The effect of stage of lactation on milk yield, somatic cell counts, mineral and fatty acid profiles in pasture-based Friesian, Jersey and Friesian × Jersey cows was investigated. Twenty Friesian, twenty Jersey and twenty Friesian × Jersey cows were randomly selected from a dairy herd. A total of 202 milk samples were collected and analysed in three stages of lactation. Genotypic differences were observed in milk yield and fat content. Friesian cows produced the highest yield and lowest fat content whereas the opposite was true for Jersey cows (P<0.01). No significant differences were observed in SCC in the different genotypes, but SCC levels were higher in mid and late lactation (P<0.001). There was no effect (P<0.005) of genotype and stage of lactation interaction on Ca, P, Mg, Na, Mn and Bo concentration. Jersey cows had the least concentration of Fe and Cu in all stages of lactation. Strong positive correlations were observed among Ca and P, Mg and Zn. Aluminium had a strong positive relationship with Bo, Fe, Mn and Zn (P<0.001). Generally, SCC had a weak positive relationship with macro elements but a significant negative relationship with microelements. Yield levels were negatively correlated with Mg, Na, Al, Mn and SCC. Pasture ALA, SFA, n-3, n-6/n-3 and PUFA/MUFA concentration did not differ across the study period. Linoleic acid was highest in the second phase which coincides with mid lactation in cows (P<0.001). Highest moisture content coincided with the least fat free dry matter content in early lactation (P<0.001). Significantly high fat content was observed in late lactation than in early lactation. Highest butyric, caproic, linoleic, n-6 and PUFA were observed for Friesian cows. All other fatty acids ratios were not significantly different among different genotypes. Highest CLA, ALA, LA, SFA, PUFA, n-6, and n-3 and atherogenicity index were observed in early lactation whereas desaturase activity indices were highest in late lactation. Strong positive correlations were observed among milk vaccenic, ALA, LA and CLA concentrations. Inverse relationships were observed between SFA and long chain fatty acids. It can be concluded, it may be of advantage to consume milk from early stage of lactation poses a lower risk to coronary diseases and are much safer to consume.

This study, being part of a larger project - "Canadian/New Zealand GxE Interaction Trial" - is comparing Canadian and New Zealand sired heifers for growth traits within Canada, since differences for growth traits were found in the Polish strain comparison (Jasiorowski et al., 1987) and due to selection programs in the two countries. Twenty Canadian Holstein and twenty New Zealand Friesian progeny tested, A.I. bulls were randomly mated to over 1,000 cows in 10 Canadian herds. 3,539 records of weight and wither height from 475 heifers (i.e. 241 Canadian and 234 New Zealand sired) were generated. Subsets of the data for different stages of heifer maturity were analyzed separately. Herd and strain effects least squares means were estimated using analysis of variance. Genetic and phenotypic and correlations and heritability for weight and wither height were estimated by a Derivative-Free Restricted Maximum Likelihood (DFREML) algorithm and an animal model (AM). No differences were found between sire strains for weight except at 15 and 18 months where sib groups of Canadian (CN) sires were heavier than their New Zealand (NZ) contemporaries (393 vs 386 kg and 447 vs 445 kg, respectively). CN sired heifers were taller at all ages except at birth, 3 and 9 months of age. At 24 months CN heifers were 136 cm while NZ heifers were 133 cm. Heritability estimates for weight at birth was 0.62 for the CN strain and 0.59 for the NZ strain. CN estimates (3 to 6 months) and NZ estimates (3 to 9 months) were close to zero. Between 9 to 24 months CN strain estimates ranged from 0.44 to 0.69 while NZ estimates were 0.17 to 0.51. The joint estimates ranged from 0.10 to 0.66. Heritability estimates for wither height for CN strain at birth and between 9 to 21 months were between 0.34 to 0.66 and close to zero between 3 to 6 and at 24 months. The NZ estimates at birth, 18, 21 and 24 months were between 0.36 to 0.93 but close to zero between 3 to 15 months. The joint estimates ranged from 0.32 to 0.75 between 12 to 24 months. Genetic correlations between weight and wither height ranged from 0.62 to 1.0 for CN strain and from -0.04 to 0.91 for NZ strain between 4.5 to 21 months. At six months of age the genetic correlation for CN strain was -0.01 and NZ strain was 0.54. At birth, both sire groups had a genetic correlation of 1.0. At 24 months NZ strain had a genetic correlation of 0.84 while that of the CN strain was 0. Genetic correlations for the joint analysis ranged from 0.61 to 1.0 for all ages except at 6 months (0.18). Phenotypic correlations between weight and wither height were between 0.33 to 0.60 for CN group and 0.33 to 0.62 for NZ group. The joint estimates were 0.36 to 0.61. There were no differences in the phenotypic variances except at 9, 12 and 15 months. Genetic variances were different at all ages except at birth for weight. / Land and Food Systems, Faculty of / Graduate

