Bovine dopamine receptors DRD1, DRD4, and DRD5: genetic polymorphisms and diversities among ten cattle breeds.

The aim of this study was to analyze the allelic frequency distribution and segregation among breeds and/or between different cattle genetic groups of four novel single nucleotide polymorphisms of the bovine DRD1 and DRD5 genes and one reported SNP from the DRD4 gene. One hundred and nine-animals from ten different cattle breeds were genotyped and allelic frequencies for each locus were estimated. There were significant differences in the allelic frequencies (P < 0.05) among breeds for the DRD1 and DRD5 markers. The allelic frequencies for markers DRD1-825A>G and DRD5-378C>T were also significantly different between groups differing in genetic background. Because differences in temperament have been reported between Bos taurus taurus and B. taurus indicus breeds and their crosses, further studies are needed to investigate if any association exists between described markers and cattle behavior traits.

Associations between endotoxin-induced metabolic changes and temperament in Brahman bulls.

The influence of temperament on the alteration of metabolic parameters in response to a lipopolysaccharide(LPS) challenge was investigated. Brahman bulls were selected based on temperament score. Bulls (10 months; 211±5kg BW; n = 6, 8 and 7 for Calm, Intermediate and Temperamental groups, respectively) were fitted with indwelling jugular catheters to evaluate peripheral blood concentrations of glucose, blood urea nitrogen (BUN),non-esterified fatty acids (NEFA), insulin, epinephrine and cortisol before and after LPS administration (0.5 µg/kg BW LPS). Feed intake was also recorded. Intermediate bulls consumed more feed than the Temperamental bulls during the challenge (p = 0.046). Pre-LPS glucose (p = 0.401) and BUN (p = 0.222) did not differ among the temperament groups. However, pre-LPS insulin (p = 0.023) was lower, whereas pre-LPS NEFA (p < 0.001),cortisol (p < 0.001) and epinephrine (p < 0.001) were greater in Temperamental than in Calm and Intermediate bulls. Post-LPS glucose was increased in Calm and Intermediate bulls but not in Temperamental bulls(p < 0.001). Insulin concentrations post-LPS were greater in Calm than in Intermediate and Temperamental bulls (p < 0.001). Concentrations of NEFA post-LPS were greater in Temperamental than in Calm and Intermediate bulls (p < 0.001). Serum BUN concentration increased post-LPS, with values being greater in Calm and Intermediate than in Temperamental bulls (p = 0.012). Collectively, these data demonstrate that animal temperament is related to the metabolic responses of Brahman bulls following a provocative endotoxin challenge.Specifically, Temperamental bulls may preferentially utilize an alternate energy source (i.e. NEFA) to a greater degree than do bulls of Calm and Intermediate temperaments. The use of circulating NEFA from lipolysis may reduce the negative metabolic consequences of an immune response by allowing for a prompt answer to increasing energy demands required during immunological challenge, compared with the time required for glycogenolysis and gluconeogenesis.

Evaluation of the effects of sire and dam calving group on age at first calving in Brahman heifers.

This study evaluated the possible effects of sire and dam calving groups on age at first calving in Brahman heifers. A total of 570 heifers born between the years 2004 and 2017 were exposed as yearlings to fertile bulls through time of pregnancy determination. A calving group was determined by calculating the mean (993 d) and standard deviation (187 d) of heifer age at first calving. Heifers considered to calve early (≤899 d; calving group = 1) or late (≥1087 d; calving group = 3) were at least half a standard deviation (94 d) away from the mean. All other heifers were considered to have an intermediate age at first calving (900-1086 d; calving group = 2). Of the 570 heifers, only heifers from a dam (n = 182) with a known age at first calving and from a sire (n = 35) with 5 or more daughters were kept to determine the effect of dam calving group and the effect of sire calving group on age at first calving and calving group in daughters, resulting in a total of 284 heifers available for analysis. Variables included were dam and sire calving groups of the heifer, heifer age at first calving, heifer calving group, heifer season of birth, and heifer year of birth. Data were analyzed using the GLM procedures of SAS and proportions were tested using Chi-square. Sire calving group did affect (P < 0.01) age at first calving and calving group in heifers, but dam calving group did not affect (P > 0.10) daughter age at first calving or calving group. Analysis of dam calving group and sire calving group effects identified a year of birth effect (P < 0.01) on daughter age at first calving and calving group, whereas there was no significant season of birth effect. The proportion of daughters calving early for sire calving groups differed significantly from the expected proportion (P < 0.01), whereas the proportion of daughters calving early for dam calving groups did not differ. An effort to produce a greater proportion of Brahman heifers capable of calving early will not be effective from the dam side but may be effective from the sire side.

