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    Studies on the measurement of calcium digestibility in raw materials for poultry and of digestible calcium requirement of broiler starters : 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, 2021) David, Laura Shiromi
    The measurement of calcium (Ca) digestibility in feed ingredients for poultry is receiving increasing attention because of recent interest in formulating diets based on digestible phosphorous (P) and the close relationship between these two minerals in their absorption and post absorptive utilisation. Data on the ileal Ca digestibility of Ca sources and factors influencing Ca digestibility in poultry are scant. The current thesis presents follow-up studies of the previous work conducted at Massey University. The Ca digestibility values of Ca sources determined in the thesis, along with previous published data, were then used to develop dietary treatments to assess the digestible Ca requirement of broiler starters. The first study reported in Chapter 3 was conducted to examine the effect of basal diet composition on true ileal Ca digestibility of four Ca sources namely, limestone, meat and bone meal (MBM), monocalcium phosphate (MCP) and dicalcium phosphate (DCP) in broiler chickens. Two basal diets, namely a maize-based diet and a maize-starch-based purified diet, with each Ca source were tested. The results showed that the average true ileal Ca digestibility was higher in the maize-based diet (0.46) than that in the purified diet (0.37). True ileal Ca digestibility of limestone, MBM, MCP and DCP were determined to be 0.51, 0.41, 0.43 and 0.32, respectively. In the study reported in Chapter 4, the effect of dietary indicator-type and dietary adaptation length on the apparent ileal Ca digestibility of limestone were evaluated. In Experiment 1, the use of two indicators namely, titanium dioxide and acid insoluble ash (Celite) were compared and the findings showed that the ileal Ca digestibility was unaffected by dietary indicator. In Experiment 2, four dietary adaptation lengths namely, 24, 72, 120 and 168 hours were examined and it was found that the Ca digestibility was unchanged between 72 and 120 hours but decreased at 168 hours of adaptation length. The third study, presented in Chapter 5, was conducted to measure the influence of age (7, 14, 21, 28, 35 and 42 days post-hatch) on the Ca digestibility of limestone for broiler chickens. The findings revealed that the apparent ileal Ca digestibility coefficients were linearly decreased from day 7 to day 42. The ileal Ca digestibility coefficients were determined to be 0.51, 0.53, 0.36, 0.34, 0.41 and 0.27 at days 7, 14, 21, 28, 35 and 42, respectively. A secondary objective of this study was to examine the influence of dietary crude protein concentration (79 and 153 g/kg) on the apparent ileal Ca digestibility at 21 days of age. It was found the apparent ileal Ca digestibility was not influenced by dietary protein concentrations. The studies reported in Chapter 6 were conducted to measure the influence of phytase doses (0, 500 and 2000 FTU/kg) on the Ca and P digestibility of soybean meal (SBM) and canola meal (CM) in broiler starters (Experiment 1) and finishers (Experiment 2). True ileal Ca digestibility coefficients of SBM and CM, with no supplemental phytase, were determined to be 0.51 and 0.53, respectively, for broiler starters and 0.33 and 0.22, respectively, for broiler finishers. True ileal P digestibility coefficients of maize-SBM diet and maize-CM diet, with no phytase were determined to be 0.89 and 0.66, respectively, for broiler starters and 0.82 and 0.57, respectively, for broiler finishers. Microbial phytase increased the true ileal digestibility of Ca and P in maize-SBM diet and maize-CM diet, but the effect was more pronounced for the maize-CM diet. Superdosing of phytase (2000 FTU/kg) increased the Ca digestibility in CM and SBM by two-fold compared to the normal phytase dose (500 FTU/kg). The studies reported in Chapter 7 were conducted to determine the ileal Ca digestibility coefficients of two limestone sources in broilers and layers. The results showed that, in both sources, the apparent ileal Ca digestibility of limestone was found to be higher in laying hens (0.62 and 0.70) compared to broilers (0.50 and 0.43). The findings indicated that laying hens absorb Ca more efficiently than broilers which may be attributed to their high demand of Ca for eggshell formation. Using Ca digestibility values of Ca sources measured in this thesis work and previous published data, a growth study (Chapter 8) was conducted to estimate the standardised ileal digestible (SID) Ca requirement for 1 to 10 day-old broilers fed different dietary concentrations of both SID Ca (3.3, 3.9, 4.4, 5.0 and 5.5 g/kg) and SID P (4, 5 and 6 g/kg). Based on response surface models, the growth performance, bone mineralisation and mineral utilisation of broiler starters were found to be optimised at 5 g/kg SID P concentration. The concentrations of SID Ca that maximised body weight gain, tibia ash, tibia Ca, tibia P and toe ash were estimated to be 3.32, 4.51, 4.72, 4.36 and 4.78 g/kg, respectively, which corresponds to SID Ca to SID P ratios of 0.66, 0.90, 0.94, 0.87 and 0.96, respectively. Bone mineralisation required more SID Ca than for growth. Most of the findings reported in this thesis are novel and contribute to the advancement of current knowledge on the measurement of ileal Ca digestibility in poultry and the factors influencing Ca digestibility. The array of factors examined were hitherto unexplored and included the effects of basal diet type, dietary adaptation length, broiler age, phytase dose, Ca source and bird type (broilers vs. layers). Another notable contribution was to establish the requirements of digestible Ca, digestible P and the ratio of digestible Ca to digestible P for broiler starters (1-10-day old).
