Beef heifers that give birth within the first 21 d of their first calving season have greater lifetime productivity and longevity. A favorable relationship exists between the number of antral follicles detectable by ultrasonography and calving date in beef heifers, indicating greater lifetime fertility in cows with more antral follicles. In contrast, Bos indicus cows have more surface antral follicles than Bos taurus cows but exhibit no advantage in fertility. Prior studies demonstrated that despite having more antral follicles, Bos indicus cows have equal numbers of primordial follicles per ovary as Bos taurus cows. Bos indicus cows do have heavier ovaries with more stromal tissue than Bos taurus cows. This study served to further compare preantral follicle populations between Bos indicus and Bos taurus cows to test the specific hypothesis that number of primordial follicles per gram of ovarian tissue are decreased in Bos indicus cows compared with Bos taurus cows. Ovaries were collected from Bos indicus cows (n = 7) and Bos taurus cows (n = 42), weighed, fixed, and sectioned for histological evaluation to determine the number of primordial, primary, and secondary follicles per ovary. The total number of follicles per ovary was divided by the weight of the ovary to determine the number of follicles per gram of ovarian tissue. Data were analyzed using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC) with species as a class effect. Ovaries from Bos indicus cows were heavier than ovaries from Bos taurus cows (12.6 ± 1.1 vs. 7.0 ± 0.5 g, respectively; P < 0.01). No difference was found between Bos indicus and Bos taurus cows in the number of primordial follicles per ovary (P = 0.64); however, Bos indicus cows had a greater number of primary and secondary follicles per ovary (P < 0.01). Upon being adjusted for ovarian weight, Bos indicus cows tended to have fewer primordial follicles per gram of ovary than Bos taurus cows (P = 0.06) but still had greater numbers of primary follicles per gram of ovary (P < 0.01). This suggests that the mechanisms controlling primordial follicle activation are different between Bos indicus and Bos taurus cows. From these results, we conclude that Bos indicus cows do not display enhanced fertility over Bos taurus cows because despite having more antral follicles, Bos indicus cows do not have larger ovarian reserves in comparison to the size of their ovaries. The USDA is an equal opportunity provider and employer.

This study was initiated to evaluate performance and patterns of cow traits and blood metabolites of 3 breeds of cows grazing bahiagrass (Paspalum notatum Flügge) pastures in central Florida. Purebred cows (n = 411) of either Angus (Bos taurus), Brahman (Bos indicus), or Romosinuano (Bos taurus) breeding, rotationally grazed (moved twice weekly) bahiagrass pastures year-round, and received bahiagrass hay supplemented with molasses and soyhulls or legume hay supplemented with unfortified molasses from October to June each production year. At monthly intervals, all cows were weighed, measured at the hip (HH), scored for BCS, and blood samples collected by jugular puncture from 10 cows per cow breed/block group for plasma urea N (PUN), glucose and non-esterified fatty acids (NEFA). Data were analyzed on cows that calved with a statistical model that included fixed effects of year, cowage, cow breed, month, block, supplement group (n = 2, but not presented), and whether the cow weaned a calf the previous year. Cow was a repeated observation over mo. Three-way interactions involving monthly patterns for cowage x year, year x lactation status the previous year, cowage × cow breed, year × cow breed, and cow breed × lactation status the previous year were significant (P < 0.001) for BW and BCS. The interaction for cowage × month was also significant (P < 0.05) for glucose, and cow breed × month was important (P < 0.01) for PUN, glucose, and NEFA. Important differences included: 1) greater BW and BCS for older cows compared to 3-yr old cows; 2) greater BW and BCS before calving for cows that did not lactate the previous year; 3) PUN levels were above 11 mg/dl except for February, August and September, and was generally greater in tropically adapted breeds; 4) GLU was greatest in Brahman, lowest in Angus, and intermediate in Romosinuano cows; and 5) plasma levels of NEFA escalated at calving and then declined, but Brahman cows maintained greater (P < 0.05) levels from calving until weaning than the other breeds. Cows that lactated the previous year had less NEFA than those that did not lactate. Brahman cows were less fertile than Bos taurus breeds, and weaned heavier calves.

