The science and practice of poultry nutrition has changed greatly over the last hundred years, moving from a backyard enterprise to the modern computer-controlled production of whole diets formulated to specific nutrient compositions. This has become possible as a result of the identification of individual nutrients and their metabolic roles. Although the word 'protein' was first used in 1834, it was not until the 1950s that the avalanche of research on protein and amino acid requirements of poultry started. Energy content of feeds did not become a consideration until the 1940s when the concept of metabolisable energy was introduced. The term 'vitamin' was first proposed in 1912 to describe the essentiality of thiamine. The term was later extended to cover other essential compounds needed in small quantities. By the 1940s all the remaining 12 vitamins had been identified, and in the 1970s the importance of the vitamin D metabolites was discovered. The importance of calcium and phosphorus for both growing and laying birds was identified in the early stages of poultry keeping and requirements and dietary ratios were established. More recently, the introduction of feed phytase has allowed lowering of both phosphorus and calcium concentrations. Carbohydrase enzymes have also been development for addition to feeds. The importance of sodium, phosphorus and chloride in maintaining electrolyte balance was identified. Trace minerals were usually supplemented in diets as inorganic salts but organic chelates or proteinates have been found in recent years to be absorbed more efficiently. Antibiotics were widely used as growth promoters but their banning, especially in Europe, has led to the search for alternative additives with growth or health benefits. Poultry nutrition is now a scientifically mature subject but changes in industrial practice can be expected to continue, though probably at a slower pace than in recent years.

1. Chemical characterisation of an extract of Solanum glaucophyllum (SG) leaves affirmed the predominant presence of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) glycosides. The compound 1-(ß-D-glucopyranosyl)-1α,25-dihydroxycholecalciferol was isolated for the first time from a natural source. 2. Vitamin D activity of the extract was confirmed by the calcaemic properties shown in a quail eggshell bioassay. The results suggested a 1,25(OH)2D3 bioavailability of approximately 15%. 3. A broiler feeding experiment replicated in time was carried out with 6 treatments. A basic control diet containing 25 μg cholecalciferol/kg was supplemented with 2.5 and 5 μg free 1,25(OH)2D3/kg, with a product based on dried SG leaves (Panbonis) providing 10 μg of 1,25(OH)2D3-glycosides/kg, with two concentrations of an SG extract providing 8.8 and 37.8 μg of 1,25(OH)2D3-glycosides/kg. 4. Tibia breaking strength and stiffness were numerically greater in all treatment groups with free 1,25(OH)2D3 and with SG products compared to controls, though the overall treatment effects only had probabilities in the range of P = 0.07 to P = 0.1. Values for both characteristics increased progressively, with additions of synthetic 1,25(OH)2D3; values with the dried SG product were similar to those with 5 μg synthetic 1,25(OH)2D3/kg. 5. Plasma calcium was mildly elevated (P < 0.05) in treatment groups. The SG extract treatment containing 37.8 μg 1,25(OH)2D3/kg gave the highest plasma calcium concentration and lowest bodyweight, signs of marginal hypervitaminosis D. Plasma 1,25(OH)2D3 concentrations were in the normal range for all treatments. 6. Tibial dyschondroplasia occurred in only one replicate. The incidences were 31% in controls but considerably lower or zero with all other treatments. 7. Bioavailability of 1,25(OH)2D3 in the SG product seemed to be higher in broiler chickens than in Japanese quails. 8. It is concluded that the inclusion of the dried SG product as a source of vitamin D3 in broiler diets at a dietary concentration of 1 g/kg, providing 10 μg 1,25(OH)2D3/kg, is safe and efficacious.

