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    Age and cereal effects on the performance, gut parameters and nutrient utilisation in the newly hatched broiler chick : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science at Massey University
    (Massey University, 2007) Thomas, Donald V
    This study was intended to provide a platform for enhanced nutritional management of modern broilers through better understanding of changes in nutritional utilisation in the newly hatched chick. Differences in performance, nutrient utilisation and the development of the gastrointestinal tract in the young broiler chicken fed diets based on different cereals were examined. Diets based on wheat, sorghum and maize and formulated to contain iso-energy and iso-lysine levels were fed to broiler chicks between days 1 and 14 post hatch. Birds fed the maize based diet grew faster (P < 0.05) than those fed the sorghum based diet. Weight gains of birds fed the wheat based diet did not differ (P > 0.05) from those fed either maize or sorghum based diets. There were numerical differences in feed:gain with the sorghum based diet having the highest feed per gain, but the differences were not significant (P > 0.05). The relative weights of digestive organs and digestive tract showed no significant cereal treatment differences (P > 0.05). The treatments had no effect (P > 0.05) on the relative length of the digestive tract or gut histology measurements. The wheat based diet contained a commercial xylanase which may have ameliorated the digesta viscosity of this diet and reduced the NSP effect on gut structure and morphology. Furthermore, gut morphology samples showed a high degree of variation, suggesting that a large sample size would be necessary for significant differences to be determined. Two experiments were conducted to investigate cereal and age effects on nutrient utilisation in the young broiler chicken. Experiment 1 determined the nitrogen-corrected apparent metabolis able eneigy (AMEn) of diets based on wheat, sorghum and maize during 14 days post-hatch. Changes in the total tract digestibility of starch and fat were also measured. The second experiment was conducted to confirm the results of Experiment 1 using wheat and maize based diets and was of 21 days duration. In both experiments, changes to AMEn with age were similar for all diets, declining from day 3 to days 5-9 and increasing again. In experiment 1, cereal effects were significant (P < 0.05) with maize and sorghum based diets having higher AMEn values than the wheat based diet, In experiment 2, cereal effects were significant (P < 0.05) with the maize based diet having a higher AMEn than the wheat based diet. In experiment 1, total tract starch digestibility determined for days 5, 7 and 14 showed no cereal differences (P > 0.05). Age effects were significant (P < 0.05) with starch digestibility declining from day 5 to day 7, and then increasing again. Total tract fat digestibility on day 7 was significantly lower for the wheat and sorghum based diets than for the maize based diet, but no cereal differences (P > 0.05) were observed on days 5 or 14. Age effect was highly significant with fat digestibility declining from day 5 to day 7 and increasing again. These results showed that nutrient utilisation is compromised during the first week of life of the broiler chick. Samples of diets and excreta from Experiment 1 were analysed for minerals to determine changes in the apparent total tract mineral retention of the broiler chick during the first two weeks post-hatch. The diet and excreta samples were analysed for calcium, phosphorus, potassium, sodium, magnesium, iron, manganese, zinc and copper, and their retention was determined. The retention coefficients of individual minerals differed widely and the retentions of major minerals were much greater than those of minor minerals. The cereal effects were significant (P < 0.05) for several minerals, with a general tendency for the sorghum diet to have greater retention than maize or wheat diets. Age effects were significant (P < 0.05) for all minerals. In general mineral retention coefficients were higher at day 3, declined to day 7 and remained unchanged to day 14. Decline in mineral retention with age was similar in all three diets. The studies reported in this thesis investigated the performance and nutrient utilisation of broiler chicks fed diets based on wheat, sorghum or maize. A significant reduction in nutrient utilisation over the period 5-9 days of age was observed suggesting that nutrient digestion and absorption is compromised during the first week of life of the broiler chick. Further work is required to identify the specific causes of the decline in digestibility during the early stages of chick development.