Our objective has been to compare the IVF and in vitro production (IVP) of embryos from low and high antral follicle count (AFC) heifers. This is the fourth year of the study with years 1 to 3 reported individually. For this report, we add data for the fourth year and present a combined analysis (years 1 to 4) for the first time. Each year, AFC was determined on ~120 Angus heifers using transrectal ultrasonography. Ten heifers with the lowest AFC and 10 heifers with the highest AFC and all with evidence of oestrous cyclicity were synchronized with two 5-mL injections of PGF2α 11 days apart. Half were harvested on Day 5 to 6 and half on Day 15 to 16 of the oestrous cycle. The IVF procedure was slightly modified each year. For year 4, the IVF procedure included protocols for semi-defined media and was as described (IVP Protocol, P. J. Hansen’s Laboratory, University of Florida). Cumulus-oocyte complexes (COC) from follicles less than 8 mm in diameter were cultured in maturation medium (5% CO2; 38.5°C) for 24 h. Matured COC were fertilized using thawed frozen semen from a bull that was purified using isolate. Motile spermatozoa were added to COC in fertilization medium at a final concentration of 1 × 106 spermatozoa per mL. About 24 h later, presumptive zygotes were placed in micro drops of development medium under oil, and cultured (5% CO2; 5% O2; balance N2; 38.5°C). On Day 3 and 8 after fertilization, cleavage and blastocyst development rates, respectively, were assessed. Data were analysed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC, USA) and the model included the effects of year (1 to 4), group (high or low AFC), and their interaction. The year × group interaction was not significant (P > 0.10). Low AFC heifers, compared with high AFC heifers, had fewer numbers of COC (P < 0.0001; 12.8 ± 1.83 v. 31.9 ± 1.86), fewer numbers of COC that cleaved (P < 0.0001; 8.0 ± 1.38 v. 21.6 ± 1.40), and fewer numbers of COC that developed to the blastocyst stage (P < 0.0001; 1.7 ± 0.58 v. 5.7 ± 0.58). Year affected the numbers of COC that cleaved (P < 0.003) and the numbers of COC that developed to the blastocyst stage (P < 0.0001). Year also influenced the percentage of COC that cleaved (P < 0.0002) and the percentage of COC that developed to blastocysts (P < 0.0001). Group (AFC) did not influence (P > 0.19) the percentage of COC that cleaved (61.2 ± 2.83 v. 66.4 ± 2.83%, for low v. high AFC, respectively). Low AFC heifers had a lower (P < 0.002) percentage of COC that developed to blastocysts (10.3 ± 1.52%) than high AFC heifers (17.6 ± 1.52%). These results indicate that high AFC heifers, compared to low AFC heifers, have more COC recovered, more COC cleaved, and more COC developed to the blastocyst stage. The percentage of COC cleaved did not differ between AFC groups; however, the percentage of COC that developed to the blastocyst stage was greater for high than low AFC heifers. This suggests a potential advantage in maternal to embryonic transition for high compared with low AFC heifers.

The objective of this research was to evaluate circulating concentrations of plasma cortisol and measures of temperament at weaning in calves (steers and heifers) and at transport in steers. Calves ( = 993) were produced from a 3-breed diallel mating design that included calves from 3 consecutive years. Breed types of calves were straightbred Angus (A), Brahman (B), and Romosinuano (R) and all F crossbred combinations (AB, BA, AR, RA, BR, and RB). At weaning (d 0) and at 24 and 72 h after weaning, blood was sampled from calves and the plasma was stored for later cortisol assay. Additionally, at each of these times, temperament was assessed as chute score, exit velocity, and pen score. About 1 mo later, steer calves ( = 471) were sampled before shipment, at arrival, and at 24 h, 72 h, 2 wk, and 4 wk after shipment (2,025 km; Brooksville, FL, to El Reno, OK). At each of these sampling times, blood was collected and plasma was stored for subsequent cortisol assay and temperament was assessed by measurement of exit velocity. At both weaning and transport, plasma concentrations of cortisol did not significantly differ ( > 0.05) among straightbreds or among crossbreds. Significant ( < 0.05) positive genetic effects were observed for plasma concentration of cortisol at weaning (heterosis for BA and direct Romosinuano effect) and transport (heterosis for RA, BR, and BA; direct Romosinuano effect; and maternal Angus effect). Assessment of temperament using the objective measurement of exit velocity or the subjective measures of chute score or pen score (1 [lowest] to 5 [highest excitability] scale, based on behavior in chute and behavior in pen with human observer, respectively) generally provided similar results: Brahman was higher than Brahman crosses, which were higher than Angus, Romosinuano, and their reciprocal crosses. For exit velocity, however, Brahman did not differ from Brahman crosses and Angus did not differ from Romosinuano or Brahman crosses. At transport, sire breed and dam breed affected exit velocity of steers, with higher ( < 0.05) estimates for Brahman than for Romosinuano or Angus. These data suggest that weaned calves and shipped steers of various breed types show a similar response to stressors in cortisol concentration. In contrast, in assessing temperament or behavioral response to humans, Romosinuano and Angus had better temperaments and were less excitable than Brahman.

The use of Brahman in cow-calf production offers some adaptation to the harsh characteristics of endophyte-infected tall fescue. Criollo breeds, such as the Romosinuano, may have similar adaptation. The objectives were to estimate genetic effects in Romosinuano, Angus, and crossbred cows for their weights, weights of their calves, and ratios (calf weight:cow weight and cow weight change:calf weight gain) across lactation and to assess the influence of forage on traits and estimates. Cows ( = 91) were bred to Charolais bulls after their second parity. Calves ( = 214) were born from 2006 to 2009. Cows and calves were weighed in early (April and June), mid- (July), and late lactation (August and October). Animal was a random effect in analyses of calf data; sire was random in analyses of cow records and ratios. Fixed effects investigated included calf age, calf sex, cow age-year combinations, sire breed of cow, dam breed of cow, and interactions. Subsequent analyses evaluated the effect of forage grazed: endophyte-free or endophyte-infected tall fescue. Estimates of maternal heterosis for calf weight ranged from 9.3 ± 4.3 to 15.4 ± 5.7 kg from mid-lactation through weaning ( < 0.05). Romosinuano direct effects (of the cow) were -6.8 ± 3.0 and -8.9 ± 4.2 kg for weights recorded in April and June. Calf weights and weight gains from birth were greater ( < 0.05) for calves of cows grazing endophyte-free tall fescue except in mid-summer. Cow weight change from April to each time was negative for Angus cows and lower ( < 0.05) than other groups. Cows grazing endophyte-free tall fescue were heavier ( < 0.05) at all times but had more weight loss in late lactation. Angus cows had the lowest ( < 0.05) ratios (negative) of cow weight change:calf weight gain, indicating an energy-deficit condition. Cows grazing endophyte-free tall fescue had more negative ( < 0.05) values for this trait but not in early lactation ( < 0.05). Estimates of heterosis ranged from 12.8 ± 9.5 to 28.6 ± 9.4 kg for cow weight, 7.9 ± 3.0 to 15.8 ± 5.0 kg for cow weight change, and 0.07 ± 0.03 to 0.27 ± 0.1 for cow weight change:calf weight gain. Direct Romosinuano effects ranged from 14.8 ± 4.2 to 49.8 ± 7.7 kg for cow weight change and 0.2 ± 0.04 to 0.51 ± 0.14 for cow weight change:calf weight gain. The adaptive ability of Romosinuano in temperate fescue regions may be favorable with respect to relative cow and calf weight but may be a consequence of lower milk-producing ability.

