Biomedical subjects

R Flores

Publications and source records attributed to R Flores.

At least 19 recordsLinked to original sources

PubMed2007

Influence of body condition and bovine somatotropin on estrous behavior, reproductive performance, and concentrations of serum somatotropin and plasma fatty acids in postpartum Brahman-influenced cows.

Ninety-nine multiparous Brahman-influenced (1/4 to 3/8 Brahman) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine somatotropin (bST) on estrous characteristics, reproductive performance, and concentrations of serum GH and plasma NEFA. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg s.c.) on d -35, -21, and -7 before initiation of the breeding season. On d -7, all cows received an intravaginal, controlled internal drug-releasing (CIDR) device. On d 0 (initiation of the 70-d breeding season), the CIDR were removed and cows received prostaglandin F2alpha (PGF2alpha). Blood samples were collected from the median caudal vein of the cows at each bST treatment and at d -28 and 0. Estrous behavior was monitored by radiotelemetry during the first 30 d of the breeding season. Growth hormone was increased (P < 0.05) in low and moderate BC cows treated with bST. The percentage of cows detected in estrus during the first 30 d of the breeding season was decreased (P = 0.05) for low BC (64%) compared with moderate BC (82%) cows. The interval to first estrus tended (P = 0.07) to be shorter in low BC-bST-treated cows (3.7 +/- 1.9 d) than in moderate BC-bST-treated cows (9.6 +/- 1.8 d). During the first 30 d of the breeding season, cows in low BC had a decreased (P = 0.02) number of mounts received and increased (P = 0.001) quiescence between mounts compared with cows in moderate BC. The number of mounts received was reduced (P = 0.04) in bST-treated cows. More (P = 0.02) cows treated with bST became pregnant during the first 3 d of the breeding season compared with non-bST-treated cows. The cumulative first-service conception rate tended (P = 0.07) to be greater for bST-low BC cows than non-bST-treated cows in low or moderate BC. On d 0, NEFA were greater (P < 0.05) in bST-treated vs. non-bST-treated cows. Low BC and bST reduced the intensity of behavioral estrus in postpartum Brahman-influenced cows. However, bST increased the first-service conception rate during the first 30 d of breeding and pregnancy rates during the first 3 d of breeding in postpartum Brahman-influenced cows.

Animal Husbandry↗

PubMed2006

Influence of dietary endophyte (Neotyphodium coenophialum)-infected tall fescue (Festuca arundinacea) seed on fecal shedding of antibiotic resistance-selected Escherichia coli O157:H7 in ewes.

The objectives were to determine the effects of short-term feeding of a toxic endophyte (Neotyphodium coenophialum)-infected tall fescue seed (Festuca arundinacea, cultivar 'Kentucky 31') on fecal shedding and intestinal concentrations of Escherichia coli O157:H7 and the concentrations of prolactin, cortisol, and NEFA in experimentally inoculated ewes. Twelve ewes (mean BW = 46 +/- 2 kg) were fed a diet containing either high endophyte-infected (HI-E) or low endophyte-infected (LO-E) tall fescue seed for 7 d. Each diet consisted of 50% (as-fed basis) tall fescue seed. Ewes were experimentally inoculated with antibiotic resistance-selected E. coli O157:H7 on d 1 of the feeding treatment, and fecal shedding of inoculated pathogens was monitored daily on d 2 to 6. On d 7, ewes were weighed and euthanized, and tissues and contents were sampled from the ileum, cecum, and rectum for quantitative enumeration of E. coli O157:H7. Urine was collected at euthanization to determine total ergot alkaloid concentrations. Ewes fed HI-E had lower (P < 0.001) DMI than did ewes fed LO-E (0.8 and 1.6 +/- 0.1 kg/d of DMI for HI-E and LO-E ewes, respectively); consequently, there was a tendency (P = 0.06) for HI-E ewes to lose 0.3 +/- 0.4 kg of BW/d and LO-E ewes to gain 0.2 +/- 0.4 kg of BW/d during the 7 d. Urinary ergot alkaloids were increased (P < 0.001) in ewes fed HI-E (47.8 +/- 9.4 ng/mg of creatinine) compared with those fed LO-E (6.2 +/- 9.4 ng/mg of creatinine). Prolactin tended (P = 0.06) to be decreased in ewes fed HI-E (7.2 +/- 7.0 ng/mL) compared with those fed LO-E (27.7 +/- 7.0 ng/mL). Fecal shedding of E. coli O157:H7 tended (P = 0.06) to be increased in HI-E ewes [5.4 cfu (log10)/g of feces] compared with LO-E ewes [4.5 cfu (log10)/g of feces]. The population of E. coli O157:H7 in luminal contents from the ileum, cecum, and rectum did not differ (P > 0.36) between treatments. Treatment did not influence (P = 0.30) the occurrence of E. coli O157:H7 in cecal or rectal tissues; however, ileal tissues from HI-E ewes tended (P = 0.12) to have an increased incidence of E. coli O157:H7. Concentrations of NEFA tended (P = 0.12) to be greater in HI-E ewes than in LO-E ewes, whereas cortisol was similar (P = 0.49) for HI-E and LO-E ewes. We conclude that short-term feeding of HI-E tall fescue seed may alter the concentrations of prolactin and NEFA, and may increase fecal shedding of E. coli O157:H7 in experimentally inoculated ewes.