1. Three experiments were carried out to determine the effects of feeding diets containing different concentrations of cholecalciferol, 1 alpha-hydroxycholecalciferol (1-HCC), 25-hydroxycholecalciferol (25-HCC), 1,25-dihydroxycholecalciferol (1,25-DHCC) and ascorbic acid on the incidences and severities of tibial dyschondroplasia (TD) at 3 weeks of age in male broiler chicks. 2. In experiment 1, replacing 75 mu g cholecalciferol/kg with the same weight of 25-HCC decreased significantly (P<0.01) the incidence of TD from 65 to 10%. 3. In experiment 2, the incidence of TD in the control group was lower, but feeding amounts of 25-HCC up to 250 mu g/kg had a linear effect on the incidence of TD that was significant at P=0.06. There was no effect or interactions with dietary addition of 250 mg ascorbic acid/kg. Dietary addition of 5 mu g 1-HCC/kg decreased TD incidence from 21 to 5%, though the effect was not significant (P>0.1). 4. TD incidence in experiment 3 was too low to determine an effect of 25-HCC or 1,25-DHCC on TD incidence, though in this, as in both other experiments, the severities of TD lesions were always lower with diets containing cholecalciferol metabolites. 5. Hypercalcaemia was not observed after feeding up to 250 mu g 25-HCC/kg in either experiments 2 or 3. 6. It is concluded that 25-HCC may be an effective practical means of improving broiler leg health by alleviating the incidence and severity of TD.

Bone breakages caused by osteoporosis in laying hens remain commonplace. Studies of this disease are complicated by the presence of medullary bone (MB), a bone type deposited during lay to provide calcium for eggshell formation. In vivo technologies such as Quantitative Computed Tomography (QCT), Dual energy X-ray Absorptiometry (DXA) and Quantitative Ultrasound (QS) could be used to assess laying hen bone but it may be difficult to separate MB and structural bone. In 12 end-of-lay hens, we measured structural (cortical) bone density (CBD) and medullary bone density (MBD) in 250micron x-ray slices prepared post-mortem on a diamond saw with a hydroxyapatite (HA) step-wedge as a reference standard. These measurements were made alongside bone breaking strength (BStr), whole bone radiographic density (RD) and histological measures of the volume fractions of bone types. Measurements of plasma total calcium (Ca) were also made. Results revealed significant correlations between tibia BStr and MB volume fraction (r =0.83, P =0.004), tibia BStr and whole tibia RD (r =0.81, P =0.006), tibia BStr and plasma Ca (r =-0.71, P =0.03), humerus BStr and whole humerus RD (r =0.91, P <0.001), MB volume fraction and whole tibia RD (r =0.79, P<0.01) and whole tibia and humerus RD values (r =0.69, P =0.04). Mean values for CBD and MBD densities (when expressed per unit total tissue) were significantly different (CBD = 1.09±0.01 mg HA/mm3 total tissue, MBD = 0.38±0.06 mg HA/mm3 total tissue, paired t-test, P <0.001). When corrections were made for volume fractions of bone types, MBD approached CBD levels in some hens (especially when volume fraction of MB exceeded 50%) but mean MBD remained significantly lower than CBD (CBD = 1.27±0.02 mg HA/mm3 bone, MBD = 1.12±0.07 mg HA/mm3 bone, paired t, P = 0.02). These results suggest that it should be possible to separate densities derived from in vivo measurements made in QCT slices into structural and MB contributions respectively. Difficulties may be encountered only when MB volume fractions are very large. However, the above correlations suggest that this may only increase overall bone strength in any case; as long as there is adequate MB surface area to allow mobilisation of calcium for eggshell formation, larger amounts of MB on endocortical surfaces may protect structural bone and may actually be beneficial for bone strength in ageing hens.