To compare the in vitro fertilization (IVF) and production (IVP) of embryos from low and high antral follicle count (AFC) heifers, AFC were determined on 106 heifers using transrectal ultrasonography. Ten heifers with the lowest AFC (avg. 13.2) and 10 heifers with the highest AFC (avg. 27.4) with evidence of oestrous cyclicity were synchronised with 2 injections of prostaglandin F2α (PGF2α); half were harvested on Days 5 to 6 and half on Days 15 to 16 of the oestrous cycle. The IVF procedures included protocols for semi-defined media and were as described (IVP Protocol, P. J. Hansen’s Laboratory, University of Florida, Gainesville, FL, USA). Cumulus-oocyte complexes (COC) from follicles less than 8 mm in diameter were cultured in maturation medium (5% CO2; 38.5°C) for 24 h. Matured COC were fertilised using thawed frozen semen from a crossbred bull that was purified using Percoll gradient separation procedures. Motile spermatozoa were added to COC in fertilization medium at a final concentration of 1 × 106 spermatozoa per mL. About 24 h later, presumptive zygotes were placed in microdrops of development medium under oil, and cultured (5% CO2, 5% O2, balance N2, 38.5°C). On Days 3 and 8 after fertilization, cleavage and blastocyst development rates, respectively, were assessed. Data were analysed using the mixed procedure of SAS (SAS Institute, Cary, NC, USA) and the model included the effects of collection day, group (high or low AFC), and their interaction. More COC (P < 0.0005) were collected from high than low AFC heifers (30.3 v. 9.3 ± 3.12 per heifer). Both the number and percentage of COC that cleaved had an interaction between collection day and group (P < 0.03). The interaction appeared to be due to low cleavage and development rates on 1 of 4 collection days (appeared not related to day of oestrous cycle). Although high compared to low AFC heifers had more COC that cleaved (18.7 v. 4.4 ± 1.84 per heifer), the percentage of cleaved COC did not differ (59.2 v. 49.8 ± 3.36%). There were no significant differences between high and low AFC heifers in the number of blastocysts (3.1 v. 0.6 ± 1.21 per heifer) or in the percentage of COC that developed to blastocysts (8.8 v. 5.2 ± 3.60%). In previous replicates (years), we reported that high AFC heifers had more COC collected, more COC that cleaved, and more COC that developed to blastocysts than low AFC heifers. In contrast, in this study numbers of COC that developed to blastocysts did not significantly differ between high and low AFC heifers. Additionally, the percentage of COC that cleaved, and that developed to blastocyst have been similar between high and low AFC heifers. Therefore, high compared to low AFC heifers may produce more IVP embryos; however, AFC does not appear to affect the competence of an oocyte to develop and mature to the blastocyst stage.

Increased numbers of antral follicles have been associated with decreased calving day, increased fertility, increased serum estradiol concentrations, increased serum progesterone concentrations, and increased estrus behavior in cattle. In addition, cows with increased fertility have been shown to have greater activity during behavioral estrus when using electronic activity detection systems. Therefore, the objective of the current study was to evaluate an electronic estrus detection system to determine if differences in estrous cycle characteristics could be detected among beef heifers differing in antral follicle number. The hypothesis was that the percent of heifers demonstrating behavioral estrus and peak activity would be decreased in heifers with low numbers of antral follicles. Estrus activity collars were placed on crossbred beef heifers (n = 359) at 12.0 ± 0.1 mo of age to monitor estrus activity, and heifers were submitted for ultrasonographic evaluation of antral follicle number at 13.5 ± 0.1 mo of age, immediately before the start of the breeding season. During a 21 d period, heifers were artificially inseminated 12 h after estrus was diagnosed by the electronic system. Following the period of artificial insemination, heifers were placed with bulls for an additional 42 d, and submitted for ultrasonographic pregnancy diagnosis 45 d after removal of the bulls. Heifers were classified as low ( < 16 follicles), medium (16–25 follicles) or high ( > 25 follicles). The percent of heifers demonstrating behavioral estrus was analyzed using the GLIMMIX procedure of SAS with antral follicle group as the fixed effect with a binomial distribution and a logit link. Length of the estrous cycle before insemination and peak activity at insemination were analyzed using the MIXED procedure of SAS with antral follicle group as a fixed effect. The percent of heifers demonstrating behavioral estrus was lower in heifers with low numbers of antral follicles compared to heifers with medium or high numbers of follicles (P = 0.02; 46.2 ± 4.2 vs. 57.5 ± 2.4%). Peak activity and estrous cycle length; however, did not differ among antral follicle groups (P > 0.1). Combined with our histological and hormonal data, these results indicate that greater numbers of antral follicles contribute to increased behavioral estrus due to increased serum estradiol concentrations; however, this does not result in a difference in peak activity calculated by the electronic system during behavioral estrus. USDA is an equal opportunity provider and employer.

