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    Investigations into the impact of feed form and age on the standardised ileal amino acid digestibility of feed ingredients for broiler chickens : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science (Poultry Nutrition) at Massey University, Palmerston North, Manawatu, New Zealand
    (Massey University, 2022) Barua, Mukti
    The importance of measurement of standardised ileal digestibility coefficients (SIDC) of amino acids (AA) in feed ingredients and their value in improving inter alia the precision of broiler feed formulations needs no elaboration. Databases on the SIDC AA of ingredients are accumulating during the past decade and various factors that influence the digestibility have been identified. Two aspects that remain unexplored hitherto in detail are the effects of feed form (FF) and broiler age. Previous AA digestibility assays were accomplished using mash diets because of the simplicity and the fact that research facilities often do not have access to pelleting equipment. As commercial broilers are fed pelleted diets, the data derived from mash diet may not be directly applicable. Another limitation is that, despite the potential age effects on AA digestibility, no study to date has investigated the influence of age on the SIDC AA in ingredients for the whole growth period of broilers. Lack of age-appropriate basal endogenous AA (EAA) flow data for the correction of apparent ileal digestibility coefficients (AIDC) is another constraint. Most of the existing EAA flow data were generated using older birds (21 to 42 d of age). The focus of this thesis research was to address these critical aspects. The first two experimental studies in Chapters 3 and 4 were conducted to determine the effect of FF (mash vs. pellet) on the SIDC AA in four grains (maize, wheat, sorghum and barley) and three protein sources (PS; soybean meal; SBM, meat and bone meal; MBM, and CM; canola meal) in broilers, respectively. Regardless of the grain type, FF had no significant (P > 0.05) influence on the SIDC of any AA, except for Cys and Pro, which were higher (P < 0.05) in mash diets. The effect of FF was more pronounced in the SIDC AA of PS. No influence of FF (P > 0.05) was observed for the SIDC of individual indispensable AA (IAA), except for His, the digestibility of which was lower (P < 0.05) in the pelleted diets. The SIDC of all individual dispensable AA (DAA), average digestibility of DAA and total AA (TAA) were reduced (P < 0.05) by pelleting. Cysteine was the most affected DAA, with a 15.4% reduction in SIDC in pelleted diets in comparison with mash. These results showed that the use of SIDC AA data generated from feeding mash diets may overestimate the AA digestibility in feed ingredients and affect the precision of broiler feed formulations. For this reason, pelleted assay diets were used in succeeding trials. The third study, reported in Chapter 5, was carried out to investigate basal EAA flow at different ages (7, 14, 21, 28, 35 and 42 d post-hatch) of broilers, following feeding of a nitrogen-free diet (NFD). The basal EAA flow of all individual and total AA were reduced quadratically (P < 0.05 to 0.001) as the birds grew older. The EAA flows were higher on d 7, then declined on d 14 and plateaued until d 35. A further decrease in the EAA flow was observed on d 42. These age-specific values were used in the correction of AIDC to SIDC in all ensuing thesis studies. The study presented in Chapter 6 was conducted to determine the influence of age on the SIDC AA in two grain sources (wheat and sorghum) in broilers. Six broiler ages (d 7, 14, 21, 28, 35, and 42 post-hatch) were investigated. Two assay diets were formulated to contain 938 g/kg of each grain as the only source of AA. Each assay diet, in pelleted form, was offered to birds for 4 d during the six periods namely d 3-7, 10-14, 17-21, 24-28, 31-35 and 38-42 prior to ileal digesta collection. In the case of wheat, no age influence (P > 0.05) was observed on the SIDC of average of IAA and DAA, though the average of TAA tended (linear, P = 0.09) to increase with advancing broiler age. In sorghum, the average SIDC of IAA, DAA and TAA were higher (linear or quadratic; P < 0.05 to 0.01) at d 7, declined at d 14 and then evened out. Among the IAA, the SIDC of Arg, His, Ile, Leu, Lys, Thr, Val, and the SIDC of all individual DAA (with the exception of Cys) reduced with advancing age (linear or quadratic, P < 0.05 to 0.001). The study reported in Chapter 7 was conducted to measure the SIDC of AA in maize and barley at six ages (d 7, 14, 21, 28, 35, and 42 post-hatch). Two assay diets were formulated to contain 938 g/kg of either maize or barley as the sole source of dietary AA. In maize, the average SIDC of IAA and TAA was affected in a quadratic manner (P < 0.05) with