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Biomedical subjects

P M Hocking

Publications and source records attributed to P M Hocking.

At least 19 recordsLinked to original sources
PubMed2006

High-fibre pelleted rations decrease water intake but do not improve physiological indexes of welfare in food-restricted female broiler breeders.

1. A 3x2 factorial experiment was conducted with three diets and two lines of broiler breeder females to evaluate the contribution of low-energy rations for improving the welfare of feed-restricted birds during rearing. Experimental diets were fed from 6 to 16 weeks of age and were created by diluting a conventional grower (Control) ration containing 11.0 MJ ME/kg with 200 (8.8 MJ ME/kg) or 400 (6.6 MJ ME/kg) g oat hulls/kg using Optimoist to facilitate the pelleting process. Welfare was assessed by changes in behaviour and physiological variables at 8, 12 and 16 weeks of age. Birds were fed restricted quantities of feed to meet recommended body weight targets. 2. There was a decrease in the proportion of observations of drinking and an increase of preening in birds fed on the two experimental diets compared with the control. There was a linear decrease in litter moisture and the number of litter changes with increasing diet dilution, and water intake at 12 weeks was higher in the control than in the two experimental diets. There were no changes in physiological indexes of welfare (heterophil-lymphocyte ratio, plasma corticosterone and antibody responses) associated with the dietary treatments. 3. There were no important differences in the growth, behaviour or physiological responses to dietary treatment between the two lines of broiler breeders. Changes with age were similar to those reported in other experiments. 4. It was concluded that low-energy pelleted diets would improve litter conditions but not improve indexes of welfare in feed-restricted broiler breeders.

Animal Feed↗
PubMed2006

Foot pad dermatitis develops at an early age in commercial turkeys.

1. A field experiment was conducted to identify the macroscopic and histological changes associated with the development of foot pad dermatitis (FPD) in growing turkeys. Two affected and two unaffected turkeys were sampled weekly from 1 to 8 and at 10 and 21 weeks of age. 2. At one week old, birds with external signs of FPD (surface skin discolouration) showed abnormal cellular changes of the foot pad integument. As the flock aged the reactions intensified, with one sample exhibiting a fully developed macroscopic lesion at 3 weeks. 3. Major pathological changes had occurred by 6 weeks and all turkeys with external signs of lesions had fully developed microscopic inflammatory cellular lesions. From 6 weeks of age onwards lesions were increasingly numerous and became more overtly necrotic. 4. Externally normal foot pads showed microscopic evidence of lesions after the turkeys reached 4 weeks. 5. We conclude that FPD lesions become severe over a short period of time and at a very early age.

Aging↗
PubMed2006

Thermoregulatory capacity and muscle membrane integrity are compromised in broilers compared with layers at the same age or body weight.

1. The effects of acute heat stress (2 h at 32 degrees C and 75% RH) on body temperature and indices of respiratory thermoregulation and skeletal muscle function were examined in two divergently selected male grandparent lines of broiler and layer-type chickens at two ages (35 and 63 d), or at a similar body weight (approximately 2.2 kg). 2. The two chicken lines exhibited markedly different baseline blood acid-base and skeletal muscle characteristics. At the same age or live weight, birds from the broiler line had significantly higher venous blood carbon dioxide tensions associated with lower blood pH. Plasma creatine kinase (CK) activities reflecting muscle membrane damage were also greatly elevated in the broiler line. 3. Exposure to acute heat stress caused an increase in deep body temperature, panting-induced acid-base disturbances and elevated plasma CK activity in both lines of chicken, an effect that increased with age. The extent of disturbances in acid-base regulation and heat-stress-induced myopathy were more pronounced in the broiler than the layer line at the same age or similar live weights. 4. It is suggested that genetic selection for high muscle growth in broiler lines has compromised their capacity to respond to an acute thermal challenge, leading to detrimental consequences for muscle function. This reduction in heat tolerance may have important implications for bird welfare and subsequent meat quality.