1. The effects upon bone quality of feeding limestone in flour or particulate form and housing type (cage or aviary) in lines of hens divergently selected for high (H) or low (L) bone strength over 7 generations were investigated.2. As in previous generations, highly significant phenotypic differences between lines were observed in all measured bone traits at peak egg production (25 weeks) and towards the end of production (56 weeks) in both cage and aviary systems.3. At 25 weeks there were no significant effects on bone variables of feeding particulate limestone although a significant reduction in osteoclast number was observed at this age. By 56 weeks osteoclast numbers were further reduced in hens fed particulate limestone and beneficial effects on some bone variables were observed in this treatment group.4. The genotypic and dietary improvements upon bone quality were independent and additive at both ages. There were very few interactive effects.5. Hens with the freedom to move in an aviary environment during the laying period had improved bone status compared to caged siblings. Environmental and genotypic effects were additive.6. There were no effects of line on egg production although H line hens had slightly higher egg production by 56 weeks. Egg numbers were unaffected by diet. Eggshell thickness and strength were unaffected by line but hens fed particulate limestone had thicker- and stronger-shelled eggs over the production period as a whole.7. We conclude that; (a) genetic selection is extremely effective in improving bone strength and resistance to osteoporosis; (b) allowing hens freedom to exercise can also improve bone strength but may increase the risk of keel damage if they do not have genetically-improved bone status; (c) feeding hens a particulate form of limestone from 15 weeks onwards can also increase bone strength and eggshell quality; (d) genetics, environment and nutrition all have independent and additive effects on bone status in laying hens but the relative effectiveness of these factors is genetics > environment > nutrition.

We have succeeded in purifying the 20S core proteasome particle from less than 1 g of skeletal muscle in a rapid process involving two chromatographic steps. The individual subunits were readily resolved by two-dimensional PAGE, and the identities of each of the 14 subunits were assigned by a combination of peptide mass fingerprinting and MS/MS/de novo sequencing. To assess the dynamics of proteasome biogenesis, chicks were fed a diet containing stable isotope-labeled valine, and the rate of incorporation of label into valine-containing peptides derived from each subunit was assessed by mass spectrometric analysis after two-dimensional separation. Peptides containing multiple valine residues from the 20S proteasome and other soluble muscle proteins were analyzed to yield the relative isotope abundance of the precursor pool, a piece of information that is essential for calculation of turnover parameters. The rates of synthesis of each subunit are rather similar, although there is evidence for high turnover subunits in both the alpha (nonproteolytic) and beta ( proteolytic) rings. The variability in synthesis rate for the different subunits is consistent with a model in which some subunits are produced in excess, whereas others may be the rate-limiting factor in the concentration of 20S subunits in the cell. The ability to measure turnover rates of proteins on a proteome-wide scale in protein assemblies and in a complex organism provides a new dimension to the understanding of the dynamic proteome.

The complete definition of changes in a proteome requires information about dynamics and specifically the rate at which the individual proteins are turned over intracellularly. Whilst this can be achieved in single-cell culture using stable isotope precursors, it is more challenging to develop methods for intact animals. In this study, we show how dietary administration of stable isotope-labelled amino acids can obtain information on the relative rates of synthesis and degradation of individual proteins in a proteome. The pattern of stable isotope-labelling in tryptic peptides can be deconstructed to yield a highly reliable measure of the isotope abundance of the precursor pool, a parameter that is often difficult to acquire. We demonstrate this approach using chickens fed a semisynthetic diet containing [2H8]valine at a calculated relative isotope abundance (RIA) of 0.5. When the labelling pattern of gel-resolved muscle proteins was analyzed, the intracellular precursor isotope abundance was 0.35, consistent with dilution of the amino acid precursor pool with unlabelled amino acids derived from degradation of pre-existing proteins. However, the RIA was stable over an extended labelling window, and permitted calculation of the rates of synthesis and degradation of individual proteins isolated by gel electrophoresis. For the first time, it is feasible to contemplate the analysis of turnover of individual proteins in intact animals.

1. As a baseline study of the nature and incidence of keel deformities in laying hens, keel condition was examined in three different strains of hen from a total of 4 different caged environments (two commercial farms and two experimental farms). Incidence of keel deformity on farms in end of lay hens ranged from 2.6 to 16.7%. Only 0.8% of younger 15-week-old pullets had deformed keels.2. Incidence of keel deformities was unchanged in 100 birds sampled from a free-range system compared to conventional caged siblings at the same farm.3. Keel condition was also examined in 5 selected generations of a study involving the use of a body-weight-restricted selection index for skeletal improvement. Divergent selection for skeletal characteristics decreased incidence of keel deformity and improved radiographic density (RD) in high bone index (BI) hens compared to low BI hens in all selected generations. Male high BI keels were also improved compared to low BI. Shear strength measured in normal keels in generation 6 (G6) of the genetic study was improved in high BI hens compared to low BI hens. For all hens in the genetic study, those with normal keels had stronger tibiotarsus and humerus breaking strengths than hens with deformed keels.4. Histopathology of keels representative of different deformities showed the presence of fracture callus material and new bone in all cases. This establishes that deformities are a result of trauma and are not developmental in origin.5. Ash contents of keels, tibiae and humeri showed no differences between hens with normal and deformed keels. There were no differences in indicators of collagen cross-linkage in other bones between hens with normal keels and those with deformed keels.6. It is concluded that lack of bone mass is the underlying cause of keel fracture and deformity in laying hens, rather than qualitative changes in bone, and that genetic selection can improve keel quality and prevent deformity.

"2004 SPRING MEETING OF THE WPSA UK BRANCH PAPERS." British Poultry Science, 45(sup1), pp. S27–S28

Osteoporosis is the major factor predisposing laying hens to the severe welfare problem of bone fractures. It arises from a generalized loss of structural bone throughout the skeleton that Starts when the hens begin to mature sexually and continues throughout the period of continuing egg production, resulting in progressively weaker bones and increasing fracture risk. When hens go out of lay, structural bone regeneration can recommence and the effects of osteoporosis can be reversed. The severity of osteoporosis is increased in hens kept in battery cages, when inactivity contributes to bone loss. The weakened bones in end-of-lay battery hens result in a high proportion of fractures, particularly in wing, keel and leg bones, occurring during depopulation.The origins of osteoporosis are mainly cellular, but nutrition has a role in helping to counter the condition, firstly by preventing deficiency, which can make the problem worse, and secondly, by promoting good nutrient supply. Provision of a particulate source of calcium is particularly helpful.Keeping birds in alternative husbandry systems that allow them more opportunity for exercise can markedly decrease the severity of osteoporosis. Bones will strengthen in response to the biochemical forces applied to them. However, hens can still experience high incidences of fractures that occur mainly during their lifetimes within the systems. Although their bones may be stronger, the hens have greater opportunities for more traumatic accidents that can still result in bone fractures. A particular problem of damage to keel bones is associated with misjudged landings on perches. Thus, replacing battery cages with furnished cages or more extensive systems such as aviaries does not necessarily improve the skeletal welfare of hens.Bone quality has been found to have a strong genetic component. A divergent selection programme based upon retrospective selection of progeny on the basis of postmortem maternal bone characteristics has resulted in the formation of two lines that show a twofold difference in bone strength after seven generations of selection. The greater bone strength has been shown to result in fewer fractures. The improvement in bone quality in the strong bone line is accounted for by more bone formation during rearing and much less structural bone resorption during the laying period. The latter effect may be related to better protection of structural bone surfaces by more medullary bone and lower osteoclast number resulting in less bone resorption. Egg production in the two lines is similar, though the strong bone line has slightly poorer eggshell quality. The birds have been selected in cages, but the same improvements in bone strength were seen when the lines were housed in an aviary. The development of more efficient in vivo methods for predicting bone quality, perhaps based on genetic markers, will allow selection for better bones to be applied in commercial breeding programmes. Application of this genetic approach should help to solve the problem of bone fractures in laying hens, in whatever husbandry system the birds are kept.

In young pullets, long bones elongate by endochondral growth. Growth plate chondrocytes proliferate, then hypertrophy, and are replaced by osteoblasts that form a network of trabecular bone. This bone is gradually resorbed by osteoclasts as the bone lengthens. Long bones widen, and flat bones are formed, by intramembranous ossification in which cortical bone formation by osteoblasts in the periosteal layer is accompanied by osteoclastic resorption at the inner endosteal surface. Growth of structural trabecular and cortical bone types continues up to the onset of sexual maturity in pullets. At this point, the large surge in estrogen changes the function of osteoblasts to forming medullary bone rather than structural bone. Medullary bone is a woven bone that acts as a labile source of calcium for eggshell formation. It lines structural bone and also occurs as spicules within the marrow cavity. It has little inherent strength but can contribute to fracture resistance. Osteoclasts resorb both medullary and structural bone so that during the period the hen remains in reproductive condition there is a progressive loss of structural bone throughout the skeleton, which is characteristic of osteoporosis. The increasing fragility of the bones makes them more susceptible to fractures. The dynamics of bone loss can be affected by a number of nutritional, environmental, and genetic factors. If the hen goes out of reproductive condition, estrogen levels fall, osteoblasts resume structural bone formation, and skeletal regeneration can take place.

1. Female chicks of a White Leghorn strain were fed three different diets from one day old: control, additional vitamin K3 (10 mg/kg), and a diet containing a combination of additional vitamin K3, sodium fluoride (10 mg/kg) and limestone in particulate rather than powdered form. At 16 weeks photoperiod was increased for half the birds from 8:16 L:D to 16:8 L:D immediately or by one hour per week to the same ultimate photoperiod for the other half. 2. Age at first egg was lower by 4.0 d for birds on the fast lighting regime but there were no overall effects of lighting on bone quality at either 25 or 70 weeks. 3. Additional vitamin K3 resulted in higher proximal tarsometatarsus cancellous bone volumes at 15 weeks and throughout the laying period compared with controls. Plasma osteocalcin concentrations were unaffected by vitamin K3 supplementation during growth. 4. The combination diet resulted in beneficial responses of 12 to 20% in most bone characteristics in hens at 70 weeks. The magnitude of these effects was similar to a previous study involving a particulate calcium source alone (Fleming et al., Poultry Science, 39: 434-440, 1998b). We conclude that the beneficial effects of the combined treatment over the lifetime of the hens were attributable mainly to the presence in the diet of a calcium source in particulate form.

This chapter examines the role of poultry breeding technology as it relates to the skeletal system. It discusses how selection, for increased productivity, has affected skeletal integrity and mineralization in layers. It also discusses how it affects bone, tendon and ligament growth, and strength and the development of musculoskeletal disease in meat-type poultry.

This paper provides a review of research on ascorbic acid as a nutrient in poultry published subsequent to a major review in this journal in 1986. Further experiments have confirmed the effects of a nutritional supply of AA in limiting the metabolic signs of stress and alleviation of the physiological consequences of stress is manifest in the performance, immunological competence and behaviour of birds. Birds under stress can recognise the stress-relieving properties of a diet containing AA and increase their intake of it, though they require a colour association to make the correct diet selection. Practical studies have generally confirmed the experimental findings, though the responses have been more variable, perhaps because of the greater difficulty in establishing the degree of stress experienced by birds under practical conditions. Optimum responses in growth, feed efficiency and/or liveability in broilers under heat stress seem to occur with supplements of about 250 mg AA/kg. Laying hens under stress, particularly climatic stress, have also shown responses to supplemental AA. This has resulted in improvements in liveability, food intake, egg production and egg quality with dietary AA concentrations in the range 250-400 mg/kg. AA can be beneficial in countering the adverse effects on shell quality of drinking water containing a high concentration of salts. The AA concentrations that have been found to be effective lie in the range 1-2 g AA/kg feed or /l drinking water, though it is possible that breed differences or additional stress factors might affect the response. Studies on the role of AA in the growth of poultry bone and connective tissues have suggested possible benefits of dietary supplementation in some stress or disease situations. AA has also been shown, to interact with a number of other vitamins and minerals.