Lactating Holstein dairy cows, fitted with appropriate blood vessel catheters, were used in two cross-over experiments to investigate effects of feeding diets with 40% steam-flaked (28 lb/bu; SF) vs dry-rolled (DR) sorghum (experiment 1; 8 cows), or 40% steam-flaked corn grain (experiment 2; 6 cows) of different flake densities, 38 lb/bu (SF38) vs 28 lb/bu (SF28), on postabsorptive nutrient fluxes. Net uptake or output of glucose, L-lactate, volatile fatty acids (VFA) and β-hydroxybutyrate (BHBA) was measured across portal-drained viscera (PDV), hepatic, splanchnic and mammary tissues. Compared to DR, feeding cows SF sorghum increased net PDV absorption of propionate by 25% (P =.08), tended to increase splanchnic output of glucose (+16%) and L-lactate (+80%; P ≤ .20), but did not alter mammary glucose or L-lactate uptake. Sorghum processing did not affect net splanchnic or mammary metabolism of acetate and butyrate. Splanchnic output of BHBA was greater (P =.08), but mammary uptake was lower (P =.09) for cows fed DR vs SF diets. For cows fed corn diets, hepatic synthesis of glucose was higher (3.0 vs 2.8 kg/d; P =.04) for SF28 vs SF38. Flake density did not affect net splanchnic or mammary metabolism of acetate. For cows fed SF38, higher (P =.03) net PDV absorption of butyrate possibly inhibited hepatic gluconeogenesis from propionate, which might explain a higher (P =.10) hepatic uptake of L-lactate. Processing of corn or sorghum did not alter estimated total net PDV absorption or total splanchnic output of energy. Net total PDV absorption of VFA tended to be greater for cows fed SF than DR (+17%; P =.17), and for SF38 than SF28 (+10%; P =.15). Total mammary uptake of energy was not different for DR vs SF, but was greater for cows fed SF28 vs SF38, due mainly to increased uptake of glucose (+25%; P < .01). In both experiments, hepatic glucose synthesis was more than adequate for milk lactose production. These changes in partitioning of nutrients and estimated energy across portal-drained viscera, liver, total splanchnic, and mammary tissues may partially explain increased milk protein synthesis (in longer term lactation studies) by dairy cows fed more extensively processed corn (SF28) and sorghum (SF) grain.

Beef production in the arid Southwest depends on range forages. Forage quality and quantity primarily results from amount, intensity and timing of precipitation. Twenty-three years (1978-2000) of precipitation and animal production data were evaluated. Two major questions addressed were: Does rainfall timing affect number and weight of calves weaned? Does grazing system reduce immediate drought impact on calf production? Three grazing systems were evaluated: Year-round grazing, Savory rotational grazing and Santa Rita rotational grazing (50-60hd, 80-150hd and 50-65hd/year respectively). Winter (P < 0.05), summer (P < 0.01) and previous fall (P < 0.01) precipitation affected calf crop. Only summer precipitation (P < 0.01) had a significant effect on weaning weight. Calf crop did vary between grazing systems (P < 0.01). Savory system had the heaviest weaning weight, total production, and lowest maintenance cost; followed by Santa Rita and year-round respectively (P < 0.01). Maintenance cost per kg calf weaned was similar between rotational systems, but higher in year-round (P < 0.01).

Four lipogenic enzymes were measured in liver and adipose tissues of 2-, 6-, 18- and 27-month-old male Fischer 344 rats. Adipose ATP-citrate lyase (EC 4.1.3.8; ATP-CL) activity increased 1.8-fold between 2 and 6 months of age. Hepatic ATP-CL activity underwent an overall 84% reduction between 2 and 27 months of age with maximum activity at 18 months. Adipose tissue fatty acid synthase (FAS) activity exhibited a linear 54% reduction between 2 and 27 months of age; while hepatic FAS activity declined, biphasically, to 14.2 IU/g protein by 27 months. Opposing age-related patterns of glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD) activity were observed in adipose tissue and liver. Adipose activity decreased between 2 and 6 months to 132.9 IU/g protein, and was unchanged thereafter; whereas liver G6PD activity increased to a maximum of 149.0 IU/g protein at 27 months. Malic enzyme (EC 1.1.1.40; ME) activity decreased between 2 and 6 months of age in both tissues. These data suggest diminished lipogenic capacity with age.

