Browsing by Subject "Poultry"

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Bone ash data in the context of phosphorus and phytase evaluation in poultry
(2021) Künzel, Susanne; Rodehutscord, Markus
Phosphorus (P) is an essential element that is crucial for various metabolic processes in the body of animals and humans. To keep the animals healthy and to obtain food products rich in nutrients, an adequate P supply is indispensable. Plant feedstuffs, the main components of poultry diets, contain P in a form that is only partially available to poultry. For this reason, poultry diets are often supplemented with mineral P. However, global rock phosphate reserves, where mineral P is mined from, are limited. Additionally, excessive P supply should also be avoided because of the environmental impact of P accumulation in the soil. Consequently, P supply not exceeding the requirements of poultry is essential to ensure animal wellbeing and to protect the environment. In order to feed diets with adequate concentrations of P, it is necessary to have suitable approaches for the determination of available P in the animal. The availability of P varies widely between feed components and it is also influenced by feed supplements and other factors. Bone ash analysis is an often-used tool to evaluate the relative bioavailability of P since a high amount of P is stored in the bones. A standard assay for bone ash analyses has never been agreed on. Therefore, many different approaches are described in the literature with an unknown impact on the results of P bioavailability studies. The main objective of the present thesis was to examine the suitability of bone ash data for the evaluation of available P in poultry with emphasis on methodological aspects. Therefore, different studies with broiler chickens and Japanese quail were conducted. The experiments comprised various aspects related to P availability in poultry. The effect of feed supplements in the form of phytase products, myo-inositol and a coccidiostat were evaluated. Furthermore, quantitative genetic analyses were performed. All experiments had in common that tibiotarsus (tibia) or foot ash data or both were used for the examination of the relative bioavailability of P. Based on the data that accrued during the studies described in the four manuscripts of this thesis, comprehensive methodological analyses were performed. The tibia and foot were compared regarding their appropriateness as a trait for the evaluation of the relative bioavailability of P by using bone ash data. The relationship between the two traits was investigated, as well as the relationship between foot or tibia ash and quantitative P measurements. Additionally, P concentration in the ash of both bone fractions was analysed and compared. Results indicated only minor differences between tibia and foot ash data. No clear preference for one of them could be deduced from the data. The left and right feet of broiler chickens were compared in terms of both ash concentration and total ash amount. Significant differences between the two feet of the same animal were detected for both traits. Consequently, not only the choice of the bone fraction but also of the body side should be considered when sampling for bone ash data. Ash data are mostly expressed as a concentration of the dry matter content of the bone. Also possible is the use of the absolute ash amount. The relationship of both ways of expression with traits of quantitative P measurements was analysed by using correlation coefficients and regression analyses. Results showed that the absolute ash amount was at least as suitable as ash concentration but has the advantage that it is easier to determine. Possible selection procedures for animals for bone ash analyses were simulated with data from two of the experiments. Often it is not possible to use all animals involved in an experiment for bone ash analyses. Therefore, the influence of sampling frequency and selection method on the outcome of P availability studies was evaluated. Results indicated that the number and selection method of animals for bone ash data might influence the results. However, it was not possible to recommend a specific selection method based on the obtained results. Estimates of heritability and genetic correlations showed the suitability of bone ash data as a proxy trait for P efficiency breeding of poultry. The absolute amount of bone ash data appeared to be most promising for this purpose. Bone ash data are a very useful and easy to determine trait to estimate the relative bioavailability of P. However, investigations performed in this thesis showed the importance of a careful selection of methods. A standardised assay would be helpful to obtain meaningful and more comparable estimates of relative P bioavailability.
Relevance of amino acid digestibility for the protein utilization efficiency in poultry
(2022) Siegert, Wolfgang; Siegert, Wolfgang
One aim of poultry nutrition research that has been pursued for decades is to decrease the ingested protein relative to the protein accreted in animal body weight or eggs, which is described in the key figure ‘protein utilization efficiency’. Increasing protein utilization efficiency aims to ensure global food and water security and to minimize the effects of excreted nitrogenous compounds on the environment and the health of animals and humans. Protein utilization efficiency can be increased by adjusting the supply of digestible amino acids to animals relative to the requirement for digestible amino acids. The predictability of amino acid digestibility of feed ingredients is a prerequisite to achieve this goal. This habilitation thesis puts knowledge gained from studies on methods of amino acid digestibility determination, influences on amino acid digestibility, and variation in amino acid digestibility within feed ingredients into the context of predictability of amino acid digestibility. Methodological, dietrelated, and animal-related influences that considerably determine amino acid digestibility are presented and evaluated. This includes feed intake, feed provisioning, feed processing, chemical composition of feed ingredients, feed enzymes, and microbiota in the digestive tract. Cropping conditions influencing amino acid digestibility are also addressed. The gained insights may contribute to make amino acid digestibility more predictable in the future. Recent attempts to predict amino acid digestibility, however, have not been sufficiently accurate to fulfill the aim of being able to formulate diets according to the requirement for digestible amino acids in practice. Suggestions for future strategies to work toward a more accurate predictability of amino acid digestibility are included. Model calculations show that increasing amino acid digestibility can considerably raise protein utilization efficiency. When amino acid digestibility is increased by an influence not related to the feed ingredient providing amino acids (e.g., supplemented enzymes), increasing amino acid digestibility by 1 percentage point raises the protein utilization efficiency by ~0.43 percentage points. An increase in protein utilization efficiency of up to 0.5 percentage points can be expected when amino acid digestibility is increased by selecting variants of a feed ingredient for higher amino acid digestibility. The thesis concludes with a critical examination of the general perception that higher amino acid digestibility and maximized protein utilization efficiency are advantageous. Situations in which lower amino acid digestibility and smaller protein utilization efficiency provide benefits are discussed.
Untersuchungen zur Variation und Rhythmik der individuellen Futteraufnahme bei Pekingenten in Gruppenhaltung
(2003) Bley, Tobias Alexander Georg; Bessei, Werner
Methods to record feed intake in group reared individuals were only available for larger domestic species, such as pigs and cattle. Similar equipment for ducks using an antenna-receiver system had to be developed for the present study. The antenna was fitted nearby the feeder and the transponder was attached to the wing mark. The feeders were connected to an electronic scale and the following characteristics were recorded by a PC continuously: number of the bird, day, time of day, time of visits to the feeder, feed consumption. The system was suitable for duckling from 14 days old onwards. Two experiments were carried out. In experiment 1 a total of 50 male Pekin-type hybrid from 14 to 49 days of age were used. In experiment 2 records were taken from 480 male and female ducks of an experimental line from day 21 to 45. The birds were raised in groups on deep litter (straw). Commercial pelleted feed and water were provided ad libitum. The distance between feeders and drinkers was 1 m in experiment 1 and 5 m in experiment 2. The following traits were extracted from the records: Number of meals per day (defined as visits to the feeder with feed intake) Duration of meals (sec.) Size of meals (grams.) Intensity of feeding (feed intake in grams. per min): feed intake per meal in relation to duration of meal Duration of pauses (sec. or min.) Duration of feed intake per day (min.) Feed intake per day (grams.) Live weight (grams.) Dates of a total of 530 ducks and containing 260000 visits to the feeder were recorded and analysed On the basis of the duration of the frequency of meals per day two distinct groups, birds with large number of short meals (HM), and birds with a small number of big meals (LM), were identified. Comparisons were made between the two meal-type groups for all traits and the circadian rhythms of feed intake. HM ducks were characterised by short duration and small size of meals, and short pauses between meals. There was only a small difference between the meal-types for the total duration of feeding and feeding intensity. HM birds were lighter than LM birds. With increasing age, number of meals per day and duration of feeding per day decreased while daily feed consumption increased. Duration and size of meals, and intensity of feeding increased with age. Changes in feeding activities were most important between 3 and 4 weeks of age. An effect of sex was only noted for the number of meals at seven weeks of age. Differences in the occurrence of pauses were found in response to the experiment, meal-type and age. With regard to the presentation and analysis of pauses the usual procedures using log survivorship functions were discussed. In the present study, however, the differences in the distribution of pauses have been demonstrated using the relative frequency for the pauses of long duration and the cumulative frequency for the pauses of shorter duration. With regard to the high variation of the duration of pauses among individuals and with age the calculation of a single meal criterion, which separates pauses within and between meals, for all individuals and over all ages was not considered useful. On the basis of the distribution of pauses of the different meal-types it seems that the meal criterion is less than one minute in the HM types, and over 35 minutes in the LM types. The circadian rhythm of feed intake was similar in both meal-type groups and shows a biphasic shape with maxima at the beginning and the end of the light period. There was also feed intake during the dark period, the consumption, however, was lower than in the light period. The power spectra of the feed intake showed main components in the 24; 12; 6 and 4.8 hours rhythms and, in addition, various different rhythms in the area of 2-4 hours. The rhythm pattern was more pronounced in the HM types as compared to the LM types. The power of the 24 hours rhythms decreased with age, while a 6 hours rhythm developed at the end of the test period. In general it can be said, that there are distinct types of temporal structures in feeding behaviour in ducks. Age-depending changes appear mainly in the early fattening phase up to 5 weeks of age. There is no general meal criterion in ducks which may be applied to all individuals and at all ages. Feed intake underlies rhythmic processes which are modified with age.