Aging↗
PubMed2006

On-farm assessment of environmental enrichment for broiler breeders.

1. A field experiment was conducted with commercial broiler breeder females to assess the hypothesis that the provision of bunches of string and bales of wood shavings would provide attractive environmental enrichment and improve welfare by decreasing aggression and feather damage. 2. The experiment was a randomised block factorial design conducted in a commercial flock of 21,600 female broiler breeders in 12 pens of 1800 chicks. Treatments were environmental enrichment (4 plastic coated bales of wood shavings and 50 bunches of string) from hatch (EE1) or 8 weeks of age (EE2) and a control treatment with no environmental enrichment. There were 4 replicates (rooms). 3. Bird activity was videotaped at 5, 10 and 16 weeks of age and subsequently scored for the number of birds using the perch or pecking at a bale, drinker, litter and section of the wall at 10-min intervals for 4 h throughout the photoperiod (24 times/d). Aggression was assessed by determining the number of aggressive acts in 2-min intervals during 8 periods of the day. The skin and feather condition of 25 birds in each pen were scored at 6, 12 and 18 weeks and the condition of the string bunches was scored at the end of the experiment. 4. The proportion of birds pecking the bales, wall and litter declined and the proportion pecking at the drinker and using the perch increased with age. The number of birds pecking at the bale was similar in EE1 and EE2 at 10 and 16 weeks of age. 5. The string bunches were not extensively used. The condition of the bunches of string in EE2 was worse than in EE1 at the end of the experiment. 6. The number of aggressive acts increased with age and there was no consistent difference between treatments. 7. There was an increase with age in the damage score for feathers over the back and wings and around the tail and vent but no differences between treatments.8. Provision of litter in the form of unopened bales of wood shavings was a commercially acceptable form of environmental enrichment, but there was no evidence that behavioural changes associated with feed restriction, including the prevalence of aggression, were improved.

Aging↗
PubMed2006

Genetic parameters for a heavy female turkey line: impact of simultaneous selection for body weight and total egg number.

1. The objective of this study was to investigate the strength of the genetic association between growth and reproduction traits in turkeys selected for body weight, conformation and egg production. 2. Two distinct populations but derived from the same heavy turkey female line and situated in different locations (UK and USA), were used to estimate genetic parameters using multivariate REML for the following traits: body weight at 14 (BW14), 19 (BW19) and 24 (BW24) weeks of age and total egg number (EGG). 3. A Box-Cox transformation was applied to egg production data to reduce the impact of non-normality. 4. The heritability estimates for each trait for the UK and USA populations, respectively, were: BW14 0.37 and 0.48; BW19 0.34 and 0.43; BW24 0.28 and 0.43; EGG 0.22 and 0.34. 5. The genetic correlation between the body weight at all ages and the total egg production was strongly negative, reaching a value of -0.75 for the UK and -0.55 for the USA population. 6. The comparison of our results with published estimates in turkeys suggests that the genetic correlation may get stronger in magnitude following selection for increased body weight. 7. This could arise from fixation during selection of genes favouring larger weights but with minimal effect on egg production, leaving the segregating genetic variation dominated by pleiotropic loci with antagonistic effects on the traits. 8. Thus, in order to avoid continued selection for body weight reducing egg production to a point where natural selection offsets selection gains, alternative selection strategies should be considered.

Animals↗
PubMed2006

QTL analysis of body weight and conformation score in commercial broiler chickens using variance component and half-sib analyses.

The aim of the study was to investigate quantitative trait loci (QTL) in previously identified regions of chicken chromosomes 1, 4 and 5 relating to 40-day body weights and conformation scores. Half-sib (HS) and variance component analyses were implemented and compared using QTL Express software. Data were from a two-generation design and consisted of 100 dam families nested in 46 sire families with trait values for 2,708 offspring. Chicken chromosome 4 showed nominal significance for QTL affecting body weight and conformation, and linkage was confirmed for both traits on chromosome 5. Results varied according to method of analysis and with common parent in the HS method.

Animals↗
PubMed2005

Effects of non-steroidal anti-inflammatory drugs on pain-related behaviour in a model of articular pain in the domestic fowl.

The optimum doses of carprofen, flunixin, ketoprofen and sodium salicylate for the treatment of inflammatory pain were determined in domestic fowl using the microcrystalline sodium urate model of articular pain. The response criteria were the changes in pain-related behaviour over 60 min commencing 1 h after an intra-articular injection of sodium urate and an intramuscular injection of a range of doses of each of the drugs. The minimum effective doses for carprofen, flunixin and ketoprofen, respectively, were 30, 3 and 12 mg kg(-1). The minimum dose for sodium salicylate ranged from 100 to 200 mg kg(-1) and did not fully restore normal behaviour.

Animals↗
PubMed2005

Limited effect of intense genetic selection for broiler traits on ovarian function and follicular sensitivity in broiler breeders at the onset of lay.

Female chicks from 6 pure lines of broiler breeders were obtained from international broiler breeder companies. The lines were from three female and two male lines and a relaxed selection line derived from one of the male lines (M2) and maintained without selection for 25 years (generations). Replicate groups from each line were reared in floor pens and fed ad libitum. An additional group of the M2 male line was feed restricted and housed in similar pens. Twenty birds from each group were photostimulated after housing them in individual cages at 14 weeks of age. Ovarian follicular dynamics and follicular sensitivity were determined after the onset of lay. Female lines had a greater proportion of atretic follicles and more groups of multiple follicles than male lines. Body weights, fatness and age at puberty were similar in male and female lines. The relaxed selection line had more abdominal fat than any of the selected lines and the ovary contained a similar number of normal yellow follicles as the selected male line. Feed restriction decreased body weight, the numbers of yellow follicles, multiple yellow follicles and the proportion of atretic yellow follicles, and increased the age at onset of lay. The response of ovarian follicles of three different sizes to exogenous gonadotrophin stimulation with PMSG was similar in small yellow follicles, 5 to 6 and 2 to 3 mm white follicles in a female line, a male line and its relaxed line fed ad libitum. The results suggest that the original lines from which modern male-line broiler stocks are derived had a relatively large number of yellow follicles and a high propensity for multiple ovulation at the onset of lay. Separate selection for different traits in male and female lines has not had a dramatic effect on ovarian function or sensitivity to gonadotrophin stimulation.

Aging↗
PubMed2005

Mapping of quantitative trait loci affecting organ weights and blood variables in a broiler layer cross.

1. A genome scan was performed to locate genomic regions associated with traits that are known to vary in birds (most commonly broilers) suffering from heart, lung or muscular dysfunction and for weight of the dressed carcass and some internal organs. 2. The F2 population studied was derived from a cross between a broiler and a layer line and consisted of over 460 birds that were genotyped for 101 markers. 3. There was strong support for segregation of quantitative trait loci (QTL) for carcass and organ weights and blood variables. We identified 11 genome-wide significant QTL (most of them for dressed carcass weight) and several genome-wide suggestive QTL. 4. The results point to some genome regions that may be associated with health-related traits and merit further study, with the final aim of identifying linked genetic markers that could be used in commercial breeding programmes to decrease the incidence of muscular and metabolic disorders in broiler populations.

Animals↗
PubMed2005

Assessing the welfare consequences of providing litter for feed-restricted broiler breeders.

1. Broiler breeder females were fed restricted allocations of a standard wheat-soy ration to meet target body weights. They were housed on raised plastic slotted floors (S) or wood shavings litter (L) from hatch to 8 weeks when each pen of 12 birds was transferred to another pen in the same block in a 2 x 2 factorial experiment (LL, LS, SL and SS). Measures of bird welfare were taken at 4 weeks of age, and at 9 and 10 weeks following transfer to the new pens. 2. At 4 weeks of age, birds reared on S spent more time standing, pecking the feeder, the wall and other birds and less time pecking the floor compared with those on L. Gentle feather pecks, strong feather pecks and strong feather pulls were more common in S than L. 3. Mean body weight was higher and coefficient of variation lower in birds on L than S at the end of the experiment. Feather loss and damage scores at 10 weeks were higher for birds reared from hatch to 8 weeks on S. 4. Birds that were reared on S continued to peck more at the pen walls after transfer to new pens but there was no other carry-over effect on behaviour. Birds on S at 9 and 10 weeks pecked more at the walls and less often at the floor, and rested less often. There was more feather pecking on S than on L in the second week post transfer. 5. Tonic immobility was greater and plasma corticosterone concentrations were lower at the end of the experiment in birds on L than S at 9 and 10 weeks of age. The heterophil-lymphocyte ratio was similar between treatments at 4 weeks and after the birds were moved to a new pen. 6. The results are consistent with the view that litter and wall pecking has de-arousing properties and that this activity is re-directed foraging that diminishes the stress of feed restriction.

Animal Welfare↗
PubMed2004

Segregation of QTL for production traits in commercial meat-type chickens.

This study investigated whether quantitative trait loci (QTL) identified in experimental crosses of chickens provide a short cut to the identification of QTL in commercial populations. A commercial population of broilers was targeted for chromosomal regions in which QTL for traits associated with meat production have previously been detected in extreme crosses. A three-generation design, consisting of 15 grandsires, 608 half-sib hens and over 15 000 third-generation offspring, was implemented within the existing breeding scheme of a broiler breeding company. The first two generations were typed for 52 microsatellite markers spanning regions of nine chicken chromosomes and covering a total of 730 cM, approximately one-fifth of the chicken genome. Using half-sib analyses with a multiple QTL model, linkage was studied between these regions and 17 growth and carcass traits. Out of 153 trait x region comparisons, 53 QTL exceeded the threshold for genome-wide significance while an additional 23 QTL were significant at the nominal 1% level. Many of the QTL affect the carcass proportions and feed intake, for which there are few published studies. Given intensive selection for efficient growth in broilers for more than 50 generations it is surprising that many QTL affecting these traits are still segregating. Future fine-mapping efforts could elucidate whether ancestral mutations are still segregating as a result of pleiotropic effects on fitness traits or whether this variation is due to new mutations.

Analysis of Variance↗
PubMed2004

Genotype, dietary manipulation and food allocation affect indices of welfare in broiler breeders.

1. An experiment was performed to compare the welfare of three broiler breeder genotypes (Label Rouge (LA), experimental dwarf (ER) and standard (SR)) fed on a Control or high Fibre diet. The LA birds were fed ad libitum and the other groups were reared to their recommended body weight targets. A group of standard broiler breeders was also fed a restricted amount of food, but to a lesser degree than SR, to achieve the same proportion of body weight (SE) as ER relative to ad libitum-fed dwarfs based on previous research. LA, ER, SR and SE are referred to as 'groups' in the text. 2. Welfare was assessed by comparing time budgets and heterophil-lymphocyte ratios (HL ratios) at 5, 10 and 15 weeks and immune responses at 15 weeks of age. In addition the weight and water content of the gastrointestinal tract at 4-h intervals at the end of the experiment were studied in LA and SR fed on both diets. 3. Body weights of LA, ER and SR fed on the Fibre diets were depressed and LA ate less of the Fibre than the Control diet. The coefficient of variation of body weight at 15 weeks was 7.9% in LA and similar (10.8 to 11.6%) in the other groups. 4. Drinking, litter-directed behaviour, resting and standing were affected by a group x age interaction with restricted birds showing increased drinking over time and less time spent resting compared to LA. The behaviour of ER birds was similar to SE. 5. HL ratios were within the normal biological range although all restricted-fed birds had an elevated HL ratio at 10 weeks of age relative to week 5 whereas LA birds had a reduced HL ratio at 15 weeks relative to 5 and 10 weeks of age. Immune responses were lower in ER and SE and the highest response was in SR. 6. No effects of diet were identified on behaviour, white blood cell counts or HL ratio. 7. With the exception of the crop, the dry weights of digesta in each section of the gut were similar in LA and SR birds. The results suggest that drinker-directed activity might be a substitute for foraging rather than an attempt to increase gut fill. 8. It is concluded that the replacement of standard with dwarf broiler breeders may improve the welfare of commercial flocks of broiler breeders by decreasing the degree of food restriction resulting in favourable changes in behaviour, for example, reduced 'drinker-directed' behaviour.