No description available.

<p>Among rhesus macaques, bi-directional aggression may occur between animals with shifting or ambiguous ranks, or between those whose relative ranks are well established. Factors that influence the latter case (here termed "insubordinate aggression") are not well understood. These factors are of interest because insubordinate aggression may be associated with stability in dominance relationships, and stability in dominance relationships is critically related to group stability. We hypothesized that in well-established female dominance relationships, the likelihood of insubordination during conflicts is influenced by characteristics of both opponents. Multivariate analysis of 11,591 dyadic conflicts among females in six captive rhesus groups shows that dyadic and individual characteristics related to weight, rank, age, and access to social support affect the likelihood of insubordinate aggression. As expected, insubordinate aggression is less likely to occur among dyads with high disparity in weight. The effects of age, rank, and access to social support are more complex. Increasing subordinate age is associated with increased modulation of insubordinate aggression according to opponent age. Age-based deference, i.e. suppression of insubordination associated with opponent age, decreases with increasing age of the lower-ranking opponent. Similarly, dyadic rank disparity has different effects on insubordination rate according to the age of the subordinate opponent. As females age, their likelihood of insubordination is less dependent on the degree to which they are outranked by their opponent. Also, the lower-ranking opponent's level of social support significantly affects her likelihood of insubordination, but the dominant animal's level of social support does not affect her likelihood of receiving insubordination. We predicted that for the lower-ranking opponent, having many maternal kin would promote insubordinate behavior, whereas for the higher-ranking opponent, having many maternal kin would inhibit insubordination. However, our results show that the dominant's matriline size has no effect on her likelihood of receiving insubordination. Further, matriline size has the opposite of the predicted effect for subordinates--subordinates with many maternal kin are significantly less likely to be insubordinate than those with few kin. We propose some possible explanations for this, which will require further investigation. Taken together, this research suggests that females gauge their degree of deference to dominants based on their own characteristics relative to their opponent's, taking into account size, age and weight differences as well as their own access to social support. Features of subordinate animals emerge as more important than those of dominants in determining the likelihood of insubordinate aggression in dyadic conflicts. Understanding determinants of insubordination will contribute to management practices aimed at maintenance of group stability, as the ultimate act of insubordinate aggression, social overthrow, poses a major welfare and management problem.