Effects of prostaglandin E and F receptor agonists in vivo on luteal function in ewes.

Loss of progesterone secretion at the end of the estrous cycle is via uterine PGF(2alpha) secretion; however, uterine PGF(2alpha) is not decreased during early pregnancy in ewes to prevent luteolysis. Instead the embryo imparts resistance to PGF(2alpha)-induced luteolysis, which is via the 2-fold increase in prostaglandins E(1) and E(2) (PGE(1), PGE(2); PGE) in the endometrium during early pregnancy. Chronic intrauterine infusion of PGE(1) or PGE(2) prevents spontaneous or an estradiol-17beta, IUD, or PGF(2alpha)-induced luteolysis. Four PGE receptor subtypes (EP(1), EP(2), EP(3), and EP(4)) and an FP receptor specific for PGF(2alpha) have been identified. The objective of this experiment was to determine the effects of EP(1), EP(2), EP(3), or FP receptor agonists in vivo on luteal mRNA for LH receptors, occupied and unoccupied LH receptors, and circulating progesterone in ewes. Ewes received a single treatment of 17-phenyl-tri-Nor-PGE(2) (EP(1), EP(3)), butaprost (EP(2)), 19-(R)-OH-PGE(2) (EP(2)), sulprostone (EP(1), EP(3)), or PGF(2alpha) (FP) receptor agonists into the interstitial tissue of the ovarian vascular pedicle adjacent to the luteal-containing ovary. 17-Phenlyl-tri-Nor-PGE(2) had no effect (P> or =0.05) on any parameter analyzed. Butaprost and 19-(R)-OH-PGE(2) increased (P< or =0.05) mRNA for LH receptors, occupied and unoccupied LH receptors, and circulating progesterone. Both sulprostone and PGF(2alpha) decreased (P< or =0.05) mRNA for LH receptors, occupied and unoccupied LH receptors, and circulating progesterone. It is concluded that both EP(3) and FP receptors may be involved in luteolysis. In addition, EP(2) receptors may mediate prevention of luteolysis via regulation of luteal mRNA for LH receptors to prevent loss of occupied and unoccupied LH receptors and therefore to sustaining luteal function.

Prostaglandin E1 (PGE1), but not prostaglandin E2 (PGE2), alters luteal and endometrial luteinizing hormone (LH) occupied and unoccupied LH receptors and mRNA for LH receptors in ovine luteal tissue to prevent luteolysis.

Loss of luteal progesterone secretion at the end of the ovine estrous cycle is via uterine PGF(2)alpha secretion. However, uterine PGF(2)alpha secretion is not decreased during early pregnancy in ewes. Instead, the embryo imparts a resistance to PGF(2)alpha. Prostaglandins E (PGE; PGE(1)+PGE(2)) are increased in endometrium and uterine venous blood during early pregnancy in ewes to prevent luteolysis. Chronic intrauterine infusion of PGE(1) or PGE(2) prevents spontaneous or IUD, estradiol-17beta, or PGF(2)alpha-induced premature luteolysis in nonbred ewes. The objective was to determine whether chronic intrauterine infusion of PGE(1) or PGE(2) affected mRNA for LH receptors, occupied and unoccupied receptors for LH in luteal and caruncular endometrium, and luteal function. Ewes received Vehicle, PGE(1), or PGE(2) every 4h from days 10 to 16 of the estrous cycle via a cathether installed in the uterine lumen ipsilateral to the luteal-containing ovary. Jugular venous blood was collected daily for analysis of progesterone and uterine venous blood was collected on day-16 for analysis of PGF(2)alpha and PGE. Corpora lutea and caruncular endometrium were collected from day-10 preluteolytic control ewes and day-16 ewes treated with Vehicle, PGE(1) or PGE(2) for analysis of the mRNA for LH receptors and occupied and unoccupied receptors for LH. Luteal weights on day-16 in ewes treated with PGE(1) or PGE(2) and day-10 control ewes were similar (P>or=0.05), but were greater (PPGE(2)>Vehicle-treated ewes. Concentrations of PGF(2)alpha and PGE in uterine venous plasma on day-16 were similar (P>or=0.05) in the three treatment groups. Luteal mRNA for LH receptors and unoccupied and occupied LH receptors were similar (P>or=0.05) in day-10 control ewes and day-16 ewes treated with PGE(2) and were lower (P

Endocannabinoid 1 and 2 (CB(1); CB(2)) receptor agonists affect negatively cow luteal function in vitro.

