281 The Effects of Whole Cottonseed Supplementation on Performance, Breeding Soundness Exams, and Manganese Superoxide Dismutase Concentrations in the Blood and Semen of Beef Bulls

The objective of this research was to determine the effects of whole cottonseed containing gossypol on post-pubertal beef bulls. In a two-year study, 46 Angus and Red Angus bulls (body weight 457.0 ± 85.2 kg; 16 to 20-months of age) were stratified by BW and randomly assigned to 1 of 3 levels of whole cottonseed supplementation while receiving ad libitum roughage. The treatments included: DD (n = 14, control; 3.18 kg/d of dried distillers grain, W/D (n = 16; 1.59 kg/d of whole cottonseed and 1.59 kg/d of dried distillers grain), or WW (n = 16 3.18 kg/d of whole cottonseed). Diets were formulated to be isocaloric and isonitrogenous. In both years, bulls were weighed, administered a breeding soundness exam, and morphological characteristics of spermatozoa were measured on d 0, 28, and 60. In year 1, blood and semen samples were collected on d 0, 28, and 60 to measure manganese superoxide dismutase activity. There was no treatment effect for blood or semen manganese superoxide dismutase concentration (P > 0.255). There was a treatment effect (P < 0.02) for average daily gain as bulls fed WW gained less compared to those fed WD and DD (0.96, 1.23, and 1.39 kg/d, respectively). No treatment effect was observed for scrotal circumference (P > 0.50). There were no treatment × time interactions, treatment, or time main effects for percentages of normal spermatozoa, spermatozoa with coiled or folded tails, or proximal droplets (P > 0.12). There was a treatment effect on the amount of swollen midpiece or abnormal head as bull in the DD treatment had a greater (P < 0.02) percentage of other abnormalities compared to WW, but WD was not different (P > 0.16). Inclusion of whole cottonseed may affect average daily gain, but does not affect reproductive parameters of beef bulls.

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.

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

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.

A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols

This retrospective study aimed to determine if the number of cows exposed per bull affects pregnancy rates of cows returning to estrus after fixed-time artificial insemination (FTAI). Data were compiled over the course of 13 breeding seasons (6 fall and 7 spring seasons) between 2010 and 2017 from the Virginia Department of Corrections herd. Available records contained data from 17 farms and 324 groups of cows (average 47 cows/group). Multiparous cows and heifers (average age per group: 5.11 ± 0.14 years; n = 14,868) were exposed to FTAI. After FTAI, animals were placed on pasture with bulls diagnosed as fertile by a breeding soundness exam for natural service of cows who did not become pregnant to FTAI (n = 7,248; average 22 cows/group). Animals were classified as pregnant to FTAI, to natural service on first return to estrus, or to natural service on second or subsequent estrus determined by fetal aging at pregnancy diagnosis. The bull:cow ratio for the total number of cows exposed ranged from 1:9 to 1:73 with an average of 1:31. The bull:cow ratio considering only open cows exposed after FTAI ranged from 1:2 to 1:44 with an average of 1:14. There was significant negative, small correlation between the bull:cow ratio for total number of cows exposed and return to estrus pregnancy rate in fall breeding seasons (P = 0.01, r 2 = 0.04) but not in spring (P = 0.90). There was a significant negative, small correlation between bull:cow ratio of open cows exposed and pregnancy rates to first return to estrus in fall herds with a single sire (P < 0.001, r 2 = 0.11). There was no correlation in fall herds using multiple sires or spring herds (P ≥ 0.12). Bull:cow ratio accounted for only 1 – 11% of variation in the pregnancy rates, thus we conclude that a decreased bull:cow ratio (up to 1:73) did not affect natural service return to estrus pregnancy rate. Cattlemen may consider a reduced number of bulls needed for natural service breeding after FTAI, which can decrease bull related costs and increase the economic feasibility of adopting FTAI protocols.

Reproductive evaluation of Charolais and Charbray bulls on the reproductive efficiency of herds in warm subhumid climate of Veracruz

Objective: To correlate the Breeding Soundness Evaluation (BSE) of Charolais andCharbray bulls in the warm subhumid climate and its effect on the Pregnancy rate andCalving interval of herds to estimate differences between breeds.Design/methodology/approach: BSE was carried out on N = 90 Bulls; Charolais (n =33) and Charbray (n = 57), evaluated in situ during the period 2017 to 2019. Bull (age, body condition, libido, and scrotal circumference), Semen (concentration, motility, and volume), Herd (Pregnancy rate and Calving interval) and environment variables (Rainy and Dry season) were analyzed with the one-way ANOVA, Factorial, Multiple regression, and Multivariate analysis.Results: Charolais and Charbray bulls show similar results in the BSE (p>0.05) in awarm subhumid climate.Limitations/implications: Year season (Rainy or Dry) do not affect (p<0.05) the BSErating. Libido is associated (p<0.05) with age (R=-0.42), sperm motility (R=0.67), spermconcentration (R=0.66) and pregnancy rate (R=0.63). Findings/conclusions: Variables with high association (p<0.05) with pregnancy ratewere libido (R=0.63), motility (R=0.60), sperm concentration (R=0.51) and age (R=-0.50); variables with high association (p<0.05) with calving interval were: age (R=0.74)and libido (R=-0.33). Charolais and Charbray bulls show similar reproductive efficiencyin herds under a warm subhumid climate in Veracruz.

Libido and serving skills of Zebu cattle bulls

The goal of this study was to evaluate the rejection rates of Zebu bulls during behavioral assessment (libido and serving ability) and the importance of this step in bull breeding soundness evaluation (BBSE). A total of 1,534 bulls reared in the state of Rio Grande do Sul, Brazil, of Nelore (1,340), Brahman (76), Guzerá (98), and Tabapuã (210) breeds were evaluated. The evaluation consisted of four steps. Step I was the general physical examination, Step II genital tract examination, Step III semen evaluation, and Step IV behavioral assessment of libido and the ability to complete copulation. To evaluate the relationship between the binary variables of approved or rejected during different steps of the BBSE, and age groups (young and mature bulls), chi-square tests and logistic regression were used. The general rejection rates in the BBSE were 5.64% and 15.20% for young and mature Zebu bulls, respectively. Problems with the sexual behavior (libido and/or serving ability) of bulls accounted for the rejection of 0.46% and 2.29% of young and mature Zebu bulls, respectively. The lack of libido and serving ability was shown to be an important problem concerning the total number of possible causes of Zebu bull rejection during the BBSE. This result suggests that the behavioral step should be performed regularly, rather than being complementary to the standard BBSE in Zebu cattle.