the values being higher at d 7 that dropped at d 14, increased and evened out between d 21 and 35, and decreased again at d 42. A linear influence (P < 0.05) was observed in the average SIDC of DAA. The SIDC of average IAA, DAA and TAA in barley was influenced (quadratic; P < 0.001) by age. The digestibility values increased from d 7 to 21 and then plateaued until d 42. The SIDC of all AA in barley increased (quadratic; P < 0.05 to 0.001) as the birds grew older. The final study, presented in Chapter 8, was conducted to determine the influence of broiler age on the SIDC AA in two PS (SBM and CM). Six age groups (d 7, 14, 21, 28, 35, and 42) were utilised. Two assay diets were formulated to contain either SBM (413 g/kg) or CM (553 g/kg) as the only source of dietary AA. In SBM, the average SIDC of IAA and TAA were not affected (linear or quadratic; P > 0.05) by age. The average SIDC of DAA in SBM was affected in a quadratic manner (P < 0.05) and the highest value was observed at d 7, that followed by a decline from d 14 to 28, and increased beyond d 35. The average SIDC of DAA and TAA in CM were higher (quadratic; P < 0.05 to 0.001) from d 7 to 14, reduced at d 21 and then increased beyond d 28. The average SIDC of IAA dropped between d 7 and 28, and followed by an increase thereafter. The novelties of this thesis research are that (i) no previous study has investigated the SIDC AA of feed ingredients from hatch to the end of broiler growth cycle, (ii) this is the first study reporting age-appropriate basal EAA flows and (iii) the use of pelleted assay diets that resembled the FF commonly used in the broiler industry. There were several original findings in this thesis. First, pelleting had substantial impact on the SIDC AA of feed ingredients and FF influence was more evident in case of ingredients with higher protein contents. Second, the EAA flow was higher in younger birds and reduced with advancing broiler age. Third, the age effect on the SIDC AA was variable depending on the ingredient and specific AA, and that the age effect on AA digestibility need to be considered in ingredient matrices for precise feed formulation.  
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    Influence of dietary fat inclusion on the ileal digestibility of amino acids in broilers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatu, New Zealand
    (Massey University, 2018) Whitehouse, Thomas Harrison
    The main focus of the present study was to examine nitrogen, dry matter and specific amino acid digestibility, particularly in the jejunum and ileum. Due to the fact that the gizzard and duodenum are primarily sites of digestion, and not absorption and due to limitations of the titanium oxide marker method, results from these segments are less applicable to the overall results. The general trend indicates that the presence of tallow in the diet increases digestibility significantly compared to diets without additional fat. The soybean oil diets generally had intermediary digestibility between the tallow and no-fat diets. Previous studies with similar fat sources indicated the opposite would be true. Differing digestibility of the different fat sources could likely be governing this effect. Future studies could involve birds of differing ages, as well as a more diverse set of fat sources to better determine which factors are affecting these digestibility rates. The speculated mechanism of action for this increased digestibility is an increase in digesta transit time caused by the increased fat content. Future studies could confirm this by using a marker technique to trace the rate of passage in the digestive tract between the different diets. Differences and digestibility between maize and wheat diets were expected, but it was unknown if there would be any major interactions between grain type and fat source in the diet in nitrogen and dry matter digestibility. The present study found no interaction. The decreases in digestibility seen by high NSP ingredients like wheat is likely related to the creation of insoluble gels in the gut. Thus, while fat and these gels may both increase the viscosity of gut contents, the composition of the viscous contents differ substantially, with the fat having less of an inhibitory effect on amino acid digestibility. The present study found no substantial interaction effects in the lower digestive segments between the grain effects (caused by NSP content) and fat effects. This indicates that, while the addition of both can alter digestive viscosity, there is no inhibitory effect exerted by either on the other. No significant effect of fat source was found on amino acid digestibility. This may be due to the fact that these samples were taken from the lower ileum, and the majority of amino acid absorption may have taken place in more proximal segments.
