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D Kratzer

Publications and source records attributed to D Kratzer.

5 recordsLinked to original sources
PubMed2006

A multiple regression model approach to contrast the performance of 2-hydroxy-4-methylthio butanoic acid and DL-methionine supplementation tested in broiler experiments and reported in the literature.

The purpose of this paper was to compile all available literature comparing the relative performance of 2-hydroxy-4-methylthio butanoic acid (HMTBA) with DL-methionine (DLM) in broiler chickens and using multiple regression techniques, to estimate the predicted dose responses and relative performance of the 2 Met compounds for gain and feed conversion (FC). A database was developed that contained all available broiler studies in which HMTBA and DLM were both present in the same study; weight gain was recorded; Met addition, age of birds, and duration of study were defined; and an unsupplemented control treatment was present. Sixty-two references complied with these criteria and included 100 experiments with 427 observations for HMTBA and 411 for DLM. Multiple regression analysis of the database was used to identify the experimental and dietary conditions that contributed to the gain and FC responses of each source of Met activity. All identified variables contributed similarly to each Met source prediction model and both gain and FC models described a quadratic dose response. Under the average conditions of the database, the predicted responses for gain and FC models did not significantly differ between HMTBA and DLM. However, a trend was observed (P < or = 0.1) for the peak gain response for HMTBA to be numerically greater than DLM, suggesting benefits of HMTBA over DLM in the region of supplementation that is commercially relevant. The experimental and nutritional conditions that contribute to the response to HTMBA and DLM were identified and are discussed in the paper. This statistical approach provided a means to summarize the results obtained from a multitude of studies conducted over the last 5 decades and has provided a meaningful estimate of the relative performance of the 2 sources of Met activity. The lack of differences between the 2 predicted models under experimental and commercial conditions supports an overall conclusion of equal performance of DLM and HTMBA when compared on an equal molar basis.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Therapeutic efficacy of water-soluble lincomycin-spectinomycin powder against porcine proliferation enteropathy in a European field study.

Controlled clinical trials to a standardised protocol were conducted into the effect of a water-soluble antibiotic on proliferative enteropathy and its causative agent (Lawsonia intracellularis) on commercial pig farms at six sites in four European countries. Clinical signs of the disease and L intracellularis-specific polymerase chain reaction (PCR)-positive pigs were detected in pens of six- to 12-week-old pigs (weighing 5 to 55 kg) immediately before each trial. Matched pens of randomised pigs were either left unmedicated (32 to 59 pigs per trial), or medicated orally with 10 mg/kg of a water-soluble combination of lincomycin and spectinomycin powder (21 and 42 mg, respectively, of antibiotic activity per litre) for either seven days (33 to 61 pigs per trial), or 14 days (33 to 61 pigs per trial), delivered via the drinking water. Investigators did not know which pens received which treatment In most of the affected pigs in each trial, diarrhoea due to L intracellularis resolved within three to seven days after the medication began, whereas most unmedicated pigs remained diarrhoeic for at least 10 days. On average the medicated pigs gained more weight than the unmedicated pigs over the 21-day trial period (P=0.01). In two trials, the absence of L intracellularis after the treatment ended was confirmed by the PCR.

Administration, Oral↗
PubMed1997

Estimating the maximum effective dose in a quantitative dose-response experiment.

A simulation study was conducted to compare several procedures for estimating the maximum effective dose in a quantitative dose-response experiment. Using four equally spaced dose levels, data were generated from four different model types: the quadratic growth curve, the Mitcherlich growth curve, the linear-linear plateau spline model, and the quadratic-linear plateau spline model. Each model type was parameterized to create three different model ranges, and for each range, data were generated from populations with three different standard deviations. The existence of unique dose-response curves is assumed; thus, all the procedures compared in this paper require that the data have been modeled by a polynomial or nonlinear regression model. An attempt was made to fit each generated data set with each of the four model types. Maximum effective dose estimation procedures were applied to a data set only when the data were adequately described by a given model. The stimulation indicated that the estimate of the maximum effective dose is influenced more by the choice of model than by the method of estimation. Because of the consistently low estimates produced when the data were modeled by the linear-linear plateau spline, this model is not recommended for use an maximum effective dose estimation experiments. The simulation also demonstrated that the design failed to provide sufficient information about the form of the dose-response curve. Designs with more than four dose levels should be considered.

Animals↗
PubMed1991

Postparturient metabolic and production responses in cows previously exposed to long-term treatment with somatotropin.

Postparturient metabolic and production responses were studied for 85 multiparous cows consisting of controls and animals that had been previously exposed to long-term treatment with bST. Older cows previously exposed to bST at high doses (51.6 mg/d) had lower milk yields than controls. However, there were no significant differences compared with controls in milk yield for lower dose (17.2 mg/d) older cows or parity 2 cow groups. The bST-treated groups had higher postpartum DMI, lower serum FFA, lower serum beta-hydroxybutyrate levels, and higher serum glucose than controls. Some bST-exposed groups had lower milk fat but higher milk protein levels. All bST-treated groups had significantly lower ratios of C18 to C4 to 10 milk fatty acids. Control cows of both parity groups were in higher body condition and weighed more than bST-treated cows prior to calving. The differences in postpartum metabolism may be attributed to differences in body composition resulting from bST treatment in the prior lactation, because use of body condition score prior to calving as a covariate did not substantially alter responses. The control cows probably had greater reserves of mobilizable lipid. These contentions are supported by changes in milk composition for bST-treated cows, which were consistent with animals of greater appetite, mobilizing less lipid. The bST-treated cows were probably more energetically efficient milk producers because they produced milk from feed rather than from mobilization of tissue stores. These data suggest that bST use in a prior lactation may have potential benefit in reducing risk of metabolic disorders associated with lipid mobilization in the postparturient period.

3-Hydroxybutyric Acid↗