Galactopoietic effects of somatotropin are the result of IGF-I and require high-quality nutrient intake. This study investigated short-term partitioning effects during recombinant bovine somatotropin (bST) administration in high yielding early lactation dairy cows. Administration of recombinant bST has been shown generally to alter results of metabolic tests in the face of unchanged basal glucose and insulin concentrations. Ten multiparous Holstein cows were subjected to rbST (Lactotropin®) and/or feed intake restriction to 80% of predicted ME requirement (80% ME). Responses to insulin challenge (0.1 IU porcine insulin/kg BW. 210 min) and hyperglycaemic clamp (+50 mg/dL whole blood, 120 min) were tested during weeks 8 (control), 9 (rbST ), 11 (80% ME) and 12 (rbST + 80% ME) postpartum. Plasma and whole blood samples were assayed for glucose concentrations. The rbST treatment decreased fasting whole-blood glucose concentration by 9.4% (P<0.0001), which was likely a remnant of control hyperglycaemia. Maximum glucose response was 4.0 mg/dL (21.7%) lower (P<0.0038) and took 6.5 minutes longer to attain (P<0.0037). Steady-state glucose infusion rate (SSGIR) decreased by 8.1 % (P<0.0001). The 80% ME treatment decreased glucose availability by 5 to 6% (P<0.0100), while no glucose responses were affected. Restricted energy intake during treatment with rbST resulted in plasma glucose increase by 5.5% (P<0.0001). Peripheral uptake and utilization of glucose increased by 5.1 % (P<0.0005). Compared to energy restriction, 80%ME + rbST did not alter effects of nutrient restriction on responses to exogenous insulin challenge. Effects were small and inconsistent. SSGIR decreased by 5.0% in the 80% ME + rbST compared to the 80% ME period (P<0.0004) and the change in the hyperglycaemic clamp in the absence of an effect in the insulin challenge may be due to differences in endogenous insulin secretion. The conclusion was that rbST treatment resulted in altered glucose metabolic responses, even with restricted energy intake. / Dissertation (MSc(Agric))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

The efficiency of utilization of dietary nitrogen can be monitored using milk urea nitrogen (MUN). Overfeeding or underfeeding of protein can be identified through the observation of deviations from target MUN concentrations. This will assist in lowering feed costs of dairy farms, and improving nutrition management of herds. Higher efficiency of utilization of dietary nitrogen might result in a reduction in environmental pollution. Non-genetic factors affecting variation in MUN were herd-test-day (HTD), lactation stage and year of calving. The contribution of HTD was the highest, ranging from 58.56% to 63.18% in parity 1 to 3. Lactation stage had the second largest contribution to the MUN variation. Differences in least squares means for MUN in various years of calving were observed. The heritability estimate for MUN was 0.09±0.01 in the first parity, and remained constant at 0.11±0.01 in the second and third parity. Heritability estimates for milk, fat and protein yield ranged from 0.40±0.01 to 0.43±0.01, 0.21±0.01 to 0.26±0.01, and 0.32±0.01 to 0.38±0.01, respectively. These estimates were within acceptable ranges for South African Holstein cattle. Genetic correlations between MUN and milk production traits were low and positive, ranging from 0.01±0.003 to 0.10±0.004 across parities. Phenotypic correlations ranged from 0.02±0.11 to 0.16±0.07, being generally higher than the genetic correlations. The positive associations between MUN and milk production traits are undesirable as the dairy cows would be less efficient in utilizing dietary protein and may result in increased environmental pollution. The genetic trend for MUN was 0.44, 0.007 and 0.049 mg/dl in the first, second and third parity, respectively. Results of the current study indicate that MUN has potential as a management tool in South African Holstein dairy herds. It might be a good indicator of the efficiency of dietary protein utilization of dairy herds, and has practical advantage as it is currently collected by the national dairy herd recording and improvement scheme. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / unrestricted

Twenty-two primiparous Holstein heifers were allocated to one of two treatments. Treatments consisted of: l) basal ration plus 226.8 g inorganic mineral supplement (control); and 2) basal ration plus 226.8 g inorganic mineral and metal proteinate supplement (50:50). Individual heifer performance was measured during the final l 0 weeks of the prepartum period. Feed intake and refusals were recorded daily. Individual heifer body weights recorded weekly did not differ significantly. Blood samples taken at 4-week intervals did not differ in plasma concentration between treatments. Calf birth weights for control heifers were not significantly higher than calves from the treatment heifers. The same twenty-two Holstein heifers used in the prepartum period were assigned to the same treatment groups for the 20-week postpartum lactation period. Treatments consisted of: 1) basal ration plus 453.6 g inorganic mineral supplement (control); and 2) basal ration plus 453.6 g inorganic mineral supplement and metal proteinate supplement (50:50). Dry matter intake and milk yield were recorded daily. Milk composition and body weights were recorded weekly. Feed and fecal samples were collected to determine apparent nutrient digestibility, using acid insoluble ash as an internal marker. Blood samples taken at. 4-week intervals showed no significant difference (Ρ < .05) in plasma mineral composition. No statistical difference was observed in milk yield between treatments (Ρ < .05). Percent lactose in milk samples from the treatment group was significantly higher (Ρ < .05) than that of the control group. Apparent nutrient digestibilities did not differ between treatment groups. Starting on day 5 postpartum, cows were observed for signs of estrus and bred at first observed estrus after 60 days postpartum. Days to first estrus were significantly lower (Ρ< .05) in the treatment group. The feet of each heifer were critically evaluated and scored according to six separate criteria at the start and at the finish of the trial. The texture category of the hoof evaluation score was significantly lower (Ρ < .05), favoring the treatment group over the control group.