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    A comparison of the nutritive value of normal and opaque-2 maize for growing pigs in diets containing meat and bone meal with and without amino acid supplementation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University
    (Massey University, 1974) Stables, Nigel Harry John
    Pig meat production in New Zealand has traditionally been associated with the dairy industry, relying upon dairy by-products (principally skim-milk and whey) as major sources of protein and energy for pig feed. However, export market prospects for milk protein led to the diversification of dairy factory products, such as the ultra-filtration of whey protein and lactose extraction of whey. The prevailing economic climate also encouraged dairy farmers to change to whole milk ,anker collection and large numbers of the supplementary pig enterprises were closed down. Despite fluctuations, market prices generally showed an increase and many farmers began investigating alternative food supplies in order to take advantage of these higher prices. Garbage and other edible waste provided only limited scope for expansion, and the main alternative appeared to be the use of cereal grains. The New Zealand pig industry, in the last 5-10 years, has therefore begun to move towards a specialised form of production based upon the use of diets containing a predominance of cereals, similar to what has prevailed in many overseas countries for a longer period. The local report of Kingma and Ryan (1971) illustrates the need for efficiency in the high cost system of production based upon meal feeding. Where skimmilk is the principal ingredient in the ration, the supply of dietary protein is generally adequate due to the high nutritive value of the protein in this feedstuff. However, when the major source of nutrients comes from cereal grains, although these provide a concentrated source of energy, the poor balance of amino acids becomes limiting to the utilization of such rations. In New Zealand there is a restricted range of feeds high in protein and suitable for incorporation into pig rations. They include skimmilk powder, buttermilk powder, meat meal, meat and bone meal, liver meal and fish meal. Alternative sources of protein in soybeans, lupins, field beans and lucerne are being investigated.
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    Aspects of dietary protein quality for the growing pig : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1984) Moughan, Paul James
    A study of several aspects of dietary protein quality for the growing pig is described. The study was conducted in three parts. Reservations regarding the interpretation of three recent empirical estimates of the ideal amino acid balance for the growing pig prompted the first part of the study. A diet (basal diet) was formulated in which enzymatically hydrolysed casein supplemented with synthetic amino acids formed the sole protein source. The balance of essential amino acids in the diet approximated the mean of the three published estimates. Eight entire male pigs (boars) of 28 Kg initial liveweight, confined in metabolism crates, were fed the basal diet for 20 days and thereafter a protein-free diet for a further eight days. Mean daily excretion of urinary urea nitrogen over six-day collection periods was 93 mg/Kg0.75 for pigs fed the basal diet and the corresponding value for the protein-free diet was 19 mg/Kg0.75. Assuming that the difference between these values was attributable to deamination of amino acids from the basal diet, this corresponds to an efficiency of utilisation of dietary protein of 0.940. It was concluded that the amino acid pattern of the basal diet approximated an ideal balance. Part two of the study entailed the determination and evaluation of estimates of the apparent ileal digestibility of crude protein and amino acids for the growing pig and included a comparison of protein digestibility in the rat and pig. Samples of ileal digesta were collected from boars prepared with T-piece cannulae in the terminal ileum. Values for the digestibility of crude protein and amino acids in barley-meal, pea-meal, meat-and-bone-meal, fish-meal and a mixture of enzymatically hydrolysed casein and synthetic amino acids are cited. In an evaluation of the determined digestibility values ten boars received a barley-, pea-, meat-and-bone-, fish-meal diet and ten a control diet containing enzymatically hydrolysed casein and synthetic amino acids as its sole protein source. The gross amino acid composition of the latter diet equalled the determined apparent ileal digestible amino acid composition of the barley-based diet. Accepting that the control protein source was completely digestible and that the two feeding regimes were iso-caloric, the similar growth characteristics of pigs on the two diets suggested that apparent ileal amino acid digestibility coefficients are accurate measures of the degree of amino acid digestion and absorption in the growing pig. Preliminary results showed close agreement between the rat and pig for the apparent ileal digestibility of crude protein in barley-, meat-and-bone- and fish-meal. In the third part of the study a deterministic computer model which simulates the digestion and metabolism of dietary nitrogen in the growing pig was constructed. The model was based on the concept of a partitioning of daily dietary nitrogen intake in pig growth. Initial validation exercises demonstrated that results obtained from simulation were in close agreement with observations from experimentation with the live animal.