The objectives of this work were to: (1) estimate heterosis and breed direct effects for cow reproduction traits of Romosinuano, Angus, and F1 cows in a temperate climate, and (2) assess the effects of the type of forage grazed (bermudagrass, endophyte-infected and endophyte-free tall fescue) during the breeding season on traits and genetic effects. Calving and weaning rate (n=666 records) were evaluated for 145 cows from 2005 through 2012. Calving interval (n=400) and day of conception within breeding season (n=547) were recorded. Mixed models included combinations of fixed effects: year of record or cow age within year of record, breed type parameterized as main and interaction effects of sire breed and dam breed of cows with records. Additive genetic effects were included as a random component. The sire breed-dam breed interaction was characterized by lower (P<0.005) Angus calving and weaning rates (0.75±0.03, 0.65±0.04, respectively) than other groups, which ranged from 0.88±0.02 (Romosinuano) to 0.92±0.04 (Romosinuano-sired F1) for calving rate and ranged from 0.81±0.03 (F1 sired by Angus) to 0.82±0.03 (Romosinuano-sired F1) for weaning rate. Romosinuano cows conceived later (P<0.02) in the breeding season (25.2±2.3d) than other groups (range from 16.9±3.1 to 17.3±1.8d). Calving and weaning rates were highest (P<0.05) for cows grazing bermudagrass during the breeding season (0.98±0.02, 0.93±0.03), and lowest for cows grazing endophyte-infected tall fescue (0.85±0.03, 0.78±0.04); cows grazing endophyte-free tall fescue were intermediate (0.94±0.02, 0.88±0.03). No interaction of forage type with sire or dam breed was detected (P>0.24). Estimates of heterosis were 0.09±0.03, 0.11±0.04, and –3.7±2.0d (P<0.05) for calving and weaning rate, and conception day within breeding season, respectively. Romosinuano direct effects for these traits were large (P<0.003) and favorable for calving and weaning rate (0.14±0.05, 0.2±0.05), but unfavorable for conception day within breeding season (8.7±2.9d; P<0.05). Angus cows had the greatest proportion of calf loss (0.33) and cows that died or were culled (0.8). Romosinuano may merit consideration for inclusion in breeding programs across forage types in temperate climates.

The objectives of this work were to compare the Criollo breed Romosinuano as straightbred and crossbred cows with Angus and Brahman in subtropical Florida and to estimate heterosis for size traits of their calves, their own weight, and maternal efficiency traits. Cows (n = 404) were born from 2002 to 2005. After their first exposure to bulls as young cows, crossbred cows were bred to bulls of the third breed, and straightbred cows were bred in to bulls of the other 2 breeds. Calves were spring-born from 2005 through 2011. Evaluated calf (n = 1,254) traits included birth weight and weight, ADG, BCS, and hip height at weaning. Cow weight (n = 1,389) was recorded at weaning. Maternal efficiency traits evaluated included weaning weight per 100 kg cow weight, weaning weight per calving interval, and weaning weight per cow exposed to breeding (n = 1,442). Fixed effects and their interactions were investigated included sire and dam breed of cow, sire breed of calf, cow age, year, calf gender, and weaning age as a linear covariate (calf traits at weaning). Direct and maternal additive genetic effects were random in models for calf traits; only direct additive effects were modeled for cow traits. Cows sired by Angus bulls from outside the research herd had calves that were heavier at birth and weaning and greater ADG, BCS, and hip height (P < 0.05). Estimates of heterosis for weaning weight, BCS, and ADG ranged from 1.3 to 13.2% for all pairs of breeds (P < 0.05). Estimates of heterosis for birth weight (3.2 to 8.2%) and hip height (2.3%) were significant for Romosinuano-Angus and Brahman-Angus. Heterosis for cow weight was 65 +/- 8 kg for Brahman-Angus (P < 0.001), and estimates for other pairs of breeds were approximately one-half that value. Heterosis for weaning weight/100 kg cow weight was 3.4 +/- 0.75 kg for Romosinuano-Angus. Heterosis estimates for weaning weight/calving interval (P < 0.001) ranged from 0.08 +/- 0.01 to 0.12 +/- 0.01. Heterosis for weaning weight/cow exposed were 31.6 7.7, 36.9 +/- 7.4, and 59.1 +/- 7.5 kg for Romosinuano-Angus, Romosinuano-Brahman, and Brahman-Angus, respectively (P < 0.001). Most aspects of Romosinuano crossbred maternal performance were acceptable; maternal performance of Brahman-Angus cows excelled.