No description available.

Two trials were designed to study the relationships of dietary fiber (ADF) and protein level and source to fecal consistency in lactating cattle. In Experiment 1, 30 cows (12 multiparous, 18 primiparous) were randomly assigned to one of six total mixed diet treatments through four 21 d periods. For Experiment 2, six primiparous cows were used in two 6 x 6 Latin squares to evaluate water consumption, apparent digestibilities of DM, AOF, NOF, and starch, and to quantitate whole corn kernel passage. Total mixed diets for both trials were formulated to contain 17% (LF) or 25% AOF (HF) with CP levels of: 15% (S15) and 22% (S22) with soybean meal (SBM) supplementation, or 22% (G22) with combination of 50% corn gluten meal (eGM) and 50% SBM. Two forage sources were evaluated: corn silage (e) and alfalfa/corn silage (Ae) (50:50 on OM basis). Fecal consistency was evaluated using a 4 point scale (l-most fluid to 4-least fluid). Experiment 1 demonstrated that lower dietary fiber reduced fecal pH (LF=6.65, HF=7.11) and fecal score (LF=2.18, HF=2.41), but increased fecal DM (LF=16.1%, HF=13.2%). Supplementing SBM (S22) decreased fecal DM (S22=14.1%, G22=15.5%) and fecal score (S22=2.01, G22=2.48). Forage source affected fecal DM (C=14%,AC=15.3%), but not pH or score. HF=13.2%). Supplementing SBM (S22) decreased fecal DM (S22=14.1%, G22=15.5%) and fecal score (S22=2.01, G22=2.48). Forage source affected fecal DM (C=14%,AC=15.3%), but not pH or score. Results of Experiment 2 support major conclusions of Experiment 1. High supplementation of SBM increased daily water consumption (S22=80.2 kg, G22=74.5 kg), and reduced fecal score (S22=1.9, G22=2.4). Forage source affected apparent corn kernel (C=21.1% ,AC=33.9%) and starch (C=96%, AC=93%) digestibilities. High protein diets resulted in greater apparent DM digestibility (S15=68.2%, S22=71.8%, G22=71%). In prediction of fecal score from dietary components and animal parameters, dietary DM percent and 4% fat corrected milk (r²=.09, Experiment 1), and DM intake (r²=.12, Experiment 2) were variables most related to fecal score. Dietary effects on fecal consistency were primarily due to ADF level and type of protein supplement. Accurate prediction of fecal consistency score from the dietary and animal parameters identified was not possible. Further study is suggested to evaluate different protein sources, the contribution of water consumption, and to clarify interactions of protein, forage source and fiber level in relation to fecal consistency. / Master of Science

The main objective of this thesis is to provide a deeper understanding of the charge transport phenomena occuring in molecular crystals. The focus is on the stability and the dynamics of the polaron as the charge carrier. To achieve this goal, a series of numerical calculations are performed using the semi-emprical "Holstien-Peierls" model. The model considers both intra- (Holstein) and inter- (Peierls) molecular interactions, in particular the electron-phonon interactions. First, the stability of the polaron in an ordered two dimensional molecular lattice with an excess charge is studied using Resilient backPropagation, RPROP, algorithm. The stability is defined by the "polaron formation energy". This formation energy is obtained for a wide range of parameter sets including both intra- and inter-molecular electron-phonon coupling strengths and their vibrational frequencies, transfer intergral and electric field. We found that the polaron formation energies lying in the range of 50-100 meV are more interesting for our studies. The second step to cover is the dynamical behaviour of the polaron. Using the stable polaron solutions acheived in the first step, an electric field is applied as an external force, pushing the charge to move. We observed that the polaron remains stable and moves with a constant velocity for only a limited range of parameter sets. Finally, the impact of disorder and temperature on the charge dynamics is considered. Adding disorder to the system will result in a more restricted parameter set space for which the polaron is dynamically stable and mobile. Temperature is included in the Newtonian equations of motion via a random force. We observed that the polaron remains localized and moves with a diffusive behaviour up to a certain temperature. If the temperature increases to values above this critical temperature, the localized polaron becomes delocalized. All this research work is coded in MATLAB software , allowing us to run the calculations, test and validate our results.

No description available.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23731号 / 理博第4821号 / 新制||理||1689(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 谷村 吉隆, 教授 林 重彦, 教授 渡邊 一也 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM