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Biomedical subjects

R B Cumming

Publications and source records attributed to R B Cumming.

At least 19 recordsLinked to original sources
PubMed1986

Incidence of a heterosis effect in adrenal responsiveness to ACTH stimulation in the chicken.

No differences exist between basal plasma corticosterone concentrations of broilers ferals and first generation large crossbreds (White leghorn x New Hampshire). Crossbreds show near double adrenal responsiveness to synthetic ACTH administration, indicating a heterosis effect for this characteristic. Extraction of chicken plasma with 30% aqueous polyethylene glycol solution eliminates the need for tedious and expensive pre-assay purification of plasma.

Adrenal Glands↗
PubMed1985

Influence of food restriction during rearing on the body composition of layer-strain pullets and hens.

The influence of two methods of food restriction during rearing on the body and liver composition of layer-type birds was investigated during and after restriction. In each of two experiments groups of birds were reared on one of three treatments: ad libitum food intake (A), time-limited food restriction (TR) or proportional food restriction (PR). All birds were fed ad libitum during the laying phase. In experiment 1, six birds from each treatment were selected at random for estimation of body and liver composition and killed at 70, 101, 162, 218 and 337 d of age. In experiment 2 four birds were selected from each treatment at 280 and 467 d of age. Body composition was predicted in experiment 2 at various times such as sexual maturity, using equations based on deuterium oxide dilution techniques. Body composition changes caused by food restriction were related to the length of restriction. Towards its end the major changes were: decreased body fat, increased total body water and increased water content of the fat-free mass for TR and PR birds compared to A birds. Some changes were not due to a reduced liveweight. Food restriction during rearing did not change body composition permanently, although predicted body fat at sexual maturity (experiment 2) was lower and protein content higher for TR and PR than for A birds. There was no demonstrable relationship between the body fat content predicted at sexual maturity and subsequent rate of lay (experiment 2).

Aging↗
PubMed1984

Specific-locus mutation rates in the mouse following inhalation of ethylene oxide, and application of the results to estimation of human genetic risk.

Male (101 X C3H)F1 mice were exposed in an inhalation chamber to ethylene oxide (EtO) in air at a concentration of (generally) 255 ppm. After accumulating total exposures of 101 000 or 150 000 ppm.h in 16-23 weeks, the males were mated to T-stock females for a standard specific-locus mutation-rate study in which 71387 offspring were observed. The spermatogonial stem-cell mutation rate at each exposure level, as well as the combined result, does not differ significantly from the historical control frequency. At the lower and higher exposure levels, the results rule out (at the 5% significance level) an induced frequency that is, respectively, 0.97 and 6.33 times the spontaneous rate; the combined results rule out a multiple of 1.64. The relationship between mouse spermatogonial stem-cell mutation rates and EtO-induced testis ethylations was compared with the relationship between Drosophila post-stem-cell mutation rates and sperm ethylations (Lee, 1980). The comparison does not rule out equal mutability per ethylation; but it cannot prove parallelism. An assessment of the mouse-Drosophila relationship will require a more efficient alkylator than EtO and the use of comparable germ-cell stages. More meaningful conclusions may be drawn by utilizing the data for direct estimation of human risk by expressing the induced mutation frequency that is ruled out (at the 5% significance level) as a multiple of control rate and extrapolating to human exposure levels. The probable absence of major stem-cell killing (and thus, possibly, cell selection) by EtO indicates that such extrapolation probably does not produce an underestimate. For a human exposure concentration of 0.1 ppm on working days during the reproductive lifespan, the mouse experimental results rule out (at the 5% significance level) an induced spermatogonial stem-cell gene mutation rate greater than 8% of the spontaneous rate; for 1.0 ppm, they rule out an induced rate roughly equal to the spontaneous rate. The induced rate for any one poststem-cell stage would have to be about 3 orders of magnitude higher than that for stem cells to constitute an equivalent risk.

Animals↗
PubMed1984

Production responses of layer strain hens to food restriction during rearing.

Production responses of laying hens to food restriction during rearing were measured in two trials. Food was restricted by two methods: time restriction (TR, food continuously available for 24 to 30 h each 72 h) and proportion restriction (PR, daily allocations of about 60 to 70% of that consumed by ad libitum fed birds (F]. The rearing treatments were applied from 42 to 162 d and from 56 to 168 d of age in experiments 1 and 2 respectively. All birds were fed ad libitum in the laying period to 437 d and 476 d of age in experiments 1 and 2 respectively. Body weight was reduced significantly in both experiments by both methods of restriction, but more so by TR. Marked compensatory growth accompanied the high food intake following the end of food restriction. There was a significant increase in average egg weight concommitant with a change in the relationship between egg weight and age. Possibly this is due to an altered pattern of food intake at onset of lay.

Age Factors↗
PubMed1984

Studies on the incidence of Salmonella carriers in broiler flocks entering a poultry processing plant in Australia.

To evaluate the practical utility of competitive exclusion as an aid in controlling Salmonella, a survey was conducted in New South Wales, Australia to determine the incidence of Salmonella in 20 broiler flocks at time of slaughter during a 12-month period. The Salmonella incidence was determined by culturing the ceca of 50 randomly selected chickens per flock. The results demonstrated a high level of carriers (more than 30%) in 6 flocks, a moderate level of carriers (11 to 30%) in 4 flocks, a low level of carriers (1 to 10%) in 2 flocks, and 8 flocks from which no Salmonella were isolated. Five Salmonella serotypes, S. eimsbeutel , S. havana, S. luanshya , S. singapore, and S. typhimurium were isolated with S. typhimurium being the most common. Salmonellae were much less frequently isolated from flocks reared on old litter than on new litter.

Abattoirs↗
PubMed1983

Effects of vision-restricting "polypeepers" on the behaviour of laying hens during adaptation, feeding, on general activity, agonistic behaviour and pecking damage.

Vision-restricting "polypeepers" have been reported to result in higher egg production with improved food utilisation in hens. In the present experiments behavioural explanations of these effects were sought. For detailed observations 128 White Leghorn X Black Australorp hens were used and for pecking damage comparisons a further 192 hens. Half were fitted with polypeepers. Birds were studied in individual cages, three-bird cages or deep litter pens by direct observation and cine-camera. Adjustment problems in feeding, stereotypic head shaking and protracted displacement neck preening occurred initially after fitting of polypeepers. Disappearance of these phenomena after about one month, however, indicated adaptation. The initial reduction of egg production associated with polypeepers, observed by others, coincided with the period of adaptation. Polypeepers resulted in less activity; birds in multiple cages and litter pens resting more, while in single cages body movement was reduced. Polypeepers caused faster eating and less wastage of both pellets and mash. In general, agonistic acts were greatly reduced in multiple cages, resulting in reduced feeding competition. Polypeepers reduced significantly the incidence of feather pecking, resulting in considerably less feather loss after three months, and more so after 14 months in lay. Over the study as a whole the reductions in activity, food spillage, agonistic behaviour and feather damage probably contribute to the lower food consumption and improved laying efficiency previously reported.

Adaptation, Ocular↗
PubMed1983

The effect of route of infection and strain of virus on the pathology of Australian infectious bronchitis.

The pathogenesis of infectious bronchitis in 4-week-old chickens was studied following administration of Australian T strain of IBV by the aerosol, conjunctival, intranasal, in-contact and drinking water routes. Infected birds showed similar patterns of clinical signs, gross and histopathological lesions. While the birds infected by the aerosol route had earlier and slightly more severe respiratory tract disease it was concluded that the pathogenesis of infectious bronchitis virus nephritis was not significantly influenced by the route used to infect the birds. In a second experiment, pathological changes produced in chickens infected with Australian S, A, A3 and T strains of IBV were compared in 18-day-old chickens infected by the aerosol route and housed in cold and warm environments. All 4 strains produced respiratory reactions and kidney lesions, and these changes were more severe and of longer duration in both respiratory tract and kidneys in the birds housed in a cold environment than those receiving supplementary heat. The viruses differed in their virulence for the trachea and kidney and the effect of a virus on the respiratory trace was independent of the effect of that virus on the kidney.

Aerosols↗
PubMed1983

Immune response of chickens to various routes of administration of Australian infectious bronchitis vaccine.

Groups of 100 two-week-old cockerels were vaccinated with the A3 strain of IB vaccine by conjunctival, intranasal, in-contact, drinking water, or aerosol routes, or were left as unvaccinated controls. Three weeks after vaccination, each group of chickens was challenged with the Appin strain of IBV. Vaccination by the conjunctival, intranasal and in-contact routes induced a good resistance to challenge, concurring with an obvious stimulation of the Harderian gland, while the drinking water route led to a low resistance to challenge, with minor changes in the gland. The results of no immune response and no resistance to challenge in the birds vaccinated by aerosol route was due to unsuccessful vaccination in the group. Application of the vaccine by the conjunctival route would appear to be a most effective route for the application of Australian IB vaccines, while the in-contact method appears worthy of further study.

Animals↗
PubMed1982

Stress by immobilization, with food and water deprivation, causes changes in plasma concentration of triiodothyronine, thyroxine and corticosterone in poultry.

Measurements were sought for assessment of stress during investigations of welfare in intensively housed poultry. Immobilization was used as a stressor in experiments involving 64 cockerels of various ages. Two parameters were found to be related to acute stress: plasma triiodothyronine (T3) concentration, which fell markedly, and plasma corticosterone concentration, which rose considerably, in all birds during severe stress. Concurrently, plasma thyroxine (T4) concentration also fell in most, but not all, birds. Thyrotrophin releasing hormone (TRH) injected intravenously after immobilization caused increases in T3 and T4 levels, suggesting that the fall in T3 and T4 during acute stress was not caused by exhaustion of hormone production by the thyroid gland but rather by inhibition of release of TRH at the hypothalamic level.

Age Factors↗
PubMed1980

Aflatoxin contamination of Australian animal feeds and suspected cases of mycotoxicosis.

Aflatoxin B1 was detected in 23 of 55 Australian feedstuffs known to be either water damaged or visibly mouldy. The highest contamination was 0.7 mg/kg of feed and the mean concentration 0.14 mg/kg. Of 36 feedstuffs purchased from local manufacturers, only a peanut meal contained aflatoxin B1 (0.5 mg/kg). Eleven feedstuffs were associated with field outbreakds of animal disease and 7 of these contained aflatoxin. However, the level of aflatoxin contamination was insufficient to account for the described disease symptoms.

Aflatoxins↗