Thirty to 40% of pregnancies are lost during the first third of pregnancy, which has been hypothesized to be due to inadequate progesterone secretion by the corpus luteum. Loss of luteal progesterone secretion during the estrous cycle is via uterine secretion of prostaglandin F(2)alpha (PGF(2)alpha). Cow luteal tissue secretion of prostaglandins (PG) E (PGE(1)+PGE(2)) and PGF(2)alpha are derived from precursors in membrane phospholipids. Cow luteal tissue secretion of PGE and PGF(2)alpha increased linearly with time in culture with the PGE: ratio being 1:1. PGE(1) or PGE(2) are luteotropic in cows and ewes and antiluteolytic in vitro and in vivo in ewes. Endocannabinoids are also derived from phospholipids and are associated with infertility, presumably by reducing implantation; however, effects of endocannabinoids on luteal function have not been addressed. The objective of this experiment was to determine the effects of endocannabinoid type 1 and 2 receptor agonists and receptor antagonists or a fatty acid amide hydrolase (FAAH; catabolizes endocannabinoids) inhibitor, PGE(1), or PGF(2)alpha on bovine luteal secretion of progesterone, PGE, and PGF(2)alphain vitro. PGE and PGF(2)alpha was increased (P< or =0.05) with time in culture, while progesterone did not change (P> or =0.05) with time in vehicle-treated luteal slices in vitro. Progesterone was increased (P< or =0.05) by PGE(1) and decreased (P< or =0.05) by PGF(2)alpha, CB(1) or CB(2) receptor agonists, or a FAAH inhibitor. Both PGE and PGF(2)alpha were decreased (P< or =0.05) by CB(1) or CB(2) receptor agonists or a FAAH inhibitor when compared to vehicle controls. It is concluded that endocannabinoid receptor agonists negatively affect cow luteal function in vitro and that the corpus luteum may also be a site for endocannabinoid decreased fertility as well as a reduction in implantation.

Is endothelin-1 luteolytic or antiluteolytic in ewes?

Endothelin-1 (ET-1) has been reported to mediate prostaglandin (PG) F(2)alpha (PGF(2)alpha)-induced luteolysis. Prostaglandins E (PGE; PGE(1)+PGE(2)) are associated with implantation, maternal recognition of pregnancy, and are antiluteolytic and luteotropic in vitro and in vivo. ET-1 increased PGE secretion by bovine luteal tissue in vitro from cows where estrus was not synchronized or when estrus was synchronized with lutalyse and did not affect luteal PGF(2)alpha or progesterone secretion, which does not support the concept that ET-1 is luteolytic or mediates PGF(2)alpha luteolysis. Therefore, the objective of this experiment was to determine whether ET-1 infused every 6h from 2400 h on day 10-1800 h on day 18 of the ovine estrous cycle either into the interstitial tissue of the ovarian vascular pedicle (IP) or intrauterine (IU) adjacent to the luteal-containing ovary was luteolytic in ewes. Treatments were: Vehicle-IP; Vehicle-IU; ET-1-IP; or ET-1-IU. Weights of corpora lutea differed (P< or = 0.05) among treatment groups. Weights of corpora lutea at 1800 h on day 18 were: VEH-IP-247+/-38 mg; VEH-IU-195+/-31 mg; ET-1-IP-626+/-74 mg; and ET-1-IU-542+/-69 mg. Luteal weights on day 18 in ET-1-IP or ET-1-IU-treated ewes did not differ (P> or =0.05), but were heavier (P< or =0.05) than in the Vehicle-IP or Vehicle-IU treatment groups which did not differ (P> or =0.05). Profiles of progesterone in jugular venous plasma of both control groups treated with Vehicle-IP or Vehicle-IU were lower (P< or =0.05) than in ewes treated with ET-1-IP or ET-1-IU, which did not differ (P> or =0.05) between ET-1-IP or ET-1-IU treatment groups. Treatment with ET-1-IP or ET-1-IU increased (P< or =0.05) the PGE:PGF(2)alpha ratio when compared to the Vehicle-IP or Vehicle-IU treatment groups, which did not differ (P> or =0.05) between each other. In summary, ET-1 prevented the decrease in luteal weights and the decline in progesterone, but increased the PGE:PGF(2)alpha ratio when compared to controls. Therefore, it is concluded that ET-1 is not luteolytic in ewes, but instead may be luteotropic or antiluteolytic by altering uterine secretion of the PGE:PGF(2)alpha ratio, since PGE(1) or PGE(2) are luteotropic in vitro and in vivo, PGE(1) or PGE(2) prevent PGF(2)alpha-induced luteolysis in vitro and in vivo, and PGE(1) and PGE(2) increase two-fold in ewe endometrium to prevent luteolysis during early pregnancy.