Animal Feed↗

PubMed2006

Diagnosis of "Maladie des feuilles cassantes" or Brittle leaf disease of date palms by detection of associated chloroplast encoded double stranded RNAs.

The "Maladie des feuilles cassantes" (MFC) or "Brittle leaf disease" of date palms is associated with the accumulation of two populations of small, chloroplast-encoded RNAs. A plasmid vector containing a cDNA with partial sequences of both of these RNA populations was used to synthesize a DIG-labeled bifunctional probe by PCR. The probe has been tested to detect, by molecular hybridization, MFC-associated RNAs from dsRNA-enriched palm leaflet preparations. Leaflet samples from MFC-affected date palm trees consistently gave a positive hybridization signal regardless of the date palm cultivar, severity of symptoms, or geographical location, whereas samples from date palm trees affected by other biotic and abiotic stresses tested negative. The assay is specific for MFC and can be used for early diagnostic purposes.

Arecaceae↗

PubMed2006

Close structural relationship between two hammerhead viroid-like RNAs associated with cherry chlorotic rusty spot disease.

Analysis of the population of cherry small circular RNAs (cscRNAs) from trees affected by cherry chlorotic rusty spot (CCRS) showed two groups of variants with similar sequence but differing in size (394-415 and 372-377 nt for cscRNA1 and cscRNA2, respectively) because of the presence or absence of a 27-nt fragment folding into a hairpin in their predicted quasi-rod-like secondary structures. These structures were preserved by co-variations and compensatory mutations, as well as by additional complex rearrangements. The variability also preserved the central conserved core and the stability of the helices of the plus and minus hammerhead ribozymes, supporting their role in replication of cscRNAs. The smaller variants most likely derive from the larger through recombination events. Possible functional relationships between cscRNAs and certain mycoviral-like double-stranded RNAs, also associated with CCRS, are discussed.

Base Sequence↗

PubMed2006

[Williams syndrome: its clinical aspects and molecular bases].

INTRODUCTION AND DEVELOPMENT: Williams syndrome is a developmental disorder with an estimated prevalence of 1 in 7,500 newborns. Its phenotype is characterized by distinctive facial features, mild to moderate mental retardation and general cognitive deficits with a non-uniform profile, having problems in some areas (psychomotricity, visuospatial integration) and relative preservation of others (language, musicality), friendly personality, occasional hypercalcemia of infancy, and a vasculopathy with supravalvular aortic stenosis. Williams syndrome is caused by a submicroscopic deletion of 1.55 Mb in the chromosome band 7q11.23, which includes 26-28 genes. The mutational mechanism consists in a misalignment between regions of almost identical sequence and the subsequent unequal recombination. The reciprocal product of this rearrangement is the duplication of this region, causing a language specific disorder. CONCLUSIONS: Clinical-molecular correlations establishment through a good phenotypic characterization and the precise analysis of breakpoints in patients with atypical and typical deletions, altogether with the design of animal models and functional studies in vitro for the genes of the interval will be important to be able to determine the exact contribution of the genes to the phenotype, to know their pathogenesis and physiopathology, and to identify therapeutic methods.

Animals↗

PubMed2006

Escherichia coli O157:H7 and Salmonella in water and soil from tall fescue paddocks.