Aging↗
PubMed2004

Different concentrations and sources of dietary fibre may improve the welfare of female broiler breeders.

1. Broiler breeder females were fed restricted allocations of food to meet target body weights. They were fed on a standard wheat-soy ration or on one of three series of rations containing 50, 100 or 200 g/kg of ground oat hulls, ground unmolassed sugar beet pulp or sunflower meal. Changes in behaviour and heterophil-lymphocyte ratio (HLR) were measured at 5, 10 and 15 weeks of age. 2. Body weight at 15 weeks of age decreased in a linear manner with increasing concentrations of the experimental ingredients. 3. Decreased spot pecking was observed in birds fed on the rations containing 50 g/kg of sugar beet pulp and 200 g/kg of oat hulls. 4. The HLR was higher in birds fed on the control diet and diets containing 50 g/kg of the high fibre ingredients. 5. Rations containing sugar beet pulp were associated with higher water contents in the gastrointestinal tract and it is proposed that this improved satiety and welfare.

Animal Feed↗
PubMed2004

Roles of body weight and feed intake in ovarian follicular dynamics in broiler breeders at the onset of lay and after a forced molt.

Three experiments were conducted to define the relationships between BW and feed intake in broiler breeder female chickens at the onset of lay and after a forced molt. In experiment 1A the number of normal yellow follicles at the onset of lay and abdominal fatness were linearly related to BW, whereas age at first egg decreased with increasing BW in a curvilinear manner. Dietary energy was shown to be the limiting factor determining the onset of lay in severely feed restricted broiler breeders in experiment 1B. The source of energy (fat or carbohydrate) did not affect the onset of lay or ovarian function. In experiment 2 birds were feed restricted or fed ad libitum to 60 wk of age and force molted. Eight weeks after the initiation of molting, restricted birds were fed to 3 or 4 kg, and the birds fed ad libitum were fed to 4 or 5 kg of BW. After photostimulation the birds were fed ad libitum or 115 g/d. Taken together, the results of these analyses suggest that rearing treatment did not affect ovarian function, postmolt. Postmolt feed restriction was associated with lower follicle numbers compared with the groups fed ad libitum and was significantly lower in the lighter (3 kg) restricted birds compared with the other groups. Follicle numbers were lower after molting than at the onset of lay, and the effects of feed restriction were commensurately smaller.

Animal Feed↗
PubMed2003

Preliminary linkage map of the turkey (Meleagris gallopavo) based on microsatellite markers.

The turkey is an agriculturally important species for which, until now, there is no published genetic linkage map based on microsatellite markers--still the markers most used in the chicken and other farm animals. In order to increase the number of markers on a turkey genetic linkage map we decided to map new microsatellite sequences obtained from a GT-enriched turkey genomic library. In different chicken populations more than 35-55% of microsatellites are polymorphic. In the turkey populations tested here, 43% of all turkey primers tested were found to be polymorphic, in both commercial and wild type turkeys. Twenty linkage groups (including the Z chromosome) containing 74 markers have been established, along with 37 other unassigned markers. This map will lay the foundations for further genetic mapping and the identification of genes and quantitative trait loci in this economically important species. Genome comparisons, based on genetic maps, with related species such as the chicken would then also be possible. All primer information, polymerase chain reaction (PCR) conditions, allele sizes and genetic linkage maps can be viewed at http://roslin.thearkdb.org/. The DNA is also available on request through the Roslin Institute.

