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The relationships between cell-mediated immune response (CMIR) of cows and calving interval and calf growth were evaluated. Calving interval was evaluated for each of the initial 7 life-time opportunities that females had to produce a calf. The number of days from when the cow had a calf until she calved again determined the cow’s calving interval for each year. The Spring breeding seasons were divided into 45-d artificial insemination and 45-d natural service periods. The Fall breeding season was natural service each year. Multiparous Brahman cows (n = 435) had records for breeding and calving dates and calf weaning weights. The CMIR (hypersensitivity response to Candida albicans measured using tail-fold thickness) was determined once for each female in the Fall and early Winter 2015. Cows were classified into response groups based on mean and SD of CMIR. High responders were those with CMIR ½ SD ≥ the mean (≥ 2.8 mm), Intermediate cows were within ½ SD of the mean (2.7-1.8 mm), and cows ½ SD ≤ the mean were Low (≤ 1.7 mm). Data were analyzed using repeated measures, mixed, and Chi Square procedures (SAS 9.4). Variables included calving interval, cow age, CMIR response group, pregnancy status, calf count, calf sex, cow sire, calf sire, and calf adjusted 180-d weaning weight. A greater proportion of High CMIR cows made it to their 6th calving interval. Chi Square analysis indicated that High CMIR cows were more likely to remain in the herd longer and produce a calf each year. Cows with High CMIR had a greater stayability (P = 0.1). Selection for High CMIR can result in selection of cows which are more likely to remain in the herd long enough to be profitable as they have a greater stayability and shorter calving intervals (about 25 days) than their Low CMIR herdmates.

The objective of this study was to determine whether prostaglandin E1 (PGE1) or prostaglandin E2 (PGE2) prevents premature luteolysis in ewes when progesterone is given during the first 6 days of the estrous cycle. Progesterone (3 mg in oil, im) given twice daily from Days 1 to 6 (estrus = Day 0) in ewes decreased (P0.05) luteal weights on Day 10 postestrus. Plasma progesterone concentrations differed (P0.05) among the treatment groups; toward the end of the experimental period, concentrations in jugular venous blood decreased (P0.05) compared with the other treatment groups. Plasma progesterone concentrations in ewes receiving PGE1 or PGE1 + progesterone were greater (P0.05) than in vehicle controls or in ewes receiving PGE2 or PGE2 or PGE2 + progesterone. Chronic intrauterine treatment with PGE1 or PGE2 prevented (P0.05) decreases in plasma progesterone concentrations, luteal weights, and the proportion of luteal unoccupied and occupied LH receptors on Day 10 postestrus in ewes given exogenous progesterone, but did not affect (P0.05) concentrations of PGF2α in inferior vena cava blood. Progesterone given on Days 1 to 6 in ewes advanced (P0.05) increases in PGF2α in inferior vena cava blood. We concluded that PGE1 or PGE2 prevented progesterone-induced premature luteolysis by suppressing loss of luteal LH receptors (both unoccupied and occupied).

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.

The influence of nutrition on puberty in beef heifers is complex and under neuroendocrine control. The stores of body fat in mammals are a determinant of the onset and maintenance of puberty. Body fat stores are greater in heifers with greater residual feed intake than in their more efficient herdmates. A 1 unit increase in residual feed intake resulted in a reduction of 7.54 d in age at puberty in Bos taurus beef heifers. However, Bos indicus-influenced heifers, which reach puberty at older ages, were not found to have sexual maturity influenced by selection for residual feed intake. The strong influence of body fat stores on return to estrus after calving does indicate that selection for leaner beef heifers could affect reproductive performance relative to puberty and postpartum rebreeding of first calf heifers. The influence of intermediary metabolism, through signals at the central nervous system, regulates the GnRH pulse generator, thereby influencing pituitary and ovarian function culminating with puberty and return to ovarian cyclicity after calving. Tropically adapted cattle (i.e., Santa Gertrudis and Brahman) selected for low residual feed intake had a lesser response of insulin to a glucose challenge than their less efficient herdmates. These studies indicate the possibility that animals with differing residual feed intake (efficiencies) may have differing intermediary metabolism and, therefore, differing rates of reaching puberty. Selection for low residual feed intake results in selection of leaner heifers that reach puberty at older ages. These leaner heifers calve later in their first and subsequent calving seasons. Selection for residual average daily gain has no negative influence on age at puberty or calving interval. Selection for residual ADG has a negative influence on age at first calving but not calving interval. There may be no acceptable method to improve feed efficiency without harming reproductive efficiency.

The mammalian digestive tract is home to trillions of microbes, including bacteria, archaea, protozoa, fungi, and viruses. In monogastric mammals the stomach and small intestine harbor diverse bacterial populations but are typically less populated than the colon. The gut bacterial community (microbiota hereafter) varies widely among different host species and individuals within a species. It is influenced by season of the year, age of the host, stress and disease. Ideally, the host and microbiota benefit each other. The host provides nutrients to the microbiota and the microbiota assists the host with digestion and nutrient metabolism. The resident microbiota competes with pathogens for space and nutrients and, through this competition, protects the host in a phenomenon called colonization resistance. The microbiota participates in development of the host immune system, particularly regulation of autoimmunity and mucosal immune response. The microbiota also shapes gut–brain communication and host responses to stress; and, indeed, the microbiota is a newly recognized endocrine organ within mammalian hosts. Salmonella enterica serovar Typhimurium (S. Typhimurium hereafter) is a food-borne pathogen which adapts to and alters the gastrointestinal (GI) environment. In the GI tract, S. Typhimurium competes with the microbiota for nutrients and overcomes colonization resistance to establish infection. To do this, S. Typhimurium uses multiple defense mechanisms to resist environmental stressors, like the acidic pH of the stomach, and virulence mechanisms which allow it to invade the intestinal epithelium and disseminate throughout the host. To coordinate gene expression and disrupt signaling within the microbiota and between host and microbiota, S. Typhimurium employs its own chemical signaling and may regulate host hormone metabolism. This review will discuss the multidirectional interaction between S. Typhimurium, host and microbiota as well as mechanisms that allow S. Typhimurium to succeed in the gut.

In previous work, an EP2 prostanoid receptor (EP2R) agonist in vivo increased mRNA expression of luteal LH receptors (LHR), unoccupied and occupied luteal; LHR, and circulating progesterone, while an EP3R or FPR agonist decreased; mRNA expression of luteal LHR, unoccupied and occupied luteal LHR, and; circulating progesterone. An EP4R and lysophosphatidic acid (LPA) LPA2R and LPA3R agonists were reported to inhibit luteal function and sirtuins have been proposed to increase prostaglandin synthesis. The objectives were to determine; whether an EP4R, LPA2R, or LPA3R agonist affect ovine luteal function in vivo or; in vitro. In addition, whether sirtuin (SIRT)-1, 2, or 3; LPA2R or LPA3R; or EP1R, EP2R, EP3R, or EP4R agonists affect caruncular endometrial PGF

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 (P0.05) among breeds for the DRD1 and DRD5 markers. The allelic frequencies for markers DRD1-825AG and DRD5-378CT 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.

A meta-analysis was conducted to examine phenotypic relationships between feed efficiency, scrotal circumference, and semen quality traits in yearling bulls. Data evaluated were obtained from 5 postweaning trials involving Angus (n = 92), Bonsmara (n = 62), and Santa Gertrudis (n = 50) bulls fed diets that ranged from 1.70 to 2.85 Mcal ME/kg DM. After an adaptation period of 24 to 28 d, feed intake was measured daily, and BW was measured at 7- or 14-d intervals during the 70- to 77-d trials. Ultrasound carcass traits (12th-rib back fat thickness, BF; LM area, LMA) and scrotal circumference (SC) were measured at the start and end of each trial. Semen samples were collected by electroejaculation within 51 d of the end of the trials when the age of bulls averaged from 365 to 444 d and were evaluated for progressive sperm motility and morphology. Residual feed intake (RFI) was calculated as the difference between actual DMI and expected DMI from linear regression of DMI on ADG and midtest BW(0.75), with trial, trial by ADG, and trial by midtest BW(0.75) as random effects. Across all studies, bulls with low RFI phenotypes (0.5 SD below the mean RFI of 0) consumed 20% less DM and had 10% less BF but had similar ADG, SC, and semen quality traits compared with high-RFI bulls (0.5 SD above the mean RFI of 0). Gain to feed ratio was strongly correlated with ADG (0.60) and weakly correlated with initial BW (-0.17) and DMI (-0.26). Residual feed intake was not correlated with ADG, initial age, or BW but was correlated with DMI (0.71), G:F (-0.70), and BF (0.20). Initial SC (-0.20), gain in SC (-0.28), and percent normal sperm (-0.17) were correlated with G:F, but only sperm morphology was found to be weakly associated with RFI (0.13). These data suggest that RFI is not phenotypically associated with SC or sperm motility but is weakly associated with sperm morphology.

This study was designed to characterize potential sexually dimorphic stress and immunological responses following a corticotropin-releasing hormone (CRH) challenge in beef cattle. Six female (heifers) and six male (bulls) Brahman calves (264 ± 12 d of age) were administered CRH intravenously (0.5 µg of CRH/kg body mass) after which serum concentrations of cortisol increased from 0.5 h to 4 h. From 1 h to 4 h after CRH administration, serum cortisol concentrations were greater in heifers than in bulls. In all cattle, increased serum concentrations of TNF-α, IL-6 and IFN-γ were observed from 2.5 h to 3 h after CRH, with greater concentrations of IFN-γ and IL-6 in heifers than bulls. Heifer total leukocyte counts decreased 1 h after CRH administration, while bull leukocyte counts and percent neutrophils decreased 2 h after CRH administration. Heifers had greater rectal temperatures than bulls, yet rectal temperatures did not change following administration of CRH. There was no effect of CRH administration on heart rate. However, bulls tended to have increased heart rate 2 h after CRH administration than before CRH. Heifer heart rate was greater than bulls throughout the study. These data demonstrate that acute CRH administration can elicit a pro-inflammatory response, and cattle exhibit a sexually dimorphic pro-inflammatory cytokine and cortisol response to acute CRH administration.

A device was developed to monitor the vaginal temperature of cattle in a research setting. This device decreases labor involved with monitoring body temperature compared with manual temperature readings, allows for continuous monitoring of vaginal temperature at 1 min intervals, and also allows for temperature measurements without the presence of a human handler or without restraint, which can agitate cattle. The device consists of a blank controlled internal drug release (CIDR) device (designed by Pfizer Animal Health as an indwelling vaginal probe) that holds an indwelling vaginal temperature probe logger. The fabrication of the vaginal probe costs approximately US $325 per unit. Similar rectal and vaginal temperature responses to lipopolysaccharide challenge were observed when vaginal and rectal temperatures were measured simultaneously in the same heifer (P40.05). Additionally, rectal and vaginal temperatures were highly correlated (r¼ 0.97; Po 0.0001). Similar to the rectal temperature monitoring device, the vaginal device allows for the measurement of vaginal temperature without the potential biases associated with the stress response produced as a reaction to the handling by and (or) presence of humans. The vaginal temperature recording device will provide researchers with an additional inexpensive tool to study physiological responses in female cattle. & 2011 Published by Elsevier Ltd.

SUMMARYThe objectives of the current study were to determine the variation structure within a day and across days when determining dry matter intake (DMI) of Coastal bermudagrass (Cynodon dactylon (L.) Pers.) pasture using dotriacontane (C32) as an external marker, to determine the optimal times for faecal collection for forage DMI estimation and to compare C31 and C33 as internal markers in estimating forage DMI in Brahman bulls. Sixteen Brahman bulls were allocated by weight to four pastures, and stocked at a moderate to low grazing pressure for 63 days from late June to the end of August. Three intake measurement periods (P1, P2, P3) were used; each period consisting of 10 days of twice daily C32 (400 mg/day) administration. Faecal collections were taken during the last 5 days (07.00, 11.00, 15.00 and 19.00 h). The C32 was individually hand fed using Calan gates, with maize gluten as a carrier for the alkane. Gas chromatography was used to determine n-alkanes in the forage and faecal samples. The concentration of C31 was less than C33 in the bermudagrass for all periods (P 31 and C33 in faeces was not significantly different (P > 0·05). The average concentration of C32 in the forage was 5·1, 7·6 and 9·6 mg/kg dry matter (DM), for P1, P2 and P3, respectively, with an average of 7·5 mg/kg DM for all periods. During P1 and P2, the estimation of forage DMI using C33 had a better fit (smaller –2 × log and Akaike's information criterion (AIC)) than using C31 either with or without adjustments for C32. The variation in estimated forage DMI decreased when forage C32 was not included. The variances of forage DMI were similar using C31 across days, but the Pearson correlations between days were low, which suggested that several days of collection were needed to estimate forage DMI accurately. Correlations between collection times within days were medium to high for all periods and varied from 0·65 to 0.97 for C31 and from 0·26 to 0·96 for C33. When all periods were analysed together, estimates of forage DMI either using C31 or C33 had low correlations between days of collection. Adjustment for C32 did not improve the variance and (co)variance matrix. In summary, C33/C32 had the lowest variation in estimating forage DMI, and at least 5 days of faecal collection were needed to decrease the variability of estimating forage DMI. The optimum times for faecal collection were 07.00 and 19.00 h, and it was important to adjust for C32 alkane concentration in estimating forage DMI in Brahman bulls grazing Coastal bermudagrass.

In an effort to determine whether tropical adaptation influences circulating concentrations of the growth-related hormone IGF-I, 3-breed diallel matings were conducted using temperate Bos taurus (Angus), tropical Bos indicus (Brahman), and tropical Bos taurus (Romosinuano). Purebred Angus, Braham, and Romosinuano and crossbred Angus-Braham, Angus-Romosinuano, and Braham-Romosinuano heifers and steers were evaluated in 2 separate calf crops from 2003 and 2004. Blood samples were obtained from 10 heifers of each breed group (n = 90) for each year at weaning and on d 0 and 84 of postweaning trials. Samples were also taken from 10 steers of each breed group (n = 90) at weaning and on d 0 and 60 of individual finishing phase feeding trials for each year. Concentrations of IGF-I were determined by RIA. Analyses included effects of sire breed, dam breed, year of record, the age of the dam of the calf in years, and interactions. Age of calf in days was investigated as a linear and quadratic covariate. Separate analyses were conducted for steers and heifers. The direct effect of Angus was to reduce (P < 0.03) heifer concentrations of IGF-I at d 84 and in the repeated measures analysis. In the repeated measures analysis, the direct effect of Romosinuano was to increase concentrations of IGF-I (P = 0.01). Relative to the temperate Bos taurus breed, plasma concentrations of IGF-I were numerically greater in male and female tropically adapted breed groups.

Seventy-four Angus and Angus × Hereford heifers were used in 2 successive years (yr 1, n = 43; yr 2, n = 31) to determine if luteal function of heifers during acute submaintenance feeding is related to variation in utilization of feed as determined by residual feed intake (RFI). Residual feed intake was determined for heifers beginning at 12.3 ± 0.1 mo of age in yr 1 and at 9.1 ± 0.1 mo of age in yr 2. Heifers were assigned to dry-lot pens (n = 6 to 9 heifers/pen) with electronic gates to measure individual feed intake of a total mixed ration for 70 and 72 d in yr 1 and 2, respectively. Residual feed intake was calculated as the difference between actual DMI and expected DMI from linear regression of DMI on mid-test BW(0.75) and ADG. At 14.4 ± 0.1 mo of age, all heifers were provided a restricted amount of feed to supply 40% of their maintenance energy requirements for 21 d. Estrous cycles of heifers were synchronized with PGF(2α) on d -10, 0, and 11 relative to start of restriction. Concentrations of progesterone in plasma on d 14 to 21 of restriction were used to determine if heifers ovulated. Overall ADG and ADFI were 0.83 ± 0.02 and 7.37 ± 0.67 kg/d, respectively, for yr 1; and 0.50 ± 0.02 and 5.66 ± 0.09 kg/d, respectively, for yr 2. There was no correlation between RFI and BW, ADG, ADFI, or ultrasound measure of backfat, nor was RFI related to concentrations of IGF-I in plasma. All heifers lost BW and had reduced backfat (P 0.5 SD below the mean) than heifers with a greater RFI (>0.5 SD above the mean). It is concluded that RFI is not related to luteal function during acute submaintenance feeding, but that short-term restriction of nutrient intake can alter luteal function that may compromise fertility, even in heifers that exhibit estrus and ovulate.

Previously, it was reported that chronic intra-uterine infusion of PGE(1) or PGE(2) every four hours inhibited luteolysis in ewes. However, estradiol-17β or PGE(2) given intra-uterine every 8h did not inhibit luteolysis in heifers, but infusion of estradiol+PGE(2) inhibited luteolysis in heifers. The objective of this experiment was to determine whether and how intra-luteal implants containing PGE(1) or PGE(2) prevent luteolysis in Angus or Brahman cows. On day-13 post-estrus, Angus cows received no intra-luteal implant and corpora lutea were retrieved or Angus and Brahman cows received intra-luteal silastic implants containing Vehicle, PGE(1), or PGE(2) and corpora lutea were retrieved on day-19. Coccygeal blood was collected daily for analysis for progesterone. Breed did not influence the effect of PGE(1) or PGE(2) on luteal mRNA for LH receptors or unoccupied or occupied luteal LH receptors did not differ (P0.05) so the data were pooled. Luteal weights of Vehicle-treated Angus or Brahman cows from days-13-19 were lower (P0.05) than those treated with intra-luteal implants containing PGE(1) or PGE(2). Day-13 Angus luteal weights were heavier (P0.05) than Vehicle-treated Angus cows on day-19 and luteal weights of day-13 corpora lutea were similar (P0.05) to Angus cows on day-19 treated with intra-luteal implants containing PGE(1) or PGE(2). Profiles of circulating progesterone in Angus or Brahman cows treated with intra-luteal implants containing PGE(1) or PGE(2) differed (P0.05) from controls, but profiles of progesterone did not differ (P0.05) between breeds or between cows treated with intra-luteal implants containing PGE(1) or PGE(2). Intra-luteal implants containing PGE(1) or PGE(2) prevented (P0.05) loss of luteal mRNA for LH receptors and unoccupied or occupied receptors for LH compared to controls. It is concluded that PGE(1) or PGE(2) alone delays luteolysis regardless of breed. We also conclude that either PGE(1) or PGE(2) prevented luteolysis in cows by up-regulating expression of mRNA for LH receptors and by preventing loss of unoccupied and occupied LH receptors in luteal tissue.

Using a retrospective evaluation of feed efficiency, this study investigated the effects of physiological age on residual feed intake (RFI) in growing heifers. Data were collected during 1973 and 1974 at the McGregor location of the Texas Agricultural Experiment Station. Heifers (n = 77) were obtained from a large crossbreeding program utilizing a five-breed diallel mating scheme using Angus, Brahman, Hereford, Holstein and Jersey breeds. At approximately 6 months of age, pre-pubertal heifers were individually penned and received ad libitum access to a balanced diet. Individual feed intake and body weight data were collected at 28-day intervals for 84 days prior to puberty and for 90 days after puberty. The diet was changed at puberty to provide a lower energy density. Considering all females as cohorts, RFI was calculated for each heifer for each period using separate models for the pre- and post-pubertal periods. A moderate, positive Pearson correlation (r = 0.48; P < 0.001) was detected between pre- and post-pubertal RFI. Furthermore, heifer RFI rank was compared between the pre- and post-pubertal periods using Spearman rank order correlation and a similar correlation (r = 0.46; P < 0.001) was revealed. This suggests that RFI determined during the pre-pubertal period may only be a moderate predictor of post-pubertal RFI. As a result, physiological age should be considered when evaluating cattle for feed efficiency using RFI.