Six 1-ha paddocks of tall fescue (Festuca arundinacea) grazed by Gelbvieh x Angus heifers from 1 March to 21 June 2005 were used to determine the prevalence of Escherichia coli O157:H7 and Salmonella in water tanks, and standing water and surface soil surrounding water tanks in tall fescue paddocks grazed by cattle. Paddocks included two each of Kentucky-31 endophyte-infected tall fescue (E+), Jesup tall fescue with the AR542 endophyte strain (MaxQ), and HiMag tall fescue with strain 4 endophyte (HiMag4). Samples were collected weekly (6 June to 5 July) from water tanks (n = 30), and standing water (n = 18) and surface soil (n = 30) surrounding the water tanks in each paddock commencing 3 weeks prior to termination of grazing until 2 weeks after cattle removal. Prevalence of E. coli O157:H7 tended (p = 0.07) to be increased in standing water and surface soil surrounding water tanks when cattle were present. Presence of cattle resulted in muddy conditions surrounding water tanks. Consumption of E+ tall fescue did not influence (p > 0.10) the prevalence of E. coli O157:H7 or Salmonella in or around water tanks. Neither E. coli O157:H7 or Salmonella were detected in water tanks. Total percentage of standing water samples positive for E. coli O157:H7 was 27.8% and 5.6% for Salmonella. Escherichia coli O157:H7 (6.7%) and Salmonella (10%) also were detected in the surface soil surrounding the water tanks. We conclude that areas surrounding water tanks in tall fescue paddocks can be reservoirs of pathogenic bacteria.

Animal Feed↗

PubMed2006

Molecular characterization of the largest mycoviral-like double-stranded RNAs associated with Amasya cherry disease, a disease of presumed fungal aetiology.

The sequence of the four large (L) double-stranded RNAs (dsRNAs) associated with Amasya cherry disease (ACD), which has a presumed fungal aetiology, is reported. ACD L dsRNAs 1 (5121 bp) and 2 (5047 bp) potentially encode proteins of 1628 and 1620 aa, respectively, that are 37% identical and of unknown function. ACD L dsRNAs 3 (4458 bp) and 4 (4303 bp) potentially encode proteins that are 68% identical and contain the eight motifs conserved in RNA-dependent RNA polymerases (RdRp) of dsRNA mycoviruses, having highest similarity with those of members of the family Totiviridae. Both terminal regions share extensive conservation in all four RNAs, suggesting a functional relationship between them. As ACD L dsRNAs 1 and 2 do not encode RdRps, both are probably replicated by those from either ACD L dsRNA 3 or 4. Partial characterization of the equivalent L dsRNAs 3 and 4 associated with cherry chlorotic rusty spot revealed essentially identical sequences.

Amino Acid Sequence↗

PubMed2006

Prevalence of Escherichia coli O157:H7 and Salmonella in beef steers consuming different forage diets.

AIMS: To compare the prevalence of faecal shedding of Escherichia coli O157:H7 and Salmonella in growing beef cattle consuming various forages. METHODS AND RESULTS: In Experiment I, faecal samples were collected from steers grazing either endophyte-infected (E+) tall fescue or common bermudagrass (CB). Steers grazing E+ tall fescue were confined to a dry-lot pen and fed CB hay ad libitum for 10 days. In Exp. II, faecal samples were collected from steers grazing either E+ or novel endophyte-infected (NE) tall fescue and treated with one of two anthelmintics: ivermectin (I) or fenbendazole (F). In Exp. I, prevalence of E. coli O157:H7 was less in E+ tall fescue steers fed CB hay than steers grazing CB. More I-treated steers shed Salmonella than F-treated steers at 42-day postanthelmintic treatment but shedding of Salmonella was similar between anthelmintics at day 63 in Exp. II. CONCLUSIONS: Faecal shedding of pathogenic bacteria was not affected by grazing E+ tall fescue. Alterations of forage diets may influence the prevalence of E. coli O157:H7, and anthelmintic treatment could affect faecal shedding of Salmonella. SIGNIFICANCE AND IMPACT OF THE STUDY: Knowledge of factors that influence shedding of pathogenic bacteria in cattle is necessary to develop on-farm intervention strategies aimed at reducing pathogen shedding.

Animal Feed↗

PubMed2006

Estrous behavior and initiation of estrous cycles in postpartum Brahman-influenced cows after treatment with progesterone and prostaglandin F2alpha.