Active immunisation against GnRH inhibits reproductive function by inducing a hypogonadotropic condition associated with gonadal atrophy. Despite economic, ethical and environmental advantages of GnRH immunisation in cattle over conventional castration methods, the technology has not yet been commercially adopted. Primarily because of the requirement for numerous booster vaccinations because of the reversibility of physiological effects, the commercial efficacy of immunocastration is currently poor. However, neonatal GnRH immunisation in sheep can result in a permanent suppression of reproduction (Brown et al., 1994; 1995; Clarke et al., 1998). These findings and a study in pigs (Molenaar et al., 1993) indicate that, the hypothalamic/pituitary gland unit (HPU) may be particularly susceptible to GnRH antibodies during a specific window of development in the pre-pubertal animal, but no long-term studies in cattle have been conducted. Therefore the primary objective of this project was to determine the effect of neonatal immunisation against GnRH in cattle. Beef cross bull (n=9; Chapter 3) and heifer calves (n=9; Chapter 4) were vaccinated against a newly developed (Pfizer®) GnRH construct vaccine at -2, 6 and 13 weeks of age. Nine calves of each sex served as negative controls, receiving saline injections only. The GnRH vaccine had proved effective (Dr. A.R. Peters, personnel communication 2000) in inducing immune responses and reducing variation between animals in unpublished industrial studies, compared to earlier vaccines, and hence was reasoned to be capable of raising GnRH antibodies despite the relative immaturity of the neonatal immune system. Following vaccination, circulating GnRH antibodies and reproductive hormones, such as FSH (Chapters 3 and 4), testosterone (Chapter 3), progesterone (to assess onset of puberty) and oestradiol (Chapter 4) were measured and additional intensive serial bleeds were carried out to assess LH parameters up to and beyond puberty (puberty defined by testes circumference in bulls). Gonadal (antral follicles and testes growth) and accessory gland development was quantified throughout the trial using ultrasound scanning. Sexual behaviour (Chapter 3) was studied from 38 weeks of age, while an assessment of sperm quality (Chapter 3), and anabolic response to vaccination was also performed post-mortem (Chapters 3 and 4). GnRH immunisation in neonatal calves did not permanently impair reproduction. A temporary suppression in reproductive function was evident through the disruption of pituitary gland function, as indicated by a reduction of LH pulse amplitude and mean plasma LH concentrations (Chapters 3 and 4). In addition, a reduction in medium- sized follicle numbers, testes growth, plasma testosterone concentration, vesicular gland length and juvenile aggression occurred. Some beneficial anabolic effects were observed e.g., carcass composition grades. Changes all occurred subsequent to increased GnRH antibody titres in immunised cattle. Despite some evidence of prolonged effects on LH amplitude and circulating testosterone after anti-GnRH titres had dissipated, all inhibited parameters, except carcass quality, returned to levels comparable to control animals by 72 weeks of age. No treatment effects on FSH concentrations, large follicle numbers, reproductive tracts (post mortem) or peri- and post-pubertal behaviours were observed following treatment. Sperm morphological abnormalities tended to be more prevalent in GnRH immunised bulls. A significant increase in GnRH antibody titres occurred at -23 weeks of age (Chapter 4), this may have been a rebound in antibody titre, possibly caused by an anti-idiotype immune response (antibody response to GnRH antibodies), or due to significant maturational changes in immune function at this time causing a delayed response to vaccination. Alternatively a novel "auto-immune" response may have been detected, which if confirmed/repeatable might be incorporated into an immunisation protocol to act as a "self-booster". However, no previous reports of such an event have been published and further investigation is urgently required. A more prolonged or permanent suppression of reproductive function may be possible following an earlier, greater and more sustained elevation of antibody titres during the neonatal period. Further development of GnRH vaccines and/or protocols (prime-boost, cytokine modulation vaccines, concomitant passive and active immunisation and pregnant cow GnRH vaccination), and studies of performance and GnRH antibody mechanism(s) of action in cattle are required. Chapters 3 and 4 provide a comprehensive study on pubertal development and neonatal GnRH vaccination, thus contributing significantly to knowledge in these fields. Currently, the vaccine used in this trial may be used to delay puberty in older calves or transiently suppress reproductive function to aid management. The economical viability of animal production systems such as beef and lamb are closely related to rates of reproduction. The Fec B gene in ewes increases ovulation rate and litter size, possibly through the development of precocious follicles, which can switch their primary dependence from FSH to LH. As a result, more follicles are selected to continue growth to an ovulatory size. The precise mechanisms by which these processes occur have recently been shown to involve oocyte follicle interactions (see section 1.1.5). Follicle development is modulated by GHIIGF and inhibin, however attempts to increase follicular development and ovulation through active inhibin immunisation alone have been variable and hence not commercially attractive. To develop successful protocols to induce twin ovulations in cows· and ewes, without superovulation, a clearer, more details understanding of follicullogenesis is required. The objective of the current study was to better understand these mechanisms through investigating interactions of GH/GF and inhibin in the ovary, follicle development, steroidogenesis, and receptor populations using an anoestrous sheep model. Spring born Mule x Charolais ewe lambs were actively immunised (n=8) against porcine inhibin α-C 1-26 peptide conjugated to KLH in NUFCA (primary and 3 boosters (NUFA», while 8 served as negative controls. Seven days following the final booster, the ewes were subdivided to give four groups: (1) controls + saline (n=4); (2) controls + rbGH (4ml s.c; 1mg. mr1; n=4); (3) inhibin immunised + saline (n=4); and (4) immunised + rbGH (n=4). Recombinant bovine growth hormone (rbGH) was given (Lm.) for 6 days. On day 4 GnRH (Receptal®; 1 ml) was injected s.c, to all animals to initiate the beginning of a new follicular wave. Blood samples were collected fortnightly to measure inhibin antibody titres, IGF-I, FSH and steroids. On the seventh day ensuing slaughter serum antibodies and ovaries were harvested. Left ovaries were intended for ISH (mRNA for P450arom) and/or immunohistochemical analysis. Follicles from right ovaries were dissected out, counted, measured and cultured in M199 at 37°C for 2 hours. Culture media was then assayed for oestradiol. Follicle shells were stored at -180°C for LH receptor binding studies. This work reports on the influence of different treatments on follicle populations. All immunised animals produced antibodies, which bound to 1251-inhibin. Using ANOVA to compare treatments it was observed that, Inhibin immunisation significantly (P<O.05) increased the number of follicles >3.5mm in diameter, but did not affect the smaller <3.5mm population. In contrast, rbGH administration led to a significant (P<O.05) elevation of follicles <3.5mm, without increasing the >3.5mm follicle numbers. These findings are in agreement with previous research. The molecular studies of left ovaries are not presented herein as due to time constraints the work was not completed and is currently on going. In conclusion, additional results of this study are required to meet the objectives of the experiment. Further research is required on dominant follicle selection if superovulatory programmes in both livestock and humans are to be more precisely controlled and readily accepted.