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    Measurement of true ileal calcium 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 at Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Anwar, Muhammad Naveed
    The recent interest towards the use of digestible phosphorus (P) in poultry feed formulations necessitates the measurement of true calcium (Ca) digestibility of feed ingredients because of the close relationship between these two minerals for their absorption and post absorptive utilisation. When this thesis research was initiated, no published data were available on Ca digestibility of feed ingredients for broiler chickens. The major objective of the studies reported in this thesis was to determine the true Ca digestibility of feed ingredients for broiler chickens. In total, nine studies were conducted. The first study (Chapter 4) was conducted to determine the effect of methodology on ileal endogenous Ca losses. Three methods, namely feeding a Ca- and P-free diet, maize gluten meal based diet and egg albumen based diet, were used. Ileal endogenous Ca losses differed among different methodologies. The highest ileal endogenous losses of 125 mg/kg dry matter intake (DMI) were recorded on the Ca- and P-free diet, followed by 77 and 43 mg/kg DMI on maize gluten meal and egg albumen diets, respectively. In the second and third studies (Chapters 5 and 6), regression and direct methods, respectively, were used to determine the true Ca digestibility of meat and bone meal (MBM). The true Ca digestibility coefficient of MBM samples were ranged from 0.41 to 0.60. No difference was observed between true Ca digestibility coefficients of MBM determined by regression and direct methods. Since the direct method is less laborious and cost effective compared to regression method, this method was used in subsequent studies (Chapters 7 to 10) to determine the true Ca digestibility of a range of Ca sources. In fourth and fifth studies (Chapters 7 and 8), the influence of dietary P, particle size and Ca to non-phytate P ratio was investigated on the true Ca digestibility of limestone for broiler chickens. The true Ca digestibility of three limestone samples varied from 0.56 to 0.62. Supplementation with recommended dietary P (4.5 g/kg) increased the true Ca digestibility of limestone when compared to diets without P. An increase in particle size from <0.5 to 1-2mm improved the true ileal Ca digestibility of limestone. Widening the Ca to non-phytate P ratio reduced the true Ca digestibility of limestone for broiler chickens. The sixth study (Chapter 9) was conducted to determine the effect of Ca source and particle size on the true Ca digestibility and total tract retention. Limestone and oyster shell were used as Ca sources. No difference was observed between the true Ca digestibility of limestone and oyster shell. An increase in particle size from <0.5 to 1-2 mm increased both the Ca digestibility and retention of both Ca sources, and increased the Ca concentration of gizzard contents. The study reported in Chapter 10 was conducted to determine the true Ca digestibility of dicalcium phosphate (DCP), monocalcium phosphate (MCP), canola meal, poultry by-product meal and fish meal, and to compare the effect of dietary adaptation length on true Ca digestibility of DCP and MCP. The true Ca digestibility coefficients of these feed ingredients were lower than MBM, limestone and oyster shell, and ranged from 0.24 to 0.33. It was speculated that the length of adaption to the assay diets may be responsible for the lower than expected estimates. The effect of dietary adaptation length (24, 48 or 72 hrs) was subsequently examined, but had no effect on true Ca digestibility of DCP and MCP. In the final study (Chapter 11), the true Ca digestibility of DCP was determined using different methodologies (regression, difference and direct methods). The true Ca digestibility coefficients of DCP were 0.34 and 0.21 with direct and different methods, respectively. A very low digestibility coefficient of 0.13 was determined by the regression method. In conclusion, the true Ca digestibility coefficient of major Ca sources (limestone, oyster shell and MBM) is not high and varied from 0.40 to 0.70. Particle size of limestone and oyster shell influenced Ca digestibility, with coarser particles having higher digestibility. The direct method appears to be suitable for the determination of true Ca digestibility of limestone, oyster shell and MBM, but may not be appropriate for other Ca sources with intrinsic imbalance of Ca and P.