The purpose of this study was to assess changes in exit velocity (EV) of Brahman calves from 21 d of age (DOA) to 56 d postweaning (231.30 ± 1.23 DOA). Spring-born calves (n = 308) from 2006 to 2008 were sired by 18 bulls. Exit velocity (m/s) was determined as the rate of speed of a calf traversing 1.83 m after being released from a working chute. Temperament score was determined as the average of EV and pen score 28 d before and at weaning (2006: 173 ± 2 DOA; 2007: 174 ± 2 DOA; 2008: 163 ± 2 DOA). Pen score was determined by separating calves into groups of 3 to 5 animals and scoring their reactivity to a human observer on a scale of 1 (calm, docile, approachable) to 5 (aggressive, volatile, crazy). The number of calves that switched temperament group was determined by ranking calves based on their EV at 21 to 24 DOA, 90 DOA, weaning, and at 56 d postweaning. The GLIMMIX procedure of SAS was used to analyze EV with DOA, birth year and sex as fixed effects, and sire and calf nested within sire included as random effects. Temperament classification (calm, intermediate, temperamental) was modeled as a fixed effect, and the linear regression of traits on DOA investigated. Spearman rank order correlations were determined between EV at 21 to 24 DOA, 90 DOA, weaning, and 56 d postweaning and correlations decreased as the number of days between EV measurements increased. Differences in EV were observed between the 2006 (2.23 ± 0.057 m/s) compared with the 2007 (1.90 ± 0.059 m/s) and 2008 (1.83 ± 0.057 m/s) calves (P < 0.001), but the 2007 and the 2008 calves did not differ (P = 0.75). The random effect of sire approached significance (P = 0.07) and accounted for some of the variation observed. Exit velocity increased as days of age increased (P < 0.001). Exit velocity of temperamental calves increased at a faster rate with age (P < 0.001; estimate of slope = 0.005 ± 0.0004 m/s daily) compared with intermediate (slope = 0.003 ± 0.0005 m/s daily; P < 0.001) and calm calves (slope = 0.0007 ± 0.0005 m/s daily; P < 0.001). Exit velocity is a useful and viable indicator of temperament classification. Results suggest that temperamental calves increase their EV at a faster rate and may be identified before weaning, which may enhance the ability of producers to select against temperamental animals.

By using the temperament selection criterion of exit velocity (EV), cattle typically exhibiting hypercortisolism and a blunted response to exogenous corticotrophin-releasing hormone (CRH) can be identified via individual behavioral responses to handling. To further characterize hypothalamic–pituitary–adrenal (HPA) axis dysfunction associated with bovine temperament, the present study compared pituitary and adrenal activity, following stimulation with exogenous vasopressin (VP), in steers with an excitable or calm temperament. Serial blood samples were collected via indwelling jugular cannula for 6 h preceding and 6 h following administration of a VP bolus. Plasma concentrations of adrenocorticotropic hormone (ACTH) and cortisol were quantified by RIA to determine pituitary and adrenal responsiveness within temperament groups. Cortisol concentrations in excitable steers during the pre-challenge period revealed an increased initial adrenal reactivity to interactions with humans. Subsequent acclimation to the experimental surroundings yielded greater baseline cortisol concentrations in the cattle with an excitable temperament. Pituitary stimulation with VP resulted in a greater ACTH output from the excitable compared to the calm animals. The data presented herein provide additional evidence that HPA axis function in cattle of an excitable temperament may be akin to a state of chronic stress. The bovine temperament model may be of further use to both decipher mechanisms associated with HPA dysfunction and to elucidate physiological phenotypes or pathologies that have parallels in other species.

The objectives of this work were to es- timate genetic effects for age and size at estimated time of first conception, and temperament in straightbred and crossbred heifers (n = 554) produced from Romo- sinuano, Brahman, and Angus cattle, and to evaluate first-parturition performance of heifers, including calf birth weight, occurrence of calving difficulty, occurrence of poor vigor in their newborn calves, and calf mortal- ity. At approximately 7 mo of age, weaned heifers were pastured with Mashona or Tuli bulls until confirmed pregnant. Body weight, hip height, exit velocity (m/s), and chute temperament score (1 = calm, no movement; 5 = continuous movement, struggling) were recorded at 28-d intervals until heifers averaged 19 mo of age. Age at first conception was estimated as age at calving minus 285 d. Regression analyses were used to estimate BW and hip height at age of first conception. Brahman heifers were older, heavier, and had greater hip height than other straightbred groups (P < 0.05) and most crossbred groups. Brahman and reciprocal Brahman- Angus heifers had greater (P < 0.05) exit velocity than Romosinuano and Angus heifers. Brahman sire and dam breed chute temperament scores were greater (P < 0.05) than those of all other breed groups. Estimates of heterosis for age at first conception were −53.7 ± 9.5 (−11%), −56 ± 10.1 (−11%), and −92.9 ± 11 d (−18%) for Romosinuano-Brahman, Romosinuano-An- gus, and Brahman-Angus, respectively (P < 0.01). Het- erosis was detected (P < 0.04) for Romosinuano-Brah- man for BW (12 ± 4.3 kg, 3.7%) and hip height (1.3 ± 0.6 cm, 1%) at first conception. Maternal heterosis for calf birth weight was 3.6 ± 0.5 (12%) and 2.4 ± 0.6 kg (8.6%) for Romosinuano-Angus and Brahman-Angus. In Romosinuano-Brahman and Brahman-Angus, het- erosis for exit velocity was 0.23 ± 0.09 (10%) and 0.5 ± 0.1 m/s (21%). The direct breed effect of Romosinu- ano was to reduce age (−58.2 ± 18.9 d), BW (−57.6 ± 10.5 kg), and hip height (−2.6 ± 1.1 cm) at the time of first conception (P < 0.01), and the direct Brahman effects (P < 0.001) were large and numerically positive for these traits (169.8 ± 20.8 d, 93.3 ± 11.6 kg, and 14 ± 1.2 cm). Use of Romosinuano in crossbreeding programs with Brahman may be useful for decreasing the age at first conception. The larger birth weights of calves born to Romosinuano-Angus cross heifers would not be desirable in southern cow-calf operations.

This study investigated whether temperament influences rectal temperature and serum concentrations of cortisol and epinephrine in response to transportation. Brahman bulls were selected based on temperament score (average of exit velocity, EV, and pen score, PS) measured 28 days prior to weaning with the 8 most Calm (0.89 ± 0.15 EV and 1.00 ± 0.00 PS), 8 most Temperamental (3.70 ± 0.29 EV and 4.88 ± 0.13 PS), and the 8 Intermediate (1.59 ± 0.12 EV and 2.25 ± 0.16 PS) selected from a pool of 60 bulls. Whole blood was collected pre- and post-transport, and rectal temperature recording devices were inserted pre-transport for continual collection of rectal temperature during transport. Bulls were transported in a trailer 770 km from Overton, TX (32.27 N, − 94.98 W, 153 m altitude) to New Deal, TX (33.74 N, − 101.84 W, 1006 m altitude). Serum cortisol and plasma epinephrine concentrations were determined. Prior to transportation (0 min) Temperamental bulls had greater rectal temperature than Calm or Intermediate bulls (P

The objectives of this study were to evaluate whether velvet antler (VA) surface temperature gradients, as measured by either a single-spot infrared temperature (SST) sensor (SSTS; exp. 1) or digital infrared temperature (DIT) imaging (DITI; exp. 2), would pattern VA growth. In exp. 1, growth rates and SST were obtained from yearling (n = 8) and mature (n = 17) red deer stags (Cervus elaphus) every 14 d following eruption through day 56 in yearlings and day 112 in mature stags. In exp. 2, growth rates and DIT (main beam VA base, mid and tip temperatures) were obtained from red deer stags (n = 31) every 14 d following eruption through day 126. Background temperatures were recorded in conjunction with thermal antler measurements. In exp. 1, yearling VA base and tip SST were positively correlated with one another (P

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 (Por=0.05), but were greater (Por=0.05) than in day-16 Vehicle-treated ewes. Progesterone profiles on days 10-16 differed (Por=0.05) among treatment groups: PGE(1)PGE(2)Vehicle-treated ewes. Concentrations of PGF(2)alpha and PGE in uterine venous plasma on day-16 were similar (Por=0.05) in the three treatment groups. Luteal mRNA for LH receptors and unoccupied and occupied LH receptors were similar (Por=0.05) in day-10 control ewes and day-16 ewes treated with PGE(2) and were lower (Por=0.05) in day-16 Vehicle-treated ewes. PGE(2) prevented loss (Por=0.05) of day-16 luteal mRNA for LH receptors and occupied and unoccupied LH receptors. Luteal and caruncular tissue mRNA for LH receptors and occupied and unoccupied LH receptors were greater (Por=0.05) on day-16 of PGE(1)-treated ewes than any treatment group. mRNA for LH receptors and occupied and unoccupied receptors for LH in caruncules were greater (Por=0.05) in day-16 Vehicle or PGE(2)-treated ewes than in day-10 control ewes. It is concluded that PGE(1) and PGE(2) share some common mechanisms to prevent luteolysis; however, only PGE(1) increased luteal and endometrial mRNA for LH receptors and occupied and unoccupied LH receptors. PGE(2) prevents a decrease in luteal mRNA for LH receptors and occupied and unoccupied receptors for LH without altering endometrial mRNA for LH receptors or occupied and unoccupied receptors for LH.

The objective of this study was to characterize residual feed intake (RFI) and to estimate phenotypic and genetic correlations with performance and ultrasound carcass traits in growing heifers. Four postweaning feed efficiency trials were conducted using 468 Brangus heifers. The complete Brangus pedigree file from Camp Cooley Ranch (Franklin, TX), which included 31,215 animals, was used to generate genetic parameter estimates. The heifer progeny from 223 dams were sired by 36 bulls, whereas the complete pedigree file contained 1,710 sires and 8,191 dams. Heifers were individually fed a roughage-based diet (ME = 1.98 Mcal/kg of DM) using Calan gate feeders for 70 d. Heifer BW was recorded weekly and ultrasound measures of 12th- to 13th-rib fat thickness (BF) and LM area (LMA) obtained at d 0 and 70. Residual feed intake (RFIp) was computed as actual minus predicted DMI, with predicted DMI determined by linear regression of DMI on mid-test BW(0.75) (MBW) and ADG with trial, trial x MBW, and trial x ADG as random effects. Overall means for ADG, DMI, and RFI were 1.01 (SD = 0.15), 9.51 (SD = 1.02), and 0.00 (SD = 0.71) kg/d, respectively. Stepwise regression analysis revealed that inclusion of gain in BF and final LMA into the base model increased the R(2) (0.578 vs. 0.534) and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake and carcass-adjusted RFI (RFIc) were strongly correlated phenotypically and genetically with DMI and FCR, but not with ADG or MBW. Gain in BF was phenotypically correlated (P < 0.05) with RFIp (0.22), but not with FCR or RFIc; however, final BF was genetically correlated (P < 0.05) with RFIp (0.36) and RFIc (0.39). Gain in LMA was weakly phenotypically correlated with FCR, but not with RFIp or RFIc; however, gain in LMA was strongly genetically correlated with RFIp (0.55) and RFIc (0.77). The Spearman rank correlation between RFIp and RFIc was high (0.96). These results suggest that adjusting RFI for ultrasound carcass composition traits will facilitate selection phenotypically independent of growth, body size, and carcass composition; however, genetic relationships may still exist between RFI and carcass composition.

Hypothalamic-pituitary-adrenal (HPA) axis function, in Brahman heifers of differing temperament, was evaluated using separate challenges with CRH and ACTH. Exit velocity (EV) measurement was used to classify heifer temperament as calm [C; consisted of 6 slowest heifers (EV=1.05+/-0.05 m/s)] or temperamental [T; 6 fastest heifers (EV=3.14+/-0.22 m/s)]. During the 6 h prior to CRH challenge, areas under the ACTH (P=0.025) and cortisol (P

The objectives of this study were 1) to compare temperament assessments, using multiple techniques and over repeated observations, to gauge temperament over the long-term and 2) to evaluate the relationship of the temperament appraisals with serum concentrations of cortisol (CS). Measures of temperament were gathered over 3 repeated observations (60-d interval) of yearling, fall-born Brahman bulls (initial BW = 320 +/- 4 kg; n = 66). Temperament assessments included exit velocity (EV), which was the rate at which the bulls exited the squeeze chute and traversed a fixed distance (1.83 m); pen scores (PEN; 1 = quiet to 5 = excited), ascertained from animal behavior while penned in small groups (n = 5); and chute scores (CHUTE; 1 = quiet to 5 = excited), determined from behavioral responses to restraint on the weigh scale. Temperament measures obtained during the initial data collection (d 0) were all positively correlated (r > or = 0.35, P 0.31, P 0.31, P 0.3). Exit velocity was positively correlated with CS within d 0 (r = 0.26, P = 0.04) and 120 (r = 0.44, P 1 SD above the mean. Mean EV (P < 0.01) decreased from d 0 (2.82 +/- 0.07 m/sec) to 120 (2.11 +/- 0.10 m/sec). Time also influenced (P < 0.01) CS; mean CS decreased between d 0 (14.6 +/- 0.7 ng/mL) and 120 (11.1 +/- 0.8 ng/mL). Measures of EV can be a valuable tool for the assessment of cattle temperament and a possible predictor of temperament and stress responsiveness to future animal handling events.

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) 0.5 h 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 21 d. Temperament influences tenderness, although the mechanism is not clear.

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.

Near infrared reflectance spectroscopy (NIRS) of faeces is a non-invasive analytical technique that has been used to determine physiological status of free-ranging herbivores. Sixty-eight faecal samples collected in April of 2000 and 2002 from adult animals maintained on ryegrass (Lolium perenne L.) were used to determine the ability of NIRS to distinguish faeces by sex and/or species in red (Cervus elaphus) versus fallow (Dama dama) deer. Two-block partial least squares procedures indicate a high degree of discrimination (R 2 > 0.90) between groups within year. Discriminant equations developed from samples within either year were ineffective in identifying sex or species in the other year’s samples ( 0.87) and, when the resultant discriminant equations were applied to validation samples withheld from calibration, correctly identified 80–100% of faecal samples grouped by sex, species, sex within species, and species within sex. Fecal NIRS successfully discriminated sex and species in red and fallow deer maintained in unisex groups on a monoculture pasture. The use of faecal NIRS to characterize wildlife population demographics and non-invasively monitor individual animal physiology should now be explored in free-ranging animals. © 2004 Elsevier B.V. All rights reserved.

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 (P0.10) 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 (P0.07) than 0.5 IU ACTH-treated heifers (13.3 +/- 1.1 ng/mL); and were lower (P0.02) 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 (P0.05) for 1.0 IU ACTH-treated heifers than all other groups. The CT:P4 ratios were lower (time x treatment, P0.01) for control heifers than all ACTH-treated heifers. Among ACTH-treated heifers, CT:P4 ratio response and CT:P4 ratio AUC were similar (P0.10) 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.

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.

Two experiments were conducted to determine the effects of nitric oxide (NO) donors, endothelin-(ET-1), and NO synthase (NOS) inhibitors on bovine luteal function in vitro. In experiment 1, estrus in Brahman cows was synchronized with Synchro-Mate-B (SMB) and day-13-14 corpora luteal slices were weighed, diced and incubated in vitro. Treatments (100 ng/ml) were: vehicle, N[see symbol in text]-nitro-L-arginine-L-methyl ester (L-NAME), N(G)-monomethyl-L-arginine acetate (L-NMMA), diethylenetriamine (DETA), DETA-NONOate, sodium nitroprusside (SNP), or ET-1. In experiment 2, estrus was synchronized with Lutalyse, a Controlled Intravaginal Progesterone Releasing Device (CIDR), or cows were not synchronized. Corpora lutea were collected, weighed, and luteal slices were weighed, diced and incubated in vitro with treatments. Treatments (100ng/ml) were: vehicle, L- NAME, L-NMMA, DETA, DETA-NONOate, sodium nitroprusside, S-nitroso-N-acetylpenicillamine (SNAP) or endothelin-1. Tissues were incubated in M- 199 for 1 h without treatments and for 4 and 8 h in both experiments with treatments in both experiments. Media were analyzed for progesterone, prostaglandins E2 and F2alpha (PGE2, PGF2alpha) by radioimmunoassay (RIA). Hormone data in experiments 1 and 2 were analyzed by 2 x 7 and 3 x 2 x 8 factorial design for analysis of variance (ANOVA), respectively. Luteal weights in experiment 2 were analyzed by a one-way ANOVA. Concentrations of progesterone in media were similar (Por = 0.05) among treatments within experiments. Concentrations of PGE2 in media in experiment 1 were undetectable in 90 and 57% of the samples at 4 and 8 h, respectively. PGF2alpha increased (Por = 0.05) with time, but did not differ (Por = 0.05) among treatments. Secretion of PGF2alpha was not affected by treatments (Por = 0.05). In experiment 2, luteal weights of the induced estrous cycle were decreased (Por = 0.05) by Lutalyse. Concentrations of PGE2 and PGF2alpha increased (Por = 0.05) with time in control of all three synchronization regimens. DETA-NONOate, SNAP, sodium nitroprusside (NO donors) and ET-1 increased (Por = 0.05) PGE2 except in the CIDR synchronized group (Por = 0.05). No treatment increased (Por = 0.05) PGF2alpha in any synchronization regimen. It is concluded that either SMB containing norgestomet or a CIDR containing progesterone alters luteal secretion of PGE2, Lutalyse lowers luteal weights in the induced estrous cycle, and NO or ET-1 given alone are not luteolytic agents. It is suggested that NO and ET-1 could have indirect antiluteolytic/luteotropic effects via increasing PGE2 secretion by luteal tissue rather than being luteolytic.

The objectives were to determine the efficacy of the HeatWatch (HW) electronic estrus detection system for monitoring behavioral estrus (including duration and intensity) in red deer hinds and to evaluate pregnancy rate to AI after detected estrus. Red deer hinds (Cervus elephus; n = 50) were allocated into two treatment groups: AI following synchronization (CIDR/PMSG) and observed estrus (induced estrus group: IE; n = 25) or AI following the detection of natural estrus (NE; n = 25) without hormonal treatment. Hinds were fitted with two HeatWatch (HW) electronic estrus detection transmitters, one above the tail (bottom) and one between the tuber coxae of the pelvic girdle (top), and visual observations for mounting activity began with the aid of young sterile red deer stags (18 months old) fitted with marking harnesses. Hinds in both groups were inseminated (10-12h after observed estrus) with frozen-thawed red deer semen using a transvaginal/cervical AI approach. Following a 26-day period of AI, hinds were placed with a mature fertile stag for an additional 30-day natural breeding period. Pregnancy diagnosis was performed 57 and 86 days after the start of AI. While the hinds were housed with the young stags, 82% were detected in estrus by visual appraisal of stag crayon marks, but only 32% of these were detected by HW. In contrast, in the hinds housed with the mature stag, 93% detected in estrus by crayon marks were also detected by HW. The top HW transmitter consistently recorded more mounts (P0.05) than the bottom transmitter. The pregnancy rate was numerically better in IE versus NE hinds (42% versus 29%, P0.10). In summary, there were no differences (P0.10) in the intensity (number) or duration of mounts (detected by HW) during estrus in IE versus NE hinds, and HW was most effective in detecting estrus in the presence of a heavier, mature stag versus a younger stag. When used in combination with transvaginal AI, an overall first-service pregnancy rate of 36.6% was achieved with AI of frozen-thawed semen in red deer hinds following detected estrus.