The objectives of this work were to compare reproduction and parturition traits of the Criollo breed Romosinuano as straightbred and crossbred cows with Angus and Brahman, to estimate heterosis and direct and maternal genetic breed effects, and to describe calf loss, cow removals from the project, the occurrence of calving difficulty, inadequate calf vigor at birth, and udder problems by cow breed groups. Cows (n = 404) were born from 2002 to 2005. After their first exposure to bulls as young cows, in all subsequent breeding seasons crossbred cows were bred to bulls of the third breed, and straightbred cows were bred to bulls of the other two breeds. Calving records (n = 1,484) from 2005 to 2011 were used to create calving and weaning rate and calving interval (excluding the interval between 2 and 3 yr of age). Final models for these traits included sire breed-dam breed interaction, cow age within year, and random animal effects. Heterosis estimates for Romosinuano-Brahman calving and weaning rate were 0.06 ± 0.02 and 0.07 ± 0.03 (P < 0.05); those for Brahman-Angus were twice as large (0.13 ± 0.03 and 0.14 ± 0.03, respectively; P < 0.001). Estimates of Brahman direct effects on calving and weaning rate were -0.12 ± 0.04 and -0.14 ± 0.05 (P < 0.05); however, Angus direct effects were beneficial for both traits (0.1 ± 0.05, P < 0.05). The effect of heterosis was to reduce calving interval by -49.2 ± 9.9 and -37.2 ± 9.7 d for Romosinuano-Brahman and Brahman-Angus, respectively (P < 0.001). Romosinuano and F1 cows sired by Romosinuano and out of Angus dams had the most occurrences of difficult births as a proportion of cows that calved (0.028 and 0.025, P = 0.04). Angus-sired crossbred cows and Brahman cows had the most occurrences of udder problems as a proportion of lactating cows (0.14 to 0.21, P < 0.04). There were more Brahman-sired cows that died or were culled as a proportion of those cows that began the project (0.1 to 0.28, P < 0.02) than cows in the other breed groups. Romosinuano-Brahman and Romosinuano-Angus cow performance was acceptable, but for most traits, those pairs of breeds had lower heterosis than Brahman-Angus.

Pubertal heifers can be classified between those with high (n = 25) or low (n = 15) antral follicle counts (AFC). The objective of this study was to determine oocyte development and maturation (e.g. fertility) in an IVF system for high- and low-AFC heifers. From a pool of 120 heifers, 10 high- and 10 low-AFC heifers were determined by transrectal ultrasonography; all heifers with evidence of oestrous cyclicity (i.e. pubertal) were synchronized with two 5-mL injections of prostaglandin F2α 11 days apart. Heifers were euthanized over 4 days on Days 15 to 16 of the synchronized oestrous cycle. A total of 15 heifers (n = 7 high and n = 8 low AFC) were at the appropriate stage of the oestrous cycle. Ovaries were collected and transported to the laboratory. Follicles less than 8 mm in diameter were aspirated. The IVF procedures and media were as previously described (Miles et al. 2004. Biol. Reprod. 71, 1919–1926). Cumulus-oocyte complexes (COC) were identified and washed in oocyte collection medium and then in maturation medium and were cultured (5% CO2; 38.5°C) for 24 h. Following maturation, COC were transferred and washed in fertilization medium. Thawed frozen semen from a crossbred bull was subjected to the swim-up procedure. Motile spermatozoa were collected and added to COC to yield a final concentration of spermatozoa per milliliter of fertilization medium. About 24 h later, presumptive zygotes were washed in development medium, placed in microdrops of development medium, and cultured for 8 days. On Days 3 and 8 after fertilization, cleavage and blastocyst development, respectively, were assessed. Data were analysed using the Proc Mixed procedure of SAS (SAS Institute Inc., Cary, NC, USA) and the model included the effects of day of collection (n = 4), group (n = 7 high- or n = 8 low-AFC heifers), and the interaction. The interaction did not differ (P = 0.10). Day of collection influenced (P < 0.05) the number of COC and the number of oocytes cleaved. High- compared to low-AFC heifers had the greater (P < 0.05) numbers of COC (42.7 ± 4.66 v. 22.1 ± 4.59), oocytes that cleaved (28.1 ± 3.60 v. 15.9 ± 3.55), and developed to blastocysts (13.2 ± 1.71 v. 6.2 ± 1.69). However, there was no difference (P > 0.10) in the percentage of COC that cleaved (65.3 ± 5.58 v. 66.2 ± 5.50%, high v. low, respectively) or that developed to blastocysts (46.7 ± 6.75 v. 42.2 ± 6.65%). In conclusion, AFC did not appear to affect oocyte maturation and development through the blastocyst stage.

Although livestock experience many stressors throughout their life, one of the most commonly experienced, and most difficult to control, is stress caused by fluctuations in environmental temperatures that extend beyond the thermoneutral (TN) zone for an animal. In swine, cold stress has long been recognized as a main cause of neonatal morbidity and mortality. A possible explanation for this increased morbidity and mortality may be related to their inability to generate a febrile response. Previously, we reported that the acute phase immune response, including the generation of fever, after exposure to lipopolysaccharide (LPS; Escherichia coli O111: B4; Sigma-Aldrich, St Louis, MO, USA) is substantially altered in neonatal pigs maintained in a cold environment (ie, 18°C). Neonatal pigs that were maintained in a cold environment and administered LPS experienced a period of hypothermia coupled with altered endocrine and proinflammatory cytokine responses that could prove detrimental. In cattle, we previously reported differences in the acute phase immune response of two diverse breeds of Bos taurus cattle (Angus and Romosinuano) when maintained under TN conditions and exposed to LPS. More recently we have reported that differences in the stress and immune responses of Angus and Romosinuano heifers varies, depending on whether the cattle were housed at either TN or heat stress air temperatures. Our data clearly show that even intermittent periods of heat stress similar to that experienced in production environments can have significant effects on the stress and innate immune responses of cattle. Understanding the effect of thermal stress on livestock is critical to developing and implementing alternative management practices to improve their overall health and well-being.