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    Vitamin D and calcium metabolism in horses in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Institute of Veterinary, Animal and Biomedical Sciences (IVABS), Massey University, Manawatū, New Zealand
    (Massey University, 2016) Azarpeykan, Sara
    The physiology of vitamin D in horses has not been studied in great depth. Few studies on vitamin D metabolites (25OHD2, 25OHD3, and 1,25(OH)2D) and their relationship to other serum analytes exist. In addition, some studies suggest that equine vitamin D physiology may be different from other species. This thesis aimed to investigate aspects of vitamin D metabolism in horses. The effect of blanketing on vitamin D synthesis and its relationship with other analytes involved in calcium homeostasis, including vitamin D metabolites (25-hydroxyvitamin D2 (25OHD2), and 25-hydroxyvitamin D3 (25OHD3), 1,25-dihydroxyvitamin D (1,25(OH)2D)), ionised calcium (iCa), total calcium (tCa), phosphorus (P), total magnesium (tMg) and parathyroid hormone (PTH) were studied in horses. Regardless of blanketing, 25OHD3 was undetectable in equine serum and 25OHD2 was the main form of 25OHD in circulation. A strong seasonal variation in serum 25OHD2, 1,25(OH)2D, iCa, tCa, P, tMg and PTH concentrations was detected, although no differences were seen between horses that were blanketed and those that were not. The circadian rhythms of serum vitamin D metabolites, iCa, tCa, P, tMg, and PTH concentrations in horses was studied over 48 h on the summer and winter solstices. A significant difference was seen between the serum concentrations of studied analytes between solstices, with no rhythm detected in winter. An in vivo study suggested that equine skin may be unable to convert 7-dehydrocholesterol (7-DHC) to vitamin D3 after exposure to ultraviolet B (UVB) light. Quantitative PCR was performed on equine kidney to study the expression of vitamin D responsive and calcium transporting genes, which were then compared to genes in sheep and dogs. The results suggested that TRPV6, calD9k /calD28k, and PMCA were the main calcium transporting pathways in the kidney of these species, and there was a high correlation between VDR and other studied genes. It was concluded that 25OHD2 is the main metabolic precursor for 1,25(OH)2D and should be considered the best available index of vitamin D status in unsupplemented horses, and that horses most likely rely on diet as their primary source of vitamin D.
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    Studies on the protective role of probiotics and milk calcium on Salmonella Typhimurium infection in mice : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Nutritional Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2000) Lin, Hai
    The current studies were carried out to evaluate the efficacy of a newly identified LAB strain - DR10TM (Bifidobacterium lactis) on host immunity and susceptibility to Salmonella typhimurium (S. typhimurium) infection in mice. In addition, the effect of elevated milk calcium levels combined with DR10TM was studied in mice infected with S. typhimurium. After initially establishing a murine infection model, the effect and efficacy of DR10TM in preventing S. typhimurium infection and stimulating immunity was examined. The results showed that DR10TM could significantly enhance resistance against S. typhimurium infection and stimulate a wide range of immune parameters including non-specific and specific immune responses. In another study the S. typhimurium infection model was used to examine the effect of milk calcium and the combination of different amounts of milk calcium with DR10TM on host immunity and prevention of S. typhimurium infection in mice. These results demonstrated that milk calcium was very effective in reducing the severity of infection and a high amount of milk calcium combined with DR10TM increased the ability of DR10TM to prevent S. typhimurium infection. The findings of the current study were significant in that they demonstrated the effect and efficacy of DR10TM on promoting enhanced resistance to enteric infection and stimulating immunity, provided additional evidence of the role played by the enhanced immune system in protecting against enteric infection, and ascertained the synergism between milk calcium and LAB in the prevention of S. typhimurium infection.