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    The nutritional value of proteins with special reference to A) The availability of amino acids in meat meals to chicks, and B) The chemical changes with heat-damage of pure proteins : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biochemistry at Massey University
    (Massey University, 1974) Wilson, Margaret Nellie
    Meat meals are highly variable in protein quality and this may be due in part to heat-damage. This possibility was investigated by estimating the available lysine content of meat meals by chick growth assay. In addition, the combined urinary and faecal excretion of dietary amino acids by chicks, fed a meat meal as the sole source of protein, was determined, and by subtraction from the amount consumed, values for the apparent retention of dietary amino acids were obtained. In a second part of the study, the mechanism of heat-damage to pure proteins was investigated. Since cross-linkages may form during heat-damage of proteins, enzymatic digests were examined for the presence of peptides with enzyme-resistant linkages. Samples of unheated and heat-damaged haemoglobin or globin were digested with either trypsin, or exhaustively, using several proteolytic enzymes. Chick growth assay for lysine. A chick growth assay for lysine was developed using wheat gluten as the protein source in a semi-purified diet. The meat meals were added to the basal diet either at the expense of starch or by isonitrogenous substitution of wheat gluten. Estimated potencies based on weight gain varied with the method of meat meal addition to the basal diet. This variation was probably due to an effect on the appetite of the chicks as estimates based on food conversion efficiency did not differ significantly with the method of meat meal inclusion. The percentage of lysine biologically available in eight meat meals ranged from 61 to 105%, suggesting that some meals had been heat-damaged. Apparent retention of dietary amino acids. Estimates of the apparent retention of essential amino acids in six meat meals ranged from 79 to 100%. The apparent retention of lysine was generally much higher than the estimated potencies by chick growth assay. The difference in the two biological estimates indicated that other factors, apart from digestibility, and absorption and urinary excretion of peptides and amino acids, must be responsible for the reduced availability of lysine in heat-damaged proteins. Tryptic digests of unheated and heated haemoglobin and globin. Several large fragments were isolated from digests of heated globin which were not present in digests of unhealed globin. The fragments had more than one amino-terminal but individual peptides could not be separated. It was not possible to determine if cross-linkages were present. Exhaustive enzyme digests of unheated and heated globin. A peptide was isolated from digests of heated globin which was not present in unheated globin digests. Results obtained indicated that the peptide was a cyclic tetrapeptide composed of equal quantities of lysine and aspartic acid. It was suggested that the peptide was the result of cross-linkages formed during heat-damage of globin, between the β-carboxyl groups of aspartic acid and the E-amino groups of lysine. It is considered that the formation of covalent bonds with the E-amino groups would account for an appreciable proportion of the decreased availability of lysine in heat-damaged proteins.
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    Egg eviction imposes a recoverable cost of virulence in chicks of a brood parasite.
    (PloS, 2009-11-11) Anderson MG; Moskát C; Bán M; Grim T; Cassey P; Hauber ME
    BACKGROUND: Chicks of virulent brood parasitic birds eliminate their nestmates and avoid costly competition for foster parental care. Yet, efforts to evict nest contents by the blind and naked common cuckoo Cuculus canorus hatchling are counterintuitive as both adult parasites and large older cuckoo chicks appear to be better suited to tossing the eggs and young of the foster parents. METHODOLOGY/PRINCIPAL FINDINGS: Here we show experimentally that egg tossing imposed a recoverable growth cost of mass gain in common cuckoo chicks during the nestling period in nests of great reed warbler Acrocephalus arundinaceus hosts. Growth rates of skeletal traits and morphological variables involved in the solicitation of foster parental care remained similar between evictor and non-evictor chicks throughout development. We also detected no increase in predation rates for evicting nests, suggesting that egg tossing behavior by common cuckoo hatchlings does not increase the conspicuousness of nests. CONCLUSION: The temporary growth cost of egg eviction by common cuckoo hatchlings is the result of constraints imposed by rejecter host adults and competitive nestmates on the timing and mechanism of parasite virulence.