Influence of transportation stress and animal temperament on fecal shedding of Escherichia coli O157:H7 in feedlot cattle.

To test the influence of transportation stress and temperament on shedding of Escherichia coli O157:H7, cattle (n=150) were classified at various stages of production as Excitable, Intermediate or Calm based on a variety of disposition scores. Presence of E. coli O157:H7 was determined by rectal swabs from live animals and from colons collected postmortem. Percentage of cattle shedding E. coli O157:H7 at arrival at the feedlot was approximately equal among temperament groups. Before shipment to the processing facility, a higher (P=0.03) proportion of cattle from the Calm group shed E. coli O157:H7 compared to the other temperament groups. When pooled across all sampling periods, cattle from the Calm group had a greater percentage test positive for E. coli O157:H7. Neither the acute stressor of transportation nor a more excitable temperament led to increased shedding of E. coli O157:H7 in cattle.

Relationship of temperament, growth, carcass characteristics and tenderness in beef steers.

Relationships of temperament evaluated at different production stages with growth, carcass characteristics and beef tenderness were determined in Bonsmara crossbred steers managed under commercial managent. Temperament was evaluated at weaning and at initiation of the finishing phase. Steers from a Roswell, NM ranch (n=156) and a Cline, TX ranch (n=21) were stratified at fall weaning by weight and source and randomly allotted to winter ryegrass at Uvalde or Overton, TX followed by feeding in a commercial feedlot near Batesville, TX. Cattle were observed for temperament (escape velocity, EV, m/s; pen and chute temperament score, PTS and CTS) at weaning and upon entry to the feedlot. Cattle were harvested at approximately 7 mm 12th rib fat. Carcass data was taken approximately 36 hrs post-mortem and 2.5cm thick steaks were removed from the 13th rib for Warner-Bratzler shear force (WBS) determination. The only measures of temperament significantly related to performance were EV and PTS. Weaning EV appeared to be more related to feedlot ADG (r=-0.26, P<0.003), ribeye area (r=-0.37, P<0.0008), yield grade (r=0.29, P<0.01) and WBS, r=0.27, P<0.005) than did the later measures of temperament. However, in-feedlot EV was associated with feedlot weights (r=-0.28, P<0.0004). Results of this research suggest temperament, particularly at weaning, is related to feedlot performance, carcass merit, and beef tenderness at a low to moderate level and evaluation of this trait may be a helpful management tool.

Relationships between numbers of antral follicles and postpartum interval in Brahman females.

