminal collection). The total testicular volume (TTV), testosterone (T), and total spermatozoa obtained from two consecutive ejaculates in the same day (SPERM) were measured, and the relationship between SPERM and TTV and T was analyzed to predict SPERM. Although all published formulas revealed statistically significant differences (p ≤ 0.05) from the ATV, our proposed formula (ItraULE) (Testicular volume = L × W × D × 0.61) did not show significant differences. In the second part of the study, in the ER as a model donor ram for its high genetic value and high demand from farmers, TTV and T showed strong positive correlations with SPERM (r = 0.587, p = 0.007 NBS; r = 0.684, p = 0.001 BS-S; r = 0.773, p < 0.0001 BS-O). Moreover, formulas were established to predict SPERM in these practical scenarios. In conclusion, the use of ultrasonography and a new formula adapted to rams could improve the prediction of SPERM considering crucial factors such as season and semen collection frequency.

Seasonal Variations in Semen Quality, Testosterone Levels, and Scrotal Size following Dietary Flaxseed Oil and Ascorbic Acid in South African Indigenous Rams

The purpose of this study was to determine the seasonal variations in semen quality, testosterone levels, and scrotal size, following dietary flaxseed oil and ascorbic acid in South African indigenous rams. A total of 22 South African indigenous rams were randomly distributed into five treatment diets from June 2021 to May 2022 (12 months). To allow for the spermatogenesis period, semen was collected after sixty days of dietary supplementation with treatment diets. Blood was collected twice a week using an 18-gauge needle and vacutainer tubes and sent to the laboratory for testosterone analysis. Semen and blood collection were repeated eight times each season. The scrotal size (circumference, length, and width) was measured using a flexible measuring tape. Data was subjected to the General Linear Model (GLM) in Minitab® 2017. Treatment means were separated using Fisher’s t-test and considered significantly different when the p-value was less than 0.05. Seasons and diet had an effect on progression, total motility, and testosterone levels. For instance, NC during the spring season had the lowest progressive motility (42.84 ± 5.32), followed by the summer (49.38 ± 4.49), winter (62.46 ± 4.35), and autumn (63.26 ± 3.58). Notably, when treatment diets were introduced, improvements were realized, and there were significant differences (p < 0.05) among the seasons following supplementation of FLAX, ASCA, and FLAX + ASCA, except for FLAX in the autumn season (53.83 ± 4.16). Total motility did not differ significantly (p > 0.05) between the seasons when the NC and PC diets were supplemented; nevertheless, there was an improvement when FLAX, ASCA, and FLAX + ASCA were supplemented. Testosterone levels were significantly influenced by the seasons when negative and PC diets were supplemented. It is noteworthy that supplementing FLAX + ASCA can reverse the influence of the season on the testosterone levels (spring, 27.52 ± 4.42; summer, 20.23 ± 5.11; autumn, 25.24 ± 3.96; and winter, 25.92 ± 4.42). In conclusion, seasons do affect semen quality and testosterone levels of South African indigenous rams. However, flaxseed oil and ascorbic acid can reverse the seasonal variations in semen quality and testosterone levels.

The Relationship between the Testicular Blood Flow and the Semen Parameters of Rams during the Selected Periods of the Breeding and Non-Breeding Seasons

The study aimed to conduct advanced semen evaluation tests during routine ram examination periods in the breeding and non-breeding seasons and to investigate their correlation with the dynamics of testicular blood flow. Semen was collected from eighteen rams, and pulse wave Doppler examination before (BBS), during (BS), and after the breeding season (ABS). Routine and advanced semen analysis, including computer-assisted sperm analysis (CASA), sperm chromatin dispersion test (SCD), and motile sperm organelle morphology examination (MSOME), were conducted. In Doppler ultrasonography, the peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index (RI), and pulsatility index (PI) were calculated. In BS period, high sperm concentration (p < 0.0001) and total sperm number/ejaculate (p = 0.008) were noted. During the BBS period, a low percentage of forwarding motility (p = 0.017) and high sperm abnormalities (p = 0.005) were found. Also during this period, both SCD and MSOME revealed high sperm DNA fragmentation (p < 0.0001) and signs of vacuolization (Grade II-IV, p < 0.05). The advanced features of higher sperm abnormalities (Grade IV of MSOME) correlated with an increase RI (ρє <0.60;0.61>) and PI (ρє <0.46;0.52>), whereas the basic percentage of sperm abnormalities correlated with the EDV (ρє <0.44;0.73>) value. One may conclude that the current preliminary study requires further research concerning the monthly examination of a ram to provide full yearly characteristics of the relation between advanced semen evaluation tests and the dynamics of testicular blood flow.

Reproductive Management of Rams and Ram Lambs during the Pre-Breeding Season in US Sheep Farms

Simple Summary

Pre-breeding management of rams and their ram lambs is critical for viable, sustainable and profitable farms. A further understanding of the management and selection criteria of the males during pre-breeding enables producers to efficiently use animal resources to maximize the reproductive potential of the animals. The reproductive management of mature rams and their lambs is complex, varying across breeds, farms, and regions of the world. It involves different aspects of animal husbandry, such as genetics, health, nutrition, behavior, economy and physiological and anatomical changes during the non-breeding season. Sound flock management must include an integrative and complete management plan for males and females that provides adequate conditions for the sheep to express their genetic potential and production level. This review article examines some of the key aspects to consider when managing mature rams and ram lambs during the pre-breeding season to ensure proper condition of the males for optimal function during the breeding season.

