C. J. C. Phillips

The transmission of Mycobacterium bovis infection to cattle

The prevalence of Mycobacterium bovis infection in cattle is increasing rapidly in some countries, including the UK and Ireland. The organism infects a wide range of mammalian hosts, and eradication of the disease is difficult if there is an extensive reservoir in the wildlife population. Existing evidence suggests that wildlife vectors include the European badger in the UK and Ireland, the brush-tailed possum and ferret in New Zealand and ungulates in some other countries. Cattle grazing field boundaries or short swards are at particularly high risk, since the chance of contact with the intermediate host or their excreta is increased. There is evidence that the transmission of the disease between cattle following movement accounts for 10-15% of outbreaks in the British Isles and that transmission can occur across farm boundaries. The prevalence the prevalence of single reactors in herds suggested that within-herd transmission was not common. In herds with infected cattle, spreading slurry is a risk factor, which can be minimised by prolonged storage of the slurry, by spreading it on fields not used for grazing or by soil injection. M. bovis also survives in water and may enter the respiratory tract during drinking. It is concluded that M. bovis infection in cattle can be transmitted by a number of routes, some of which can be controlled by appropriate husbandry, but that circumstantial evidence suggests that the existence of a widespread intermediate host is the greatest contributor to infection in cattle.

Principles of cattle production

This introductory level textbook covers the welfare and environmental implications of producing cattle as well as traditional subjects such as nutrition, reproduction and housing. Its broad, international coverage includes feedlot systems, transport, subsistence farming systems and the contribution of cattle production systems to land, air and water pollution. It is an invaluable resource for undergraduate students of animal science, veterinary medicine and agriculture, as well as diploma and certificate courses and industry personnel.

Modeling Cadmium Uptake and Accumulation in Plants

Models of cadmium uptake and accumulation by plants are potentially of value in evaluating both the soil and plant components, in order that limits can be established, particularly in relation to soil concentrations, to restrict cadmium in the human food chain. Although the theoretical pattern of uptake is believed to follow a Mitserlich function, the best estimates to date that are based on empirical data use only linear functions, due to a paucity of suitable data, with r2 values of 0.35 and 0.62 for maize and ryegrass, respectively. A feature of these empirical models is the strong dependence of cadmium uptake on the interaction between soil cadmium concentration and soil pH. Insufficient data currently exist to develop empirical models of foliar cadmium uptake. Mechanistic models are not well developed, but the most realistic models assume that ions are transported to roots by mass flow and diffusion and are absorbed at rates that depend on their concentration at the root surface, following Michaelis–Menten kinetics. However, the level of agreement with empirical data is unsatisfactory and further work is required to isolate the key variables contributing to the errors, in particular the role of ectomicorrhizal fungi on root uptake. The influences of root exudates and soil temperature on the solubility of different Cd species in the rhizosphere of apical root zones also require more detailed evaluation before incorporation into mechanistic models, and the absence of an accurate technique for estimating root surface area is an impediment. A further disadvantage of existing mechanistic models is the necessity for difficult and expensive root measurements, restricting their value for field predictions. Mechanistic foliar cadmium uptake models have been developed, but key variables such as translocation of heavy metals into the plant and the resuspension of the pollutants into the atmosphere have so far been ignored. Differential adherence of wet and dry particles to the leaves and the influence of soil splash on stem and leaf uptake remain to be effectively quantified. Although the parameters described so far may be generalized for a number of different soil and plant systems, the differences between genotypes on phytochelatin production and differential translocation rates cause major variation in accumulation rates and will ensure that both empirical and mechanistic models are genotype specific. Cadmium transport within the plant can be effectively dichotomized into short distance transport from the root to the stele, assumed to be a symplastic transport across the root cortex, and long distance transport to the shoots, mainly in the ionic form in xylem and phloem. Uptake into seeds is not well understood, even though it is of major importance for uptake into cereal grains. It is concluded that there is currently only a limited understanding and quantification of key parameters which would allow a comprehensive mechanistic model of Cd uptake by different plant genotypes to be constructed, and also that there is a limited number of empirical observations of key endpoints for an empirical model. Further work on these aspects is essential to facilitate the construction of effective models to control excessive Cd accumulation in the human food chain.

The increase in activity during oestrus in dairy cows

Abstract In two experiments the effects of cow age, parity, milk yield, lactation stage and nutrition on the increase in locomotion at oestrus (locomotion coefficient, LC) were examined. In Experiment 1, the LC of 49 cows was recorded with electronic pedometers. LC decreased with advancing lactation and tended to increase with cow parity number, but was unrelated to the dioestrus locomotion rate, and the cows age or milk yield. The profile of the activity changes over oestrus was examined. Activity increased gradually from 80 h to 16 h before oestrus, whereupon it increased more rapidly and linearly to peak oestrus, followed by an exponential decay with no refractory period. In Experiment 2, 18 cows were offered high or low concentrate levels (Treatments H and L). The effect of treatment on the locomotion rate for 3 days before to 3 days after oestrus was not significant, except during metoestrus when cows in Treatment H walked further. LC was not affected by treatment. Across treatments cows that did not conceive had an inverse relationship between LC and both milk yield and liveweight gain. Cows that did conceive did not show such relationships, but cows with a high energy intake had an increased LC.

The accumulation of potentially-toxic metals by grazing ruminants

The main factors affecting the accumulation of potentially-toxic metals (PTM) by grazing animals are the presence of the metal, its concentration in herbage and at the soil surface, and the duration of exposure to the contaminated pasture and soil. In addition, the elapsed time between the contamination of the pasture and grazing, the quantity of soil ingested together with herbage, the mechanism of absorption of the metal into blood and the presence or absence of antagonistic metals can interact to influence the rate and extent of accumulation of heavy metals in edible body tissues. Models of the accumulation of metals by grazing animals may be used to determine the statutory limits of radionuclides and PTM in soils under grazed pastures. Meta-analysis of existing data, using a random-effects model, is a useful approach to understanding the factors affecting the accumulation of some metals, e.g. Cd. The target edible body tissues for the accumulation of most PTM are the liver and kidneys, with the exception of radiocaesium, which accumulates in muscle to a greater extent than in other tissues. The livers and kidneys of mature livestock that have been grazed on areas of pasture at the legal limit of contamination by Cd for more than one grazing season should be removed from the human food chain in order to reduce the risk of intake of Cd by the human population.

A survey of aged horses in Queensland, Australia. Part 2: Clinical signs and owners' perceptions of health and welfare.

OBJECTIVE To describe the prevalence and risk factors for clinical signs of disease and owner-reported health or welfare issues of aged horses in Queensland, Australia. METHODS Owners of horses were contacted via an equestrian organisation in Queensland and asked to complete a questionnaire about their horses aged 15 years and older, to gain information about clinical signs observed in the horse and disease history. Owners were asked to identify health or welfare issues they felt were important in aged horses. RESULTS Owners were able to identify many clinical signs of disease, with 83% of horses having at least one reported clinical sign of disease. Muscle stiffness (33%), lameness (28%), ocular discharge (22%), change in hair coat (22%) and skin problems (21%) were the most commonly reported signs. Increasing age was a risk factor for the presence of clinical signs of disease. Ponies had an increased risk of both laminitis and hirsutism, whereas Thoroughbreds had an increased risk of stereotypies, wounds, weight loss and musculoskeletal signs. Owners reported a known disease or disorder in their horses less frequently than the clinical signs of disease. Owners reported weight loss (28%), arthritis/lameness (24%) and teeth/dental care (18%) as the most important health issues, followed by welfare issues (8%). CONCLUSION Owners demonstrated concern for the health and welfare of their aged horses, but the lack of appropriate recognition of the significance of clinical signs and limited veterinary care suggest a need for increased client communication and veterinarian-client interaction.

The welfare of livestock during sea transport.

Large numbers of livestock are reared for transport overseas, and the long duration of the journey and the changes in the animals’ environments provide special challenges compared to other short distance transport. A description is provided of the most common methods of transporting live animals by sea for slaughter internationally. The biggest exporter in the world is Australia and the main markets are South-east Asia and the Middle East. The most common livestock transported are cattle and sheep, but goats, camels, buffalo, pigs and horses may also be transported alive. It is emphasized that multiple factors impacting on animal welfare are involved before, during and after the ship voyage; these include mustering, shearing (in the case of sheep), transport to feedlots and several changes of environment that can cause fear and anxiety. Information on the welfare of exported cattle and sheep on transport ships from Australia comes mainly from a survey of expert opinion completed in 2005. This found that the major stressors on ship were believed to be clinical diseases, especially inappetence and salmonellosis in the case of sheep, heat stress, high stocking density and high ammonia levels. The reported mortality rate is considerably greater for sheep than cattle, particularly due to failure to eat in the sheep, but has tended to decline for both species over the last five years. Other potential stressors, about which little is known, include noise, motion sickness, changes in lighting patterns and novel environments.

Variation in the milk production, activity rate and electrical impedance of cervical mucus over the oestrous period of dairy cows

Abstract In a series of four experiments, variation in activity levels, milk production and cervical mucus resistance (CMR) was recorded over the perioestrous period. Activity levels were increased on the day of oestrus in all cows by a mean factor of 2.3, which was inversely related to the non-oestrous activity level. An algorithm was developed for results obtained in Experiments 1 and 2 which detected all observed oestrous periods with no false positives. Milk yield was significantly reduced on the day of oestrus in two of the three experiments in which this was measured, and this was manifested as a reduction in milk yield at the first milking after the onset of oestrus followed by a smaller compensatory increase at the subsequent milking. These changes were not found in all cows and only proportionately 0.33 of cows could be detected in oestrus using milk yield changes. The reduction in milk yield at oestrus was associated with a reduction in milk fat content. Cervical mucus resistance reached a nadir on the day of oestrus, but the rate of change was not sufficiently high to allow good detection of oestrus.

A survey of aged horses in Queensland, Australia. Part 1: management and preventive health care

OBJECTIVE To describe management practices and routine preventive care of aged horses in Queensland, Australia, including effects of owner characteristics, affiliation to an equestrian group and retirement of the horse. METHODS Owners of horses were contacted via Equestrian Australia (EA) and asked to complete a questionnaire about their aged horses (e.g. age, breed, sex and colour); their use and management, including preventive health care; and use of equine healthcare providers. RESULTS Horses aged 15 years or greater represented one-third of the total horses owned in the population sample. The median age of the horses was 20.7 years (range 15-44 years). Basic husbandry and preventive health care varied depending on demographic region, age of the horse and its use. Affiliation with EA was associated with the breed and use of the horse, but not with management or preventive health care other than frequency of hoof care visits. Retired horses had reduced basic husbandry and preventive health care compared with non-retired horses. There was reduced preventive health care in rural compared with urban areas. The majority (61%) of horses in the current study had not been visited by a veterinarian in the previous 12 months. CONCLUSION Aged horses constitute a large subgroup of the Australian horse population. Although basic management is at a high level for most aged horses, it appears to be reduced following the horses retirement and in the more rural areas. There was limited veterinary involvement in preventive healthcare strategies for aged horses, especially in rural areas.

Perceptions of the importance of different welfare issues in livestock production.

The opinions of seven respondent groups about the relative importance of different practices pertaining to the welfare of Australian beef cattle, sheep and goats were surveyed. Respondent groups comprised farmers, livestock transportation representatives, veterinarians, meat processors, animal welfare advocates, animal welfare scientists and government officers. The survey consisted of a web-based adaptive conjoint analysis questionnaire, which was administered to a sample population that was selected randomly for large respondent groups and comprehensively for small groups. The hierarchy of opinion concerning the importance of the different beef cattle practices was: stockmanship > ground (road and rail) transport > spaying > food supply > dehorning > stunning > shelter > identification > pretransport food and water deprivation > castration > sea transport > mustering > confinement. For sheep/goat practices the hierarchy was: parasite control > mulesing > shelter > stockmanship > tail docking > ground transport > feeding > predation > stunning > castration > pretransport food and water deprivation > sea transport > mustering. The method of performing invasive procedures was perceived as less important than the provision of pain relief. Differences in opinion were evident between respondent groups, with animal welfare advocates tending to focus on painful procedures more than those with direct involvement in the industry.