The major objective of this experiment was to determine whether the bovine placenta could be stimulated to secrete progesterone, since the bovine placenta secretes little progesterone when the corpus luteum is functional. Secondly, we wanted to determine whether reported abortifacients or progesterone or estrogen receptor antagonists affected bovine placental prostaglandin secretion. The ovine placenta secretes half of the circulating progesterone at day 90 of pregnancy and PGE2 appears to regulate ovine placental progesterone secretion. Calcium has been reported to regulate placental progesterone secretion in cattle. Diced 186-245-day placental slice explants from six Brahman and six Angus cows were incubated in vitro at 39.5 degrees C under 95% air: 5% CO2 at pH 7.2 in 5 ml of M-199 for 1 h in the absence of treatments and for 4 and 8 h in the presence of treatments. Treatments were: vehicle; R24571; compound 48/80; IP3; PGE2; CaCl2; cyclosporin A; lipopolysaccharide (endotoxin) from Salmonella abortus equi., enteriditis, and typhimurium; monensin; ionomycin; arachidonic acid; mimosine; palmitic acid; progesterone, androstenedione; estradiol-17beta; A23187; RU-486; or MER-25. Jugular and uterine venous plasma and culture media were analyzed for progesterone, PGE2 and PGF2alpha by radioimmunoassay (RIA). Plasma hormone data were analyzed by a One-Way Analysis of Variance (ANOVA). Hormone data in culture media were analyzed for breed and treatment effects by a Factorial Design (2 breeds, 2-range of days, 21 treatments) for ANOVA (2 x 2 x 21). Since hormone data secreted by placental tissue in vitro did not differ (Por = 0.05) by breed or range of days of pregnancy, data were pooled and analyzed by a One-Way ANOVA. Concentrations of PGE2 in uterine venous blood were two-fold greater (Por = 0.05) in Angus than Brahman cows. PGE2 and PGF2alpha in vehicle controls increased from 4 to 8h (Por = 0.05), but not progesterone (Por = 0.05) Progesterone in culture media treated with RU-486 increased (Por = 0.05) at 4 and 8 h compared to vehicle controls and was not affected by other treatments (Por = 0.05). Concentrations of PGE2 in media at 4 and 8 h were lower (Por = 0.05) when compared to controls except treatment with PGE2 at 4 and 8h and RU-486 at 8h (Por = 0.05). PGF2alpha was increased (Por = 0.05) by RU-486 at 8h and no other treatment affected PGF2alpha at 4 or 8 h (Por = 0.05). In conclusion, modulators of cellular calcium signalling pathways given alone do not affect bovine placental progesterone secretion at the days studied and progesterone receptor-mediated events appear to suppress placental progesterone, PGF2alpha, and PGE2 secretion in cattle. In addition, PGE2 does not appear to regulate bovine placental progesterone secretion when the corpus luteum is functional and bacterial endotoxin does not appear to affect bovine placental secretion of PGF2alpha or PGE2.

We conducted several experiments to better understand the relationship between brown adipose tissue (BAT) metabolism and thermogenesis. In Exp. 1, we examined perirenal (brown) and sternum s.c. adipose tissue in 14 Wagyu x Angus neonates infused with norepinephrine (NE). Perirenal adipocytes contained numerous large mitochondria with well-differentiated cristae; sternum s.c. adipocytes contained a few, small mitochondria, with poorly developed cristae. Lipogenesis from acetate was high in BAT but barely detectable in sternum s.c. adipose tissue. In Exp. 2, we compared perirenal and tailhead adipose tissues between NE-infused Angus (n = 6) and Brahman (n = 7) newborn calves. Brahman BAT contained two-to-three times as many total beta-receptors as Angus BAT. The mitochondrial UCP1:28S rRNA ratio was greater in Brahman BAT than in BAT from Angus calves. Lipogenesis from acetate and glucose again was high, but lipogenesis from palmitate was barely detectable. Tail-head s.c. adipose tissue from both breed types contained adipocytes with distinct brown adipocyte morphology. In Exp. 3, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types, whereas the UCP1 gene expression tripled during gestation in both breed types. At birth, palmitate esterification was twice as high in Angus than in Brahman BAT and was at least 100-fold higher than in BAT from NE-infused calves from Exp. 2. Uncoupling protein-1 mRNA was readily detectable in tailhead s.c. adipose tissue in all fetal samples. In Exp. 4, male Brahman and Angus calves (n = 5 to 7 per group) were assigned to 1) newborn treatment (15 h of age), 2) 48 h of warm exposure (22 degrees C) starting at 15 h of age, or 3) 48 h of cold exposure (4 degrees C) starting at 15 h of age. Brahman BAT adipocytes shrank with cold exposure, whereas Angus BAT adipocytes did not. Similarly, BAT from neonatal lambs (Exp. 5; n = 6 per group) was depleted of lipid in response to cold exposure, although UCP1 gene expression persisted. In Exp. 4, NE stimulated lipogenesis from palmitate in BAT incubated in vitro. Lipogenesis from palmitate was higher in Angus than in Brahman BAT, and increased with both warm and cold exposure. These studies suggest that BAT from Brahman calves may be exhausted of lipid shortly after birth during times of cold exposure.