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    Amino acid digestibility in meat and bone meal for the growing pig : the development of a digestibility assay based on the laboratory rat : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 1993) Donkoh, Armstrong
    The study involved developing and applying a routine ileal amino acid digestibility assay, based on the sampling of digesta from the euthanased laboratory rat, with specific application to the digestion of meat and bone meal (MBM) protein by the growing pig. The work was conducted in six separate experiments. 1. The first experiment aimed to evaluate the slaughter method as a technique for sampling ileal digesta in the pig under defined sampling conditions. In a preliminary investigation, the influence of time after feeding (3, 4, 5, 7, 9 and 11 hours) on the amount of digesta obtained from the terminal 20 cm of ileum and apparent ileal nitrogen (N) digestibility was determined. Thirty-six 30 kg liveweight entire male pigs were given a semi-synthetic diet containing meat and bone meal (MBM) as the sole protein source and chromic oxide as an indigestible marker. The animals were given the MBM diet for 14 days and were killed by intracardial injection of a barbiturate on the 14th day. Digesta were flushed from the terminal ileum using deionised water. Secondly, the effect of site in the ileum for sampling digesta at 9 hours post-feeding was determined using 12 entire male pigs. The animals were equally and randomly allocated to two sampling sites (the terminal 0-20 cm or 0-40 cm of ileum). Further samples of ileal digesta were taken at regular 20 cm intervals up the final 140 cm of ileum of each pig. Sampling at 9 hours after the start of feeding resulted in the greatest and least variable sample size as well as the highest N digestibility. Sampling site within the terminal ileum had no significant (P > 0.05) influence on the apparent digestibility of nitrogen. In the same study, comparison of apparent ileal amino acid digestibility in MBM, under the defined sampling conditions, was made between 8 pigs whose digesta were sampled from the terminal 20 cm of ileum at death 9 hours after the commencement of feeding, and 8 pigs with simple T-cannulas and with hourly collection of digesta over 10 hours on the final 2 days of the 14-day study. The simple T-cannulated animals were accepted as the control. There was no significant (P > 0.05) effect of digesta collection procedure on the apparent ileal N and amino acid digestibility coefficients. Faecal N and amino acid digestibility coefficients in intact pigs were identical to those in pigs fitted with a simple T-piece cannula in the distal ileum. Faecal digestibility values in both intact and cannulated pigs were, however, considerably (P < 0.05) higher than the corresponding ileal values. It was concluded that the slaughter technique is a viable alternative to simple T-cannulation for the determination of N and amino acid digestibility in the pig given a semi-synthetic MBM diet. 2. The second experiment determined the optimal digesta sampling conditions with the slaughter method applied to the laboratory rat. The effect of time after feeding (1, 2, 3, 4, 5 and 6 hours) on the amount of digesta obtained from the terminal 20 cm of ileum and apparent ileal N digestibility was investigated. Thirty-six 190 g male rats received a semi-synthetic diet whose sole protein source was meat and bone meal. Chromic oxide was added to the diet an indigestible marker. The animals were given the MBM diet for 14 days and were killed by CO2 asphyxiation on the 14th day. Digesta were sampled from the terminal ileum. Furthermore, the effect of site within the terminal ileum (0-5, 0-10, 0-15 and 0-20 cm) for sampling digesta 4 hours post-feeding was determined with 72 male rats. The optimal time for sampling digesta was 4 hours after the start of feeding, while 20 cm of ileum was the maximum length of ileum sampled without affecting apparent N digestibility. Significantly (P < 0.05) higher quantities of digesta were collected from the terminal 20 cm of ileum compared to the shorter ileum lengths. 3. In experiment three, the use of the rat as a model animal for allowing the determination of apparent ileal amino acid digestibility in the growing pig, using the slaughter method was evaluated. Sixteen male rats and 16 male pigs were fed diets containing chromic oxide and as the sole protein source, meat and bone meals which were expected to differ in their quality. Ileal contents from the terminal 20 cm of ileum were collected after slaughter of the rats and pigs, 4 and 9 hours after the start of feeding, respectively. Inter-species comparison made under the defined conditions, indicated close agreement between the rat and pig for the ileal digestibility of N and most of the amino acids in each of the two different meat and bone meals evaluated. It was concluded that the growing rat is a satisfactory model for the growing pig. for determining ileal amino acid digestibility in meat and bone meal. The measurement of digestibility at the terminal ileum indicated differences in amino acid digestibility between two meat and bone meals, however, the faecal approach which generated significantly higher digestibility coefficients than the ileal digestibility method, did not allow the differences in amino acid digestibility to be detected. 