<p> Study objectives were to determine the effectiveness, reproducibility, and repeatability of dental evaluation for estimating cattle age. Cattle (n = 400) aged 1.5 to 20 yr were evaluated by 3 technicians for estimated age via dentition. A subset (n = 383) was aged again 4 wk later by the same observers. Age estimations were most accurate in YOUNG (&le; 5 yr old) cattle with at least 95.7% rate of accuracy within 2 yr across all observers and observation events. For MIDDLE (6 to 10 yr old) and OLD (> 10 yr old) cattle, these accuracies were 81.5 and 62.1%, respectively. Reproducibility proved high, with all observers consistently assigning age estimates within 1 yr of one another for more than 9 out of 10 YOUNG animals; all observers agreed on at least every 8 out of 10 estimations for all age groups within 3 yr. Repeatability was less consistent.</p>

The thesis examined the effects of climatic change on livestock production within Scotland. In order to achieve this, a systems model of the dairy, beef and sheep enterprises was developed. Climatic change primarily affects livestock production through its effects on forage production. Under climatic change, the model predicted that the length of the growing and grazing season will increase with the extensions occurring at both ends of the season. Relative to current climatic conditions elevated CO2 concentrations coupled with the associated changes in climate resulted in an enhancement in harvestable dry-matter yield that ranged from 20% to nearly 60% and increases in the percentage of white clover in the harvestable material by up to 126% In general, global warming is predicted to increase forage and livestock production within Scotland. However, the location of the site is also important in determining the effect of climate change as the magnitude and, in some cases, the directions of the changes varied between sites. The effects of climate change were also dependent on the actual level of changes in temperature. In addition, there were interactions between CO2 concentration and both temperature and rainfall, as well as interactions between temperature and rainfall. Although the three enterprises showed similar trends in their response to climate change, there were differences in the magnitude of the response as well as differences in the factors that resulted in significant changes. There were also differences in the response of the grazed and the ungrazed swards. This underlines the complexity of the interactions and the difficulty of extrapolating the results to other locations and to other levels of climatic conditions. The advantage of developing a model is that all these complex interactions can be captured and potentially the site - specific consequences of climate change on forage and livestock production predicted.

No description available.

Mercury is an environmental contaminant of concern, particularly for fish eating populations. The objective of this study was to assess the effects of selenium, vitamin E, and phytate on methylmercury (MeHg) toxicity and kinetics in rats. Results show that increased selenium increases McHg in the liver, kidney, and frontal lobe of the brain, while increased vitamin E increases MeHg in the kidney but lowers McHg in the liver. Increased phytate resulted in a significant increase in MeHg in the frontal lobe. Methylmercury-treated rats on all diets showed an increased trend in muscarinic acetylcholine receptor (mAChR) binding in comparison with untreated rats. There was no change in monoamine oxidase (MAO) activities in all treatment groups. These results suggest that nutrients can alter the toxicokinetics of MeHg but none of them show clear protection in neurotoxicity in adult rats.