Abstract

In sheep farms, achieving economic and productive efficiency and sustainability goals is directly related with the reproductive management of the animals. Genetically, the male contribution to the offspring is 50%, but in practical terms, there is a greater potential impact of the ram on reproductive results, because one male has the potential to affect a large group of females and therefore greatly affects the entire flock. Unfortunately, the selection of males for breeding in the US sheep industry has been traditionally conducted based on phenotypical traits, without a genetic/reproductive evaluation, and/or health assessment or records. Therefore, it is important to establish integrative management practices to select the rams and ram lambs to be used in the breeding season. Among these practices are genomic testing, a comprehensive breeding soundness evaluation and assessment of health status and records of the males before the breeding season, to detect and correct potential issues.

Reproductive seasonality of male dromedary camels

Reproductive seasonality has been reported in numerous species, including male dromedary camels, yet investigations into seasonal changes in camel semen quality have yet to be conducted. The aim of this study was to characterise the seasonal changes in camel semen quantity and quality as well as correlate these changes to testis and accessory sex gland morphology, sexual behaviour, libido and environmental factors such as day length and ambient temperature in Oman. Semen was collected twice a month for a year and testicular and accessory sex organ biometry recorded once a month via ultrasonography (n = 8 bulls). Blood samples were collected monthly to assess testosterone levels. Results indicated that testes and accessory sex glands size increased during October-April, peaking with testosterone concentrations during January (P<0.05). The sexual behaviour and libido of camels was also greater during the months of October-April (P<0.05). Attempts to collect semen were 100% successful during November-February. Semen volume, as well as sperm gross activity, concentration, motility, average path velocity and percentage with intact acrosomes were the greatest during January and decreased from May-September (P<0.05). Changes in values for semen variables, testosterone concentrations and sex organ anatomy were also highly correlated with seasonal changes in day length and ambient temperatures. In conclusion, a clearly defined reproductive season was observed in male camels in Oman ranging from December-March, with peak reproductive function occurring during December-January. To increase the success of breeding programs, matings or semen collections should be timed to occur when reproductive function is maximal.

Differences in the thermal sensitivity and seminal quality of distinct ovine genotypes raised in tropical conditions

For different ovine breeds to maximize their reproductive capacity in countries with tropical climate, it is important to evaluate their potential for thermal resilience and consequences on their reproductive traits. Therefore, the objective of this study was to evaluate the effect of thermal environment temperatures of climate seasons in a tropical climate region on the surface temperatures of the scrotum, testicular biometric characteristics, seminal quality and serum testosterone concentration of rams of different genotypes. Breeders of four different genotypes (Dorper, n = 8, Texel, n = 8, Santa Inês, n = 9 and Morada Nova, n = 8) were used throughout the four climate seasons. Higher thermal challenge was recorded in the spring and summer. In the summer increase in scrotal surface temperature was detected by infrared thermography (P < 0.05), mainly in the regions of the distal testicular pole and tail of the epididymis. The animals of the Texel genotype had higher rectal temperature in the summer. In spring, this genotype also had the highest testicular pole (32.2 ± 0.5 °C; P < 0.05) and distal (29.9 ± 0.4 °C; P < 0.05) temperatures and a higher mean testicular temperature (31.7 ± 0.4 °C; P < 0.05). The Morada Nova genotype showed a higher surface temperature gradient between testicular poles (2.96 ± 0.1 °C; P < 0.05), especially in spring. Genotype-dependent thermal sensitivity was detected for the thermal gradient between the testicular poles, reflecting the seminal quality. There was a positive correlation of the thermal gradient between testicular poles with sperm membrane integrity and negative correlation with total sperm defects. The Texel genotype showed less progressive motility and higher percentage of sperm defects. There was no difference in testosterone concentration between genotypes and in the different seasons (P > 0.05). Thus, the indigenous genotypes showed a greater capability to maintain the scrotum-testicular thermoregulation. Dorper animals resembled the indigenous sheep genotypes, in terms of seminal characteristics, unlike Texel animals, which showed lower adaptability and lower seminal quality.

Changes in melatonin concentrations in seminal plasma are not correlated with testosterone or antioxidant enzyme activity when rams are located in areas with an equatorial photoperiod

In temperate climates, photoperiod and melatonin regulate ram reproduction, modulating hormonal secretions, sperm quality, and seminal plasma composition. Information on the effect of an equatorial photoperiod (12L:12D) on ram reproduction, however, is scarce, and no data on hormonal concentrations and antioxidant enzyme activity in seminal plasma have been reported. Thus, the variation was investigated of melatonin and its relationship with testosterone and antioxidant enzyme activity in the seminal plasma of three sheep breeds in Colombia, when there was a consistent photoperiod during two dry and two rainy seasons per year. Semen was collected once a week from 12 mature rams (four of each breed: Colombian Creole, Hampshire, and Romney Marsh). Seminal plasma was obtained by centrifugation. The concentration of melatonin and testosterone were quantified along with the enzymatic activity of glutathione peroxidase (GPx), glutathione reductase (GRD), and catalase (CAT). Correlation analyses between melatonin and testosterone concentrations or enzymatic activity were also performed. Melatonin concentration was affected by season (P < 0.05) but not breed, with lesser concentrations in the first rainy season. Testosterone concentration, however, was affected by breed and season, with greater concentrations (P < 0.01) in the Hampshire and Romney Marsh rams during the second dry season. Regarding antioxidant enzyme activity, there was only seasonal variation in GPx activity (P < 0.05). When correlation analyses were used for data assessments, there was a negative correlation between melatonin and testosterone concentrations in Hampshire rams. In conclusion, melatonin concentrations in seminal plasma of rams that were located in an area with an equatorial photoperiod was affected by the climatological season but there was no positive correlation with testosterone concentration or antioxidant enzyme activity.