4. Experiment four was undertaken to compare a recently-developed peptide alimentation method and the protein-free and regression methods for determining endogenous ileal N and amino acid excretion in the rat, and was aimed at the development of a true ileal digestibility assay with application to meat and bone meal. Preliminary investigations determined the effect of the time of sampling of digesta from rats given a protein-free (PF) or an enzymically hydrolysed casein (EHC) based diet, on ileal digesta and endogenous N excretion. There was a significant (P < 0.05) effect of the time of sampling on the amount of digesta collected and the endogenous N excretion for both the EHC- and PF-fed rats. The amount of digesta collected from the terminal 20 cm of ileum and the endogenous N excretion for both the EHC- and PF-fed rats were least variable at 3 hours post-feeding. In the main study, endogenous ileal amino acid excretions were determined in the growing rat fed an EHC-based diet and with subsequent treatment of the digesta using ultrafiltration (n = 6) or in 6 rats given a PF diet or by extrapolation from data for 30 animals given 5 diets which contained graded levels of MBM as the protein source. For the EHC treatment, the ileal digesta precipitate plus retentate was used to determine the endogenous flows. Such processing excludes unabsorbed dietary amino acids from the measure of endogenous loss. Chromic oxide was the reference marker in all the diets. The endogenous flows determined by the protein-free and the regression method were similar but both significantly (P < 0.01) lower than those for rats fed the EHC-based diet. The mean (±SE) endogenous ileal N flows determined by the peptide alimentation method, the protein-free and regression approaches were 1866 (±30.8), 1103 (±22.6) and 1019 (±3.6) μg g-1 FDMI, respectively. It was concluded that endogenous amino acid flows at the terminal ileum were underestimated when determined using the traditional protein-free or regression methods. 5. The effect of dietary protein content (25, 60, 95, 130, 165 and 200 g CP kg-1 diet) on the apparent and true ileal digestibility of N and amino acids was investigated. Semi-synthetic diets in which the protein content was varied by the inclusion of graded amounts of MBM (50 to 400 g kg-1 diet) at the expense of maize starch were fed to 36 growing rats for 14 days. On the 14th day, the rats were fed and euthanased 4 hours after the start of feeding and digesta were collected from the terminal 20 cm of ileum. Endogenous amino acid excretion was determined for 18 rats given an EHC-based diet. The EHC-fed rats were euthanased 3 hours after the start of feeding and digesta were collected from the terminal 20 cm of ileum. The true ileal digestibility values determined with reference to chromium as a marker, were higher than the corresponding apparent estimates. Apparent digestibility of N and amino acids significantly (P < 0.001) increased with increasing dietary protein level, however, dietary protein content had no significant (P > 0.05) effect on the true ileal digestibility of N and amino acids. The mean apparent ileal digestibility of N in MBM ranged from 65.6 to 75.3%. The corresponding range of true ileal digestibility of N was 76.9 to 78.2% 6. The final experiment generated data on the nutrient compositions of meat and bone meals collected from eight processing plants throughout New Zealand. The true ileal digestibility of the amino acids in the meat and bone meals were also determined using the rat assay developed in the previous studies. Endogenous amino acid excretion, used for the correction of apparent digestibility values to true estimates, was determined for rats given a protein-free or an enzymically hydrolysed casein diet. The meat and bone meals were variable in their nutrient composition and in the true ileal digestibility of protein and amino acids. The true nitrogen and amino acid digestibility coefficients based on endogenous flows determined by the EHC method were markedly higher than with the protein-free diet. The true ileal N and lysine digestibility coefficients based on the respective endogenous flows for rats fed the EHC diet ranged from 62.7 to 88.9% and 66.4 to 92.3%, respectively. Values determined with endogenous flows for rats fed the protein free diet ranged from 59.0 to 85.2% for N, and 63.2 to 88.9 for lysine. The variable ileal digestible N and amino acid contents of meat and bone meals emphasise the limitation of tabulated analytical values and the need for a routine relatively inexpensive digestibility assay.