The effects of differing nutritional levels and body condition score on scrotal circumference, motility, and morphology of bovine sperm

Bulls often experience various levels of nutrient availability throughout the year. Nutritional management is a critical factor on overall ejaculate composition and the ability to get females pregnant. We hypothesized that differing nutritional levels and body condition score (BCS) affects reproductive fertility parameters in bulls. Mature Angus bulls (n = 11) were individually housed and randomly assigned to one of two dietary regimens: 1) over-fed (n = 5) or 2) restricted (n = 6). Bulls were fed the same ration at different volumes to achieve desired effects resulting in 8 individual treatments: gain to an over-fed body condition score ([BCS]; GO), gain after nutrient restriction (GR), loss after an over-fed BCS (LO), loss from nutrient restriction (LR), maintenance at ideal adiposity (BCS = 6) after overfeeding (IMO), maintenance at ideal adiposity after nutrient restriction (IMR), maintenance at an over-fed BCS (BCS = 8; MO), and maintenance at a restricted BCS (BCS = 4; MR). Body weight (BW) and BCS were recorded every two weeks to monitor bull weight and BCS changes. Scrotal circumference was measured every 28 d. Body fat and sperm motility and morphology were evaluated every 84 d. Scrotal circumference, motility, and morphology were normalized to the initial value of each bull. Thus, allowing the individual bull to serve as a control. Statistical analyses were conducted with PROC GLIMMIX of SAS as a complete randomized design to determine if treatment influenced BW, BCS, scrotal circumference, motility, morphology, and adipose thickness. Scrotal circumference (P < 0.001) had the least amount of deviation from initial during the LR (0.29 ± 0.44) treatment and the greatest during the MO (3.06 ± 0.44), LO (2.28 ± 0.44), MR (2.43 ± 0.44), GR (3.03 ± 0.44) and IMR (2.91 ± 0.44) treatments. Sperm motility was not affected by nutritional treatments (P = 0.55). Both head and total defects of sperm differed (P = 0.02) due to nutritional treatments. Increased head abnormalities occurred during the LO (37.60 ± 8.61) treatment, with no differences between the other treatments. Total defects increased during the LO (43.80 ± 9.55) treatment with similar increases in bulls during the GR (29.40 ± 9.55) and IMR (35.60 ± 9.55) treatments. In conclusion, male fertility was impacted when a deviation from a BCS of 6 occurred which could be detrimental to reproductive and beef production efficiency.

Sperm DNA 5-mC and RNA m 6A methylation are differently affected during periods of body weight losses and body weight gain of young and mature breeding bulls

Aiming to characterize the effects of nutritional status on epigenetic markers, such as DNA 5-mC methylation and RNA m 6A methylation, of bovine sperm, twelve Angus × Hereford crossbred breeding bulls were submitted to nutritional changes for a period of 180 days: no change in BW (Phase 1 = 12 d); BW loss (Phase 2 = 78 d); and BW gain (Phase 3 = 90 d) in a repeated measures design. Animals were fed Beardless wheat (Triticum aestivum) hay and mineral mix. Statistical analyses were performed using SAS 9.4 (SAS Inst., Cary, NC). Higher levels of RNA m 6A (P = 0.004) and DNA methylation (P = 0.007) of spermatic cells were observed at Phase 2 compared with Phase 1. In Phase 3, sperm RNA m 6A methylation levels continued to be higher (P = 0.004), whereas the DNA of sperm cells was similar (P = 0.426) compared with the Phase 1. Growing bulls had a tendency (P = 0.109) of higher RNA m 6A methylation levels than mature bulls. Phase 2 altered scrotal circumference (P < 0.001), sperm volume (P = 0.007), sperm total motility (P = 0.004), sperm progressive motility (P = 0.004), total sperm count (P = 0.049), normal sperm (P < 0.001), abnormal sperm (P < 0.001), primary sperm defects (P = 0.039), and secondary sperm defects (P < 0.001). In Phase 3, bulls had scrotal circumference, sperm volume, sperm motility, sperm progressive motility, total sperm count, normal and abnormal spermatozoa, and primary and secondary spermatozoa defects similar to Phase 1 (P > 0.05). Serum concentrations of insulin-like growth factor-1 (IGF-1) and leptin decreased during Phase 2 (P = 0.010) while no differences (P > 0.05) were detected between Phase 3 and 1; growing bulls tended (P = 0.102) to present higher leptin levels than mature bulls. Specific for mature bulls, DNA methylation was positively correlated with leptin concentration (0.569, P = 0.021). Whereas for young bulls, DNA methylation was positively correlated with abnormal spermatozoa (0.824, P = 0.006), primary spermatozoa defect (0.711, P = 0.032), secondary spermatozoa defect (0.661, P = 0.052), and negatively correlated with normal spermatozoa (−0.824, P = 0.006), total sperm count (−0.702, P = 0.035), and sperm concentration (−0.846, P = 0.004). There was no significant correlation (P > 0.05) between RNA m 6A and hormones and semen traits. In conclusion, the nutritional status of breeding bulls alters epigenetic markers, such as DNA methylation and RNA m 6A methylation, in sperm, and the impact of change seems to be age-dependent. These markers may serve as biomarkers of sperm quality and fertility of bulls in the future. Detrimental effects on sperm production and seminal quality are observed at periods and places when and where environmental and nutritional limitations are a year-round reality and may carry hidden players that may influence a lifetime of underperformance.