Spring-calving, crossbred (1/4 to 3/8 Brahman) primiparous (n = 56) and multiparous (n = 102) beef cows were used to evaluate the effects of progesterone, delivered via a controlled internal drug-releasing (CIDR) device, and prostaglandin F(2alpha) (PGF(2alpha)) on estrous behavior, synchronization rate, initiation of estrous cycles, and pregnancy rate during a 2-yr period. To determine luteal activity, weekly blood samples were collected 3 wk before initiation of a 75-d breeding season. Treated cows received a CIDR for 7 d beginning on d -7 of the breeding season. On d 0, CIDR were removed, and cows receiving CIDR were administered PGF(2alpha); control cows received no treatment. Cows were exposed to bulls, and estrous activity was monitored using a radiotelemetry system for the first 30 d of the breeding season. Treatment with CIDR-PGF(2alpha) increased (P < 0.05) the number of mounts received (22.5 +/- 3.0 vs. 13.7 +/- 3.9 for CIDR-PGF(2alpha) vs. untreated control cows, respectively) but did not influence duration of estrus or quiescence between mounts. Number of mounts received and duration of estrus were greater (P < 0.05) in multiparous compared with primiparous cows. Synchronization of estrus was greater (P < 0.05) in cows treated with CIDR-PGF(2alpha) (56%) compared with control cows (13%) during the first 3 d of the breeding season. More (P < 0.05) anestrous cows treated with CIDR-PGF(2alpha) than anestrous control cows were in estrus during the first 3 d (59 vs. 12%) and 30 d (82 vs. 63%) of the breeding season. Treatment with CIDR-PGF(2alpha) decreased (P < 0.05) the interval to first estrus after treatment during the first 30 d of the breeding season compared with control cows (5.5 +/- 1.1 vs. 9.0 +/- 1.4 d). First service conception rate was greater (P < 0.05) in CIDR-PGF(2alpha)-treated cows compared with control cows. Cyclic cows at initiation of the breeding season had an increased (P < 0.05) 75-d pregnancy rate compared with anestrous cows, and the pregnancy rate tended (P = 0.10) to be greater in multiparous compared with primiparous cows. We conclude that treatment of Brahman-influenced cows with progesterone via a CIDR for 7 d, along with administration of PGF(2alpha) at CIDR removal, increases the number of mounts received, improves synchronization and first service conception rates, decreases the interval to first estrus after treatment, and may be effective at inducing estrous cycles in anestrous cows.

Animals↗

PubMed2005

Mycorrhizal synthesis of Lactarius indigo (Schw.) Fr. with five Neotropical pine species.

This paper describes for the first time the ectomycorrhiza synthesized between two Guatemalan strains of Lactarius indigo (Schw.) Fr. and the Neotropical species Pinus ayacahuite var. ayacahuite Ehren, P. hartwegii Lindl., P. oocarpa Schiede ex Schltdl. var oocarpa, P. pseudostrobus Lindl. and P. rudis Endl. The synthesis was carried out in a controlled growth chamber using plastic containers with peat moss-vermiculite substrate and mycelial inoculum. Mycorrhiza were obtained 25 days after inoculation. A description of the morphology, appearance and structure of mantle and Hartig net is given for each combination. Mycorrhiza were saffron to cinnamon greenish with age, with a net of saffron laticifers visible through outer mantle; orange latex secreted when injured. Cystidia-like emanating hyphae were observed on the mantle surface of young mycorrhiza. Plectenchymatous mantle with abundant interhyphal gelatinous material.

Agaricales↗

PubMed2004

The complete nucleotide sequence of a Spanish isolate of Citrus psorosis virus: comparative analysis with other ophioviruses.

The complete genomic sequence (11278 nt) of Citrus psorosis virus (CPsV), isolate P-121 from Spain, was determined and compared with those from isolate CPV-4 and from other ophioviruses. The three RNAs of P-121 had similar size and identical organization as those of CPV-4. The 24K and the RdRp proteins were potentially encoded in the viral complementary (vc) strand of RNA 1, the 54K protein potentially encoded in vcRNA 2 and the coat protein encoded in vcRNA 3. These four proteins from P-121 and CPV-4 had 87, 92, 93 and 94% amino acid identity, respectively, but only 22, 38, 25 and 33% identity with their homologous proteins from Mirafiori lettuce big vein virus (MLBVV), the only other ophiovirus completely sequenced. Biological and genetic differences between CPsV and MLBVV (and the other ophioviruses), would support their future allocation in different genera within a tentative family Ophioviridae.

Base Sequence↗

PubMed2004

In vitro cytoskeleton changes of mouse neurons induced by purified HTLV-1, and PBMC from HAM/TSP patients and HTLV-1 carriers.