The objective was to identify single nucleotide polymorphism (SNP) associated to fertility in cows raised under a subtropical environment. Re-sequencing of nine genes associated to GH-IGF endocrine pathway, which are located in bovine chromosomes 5, 16 and 20, identified 73 SNP useful for associative genetic studies; however, only seven resulted as polymorphic and unique to the Romosinuano breed. Then, DNA samples were extracted from 129 beef heifers and used to determine genotypes corresponding to each SNP. Mixed model analysis identified one SNP from the PAPP-A2 gene (C/T, rs110490898) as predictor (P < 0.05) of reproductive performance. The allele T was the most favorable allele (P < 0.05), because it was associated with lower age at first calving (-37.1 +/- 14.4 d) and age at second calving (-65.43 +/- 30.8 d). In the contrast analysis, the linear term resulted as significant and quadratic term as non significant, which suggested an additive effect of the alleles. These results provide evidence to support the PAPP-A2 gene as a candidate gene associated to reproductive performance in heifers and first-calf cows from the Romosinuano breed, raised under a subtropical environment.

Beef cows in the subtropical USA must be adapted to the stressors of the environment, typically supplied by using Brahman (Br) breeding. Calves produced in the region, however, are usually grown and finished in more temperate regions, and have a perceived reputation for poor ADG and feed efficiency during finishing. Compromised fertility and carcass quality often associated with the Br have increased interest in tropically adapted Bos taurus breed types. The objective of this study was to evaluate 3 breeds [An = Angus (Bos taurus, temperate); Br (B. indicus, tropical); and Ro = Romosinuano (B. taurus, tropical)] and all possible crosses during various segments of post-weaning growth, and for feed efficiency during the finishing phase. Steer calves (n = 473) born over 3 yr were weaned in late September, backgrounded for at least 21 d (BKG), shipped 2,025 km to El Reno, OK, in October, fed a preconditioning diet for 28 d (RCV), grazed wheat (Triticum aestivum L.) pasture from November to May (WHT), finished on a conventional feedlot diet (FIN), and serially harvested after approximately 95, 125, and 150 d on feed. Body weight and ADG during each segment were tested using a mixed model that included calf age at weaning, year (Y), breed of sire (SB), breed of dam (DB), and interactions. In addition, winter treatment (continuous wheat or reduced grazing of wheat with supplement) was included for the wheat and feedlot phases. Sire within SB × SB [and pen (barn × year) for feedlot phase] were considered random. The SB × DB interaction was significant for all traits (P < 0.01) except exit velocity taken at weaning and ADG during FIN, but both traits were affected by 3-way interactions with Y or harvest group. Tropically-adapted purebred steers had greater (P < 0.01) ADG than AnAn through weaning and BKG in FL but the reverse was true during the RCV and WHT segments. Similar, but less pronounced results were noted for F(1) steers with 100% tropical influence compared with those with only 50%. Heterosis was numerically greater for most traits for An × Br (11 to 64%) compared with An × Ro and Br × Ro (3 to 42%), which were similar. In a subset of the steers (n = 261), G:F was not influenced by level of tropical breeding, but tropically adapted steers were more efficient (P < 0.05) by residual feed intake. No heterosis was evident. These data show that in temperate zones, winter is the period when productivity of tropically adapted cattle is compromised.

The objectives of this work were to estimate heterosis and breed genetic effects for carcass quantity, quality, and palatability traits of steers (Bos spp.) produced from matings of Romosinuano, Brahman, and Angus cattle. Steers (n = 464) were weaned at 7 mo of age and transported to the Southern Great Plains where they grazed winter wheat for 6 mo and were then fed a finishing diet until serial slaughter after different days on feed (average 130 d). Carcass quality and quantity traits were measured; steaks (aged 7 d) were obtained for palatability evaluation. Heterosis was detected for BW, HCW, dressing percentage, LM area, and yield grade for all pairs of breeds. Generally, Romosinuano-Angus heterosis estimates were smallest, Romosinuano-Brahman estimates were intermediate, and Brahman-Angus heterosis estimates were largest. The direct Romosinuano effect was to decrease (P < 0.05) BW (-67 ± 16 kg), HCW (-48 ± 10 kg), dressing percentage (-1.4 ± 0.5 units), 12th rib fat thickness (-5.2 ± 0.8 mm), and yield grade (-0.9 ± 0.1), and to increase LM area per 100 kg HCW (3.6 ± 0.3 cm(2)/100 kg). Significant Brahman direct effects were detected for BW (34 ± 17 kg), HCW (29 ± 10 kg), dressing percentage (1.6 ± 0.6 %), LM area per 100 kg HCW (-3.3 ± 0.4 cm(2)/100 kg), and yield grade (0.6 ± 0.1). Significant Angus direct effects were to increase 12th rib fat thickness (3.8 ± 1 mm). Among sire breed means, Romosinuano had reduced (P = 0.002) marbling score (393 ± 9) than Angus, but greater mean sensory tenderness scores (5.8 ± 0.1), and reduced percentage Standard carcasses (10 ± 2%) than Brahman (P < 0.002). Angus sire breed means for marbling score (475 ± 10), overall tenderness (5.8 ± 0.1), and percentage Choice carcasses (75 ± 5%) were greater (P < 0.05) than Brahman sire breed means (360 ± 11, 5.4 ± 0.1, 31 ± 5%). From consideration only of characteristics of the end product of beef production, Romosinuano did not provide a clearly superior alternative to Brahman for U.S. producers, as they had some quality and palatability advantages relative to Brahman, but at lighter HCW.