Study on effect of hair coat color on various reproductive attributes of Cholistani service bulls

The objective of the present study was to assess the possible effect of hair coat color on various orchidometric, seminal and andrological attributes of black-coated and brown-coated Cholistani service bulls. Adult Cholistani bulls (n= 8) were grouped as black-spotted (n= 4) and brown-spotted (n=4). Semen collection was performed once weekly (2 ejaculates/collection) using artificial vagina (AV) throughout the study period (October-May). Semen samples were evaluated for various physical attributes. Body weight and orchidometric attributes of the bulls were attained using calipers. Blood sampling was performed twice weekly and serum testosterone level was deduced through automated analyzer. The scrotal circumference, Scrotal Skin Fold Thickness and Paired Testicular Volume were significantly higher (P<0.05) in black-spotted Cholistani bulls as compared to brown-spotted bulls. Similarly, the ejaculatory volume (5.8±0.1 mL) and individual sperm motility (63.3±1.4%) were significantly higher (P<0.05) in black-spotted bulls. Percentage of live spermatozoa, and spermatozoa with normal morphology and acrosome was also higher in black-spotted bulls though statistically non-significant (P>0.05). Amongst post-thaw seminal attributes, percentage of live spermatozoa, and spermatozoa with normal morphology and acrosome were significantly higher (P<0.05) in black-spotted bulls. Similarly, serum testosterone level in black-spotted Cholistani bulls (6.9±0.3 ng/mL) was significantly higher (P<0.05) compared to brown-spotted bulls (5.4±0.3 ng/mL). The black-spotted Cholistani service bulls showed substantially better orchidometric and seminal attributes allied with higher serum level of testosterone.

Growth rate, scrotal circumference, sperm characteristics, and sexual behavior of mixed-breed goat bucks fed three leguminous trees

Aim of study: To investigate the effect of feeding foliage of leguminous trees on growth rate, semen characteristics, and sexual behavior of bucks. Area of study: Northeastern Mexico (23°44' N, 99°8' W). Material and methods: Twenty-two young goat bucks were randomly allocated to one of four treatment groups: 33% alfalfa hay (dry matter basis), 33%; Acacia farnesiana; Leucaena leucocephala; or Prosopis laevigata foliage (n=4 for alfalfa; n=6 for the rest of groups). Main results: Average daily gain (ADG) did not differ between bucks fed alfalfa, A. farnesiana, or L. leucocephala (120 ± 26, 134 ± 37, and 103 ± 29 g/d, respectively), but ADG of bucks offered P. laevigata was the lowest (72 ± 8 g; p<0.05). Bucks fed alfalfa had the highest feed efficiency (6.59 ± 1.25 kg of feed consumed/kg of gain; p<0.05) and bucks offered leguminous trees had the lowest (average 9.85 ± 2.3). Bucks offered alfalfa, and A. farnesiana had increased (p<0.05) scrotal circumference (26.6 ± 0.4 and 25.8 ± 1.5 cm) than bucks fed L. leucocephala, or P. laevigata (24.3 ± 1.2 and 24.1 ± 2.0 cm). Mean ejaculate volume was two-fold higher in alfalfa-fed bucks than all other dietary treatments. Sexual behavior did not differ among bucks fed the different legumes. Research highlights: Foliage of both A. farnesiana and L. leucocephala could totally replace alfalfa hay for rearing growing goat bucks in confinement without affecting daily weight gain, most semen characteristics, and copulation ability. P. laevigata reduced body weight and reproductive function.