HTLV-1 is the causative agent of HAM/TSP. This neurological disease affects the CNS producing damage of the motor tracts at the spinal cord. The HAM/TSP pathogenesis remains undefined. It could include direct and indirect actions of HTLV-1. We studied the effect of purified HTLV-1 and the PBMC of 22 Chilean patients co-cultivated with fetal neurons of mouse (CNh cells): 8 HAM/TSP, 8 HTLV-1 carriers, and 6 non-infected controls. The viral antigens and provirus in CNh cells was evaluated with monoclonal and polyclonal antibodies reacting with HTLV-1 by immunofluorescence assay and PCR at 0, 7 and 15 days of co-cultures, respectively. Viral antigens were detected in 0.1-0.5%, and 0-0.3% of the neurons incubated with lymphocytes of HAM/TSP patients and HTLV-1 carriers, respectively. Neurons incubated with cells of 7 HAM/TSP patients, and 3 HTLV-1 carriers showed the presence of nucleotide sequences of tax gene. These results would be showing that CNh cells would express viral antigens and provirus. The HTLV-1 or their proteins were capable in vitro to produce structural and growth changes in the cytoskeleton of CNh neurons. In this series, the purified HTLV-1 was more effective in the neural changes than PBMC of HAM/TSP or HTLV-1 carriers.

Animals↗

PubMed2003

Polymorphism of a specific region in gene p23 of Citrus tristeza virus allows discrimination between mild and severe isolates.

The pathogenicity determinants of Citrus tristeza virus (CTV) are presently unknown, although transgenic Mexican limes over-expressing CTV p23, an RNA-binding protein involved in regulating the asymmetrical accumulation of viral RNA strands, display typical CTV symptoms. Here we compared the predominant sequence variants of gene p23 from 18 CTV isolates of different geographic origin and pathogenicity characteristics. Phylogenetic analysis of these sequences revealed three groups of isolates: i) mild, inducing only symptoms in lime and/or decline of citrus species grafted on sour orange rootstock, ii) severe, causing additionally stem pitting on sweet orange and/or grapefruit, and iii) an atypical group of isolates inciting variable symptoms. The sequences of the isolates located at the periphery of each group were recombinants. Pairwise comparisons of the predicted amino acid sequences showed that residues at positions 78-80 were characteristic of each group of isolates. Group-specific primers based on these differences allowed RT-PCR detection of each sequence type in dsRNA-rich preparations from infected tissues. While mild isolates contained only the sequence characteristic of this group, most severe isolates contained the sequences characteristic of their group, and additionally, sequences characteristic of the mild and/or the atypical groups, suggesting that the severe phenotype is associated with the presence of the severe and/or the atypical sequence types. This association can be exploited for quick detection of potentially damaging sequence variants and for monitoring cross protection.

Amino Acid Sequence↗

PubMed2003

Identification in eggplant of a variant of citrus exocortis viroid (CEVd) with a 96 nucleotide duplication in the right terminal region of the rod-like secondary structure.

Analysis of eggplants, kept for years under greenhouse conditions after having been mechanically inoculated with nucleic acid preparations from field-grown eggplants containing two viroids, Eggplant latent viroid (ELVd) and Citrus exocortis viroid (CEVd), revealed the presence of an additional larger viroid RNA. Molecular characterization of this RNA showed that it is a stable 467-nt variant of CEVd with a 96-nt duplication of the right terminal region (CEVd-D96) that preserves the rod-like secondary structure. The coexistence in eggplant of CEVd (371nt) and CEVd-D96, and the fact that they have an almost identical sequence, strongly suggests the emergence of the latter from the former through an internal recombination mediated by a jumping RNA polymerase with low processivity. CEVd-D96 from eggplant is similar to the CEVd-D92 variant characterized previously in a hybrid tomato, suggesting that certain hosts may play a critical role in selecting and replicating this class of enlarged variants.

Base Sequence↗

PubMed2003

Eggplant latent viroid, the candidate type species for a new genus within the family Avsunviroidae (hammerhead viroids).

Viroids, small circular RNAs that replicate independently and in most cases incite diseases in plants, are classified into the families Pospiviroidae, composed of species with a central conserved region (CCR) and without hammerhead ribozymes, and Avsunviroidae, composed of three members lacking CCR but able to self-cleave in both polarity strands through hammerhead ribozymes. Here we report the biological and molecular properties of Eggplant latent viroid (ELVd). Purified circular ELVd induces symptomless infections when inoculated into eggplant seedlings. ELVd can be transmitted horizontally and through seed. Sequencing 10 complete cDNA clones showed that ELVd is a circular RNA of 332 to 335 nucleotides with high variability. This RNA can adopt a quasi-rod-like secondary structure of minimal free energy and alternative foldings that permit formation of stable hammerhead structures in plus and minus strands. The ribozymes are active in vitro and, most likely, in vivo. Considering the ELVd properties to be intermediate between those of the two genera of family Avsunviroidae, we propose ELVd as the type species of a third genus with the name ELAVIROID:

Base Sequence↗

PubMed2002

Effects of anabolic implants of oestradiol alone or in combination with trenbolone acetate on the ultrastructure of mammary glands in female lambs regarding their interference in prolactin secretion.