To determine relationships of ovarian antral follicle count (AFC) on d 28 postpartum with postpartum interval (PPI) and AFC on d 8 post-estrus, three-dimensional ultrasonography was performed on multiparous (n = 47) and primiparous (n = 20) Brahman cows on d 28 postpartum and on d 8 post-estrus. Follicles were evaluated to determine numbers of total, small (≤17 mm3), medium (17 mm3-67 mm3), and large follicles (≥67 mm3) on each ovary. Estrus was detected using vasectomized, penile-deviated bulls fitted with chin-ball markers during the AI period and with tail paint during the natural service period. Cows with AFC ≥ ½ SD above the mean were classified as high, those within ½ SD of the mean were classified as intermediate, and those ≥ ½ SD below the mean were classified as low. Classes of AFC for total follicles included low (L ≤ 73), intermediate (74 ≤ I ≤ 112), and high (H ≥ 113). Classes of AFC for small follicles included low (L ≤ 55), intermediate (56 ≤ I ≤ 87), and high (H ≥ 88). Classes of AFC for medium follicles included low (L ≤ 13), intermediate (14 ≤ I ≤ 23), and high (H ≥ 24). Classes of AFC for large follicles included low (L ≤ 2), intermediate (3 ≤ I ≤ 4), and high (H ≥ 5). Cows with PPI ≥ ½ SD above the mean were classified as long, those within ½ SD of the mean were classified as intermediate, and those ≥ ½ SD below the mean were classified as short. Classes of PPI included short (S ≤ 47 d), intermediate (48 d ≤ I ≤ 75 d), and long (L ≥ 76 d). The PROC MIXED procedure of SAS was used to analyze potential differences among classes of AFC and PPI. The PROC REG procedure of SAS was used to analyze relationships between AFC and PPI and between AFC on d 28 postpartum and on d 8 post-estrus. The PPI differed among classes of total (P < 0.01; L = 76.2 ±â€¯6.0, I = 61.7 ±â€¯4.5, H = 43.8 ±â€¯6.5), small (P < 0.01; L = 74.3 ±â€¯5.6, I = 64.6 ±â€¯4.8, H = 42.9 ±â€¯5.9), and medium AFC (P = 0.04; L = 72.3 ±â€¯5.9, I = 59.3 ±â€¯5.8, H = 52.1 ±â€¯5.8). The PPI did not differ among classes of large AFC (P = 0.81). As total AFC on d 28 postpartum increased, PPI decreased (P < 0.01, Adj.R2 = 0.13). Total AFC on d 8 post-estrus was positively associated with total AFC on d 28 postpartum (P < 0.01, Adj.R2 = 0.66). These results suggest that: a) populations of total, small, and medium follicles in the postpartum period predict PPI in Brahman females and b) total AFC in Brahman females are consistent.

Evaluation of tropically adapted straightbred and crossbred beef cattle: Cortisol concentration and measures of temperament at weaning and transport.

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.

Association of SNPs in dopamine and serotonin pathway genes and their interacting genes with temperament traits in Charolais cows.

Cattle temperament is a complex trait, and molecular studies aimed at defining this trait are scarce. We used an interaction networks approach to identify new genes (interacting genes) and to estimate their effects and those of 19 dopamine- and serotonin-related genes on the temperament traits of Charolais cattle. The genes proopiomelanocortin (POMC), neuropeptide Y (NPY), solute carrier family 18, member 2 (SLC18A2) and FBJ murine osteosarcoma viral oncogene homologue (FOSFBJ) were identified as new candidates. Their potential to be associated with temperament was estimated according to their reported biological activities, which included interactions with neural activity, receptor function, targeting or synthesis of neurotransmitters and association with behaviour. Pen score (PS) and exit velocity (EV) measures were determined from 412 Charolais cows to calculate their temperament score (TS). Based on the TS, calm (n = 55; TS, 1.09 ± 0.33) and temperamental (n = 58; TS, 2.27 ± 0.639) cows were selected and genotyped using a 248 single-nucleotide variation (SNV) panel. Of the 248 variations in the panel, only 151 were confirmed to be polymorphic (single-nucleotide polymorphisms; SNPs) in the tested population. Single-marker association analyses between genotypes and temperament measures (EV, PS and/or TS) indicated significant associations of six SNPs from four candidate genes. The markers rs109576799 and rs43696138, located in the DRD3 and HTR2A genes, respectively, were significantly associated with both EV and TS traits. Four markers, rs110365063 and rs137756569 from the POMC gene and rs110365063 and rs135155082 located in SLC18A2 and DRD2, respectively, were associated with PS. The variant rs110365063 located in bovine SLC18A2 causes a change in the amino acid sequence from Ala to Thr. Further studies are needed to confirm the association of genetic profile with cattle temperament; however, our study represents important progress in understanding the regulation of cattle temperament by different genes with divergent functions.

Evaluation of the influence of prenatal transportation stress on GnRH-stimulated luteinizing hormone and testosterone secretion in sexually mature Brahman bulls.

This study examined the relationship of prenatal transportation stress (PNS) with exogenous GnRH-induced LH and testosterone secretion in sexually mature Brahman bulls. Brahman cows (n = 96; 48 were stressed by transportation at 5 stages of gestation and 48 were controls) produced a calf crop of 85 calves. All bulls (n = 46) from this calf crop were electroejaculated every 2 wk beginning at a scrotal circumference of 24 cm until sexual maturity (SM; i.e., 500 million sperm/ejaculate). The initial 11 control and 12 PNS bulls to reach SM were selected for the experiment. Within 7-21 d after reaching SM, bulls were fitted with jugular cannulas, from which blood samples were collected at 15-min intervals for 6 h prior to exogenous GnRH administration (10 ng/kg BW; i.v.) and for 6 h after GnRH. Serum concentrations of LH, testosterone, and cortisol were determined by RIA. Age and body weight did not differ ( > 0.1) between PNS and control bulls at the time of the experiment. All bulls responded similarly to exogenous GnRH, indicating no influence of PNS on LH or testosterone response to GnRH. More ( < 0.01) PNS (9 of 11) than control (3 of 12) bulls exhibited an endogenous pre-GnRH LH pulse, and more ( = 0.02) PNS (9 of 11) than control bulls (4 of 12) exhibited a pre-GnRH testosterone response to LH. The average concentration of testosterone during the 60 min (time -60, -45, -30, -15, and 0 min relative to GnRH) immediately preceding GnRH, tended to be greater ( = 0.07) in PNS (1.46 ± 0.30 ng/mL) than control (0.68 ± 0.28 ng/mL) bulls. During that time span serum cortisol was lower ( < 0.01) in PNS (4.00 ± 0.91 ng/mL) than control (7.8 ± 0.87 ng/mL) bulls. A treatment by time interaction ( = 0.03) affected testosterone concentrations from time -240 to 360 min relative to GnRH. Results from this study indicate that PNS did not affect pituitary responsiveness to GnRH or testicular responsiveness to GnRH-induced LH secretion.

Prostaglandins and reproduction in female farm animals.

Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, pyometra, and chronic endometritis. Improved therapeutic uses for prostaglandins will be developed when we understand better their involvement in implantation, maintenance of luteal function, and establishment and maintenance of pregnancy.

Influence of animal temperament and stress responsiveness on the carcass quality and beef tenderness of feedlot cattle.

Three groups of steers (A, B, C) were used to study the effect of temperament (Calm, Intermediate, and Excitable) on meat quality. Temperament was based on exit velocity, pen scores, and chute scores. Temperament traits were consistent across evaluations, and values decreased (P<0.05) in magnitude over time. Increasing excitability was associated with higher (P<0.05) serum cortisol concentrations. Carcasses from cattle with calm temperaments had higher (P<0.05) 0.5h postmortem pH values than those from Intermediate and Excitable cattle (0.1 and 0.2 units, respectively). Group C Excitable steers had higher (P<0.05) WBS values than the calmer Group C steers. This trend was observed in Group A steers, although the values were not statistically different. Correlations were highest between temperament values and tenderness after 21d. Temperament influences tenderness, although the mechanism is not clear.

Prenatal transportation stress alters temperament and serum cortisol concentrations in suckling Brahman calves.

This experiment examined the relationship between prenatal stress and subsequent calf temperament through weaning. The prenatal stressor used was repeated transportation of pregnant Brahman cows for 2 h at 60 ± 5, 80 ± 5, 100 ± 5, 120 ± 5, and 140 ± 5 d of gestation. Prenatally stressed calves ( = 41) were compared with controls ( = 44; dams did not undergo transportation during pregnancy) from 2 wk of age until weaning (average age at weaning = 174.8 ± 1.3 d). Temperament was defined by pen score (PS; 1 = calm and 5 = excitable), exit velocity (EV; m/sec), and temperament score (TS; (PS + EV)/2) and was recorded for each calf on d -168, -140, -112, -84, -56, -28, and 0 relative to weaning (d 0 = weaning). Cortisol concentrations were determined in serum samples obtained on d -168, -140, -28, and 0 relative to weaning. Birth weight and weaning weight were not different between treatment groups ( > 0.1). Pen score was greater ( = 0.03) in prenatally stressed calves (2.84 ± 0.21) relative to controls (2.31 ± 0.21). Exit velocity was greater ( < 0.01) in prenatally stressed calves (2.1 ± 0.14 m/sec) than in controls (1.61 ± 0.14 m/sec). Exit velocity was affected by a treatment × calf sex interaction ( = 0.04) and was greater in prenatally stressed females. Exit velocity was also affected by day ( < 0.0001). Temperament score was greater ( = 0.01) in prenatally stressed calves (2.45 ± 0.16) than in controls (1.95 ± 0.16). Temperament score was affected by day ( < 0.01). Basal cortisol concentrations were greater ( = 0.04) in prenatally stressed calves (15.87 ± 1.04 ng/mL) than in controls (13.42 ± 1.03 ng/mL). Basal cortisol concentrations were greater ( < 0.01) in females (16.61 ± 1.06 ng/mL) than in males (12.68 ± 1.02 ng/mL). Cortisol concentrations were positively correlated ( < 0.01) with PS ( = 0.55, < 0.01), EV ( = 0.4, < 0.01), and TS ( = 0.55, < 0.01). Overall, suckling Brahman calves that were prenatally stressed were more temperamental and had greater circulating serum concentrations of cortisol than control calves.

Effects of leptin on gonadotropin-releasing hormone release from hypothalamic-infundibular explants and gonadotropin release from adenohypophyseal primary cell cultures: further evidence that fully nourished cattle are resistant to leptin.

In rodents and pigs, leptin stimulates the release of gonadotropin-releasing hormone (GnRH) from hypothalamus, gonadotropins from adenohypophyseal (AP) explants and cells, and luteinizing hormone (LH) from full-fed animals. In the current studies, we investigated whether leptin could stimulate the release of GnRH from bovine hypothalamic-infundibular (HYP) explants and gonadotropins from bovine adenohypophyseal cells. In Experiment 1A, HYP explants collected from 17 bulls and seven steers were incubated with Krebs-Ringer bicarbonate buffer (KRB) containing 0, 10, 100, or 1000 ng/ml recombinant ovine leptin (oleptin) for 30 min after a 3-h period of equilibration. None of the doses of leptin affected (P > 0.05) GnRH release into the media. In Experiment 1B, HYP explants collected from six steers were incubated with KRB containing 0 or 1000 ng/ml oleptin for two consecutive 30-min periods and challenged with 60 mM K(+) afterwards. Leptin did not affect (P > 0.05) basal or K(+)-stimulated release of GnRH. In Experiment 2, adenohypophyses from steers were collected at slaughter and cells dispersed and cultured for 4 days. On day 5, cells were treated with media alone (control) or media containing 10(-11), 10(-10), 10(-9), and 10(-8)M oleptin. Three independent replications were performed. None of the doses of leptin stimulated (P > 0.05) the release of LH. Although leptin at 10(-11), 10(-10), and 10(-9)M increased (P < 0.03) slightly the release of FSH compared to control-treated cells in one replicate, this effect was not confirmed in the other two replicates. Results support the hypothesis that leptin has limited effects on the release of GnRH and gonadotropins in full-fed cattle and reiterate important species differences in responsiveness to leptin.

Plasma progesterone response following ACTH administration during mid-gestation in the pregnant Brahman heifer.

Previous reports of adrenal progesterone (P4) contributions during late gestation in cattle, and ACTH-induced P4 responses in the non-pregnant heifer, prompted a retrospective investigation to evaluate the plasma P4 response and the relative ratio of plasma cortisol (CT) to P4 following ACTH administration during mid-gestation in pregnant Brahman heifers. Twenty-three pregnant (139.0 +/- 5.0 days of gestation) Brahman heifers received one of the following treatments: 0 (saline; n = 5), 0.125 (n = 4), 0.25 (n = 5), 0.5 (n = 4), or 1.0 (n = 5)IU of ACTH per kg BW. Blood samples were collected at -15 and -0.5 (time 0), 15, 30, 45, 60, 75, 105, 135, 165, 195, and 255-min post-ACTH challenge. Plasma P4 and CT were quantified by RIA. Pre-ACTH P4 did not differ (P > 0.10) among ACTH treatment groups (pooled, 12.1 +/- 0.6 ng/mL). Among peak P4 values at 15-min post-ACTH infusion, control P4 (9.6 +/- 1.2 ng/mL) tended to be lower (P < 0.07) than 0.5 IU ACTH-treated heifers (13.3 +/- 1.1 ng/mL); and were lower (P < 0.02) than 0.25 and 1.0 IU ACTH-treated heifers (14.7 +/- 1.1 and 22.2 +/- 3.7 ng/mL, respectively). During the primary P4 response period (0 to 75-min post-ACTH), the area under the curve (AUC) was greater (P < 0.05) for 1.0 IU ACTH-treated heifers than all other groups. The CT:P4 ratios were lower (time x treatment, P < 0.01) for control heifers than all ACTH-treated heifers. Among ACTH-treated heifers, CT:P4 ratio response and CT:P4 ratio AUC were similar (P > 0.10) following ACTH challenge. In conclusion, acute increases in ACTH elevated plasma P4, likely of adrenal origin, in mid-gestation pregnant heifers, while the CT:P4 ratio (relative output) remained constant irrespective of ACTH dose (0.125-1.0 IU). Whether ACTH-induced increases in P4 in pregnant animals are of physiological significance (e.g., an accessory role in the maintenance of pregnancy during periods of acute stress) remains to be determined.

Physiological and metabolic responses of gestating Brahman cows to repeated transportation.

This study characterized physiological responses to repeated transportation (TRANS) of gestating cows of differing temperaments. Cows were classified as Calm (C; = 10), Intermediate (I; = 28), or Temperamental (T; = 10). Based on artificial insemination date and pregnancy confirmation, cows were TRANS for 2 h on d 60 (TRANS1), 80 (TRANS2), 100 (TRANS3), 120 (TRANS4), and 140 (TRANS5) ± 5 d of gestation. Indwelling vaginal temperature (VT) monitoring devices were inserted 24 h before each TRANS with VT recorded from 2 h before TRANS and averaged into 5-min intervals through 30 min after TRANS. Serum samples were collected before loading and on unloading from the trailer to determine concentrations of cortisol, glucose, and nonesterified fatty acids (NEFA). Data were analyzed by repeated measures analysis in SAS. Serum cortisol concentrations were affected by temperament ( < 0.001), with T cows having the greater concentrations of cortisol before each TRANS event. All cows (100%) regardless of temperament exhibited elevations in cortisol following each TRANS event. Peak VT was greater ( < 0.001) at TRANS1 relative to all other TRANS events regardless of cow temperament. During TRANS, the T cows tended ( < 0.09) to have greater peak VT (39.86 ± 0.15°C) compared to C (39.41 ± 0.16°C) and I cows (39.55 ± 0.08°C). Area under the VT curve decreased ( = 0.002) from TRANS1 through TRANS5. Pre-TRANS serum glucose concentration at TRANS1 was greater ( < 0.03) for T (68.13 ± 4.31mg/dL) compared to I (53.42 ± 2.78 mg/dL) and C cows (52.76 ± 4.60 mg/dL). The C and I cows had greater changes in NEFA concentration between pre- and post-transport, and T cows showed the least change ( < 0.001). Cow VT and serum glucose concentration decreased in all temperaments ( < 0.01) with repeated TRANS; however, serum NEFA concentration post-TRANS did not vary ( > 0.10) with repeated TRANS events. Serum glucose concentrations were affected ( < 0.02) by a TRANS event by temperament interaction with T cows taking more TRANS events to decrease their change in glucose concentration compared to C and I cows. These results demonstrate that temperament influences physiological responses to stress in gestating Brahman cows. Although repeated transport in our study is confounded with day of gestation, seasonal changes, and learning from repeated handling and transport, repeated transport is a useful model of repeated stress in studying the effects of temperament.

The effect of aspirin administration and parity on plasma salicylate concentrations and postpartum reproductive parameters in Brahman cows.

Forty pluriparous (M) and 20 primiparous (P) suckled Brahman cows were used to evaluate the effect of aspirin and parity on plasma 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM) and progesterone (P4) concentrations and some reproductive parameters. On Day 7 after calving (PP), the cows were allocated within parity into 2 groups: the aspirin group received concentrate containing aspirin at a rate of 100 mg/kg of body weight every 12 h until Day 13 PP; and the control received concentrate every 12 h for the same interval. Blood samples were collected after first and last aspirin feeding and daily from Day 1 PP to Day 6 PP and from Day 14 PP to Day 21 PP, twice daily from Day 7 PP to Day 13 PP, and weekly until first non-return to estrus. Plasma salicylate concentrations in the aspirin group cows were affected by parity (P < 0.01) and time after feeding (P < 0.0001). P cows showed higher plasma salicylate concentrations with a later peak and slower decrease than M cows. Aspirin-treated P cows had longer PP intervals than either control P, control M, or aspirin-treated M cows. Cows receiving aspirin had a lower pregnancy rate, an increased incidence of abnormal estrous cycles, and a decline in the presence of corpora lutea after estrus. Cows that formed a corpora lutea and had received aspirin had higher P4 release between Day 6 and 14 after estrus. Aspirin-treated cows that did not form corpora lutea had lower P4 release between Days 9 and 14 after estrus. A treatment by parity interaction affected mean PGFM proportions (P < 0.01) during the treatment period. Aspirin-fed P cows increased PGFM release as measured by mean proportion of Day 6 PP values. Aspirin-fed M cows showed a decrease in mean PGFM proportions. Aspirin feeding during the early PP showed different effects on some reproductive parameters in P and M Brahman cows, indicating differences in PP physiology between parities.