Correlations between body measures with live weight in young male goats

Data analysis in goat production, such as those related to body and scrotal measurements, indicate the productive and reproductive animal development. The current study aimed to evaluate the correlations between thoracic perimeter (TP), body length (BL), body compacity (BC), body volume (BV), and scrotal circumference (SC) with body weight (BW) in young male goats of Saanen and Boer breeds. It was used 38 Saanen and 24 Boer male goats, with age average of 7.2 ± 2.0 months. Thoracic perimeter and body length measurements were obtained using a tape measure (cm) and the live weight (kg) a mechanic scale. The variables body compacity (BC) and body volume (BV) were calculated using the equations: and . Boer breed showed live weight and body compacity higher than Saanen breed (p < 0.05). Regarding correlations between biometric measurements and body weight, we did not find any statistical differences between the breeds (p > 0.05). The scrotal circumference presented the lowest association with body weight (p < 0.05). However, all biometric measurements showed highly significant correlations with live body (p < 0.01). In conclusion, thoracic perimeter was the main measure of body weight predictor, considering efficiency and practical aspects.

PSVII-29 Genetic analysis of frame score and performance traits in Nellore cattle – reproduction and productivity traits

Frame score systems developed for Bos taurus breeds do not translate well for Bos indicus breeds, as these tend to be taller. We evaluated a novel frame score system for Nellore cattle raised on pasture [Guimaraes et al., 2020 J, Anim. Sci. 98 (Suppl. 4)]. Traits included adjusted scrotal circumference (cm) at 365 (SC365) and 450 (SC450) days of age, age at first calving (AFC, d), early heifer pregnancy (EHP, % calving as two-year-olds), stayability (STAY, % of cows remaining in the herd over 76 months of age, calving at least three times), and accumulated productivity (AP, kg of calf weaned per cow per year). In this study, we applied the previously developed equations (that also include hip height (HH, cm) and age to 12,049 records from the National Association of Breeders and Researchers (ANCP) database:FSmales= -20.35 + 0.1305*REA + 0.2633*BF - 0.5901*RF + 0.1139*HH + 0.0056*AGEFSfemales = -11.87 + 0.1316*REA - 0.2457*BF - 0.6218*RF + 0.1139*HH + 0.0009507*AGEThe (co)variance components and genetic parameters were estimated using a linear animal model or a threshold animal model depending on the trait. The heritability estimate for frame score was moderate (0.30). Estimated genetic correlations for reproductive traits were low to moderate (SC365, 0.06; SC450, 0.04; AFC, 0.18; EHP, -0.24; STAY, 0.06; AP, 0.25). The estimates support the notion that larger frame animals are later maturing but have greater lifetime productivity. The new frame score may be a useful tool for genetic selection of animals that are best suited to their environment.

PSXII-14 Estimation of phosphatidylserine positive sperm in fresh bull semen

Previous research demonstrated that phosphatidylserine (PS), a marker for apoptosis, plays a role in murine sperm fertilization capacity; however, less is known of the role of PS in bovine fertilization. The objective of this experiment was to determine the concentration of PS positive sperm on fresh bovine semen (n = 4). A breeding soundness evaluation was performed and electroejaculation was used to collect semen which was immediately evaluated for ejaculate density and gross motility through visual evaluation. Semen smears of semen mixed with an eosin-nigrosin strain were prepared on glass microscope slides. Semen was mixed with OptiXcell™ (IMV Technologies) semen extender, a 0.5 mL sample from each bull was washed with non-capacitating media and then incubated at 37.5°C 5% CO2 with capacitating media for 60 minutes. Samples were stained with Annexin V FITC and 7AAD for 15 minutes each. Samples were analyzed using a Flow Cytometer to determine the percentage of PS positive sperm. Bull 1 had a scrotal circumference of 37.5 cm, ejaculate density of 400–750 million sperm/mL, very good gross motility, 78% sperm with normal morphology, and 14.65% PS positive sperm. Bull 2 had a scrotal circumference of 37 cm, ejaculate density of 400–750 million sperm/mL, very good gross motility, 84% sperm with normal morphology, and 17.05% PS positive sperm. Bull 3 had a scrotal circumference of 39.5 cm, ejaculate density of 250–400 million sperm/mL, fair gross motility, 48% sperm with normal morphology, and 12.8% PS positive sperm. Bull 4 had a scrotal circumference of 38 cm, ejaculate density of 400–750 million sperm/mL, good gross motility, 68% of sperm with normal morphology, and 12.65% PS positive sperm. Our data demonstrate the possibility of identifying live PS positive sperm in fresh ejaculate from bulls. The possibility exists that PS plays a role in sperm oocyte fusion and fertilization in the bovine.