The side-effects of anabolic steroid implants on mammary gland ultrastructure were evaluated in female lambs treated with oestradiol (n = 10) and with oestradiol plus trenbolone acetate (n = 10). Ten non-implanted lambs were used as controls. Apart from the ultrastructural study of the mammary gland, an assessment of the prolactin pituitary cell population was carried out by immunological methods. Our results showed that oestrogenic implants exert stimulating effects on mammary gland development, both by activating the synthesis process at mammary gland cell levels and by increasing prolactin pituitary production. Nevertheless, there was no evidence of secretory products in the lumen of the gland. Implants containing trenbolone acetate counteracted the mammary stimulus of oestrogens showing ultrastructural images of cell autolysis and necrosis.

Anabolic Agents↗

PubMed2002

Two chloroplastic viroids induce the accumulation of small RNAs associated with posttranscriptional gene silencing.

In plants, posttranscriptional gene silencing (PTGS) has been reported for cytoplasmic RNAs from endogenous nuclear genes, transgenes, viruses, and, recently, for a viroid with nuclear replication and accumulation. However, phenomena of this kind have not been described for mitochondrial or chloroplastic RNAs. Here we show that viroids that replicate and accumulate in the chloroplast are also targets of PTGS and this process may control viroid titer.

Cell Nucleus↗

PubMed2002

Relationships of metabolic hormones and serum glucose to growth and reproductive development in performance-tested Angus, Brangus, and Brahman bulls.

Understanding mechanisms that regulate growth and reproduction are important for improving selection strategies in cattle. In this study, Angus, Brangus, and Brahman bulls (n = 7 per breed) of similar age were selected from a group of 65 weanlings. Bulls were evaluated after weaning (i.e., approximately 6 mo of age) for 112 d for serum concentrations of metabolic hormones and glucose, growth, and reproductive traits. Performance data and blood sera were collected on d 0, 28, 56, 84, and 112. Sera were also collected in periods from d 50 to 59 (56D) and 103 to 112 (112D). Angus bulls were heavier (P < 0.05) throughout the study than Brahman bulls and were heavier than Brangus bulls on d 56, 84, and 112. Initial and final BW for Angus, Brangus, and Brahman bulls were 292.7, 260.6, and 230.4 and 468.3, 435.6, and 350.7 +/- 12 kg, respectively. Conversely, Brahman bulls had greater hip height (P < 0.05) than Brangus, and Brangus were taller (P < 0.05) than Angus. Angus bulls had the greatest (P < 0.05) scrotal circumference (SC) and Brahman bulls the least. Mean SC across days was 31.5, 29.7, and 25.0 +/- 0.6 cm for the three respective breeds. Serum testosterone was greater (P < 0.01) in Angus and Brangus bulls (10.0 and 8.9 +/- 1.4 ng/mL) than in Brahman bulls (4.0 +/- 1.4 ng/mL) throughout the study. After d 112, 100, 86, and 57% of the Angus, Brangus, and Brahman bulls passed a breeding soundness exam (P = 0.51). Serum concentrations of IGF-I and leptin were greater (P < or = 0.06) in Angus bulls on d 56, 84, and 112 than in Brangus and Brahman bulls. Serum concentrations of GH (P < 0.08) and glucose (P < 0.03) were greater in Brangus bulls than in Angus or Brahman bulls throughout the study. Prediction analyses suggested that serum concentrations of leptin could be used to predict (P < or = 0.08) BW and SC (R2 > 0.82) in the 56D and 112D periods among these breeds. Leptin was also useful in predicting (P < or = 0.09) serum concentrations of GH and testosterone in the 112D period (R2 > 0.32). Residual correlation analyses with the effect of breed removed suggested that leptin was correlated (r > or => 0.53, P < 0.05) with both SC and serum testosterone. Angus and Brahman cattle differ in phenotype, level of adiposity, and rate of sexual development. Data herein suggest that these characteristics could be due to varying mechanisms by which metabolic hormones such as leptin, GH, and(or) IGF-I are regulated.

Animals↗