Objectives were to determine effects of lasalocid on reproductive performance and serum concentrations of leptin and IGF-I, and to correlate concentrations of leptin and IGF-I with reproductive performance of beef cows. Forty-one purebred, multiparous Brahman cows were blocked to control (C; n = 20) or lasalocid (L; n = 21) treatments by BW, BCS, and predicted calving date. Treatment began 21 d before expected calving. Cows were each fed 1.4 kg daily of an 11:1 corn:soybean meal supplement, with the L group receiving 200 mg of lasalocid/cow daily. Cows and calves were weighed, and cow BCS was assessed at calving and at 28-d intervals thereafter. Blood samples were collected weekly precalving, at parturition, and twice weekly thereafter. Sterile marker bulls were maintained with cows for estrous detection. Six days after estrus, ovaries were evaluated for corpus luteum formation, and blood samples from d 6, 7, and 8 after estrus were collected. Serum samples were assayed for progesterone (P4), IGF-I, and leptin concentration. Progesterone concentrations > 1 ng/mL were considered indicative of a functional corpus luteum. Treatment ended after completion of a normal estrous cycle, and cows removed from treatment were placed with a fertile bull equipped with a chinball marker. There were no treatment differences in calving date, calf sex, cow BW, BCS, calf BW, calf ADG, or in serum concentrations of P4, IGF-I, or leptin. Prepartum cow ADG was increased (P 0.18) for serum IGF-I concentrations. At calving, leptin was positively correlated with IGF-I (P < 0.04; r = 0.32), BCS (P < 0.06; r = 0.29), and cow BW (P < 0.02; r = 0.36), and was negatively correlated with PPI (P < 0.06; r = -0.29). These results provide evidence that feeding an ionophore before calving and during the postpartum period may increase the number of cows that rebreed to maintain a yearly calving interval. Cows with higher concentrations of leptin postpartum may exhibit shorter PPI.

Fifteen yearling fallow bucks were randomly assigned by BW to one of three treatment groups: control (C; n = 5), melengestrol acetate (MGA; n = 5), and zeranol (Z; n = 5), to evaluate effects on testicular development, aggressive behavior, antler growth, sexual activity, ADG, and BW. Zeranol-treated bucks received zeranol ear implants (36 mg) at 90-d intervals, and MGA-treated bucks received MGA in the ration (100 microg x animal(-1) x d(-1)). Bucks grazed ryegrass/Coastal bermudagrass pasture and were supplemented with 3:1 corn/soybean meal at 0.45 kg x animal(-1) x d(-1). Body weights, body condition scores (BCS), blood samples, and testis measurements were obtained at d 0 and at 14-d intervals for 229 d. As bucks reached hard antler (7/15 to 8/25), antlers were harvested and weighed, and ejaculates were collected at 14-d intervals. Aggression was evaluated using 10-min video sessions scoring body blows, avoidance, head pushes, and head bunts. Scrotal circumference (SC) and paired testis volume were affected by a day x treatment interaction (P < 0.01); testes of zeranol-treated bucks were smaller than those of control or MGA-treated bucks. First sperm in the ejaculate tended to be delayed (P < 0.10) in zeranol-treated bucks compared with control and MGA-treated bucks. Melengestrol acetate-treated bucks had a maximum sperm concentration in the ejaculate that was three times (P < 0.05) that of control bucks and nine times (P < 0.05) that of zeranol-treated bucks. Antler weight was the least (P < 0.01) for bucks receiving zeranol and greatest (P < 0.10) for MGA-treated bucks; intermediate values were recorded for the control bucks. Aggressive behavior was delayed (P < 0.05) for zeranol-treated bucks until treatment effects were overcome. Melengestrol acetate-treated bucks had decreased (P < 0.01) aggressive behavior compared with control bucks. Melengestrol acetate-treated bucks had increased (P < 0.05) serum testosterone concentrations compared with control and zeranol-treated bucks. Human chorionic gonadotropin-stimulated peak serum testosterone concentrations for zeranol-treated bucks were delayed (P < 0.01) compared with control and MGA-treated bucks. Although zeranol-treated bucks overcame treatment effects, they were never able to reach testicular measurements or sperm concentrations equal to those of the control or MGA-treated bucks. Zeranol and MGA treatments may have both positive and negative effects that can be utilized when producing slaughter bucks.

The site of semen deposition (vaginal, cervical or uterine) and the time required for transvaginal artificial insemination (AI) using the Gourley Scope method of AI vs. a standard speculum-guided AI gun was assessed in three species of farmed deer (fallow, red and white-tailed deer). Pregnancy rates using these two transvaginal AI methods were also compared in a commercial herd of fallow does. The estrous cycles of fallow ( n =53), red ( n =27) and white-tailed ( n =27) deer were synchronized using half of a Norgestomet ear implant inserted for 14 days. Following implant removal, does were artificially fix-time inseminated with frozen-thawed semen using either a 0.5 ml standard French-style speculum-guided AI gun or the Gourley Scope method of AI. The time-frame (i.e., duration in minutes) for the AI procedures performed on each animal and the location of semen deposition was recorded. To assess effectiveness of AI, transrectal ultrasonography was conducted in fallow deer 45 days post-AI for pregnancy diagnosis. In fallow does and red deer hinds, use of the Gourley Scope (96.3 and 100%, respectively) enabled a greater ( P P P

Brahman calves experience greater neonatal mortality than Angus calves if cold-stressed. To establish a developmental basis for this, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Overall fetal BW tended (P = 0.08) to be greater for Angus than for Brahman fetuses. There was no difference between breed types in total brown adipose tissue (BAT) mass or grams of BAT/kg BW. Brown adipocyte density decreased 56%, whereas lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types. Glycerolipid synthesis from palmitate declined by 85% during the last trimester but still contributed 98% to total lipid synthesis at birth. The fetal age x breed interaction was significant for lipogenesis from glucose (P = 0.05) and palmitate (P = 0.005); rates were higher at 96 d before birth in Brahman BAT but declined to similar rates by birth. Uncoupling protein-1 (UCP1) mRNA tripled during gestation in both breed types (P = 0.002), whereas mitochondrial cross-sectional area did not change (P = 0.14) during gestation. Neither the breed nor the age x breed effect was significant (P > or = 0.24) for UCP1 mRNA concentration or mitochondrial cross-sectional area. In both breed types, a marked decrease in BAT UCP1 mRNA between 24 and 14 d prepartum was associated with a similar reduction in lipogenesis from palmitate and a noticeable change in BAT mitochondrial morphology, as the mitochondria became more elongated and the cristae became more elaborate. Uncoupling protein-1 mRNA initially was elevated in Angus tailhead s.c. adipose tissue, but was barely detectable by birth, and tended to be greater overall (P = 0.09) in Angus than in Brahman BAT. If uncoupling protein activity in s.c. adipose tissue persists after birth, then s.c. adipose tissue may contribute more to thermogenesis in Angus newborn calves than in Brahman calves. In contrast, we did not observe differences in ontogenic development of perirenal BAT that could explain the documented differences in thermogenic capacity between Angus and Brahman newborn calves.