Evaluation of seminal characteristics of Pelibuey and East Friesian rams at two different times of the year

Objective: To determine the changes in seminal quality of Pelibuey and East Friesian rams during the non-breeding (long days; March-June) and breeding seasons (short days; September-December) at 19° north latitude. Design/methodology/approach: To determine changes in seminal quality over time, seminal parameters of rams, collected with an artificial vagina were evaluated over 32 weeks. An analysis of variance was performed with a completely randomized design in a 2 x 2 factorial arrangement (breed and season). Results: No differences were found within breeds or between breeds in the same season in the evaluated seminal parameters; however, differences were reported between seasons in the live weight parameters, lower in the non-reproductive season, in addition to an increased scrotal circumference and mass motility during the reproductive season. Study limitations/implications: Semen parameters estimation, in field trials, is subjective compared to computerized semen evaluation systems, it is therefore desirable to have extensive experience in semen evaluation at the field level before starting the study. To confirm the results obtained in this study, a new experiment with a larger number of experimental units is suggested. Findings/conclusions: It is concluded that in the environmental and management conditions, where the seminal evaluation took place, no differences were found between breeds, suggesting that the Pelibuey and East Friesian breeds at 19° north latitude do not decrease their seminal parameters during the non-breeding season compared to the breeding season. This suggest that these two sheep breeds are able to reproduce, in such conditions, all year round.

Metafounders May Reduce Bias in Composite Cattle Genomic Predictions

Metafounders are pseudo-individuals that act as proxies for animals in base populations. When metafounders are used, individuals from different breeds can be related through pedigree, improving the compatibility between genomic and pedigree relationships. The aim of this study was to investigate the use of metafounders and unknown parent groups (UPGs) for the genomic evaluation of a composite beef cattle population. Phenotypes were available for scrotal circumference at 14 months of age (SC14), post weaning gain (PWG), weaning weight (WW), and birth weight (BW). The pedigree included 680,551 animals, of which 1,899 were genotyped for or imputed to around 30,000 single-nucleotide polymorphisms (SNPs). Evaluations were performed based on pedigree (BLUP), pedigree with UPGs (BLUP_UPG), pedigree with metafounders (BLUP_MF), single-step genomic BLUP (ssGBLUP), ssGBLUP with UPGs for genomic and pedigree relationship matrices (ssGBLUP_UPG) or only for the pedigree relationship matrix (ssGBLUP_UPGA), and ssGBLUP with metafounders (ssGBLUP_MF). Each evaluation considered either four or 10 groups that were assigned based on breed of founders and intermediate crosses. To evaluate model performance, we used a validation method based on linear regression statistics to obtain accuracy, stability, dispersion, and bias of (genomic) estimated breeding value [(G)EBV]. Overall, relationships within and among metafounders were stronger in the scenario with 10 metafounders. Accuracy was greater for models with genomic information than for BLUP. Also, the stability of (G)EBVs was greater when genomic information was taken into account. Overall, pedigree-based methods showed lower inflation/deflation (regression coefficients close to 1.0) for SC14, WWM, and BWD traits. The level of inflation/deflation for genomic models was small and trait-dependent. Compared with regular ssGBLUP, ssGBLUP_MF4 displayed regression coefficient closer to one SC14, PWG, WWM, and BWD. Genomic models with metafounders seemed to be slightly more stable than models with UPGs based on higher similarity of results with different numbers of groups. Further, metafounders can help to reduce bias in genomic evaluations of composite beef cattle populations without reducing the stability of GEBVs.