The objectives of this study were to characterize rectal temperature and coat score under subtropical North American summer conditions for straightbred and crossbred Romosinuano, Brahman, and Angus cattle, to estimate heterosis and breed direct and maternal effects in a subset of those, and to estimate heritability and genetic correlation of these traits. Records of cows (n=612 cows; 1861 total records) and calves (n=1588) from summer days in subtropical Florida, USA, were evaluated using animal models. Records of cows and calves from 2 management groups were analyzed separately. In the first management group, cows were all straightbred as were their calves; most of these cows were dams of cows in the other management group. Cows in that second management group were produced from all possible matings of Romosinuano, Brahman, and Angus bulls and cows; breed groups were 3 straightbred groups and 3 groups of F1 cows (reciprocal crosses combined). Calves of these cows were 3-breed crosses (all F1 cows were mated to bulls of the 3rd breed) and F1 crosses (straightbred cows were bred in approximately equal numbers to bulls of the other 2 breeds). Angus straightbred and crossbred cows and calves had the highest rectal temperature and coat score (subjective score where larger numbers indicated greater quantity of hair on the coat) means in all 4 analyses. In the second management group (straightbred and crossbred cows raising crossbred calves), Romosinuano straightbreds and F1 Romosinuano–Brahman cows had the lowest (P<0.001) rectal temperature and coat score means. Heterosis for rectal temperature was −0.2±0.05 and −0.24±0.05 °C for Romosinuano–Angus and Brahman–Angus, respectively (P<0.001). Heterosis for coat score was −1.4±0.2, −0.9±0.2, and −2±0.2 for Brahman–Angus, Romosinuano–Brahman, and Romosinuano–Angus, respectively (P<0.001). Direct effects of Romosinuano and Brahman reduced rectal temperature and coat score; direct effects of Angus increased both. Estimates of heritability were 0.19±0.03 and 0.27±0.04 for rectal temperature and coat score, respectively. Permanent environmental effects as proportions of phenotypic variance were 0.03±0.02 and 0.17±0.04 for rectal temperature and coat score, respectively. The estimate of genetic correlation of these traits was 0.24±0.09. With respect to these traits, Romosinuano may offer benefits of tropical adaptation at least to the extent of Brahman under Florida summer conditions.

Increasing the availability and improving the quality of surface water in south Florida by temporarily flooding previously drained pastureland is one of the goals of Northern Everglades Restoration Initiative. Bahiagrass (Paspalum notatum Fluegge) is one of the most important forage grasses in the region and although tolerant to short‐ term flooding, bahiagrass is classified as a facultative upland (FACU+) species that suggest dry matter production and plant persistence might be reduced under periods of extended waterlogging. A 2‐yr greenhouse study was conducted in 2008 and 2009 to determine the effect of flooding duration on dry matter yield (DMY) and crude protein content (CPC) of bahiagrass compared to two flooding tolerant forages, limpograss (Hemarthria altissima Poir), and maidencane (Panicum hematomon Schult) and to determine if N fertilization could be used to mitigate flooding effects. Dry matter production and CPC levels varied with flooding durations (P ≤ 0.001) and levels of N fertilization (P ≤ 0.001). Averaged across flooding duration and levels of N, limpograss had the greatest dry matter yield of 11.6 t ha−1 followed by maidencane (8.6 t ha−1) and bahiagrass (8.5 t ha−1) while bahiagrass had the highest CPC of 6.9% followed by maidencane (6.0%) and limpograss (3.7%). The overall yield response of the three forage species: bahiagrass (R2 = 0.95**); limpograss (R2 = 0.93**); and maidencane (R2 = 0.99**) were linearly related to increasing levels of N fertilization. Crude protein contents of three forage species: bahiagrass (R2 = 0.97**), limpograss (R2 = 0.99**), and maidencane (R2 = 0.87**) were also linearly related to increasing levels of N fertilization. Averaged across forage species, dry matter yield of forages fertilized with 200 kg N ha−1 with no flooding were statistically comparable with plants that were fertilized with 200 kg N ha−1and flooded for 84 d. Our results support our hypothesis that the negative impact of flooding could be mitigated by N fertilization.

A study was conducted to evaluate DMI and feeding behavior of feedlot beef steers fed diets that varied in the proportion of wheat dried distillers grains with solubles (DDGS), with DDGS replacing barley grain or silage. Eighty crossbred steers (486 ± 28 kg) were randomly allotted to 8 pens (2 pens per treatment). The pens were fitted with the GrowSafe system and the steers were tagged with transponders enabling continuous recording of feeding behavior of individual steers, including frequency and duration of visits to the feed bunk and individual feed intake. Steers were fed 1 of 4 diets: control, low (25DDGS), medium (30DDGS), and high (35DDGS) wheat DDGS (DM basis). The control diet consisted of 15% barley silage, 85% barley grain concentrate; the 3 DDGS diets were formulated by substituting 20% barley grain and 5, 10 and 15% silage, respectively, with 25, 30 and 35% wheat DDGS such that the 35DDGS diet contained no silage. In comparison to control, calves fed 25DDGS had greater (P < 0.01) DMI (9.5 vs. 11.3 kg/d) and feeding time (84 vs. 112 min/d), but feeding rate (115 vs. 108 g/min), meal frequency (9.3 vs. 10.8, meal/d), and meal length (9.9 vs. 10.9 min/meal) were not different. With increasing substitution of wheat DDGS for silage, DMI (11.3 to 10.7 kg/d; P < 0.05), feeding time (112 to 89 min/d; P < 0.01), and meal length (10.9 to 8.3 min/ meal; P < 0.01) linearly decreased, but feeding rate (108 to 134 g/min) and meal frequency (10.8 to 15.4 meal/d) linearly increased (P < 0.01). The results indicate that feeding a diet containing moderate levels of wheat DDGS with adequate silage increased DMI but longer feeding time was required. In contrast, when diets contained minimal (i.e., 5%) or no silage, steers increased feeding rate and meal frequency to consume more feed.