Animals↗
PubMed2003

Effects of dietary protein concentration and specific amino acids on body weight, body composition and feather growth in young turkeys.

1. Two randomised block factorial experiments were conducted to investigate the relationships between the effects of dietary crude protein and specific amino acid concentrations on the relative growth of the body and feathers of young turkeys. 2. Decreasing dietary crude protein concentration from 300 to 180 g/kg in experiment 1 reduced the body and breast muscle weights of a large male line of turkeys proportionally by 0.44 and 0.52 compared with 0.19 and 0.24 in a small traditional line. 3. Decreasing dietary crude protein concentration was associated with a maximum reduction in feather weight of 0.18 and 0.24 respectively in male line and traditional turkeys. The length of the feathers in the cranial region of the breast decreased from 26 to 19mm in the traditional line compared with an increase from 14 to 25 mm in male line turkeys. 4. Decreasing dietary crude protein concentration was associated with an increase in the fat content of the feather-free carcase. Male line turkeys had a higher carcase fat and lower feather dry matter content than the traditional turkeys. 5. It was concluded that dietary crude protein was preferentially partitioned to feather rather than muscle growth in the male line in contrast to a traditional line of turkeys in which the growth of feathers and muscle were affected equally. 6. In experiment 2, the amino acids arginine, valine, methionine and tyrosine were added separately to a common basal ration (180g CP/kg) to raise their concentration to that of the control ration (260 g CP/kg). Each ration was fed ad libitum to male line turkeys from 2 to 6 weeks of age. 7. Amino acid supplementation increased body and breast muscle weights. 8. Compared with the basal ration, tyrosine was associated with a reduction in feather weight whereas valine had no effect. Supplementation with arginine and methionine resulted in increased feather weights that were similar to that of the controls. 9. It was concluded that arginine and methionine were used preferentially and are essential for feather growth. Excess amino acids that are not required for feather growth such as tyrosine and valine were used for increased body growth and resulted in relatively poor feather cover. 10. The results suggest that feather growth was maintained as much as possible at the expense of body growth when the amino acid concentration of the ration was less than that required to maximise body and muscle weight gain in large male line turkeys.

Amino Acids↗
PubMed2003

Genetic variation for egg production, egg quality and bone strength in selected and traditional breeds of laying fowl.

1. A multi-breed experiment was conducted with 25 commercial and traditional lines of laying fowl to determine the extent of between-breed genetic variation for adult body weight, sexual maturity, rate of lay, egg weight and egg composition to 55 weeks of age. The genetic variability for bone strength and eggshell strength was determined at 55 weeks of age and a comparison of commercially selected and traditional breeds was performed. 2. The proportion of the total variation that was associated with breed or line of origin was high (> 0.8) for body weight, sexual maturity and shell colour; moderately high (0.4 to 0.7) for rate of lay, early and late egg weight, weights of egg yolk, albumen and shell at 55 weeks; and low (< 0.4) for egg weight at 42 to 45 weeks, albumen quality and the number of egg inclusions. 3. There were no detectable differences between breed within category (traditional and commercial lines) for rate of lay, and estimates of breed variation for egg weight and egg components were substantially decreased within category compared with the overall analysis. 4. Commercial lines displayed earlier sexual maturity, greater rates and persistency of lay, and higher egg weights at earlier (32 to 35 weeks) and later (52 to 55 weeks) ages. At 55 weeks, the larger eggs from commercial birds contained more albumen of higher quality and paler yolks of similar weight to those from traditional breeds. The relative weight of the eggshell was similar in both categories. 5. There was considerable genetic variation between commercial lines for bone density and a moderate proportion of genetic variability for bone strength. Commercial lines had very weak bones compared with traditional lines but there was relatively little genetic variation for eggshell strength. The results suggest that eggshell quality is maintained in genetically selected lines at the expense of bone strength and bone radiographic density.

Animals↗