Biomedical subjects

P M Hocking

Publications and source records attributed to P M Hocking.

At least 73 records · Page 4Linked to original sources

PubMed1996

Comparative development of the antitrochanter in three strains of domestic fowl.

Lameness and musculoskeletal disease were more frequent in two strains of broilers (selected [S] and relaxed [R]) than in an unselected layer (J). Defective fibrocartilage accounted for 0.15 of the total area of antitrochanteric cartilage at 29 weeks of age in the S-strain birds. There was more retained hyaline cartilage in the R- and S-strain birds at 15 weeks, and at 22 and 29 weeks there was delayed ossification. Occluded blood vessels, death of chondrocytes and degenerate areas of fibrocartilage occurred only in the broiler strains; they were worse in the S-strain and degenerate fibrocartilage occurred more frequently and in larger amounts. The area, length and depth of cartilage were larger in the heavier strains but the differences were considerably smaller than the difference in their relative bodyweights. The degeneration of the antitrochanter appeared to be associated with a reduction in the blood supply to the underlying hyaline cartilage and with the death of chondrocytes and the degeneration of matrix within the fibrocartilage of the antirochanter.

Acetabulum↗

PubMed1996

Relationships between the degree of food restriction and welfare indices in broiler breeder females.

1. Broiler breeder females were fed ad libitum, or according to a commercial food restriction programme or to gain 0.85, 0.70, 0.55, 0.40 or 0.25 of the body weight of ad libitum-fed birds. Several indices of the welfare of the birds were assessed at 3-weekly intervals to 18 weeks of age and related to body weight by regression analysis. Results for 6, 12 and 18 weeks of age are presented in detail. 2. Water intake was consistently higher in the 0.25, 0.40 and commercial restriction treatments. 3. There was a negative curvilinear relationship at each age group between body weight and the heterophil-lymphocyte ratio and plasma corticosterone concentration. 4. There was a positive relationship between the plasma concentration of creatine kinase and body weight at 12 and 18 weeks of age. The relationships between body weight and the plasma activity of alkaline phosphatase and aspartate transaminase changed with the age and there were no differences between treatments for lactate dehydrogenase. 5. The time spent resting increased with body weight at each age. The relationship between time spent preening and body weight changed with age whereas that for oral activities was similar among restricted birds at 6, and among all treatments at 12 weeks of age. At 18 weeks there was an increase in oral activities with decreasing body weight. 6. Fearfulness was positively related to body weight. The response of the comb to phytohaemagglutinin injection was similar in all treatments and the antibody titre to injections of sheep red blood cells was curvilinear. 7. A principal components analysis of all measured traits at 6, 12 and 18 weeks of age was conducted. Most of the variables were redundant but at least one from each of the different classes of welfare indices was retained at 6 and 12 weeks of age. 8. It was concluded that a body weight during rearing in the range of 0.5 to 0.85 of ad libitum might provide for optimum welfare of broiler breeder females.

Alkaline Phosphatase↗

PubMed1996

Role of body weight and food intake after photostimulation on ovarian function at first egg in broiler breeder females.

1. The role of body weight during rearing and food allocation after photostimulation on ovarian function in broiler breeder females was examined in two experiments. In experiment 1 birds were fed ad libitum, or to grow to 0.7 or 0.4 of ad libitum-fed body weight at 20 weeks of age. After photostimulation at 16, 19 and 22 weeks respectively they were fed ad libitum, 145 g/d or 115 g/d in a factorial design. The ovary of each bird was examined after it had laid an egg. In experiment 2, restricted birds (0.4 of ad libitum-fed body weight) were fed 125 g/d after laying an egg or ad libitum and a third group were given 125 g/d for 3 to 4 weeks and then fed ad libitum. The ovaries of these birds were examined 6 to 7 weeks after their first egg. 2. Food restriction after photostimulation had little effect on ovarian function in birds fed ad libitum during rearing. These birds had 2 to 3 hierarchies of yellow follicles of similar size. Restricted birds fed ad libitum after photostimulation had a large increase in the numbers of yellow follicles (1.7 to 2.0 hierarchies) compared with birds fed 145 g/d or 115 g/d which had 1.2 to 1.6 hierarchies of yellow follicles. 3. Age at first egg was largely a function of rearing treatment but feeding 115 g/d to the 0.4 treatment birds delayed the onset of lay compared with the other treatments. 4. Ad libitum feeding in restricted birds after the onset of lay resulted in a similar increase in the number of yellow follicles as the response to ad libitum feeding after photostimulation. 5. The prevalence of birds with atretic follicles was relatively high in birds fed ad libitum during rearing and in restricted birds fed ad libitum after photostimulation. 6. Yolk weight increased with age at photostimulation and food restriction decreased yolk weight by about 1 g compared with ad libitum feeding after photostimulation.

Animals↗

PubMed1995

Differential sensitivity of ovarian follicles to gonadotrophin stimulation in broiler and layer lines of domestic fowl.

Differences in the reproductive potential of female broiler parent and layer fowl are related to differences in the recruitment of follicles to the preovulatory hierarchy. Broiler and laying hens were fed ad libitum or a restricted diet during rearing and ad libitum after sexual maturity. The sensitivity of thecal tissue, from ovarian follicles of different sizes, from layer and broiler fowl to stimulation by pregnant mares' serum gonadotrophin (PMSG) was determined to test the hypothesis that differences in egg production are associated with changes in the sensitivity of ovarian follicles to stimulation by gonadotrophin. The activity of ornithine decarboxylase 0.5-4 h after injection of 200 iu PMSG kg-1 body mass was assessed in thecal tissue from small white follicles 2-3 and 5-6 mm in diameter and in the smallest preovulatory yellow follicle. Basal activity was similar in layers and broiler breeders. PMSG-stimulated ornithine decarboxylase activity in follicles of 5-6 mm diameter was greater in broiler breeders than in layers. There was no difference between the lines in PMSG-stimulated ornithine decarboxylase activity in follicles of 2-3 mm diameter or in small yellow follicles. It was concluded that the low egg production and high prevalence of eggs with defective shells in broiler parents compared with layers may be related to the increased sensitivity of follicles to endogenous gonadotrophins at the critical stage of recruitment to the preovulatory hierarchy.

Animal Nutritional Physiological Phenomena↗

PubMed1994

Assessment of the welfare of food restricted male broiler breeder poultry with musculoskeletal disease.

The general and sexual activity of food restricted male broiler breeder poultry was assessed for evidence of behavioural changes associated with musculoskeletal lesions. The activity and fertility of male birds given betamethasone (an anti-inflammatory steroid) or saline were compared in a two-period crossover experiment. Behavioural changes occurred and the birds' mating activity and fertility were decreased when they were given the steroid, but these effects were not associated with the presence of lesions. In a second experiment, there were no differences in sexual motivation between birds either with or without leg disorders. The birds were trained to walk down an alley for their food and the speed of walking was compared in a two-period crossover experiment. Betamethasone decreased their walking speed in period one and the carryover effect was significant in period two. Naloxone decreased the walking speed of birds with lesions more than of those without lesions. This effect was taken as evidence for analgesia by endogenous opioids and may help to explain the lack of response of the birds to the analgesic agent. The evidence that these food restricted male broiler breeder birds experienced pain was equivocal.

Animals↗

PubMed1994

Plasma growth hormone and insulin-like growth factor-I (IGF-I) concentrations at the onset of lay in ad libitum and restricted broiler breeder fowl.

1. Plasma concentrations of growth hormone (GH) and insulin-like growth factor I(IGF-I) were determined in individually caged broiler breeder females from 17 to 30 weeks of age. The birds were fed ad libitum or restricted during rearing in a randomised block design. Restricted birds were fed ad libitum after laying an egg and egg production was recorded to 54 weeks. 2. GH concentrations were higher in restricted compared with ad libitum-fed birds at 17 to 21 weeks of age and were similar thereafter. Plasma IGF-I concentrations were higher in restricted compared with ad libitum-fed birds throughout the sampling period of the experiment. 3. The age at first egg was delayed by about two weeks in restricted birds. At 54 weeks of age they had laid 114 compared with 67 eggs in birds fed ad libitum throughout and had produced less than half the number of eggs with defective shells. 4. It was suggested that differences in egg production between ad libitum and restricted broiler breeder females could be related to changes in the pattern of GH and/or IGF-I secretion.

Aging↗

PubMed1994

Haematology and blood composition at two ambient temperatures in genetically fat and lean adult broiler breeder females fed ad libitum or restricted throughout life.

1. Genetically fat and lean adult broiler breeder females were fed ad libitum or restricted throughout life. At one year of age, comparisons of blood viscosity and haematology and changes in blood chemistry after exposure to thermal stress were conducted. 2. Whole blood viscosity was more than twice as high, and plasma triglyceride and haemoglobin concentrations were over 30% higher in fat line than in lean line females fed ad libitum or in restricted birds of both genotypes. 3. Mean cell haemoglobin concentration was higher and mean cell volume lower in fat compared with lean line females. 4. Food restriction was associated with lower plasma triglyceride concentrations, lower numbers of heterophils and monocytes and a lower heterophil-lymphocyte ratio. 5. Fat line birds had a higher blood pCO2 and lower pH than lean line birds. 6. Thermal stress was associated in ad libitum-fed birds with a rise in blood pH and a decrease in pCO2, and in restricted birds with a decline in blood pH and an increase in pCO2. 7. Blood creatine kinase activity increased in all groups under thermal stress.

Animals↗

PubMed1993

Defective Down syndrome in chicks is not caused by riboflavin deficiency in breeders.

1. Riboflavin-deficient practical and semi-purified diets were fed to broiler breeder hens. 2. Yolk and albumen riboflavin concentrations were depressed by the deficient diets and cases of curled toes were seen in the chicks. 3. The few instances of defective down did not resemble cases seen in field outbreaks of a condition involving depressed hatchability and a defective down syndrome. 4. It is concluded from observations in this experiment and in the field outbreaks that there is a condition in breeding chickens causing depressed hatchability and defective down that is not attributable to riboflavin deficiency.

Animals↗

PubMed1993

Modification of intra-ovarian follicular distributions in broiler breeder hens by ad libitum or restricted feeding.

1. Ovarian follicles in broiler hens from 3 lines fed ad libitum or food restricted were examined at point of lay and from 2 of these lines at 47 weeks of age. The lines were Ross 1 birds and birds selected to be lean or fat on the basis of their plasma very low density lipoprotein concentrations at 7 weeks of age. 2. Follicles of diameter greater than 1.4 mm were classified into size groups, and the numbers in these groups in the anterior and posterior halves of the ovary were compared for the effects of line and feeding régimen. 3. There were more yellow follicles (> 8 mm diameter) in the anterior half of the ovary, and this difference was greater for ad libitum birds. Ad libitum feeding did not influence the number of yellow follicles in the posterior segment of the ovary. 4. The increase in numbers of yellow follicles in the anterior segment of the ovary differed according to line at point of lay, but not at 47 weeks of age. 5. Birds of 47 weeks of age showed higher numbers of follicles 1.4-6 mm in diameter in the posterior segment of the ovary, and smaller numbers of follicles 6-8 mm in diameter. Thus, although large numbers of white follicles were in the earlier stages of growth, there were fewer ovulable yellow follicles because of higher levels of atresia.

Animals↗

PubMed1993

Effects of body weight at sexual maturity and the degree and age of restriction during rearing on the ovarian follicular hierarchy of broiler breeder females.

1. Groups of 18 birds were reared to 10 different body weight targets in a randomised block experiment to assess the effect of body weight and the degree and age of restriction on ovarian function at first egg. 2. There was no effect of age at restriction (15 to 18 compared with 19 to 22 weeks) on the number of yellow follicles. 3. The treatment with the larger body weight of two groups given the same degree of restriction (maintenance) had more follicles than the treatment which had a smaller body weight. 4. There was a positive linear relationship between the number of yellow follicles and body weight and food intake. Addition of the weight of fat or age at first egg to the model increased the residual mean squares. 5. The proportion of atresia among yellow follicles and the incidence of internal ovulation increased with body weight at first egg. 6. It was concluded that the physiological processes occurring during rearing which underlie ovarian function are reflected solely in the body weight and food intake of broiler breeders at first egg.

Aging↗

PubMed1993

Optimum size of feeder grids in relation to the welfare of broiler breeder females fed on a separate sex basis.

1. The rate of eating food was studied in two experiments to assess the relationship between head width and size of feeder grids in broiler breeder females. 2. The optimum grid size for food intake was 4 mm wider than head width. 3. Physical injury should be avoided if the grid aperture is 2 mm wider than the maximum head width in the flock measured at the posterior edge of the mandibles. 4. The rate of eating was decreased in all grid sizes examined compared to feeders without grids but the importance of this observation for the welfare of broiler breeders is not clear.

Animal Welfare↗

PubMed1992

Muscle protein degradation assessed by Nt-methylhistidine excretion in mature White Leghorn, dwarf broiler and normal broiler males maintained on either low- or high-protein diets.

Protein degradation rates were assessed by the excretion of Nt-methylhistidine (NtMH) in four strains of mature chickens, two White Leghorns and two broilers (dwarf and normal), fed on diets containing two levels of dietary protein. Over 0.9 of labelled NtMH was recovered within 7 d of injection from three White Leghorn, three dwarf and three normal broiler males. Protein degradation, measured by NtMH output, was related to adult body-weight by the power 0.71 and strain intercepts were significantly different. Strain differences disappeared when the rate of output of NtMH per unit lean was evaluated. The rate of output of NtMH per unit muscle was higher in birds fed on a low-protein diet of 100 g crude protein (nitrogen x 6.25; CP)/kg compared with males fed on 150 g CP/kg. It was concluded that the lower rate of protein degradation in broiler compared with layer strains at young ages is related to increased adult body-weight in agreement with well-established biological principles.

Animals↗

PubMed1992

Differential leucocyte responses to various degrees of food restriction in broilers, turkeys and ducks.

1. White blood cell responses of broilers, turkeys and ducks were examined at regular intervals after being subjected to various degrees of food restriction. 2. Restricted-fed broilers showed increases in heterophil and basophil numbers, together with a corresponding decrease in lymphocytes. The heterophil/lymphocyte ratio was raised. There were no differences between broiler strains. 3. After only one week of feeding restricted diets, heterophils were significantly raised in selected and unselected 2-week-old ducks. At 21 weeks of age, those ducks receiving 50% of food required to achieve their ad libitum-fed body weight had raised heterophils. 4. Ducks receiving food to achieve 25% of ad libitum-fed birds produced a marked basophilia, but no heterophilia. 5. After two weeks of food restriction, turkeys responded with significant heterophil/lymphocyte ratios following two degrees of restricted feeding. 6. It was concluded that in some poultry, a heterophilia may be the response to mild to moderate stress but a basophilia may result after severely stressing birds.

Animals↗

PubMed1992

Effects of photostimulation at 18, 24 and 30 weeks of age on the productivity of female turkeys fed ad libitum or restricted until point of lay.

1. Turkey females were fed ad libitum or restricted from 6 weeks of age to achieve mean body weights of 0.6 of ad libitum fed birds on photostimulation at 18, 24 or 30 weeks of age. Body weight, food intake, egg production and hatchability were recorded to 54 weeks of age. 2. Restricted turkeys were fed ad libitum after first egg or 36 weeks of age. Food intake after 30 weeks of age averaged 170 g/bird/d and was similar for all treatments. At 54 weeks of age, restricted turkeys photostimulated at 24 and 30 weeks were not as heavy as turkeys photostimulated at 18 weeks and ad libitum fed turkeys. 3. A large proportion of restricted turkeys photostimulated at 18 weeks of age did not commence lay until 30 to 40 weeks and a significant number of restricted birds photostimulated at 24 weeks had short laying cycles. Restricted birds photostimulated at 30 weeks came into lay and showed similar persistency of lay to ad libitum fed turkeys. 4. Ad libitum fed turkeys laid 115.0, 122.0 and 101.0 and restricted turkeys 92.4, 99.5 and 103.4 eggs when photostimulated at 18, 24 and 30 weeks, respectively. The number of non-settable eggs was lower in restricted compared with ad libitum fed turkeys and declined with age at photostimulation. 5. Egg size at the end of the experiment was similar for ad libitum fed turkeys and restricted birds photostimulated at 18 weeks but was 2.3 g lower for restricted birds photostimulated at 24 and 30 weeks of age. 6. Hatchability was higher, and the proportion of second quality poults was lower with eggs from restricted turkeys. The mean numbers of poults hatched were 59.9, 75.1 and 66.0 for ad libitum fed and 71.7, 65.7 and 79.4 for restricted turkeys photostimulated at 18, 24 and 30 weeks of age.

Age Factors↗

PubMed1992

Genetic and environmental control of ovarian function in turkeys at sexual maturity.

1. The relationships between the numbers of ovarian yellow follicles and body weight was investigated in four strains of turkeys photostimulated at 24 or 30 weeks of age. The birds were fed ad libitum or control fed to reach 0.8 or 0.6 of the body weight of ad libitum-fed birds at 24 weeks of age. 2. There were more yellow follicles at 24 compared with 30 weeks of age. 3. The number of yellow follicles was higher in bigger strains. 4. Body weight control reduced the number and the proportion of similar sized yellow follicles. The effect decreased with increasing strain body weight. 5. There was a linear relationship of 0.633 between log yellow follicle number and log body weight. The intercept was higher in turkeys photostimulated at 24 compared with 30 weeks of age.

Adipose Tissue↗

PubMed1992

Bilateral testicular asymmetry and supernumerary testes in the domestic fowl (Gallus domesticus).

1. The left and right testis weights from 378 males in 7 experiments were recorded. 2. The relationship between the right and left testis weights was similar in males of different ages, strains and body weights. 3. The left as a proportion of total testes weight was approximately normally distributed about a mean of 0.515. 4. The left testis was greater than the right testis weight in 0.67 of males. 5. The linear regression of the natural logarithm of the right on that of the left testis weights was -0.04 + 0.99X (r2 = 0.98) and it was concluded that, in general, the left and right testes were of similar weight. 6. Three cases of triorchidism (two left testes) occurred, suggesting that this may not be a rare condition in the domestic fowl.

Animals↗

PubMed1992

Changes in ovarian function of female turkeys photostimulated at 18, 24 or 30 weeks of age and fed ad libitum or restricted until point of lay.

1. Females from a medium body weight strain of turkeys were fed ad libitum or restricted to 0.6 of ad libitum-fed body weight at sexual maturity and were photostimulated at 18, 24 or 30 weeks of age. Ovarian follicular structure was assessed in 8 birds from both rearing treatments at photostimulation, after photostimulation for 6 or 12 weeks and at 55 weeks of age. 2. The patterns of small white follicles and of larger yellow follicles were similar in restricted and in ad libitum-fed turkeys for birds in lay at the same age, regardless of the time elapsed since photostimulation. 3. Among birds in lay the number of normal yellow follicles and the proportion of multiple yellow follicles declined with age. A relatively low proportion of restricted birds photostimulated at 18 and 24 weeks were in lay after 12 weeks of photostimulation. 4. For birds in lay the number of white follicles 1.4 to less than 1.8 mm in diameter increased and the number greater than 1.8 mm declined with age. There was a corresponding increase in the rates of atresia in follicles 1.8 to less than 5.0 mm in diameter.

Age Factors↗

PubMed1992

Plasma oestrogen and triglyceride concentrations and reproductive characteristics of broiler chickens after ten generations of selection at seven weeks of age for high or low plasma very low density lipoprotein concentration.

1. Day old female chicks from two lines of broilers, selected for high or low plasma concentrations of very low density lipoproteins, were fed ad libitum or restricted until point of lay. All birds were fed ad libitum after laying an egg, and aspects of growth and reproduction were measured to 40 weeks of age. 2. Compared with lean line birds the growth rate of fat line females fed ad libitum declined from 16 weeks of age. 3. Mortality from apparently stress-related causes in ad libitum fed fat line females increased from 16 weeks of age and was 71% overall, compared with 26% in ad libitum fed lean line females. Mortality in the corresponding restricted birds was 20% and 7%, respectively. 4. Few fat line females fed ad libitum commenced lay and those which were restricted during rearing stopped laying after the initiation of ad libitum feeding. Egg productions in lean line birds fed ad libitum or restricted were similar. 5. Fat line females fed ad libitum had few yellow follicles and a high rate of atresia at first egg and between 37 and 39 weeks, as did restricted fat line birds between 37 and 39 weeks of age after being fed ad libitum. 6. Plasma concentrations of oestradiol-17 beta were 5-fold higher in fat compared with lean line females at 35 weeks of age. There was a similar large difference in concentrations of plasma triglyceride which reached 59 mg/ml in fat line females fed ad libitum.

Age Factors↗