Our primary objective of this experiment was to evaluate potential genetic differences between two diverse Bos taurus breeds [Angus (AG) and Romosinuano (RO)] in response to an endotoxin challenge. Eighteen steers (n = 9 steers/breed; 299.4 ± 5.2 kg BW) were acclimated to environmentally controlled chambers maintained at thermoneutrality (19.7 °C) and then fitted with indwelling jugular catheters and rectal temperature (RT) recording devices 1 d before the endotoxin challenge. The next day, blood samples were collected at 30-min intervals from −2 to 8 h, and RT was measured continuously at 1-min intervals throughout the study. At time 0, all steers received an intravenous bolus injection of lipopolysaccharide (LPS; 2.5 μg/kg BW). Serum samples were stored at −80 °C until analyzed for cortisol, proinflammatory cytokines [tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and interferon gamma (IFN-γ)], and acute phase proteins (serum amyloid A, acid soluble protein, ceruloplasmin, and α-acid glycoprotein). Rectal temperatures increased in both breeds within 1 h after LPS, with RO producing a greater increase in RT than AG steers (P < 0.001). Serum cortisol and TNF-α increased (P < 0.01) in both breeds within 1 h after the LPS challenge. For cortisol, an overall breed effect (P < 0.02) was detected, such that AG steers had a higher cortisol response than RO steers. A breed × time interaction (P < 0.01) was observed for TNF-α, such that the response was delayed and extended in the RO steers compared with the AG steers. At 2 and 2.5 h after LPS, TNF-α concentrations were greater (P < 0.03) in RO steers than in AG steers. For IL-1β, a breed × time interaction (P < 0.04) was also observed. At 3 h after LPS, IL-1β concentrations were greater (P < 0.01) in RO steers than in AG steers. Serum IL-6 and IFN-γ increased (P < 0.01) in a similar manner in both groups after the LPS challenge. These data show differences in the innate immune response between two diverse Bos taurus breeds which may provide insight about differences observed in productivity, heat tolerance, disease resistance, and longevity among cattle breeds.

This study measured physiological, immunological, and endocrinological responses of Bos indicus cattle of differing temperaments to transportation. Based on temperament score (TS) the 7 most Calm (TS=0.84±0.03) and 8 most Temperamental (TS=3.37±0.18) Brahman bulls were selected from our research herd. Prior to transportation bulls were fitted with heart rate monitors, indwelling jugular vein catheters, and rectal temperature recording devices that enabled continuous collection of data and samples during transport. The bulls were loaded into individual stalls in a trailer, and each catheter extension was attached to an IceSampler™ device that was programmed to collect blood samples at 15- and 30-min intervals. The trailer remained stationary for 120min prior to the initiation of transportation to acclimate bulls to the stalls. The bulls were then transported for 4h (390km roundtrip; average of 91km/h). Collected blood samples were analyzed for cortisol, epinephrine, and norepinephrine. Additional blood samples were collected for isolation of peripheral blood mononuclear cells (PBMCs) to determine proliferation, IgM production, and gene expression. Heart rate fluctuated in Temperamental but not in Calm bulls throughout the study (time×temperament interaction P=0.04). Rectal temperature increased over time (P<0.001) but was not affected by temperament (P=0.57). Change in rectal temperature may be partially attributable to the change in ambient temperature as the two were highly correlated (r=0.73 and 0.72 for Calm and Temperamental bulls, respectively; P<0.001). Cortisol concentrations increased in Calm but not Temperamental bulls in response to transportation (time×temperament interaction P=0.01). Epinephrine concentrations were unchanged in Calm but decreased in Temperamental bulls (time×temperament interaction P=0.07) throughout the study. Norepinephrine concentrations were not affected by transportation (P=0.36) or temperament (P=0.93). The production of IgM by PBMCs was not affected by temperament (P=0.40) or transportation (P=0.28). Proliferation of PBMCs was not affected by temperament (P=0.98) but tended (P=0.06) to be greater post-transportation. The expression of the glucocorticoid receptor (P=0.02) and toll-like receptor 4 (P=0.08) mRNAs decreased in response to transportation. In summary, these data indicate that transportation only affected cortisol concentrations in Calm bulls. Additionally, temperament influenced cortisol and epinephrine concentrations as well as heart rate. However, there was no influence of temperament, and limited influence of transportation, on PBMC functions. While transportation has been purported to be a stressor in cattle, the temporal pattern observed while the bulls were on the trailer is suggestive that the stress occurred prior to loading the bulls into the trailer.