Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 21

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
A four-generation study with at least 60 laying hens (LSL) and 10 cockerels (LSL) was carried out to investigate the influence of genetically modified maize (Bt 176) on animal health and feed intake, laying performance, feed efficiency, and hatchability of chickens and to compare GM-maize with its near isogenic counterpart. The chickens were divided into two groups (one pen/group) of at least 30 hens each and 3 cockerels. The diets contained 400 (chickens and pullets) or 500 g · kg–1 (laying hens) isogenic or genetically modified maize (Bt 176), respectively. Feed and water were provided ad libitum. Eggs for hatching were collected when the laying hen was aged 31 weeks. In the 31st week of life, brooding eggs were collected and brooded for every group. One-day-old chickens from each group were sex sorted and allocated to one pen per group. There were no significant differences in composition between the two maize varieties. For every generation, as well as the average of all four generations, there was no significant influence on the feed intake of chickens (32.2 and 32.0 g per day), pullets (68.4 and 70.4 g per day) and layers (114.9 and 112.9 g per hen per day for control and Bt-maize), body weight of chickens (652 and 636 g), pullets after 18 weeks (1316 and 1305 g), and laying hens after 31 weeks (1656 and 1626 g for control and Bt-maize), laying intensity (83.5% and 83.3%), fertility of eggs (96.6% and 97.5%), or hatchability of living chicks (86.8% and 88.0% for control and Bt-maize). In conclusion, feeding of 400 (grower) or 500 g · kg–1 (layer period) Bt-maize to chickens, pullets and laying hens for four generations did not significantly influence feed intake, growth, laying or breeding performance compared with an isogenic counterpart.
The world´s population is still growing up and asking for more and better food. High yielding plants with low external inputs should be the main aim of plant breeding to meet the higher demand for man and animal. Apart from traditional breeding plant biotechnology seems to have a certain potential to contribute to this objective. Safety and nutritional studies with such modified plants are the most important prerequisites for public acceptance of derived feed and food. The first step for safety and nutritional assessment of modified plants is the compositional analysis of potential food/feed and including the newly expressed proteins and other new constituents and the comparison with conventional counterparts. In vitro studies and experiments with laboratory animals are the next steps for assessments. Feeding studies with target animals are of special concern for nutritional assessment and are considered in more detail in the present paper.
Sustainability in relation to the human food chain is defined as the global balance/equilibrium between efficient use of limited natural resources (such as arable land, water, fuel, etc.), emissions (e.g., carbon dioxide, methane, nitrous oxide (laughing gas), etc.), and socio-economic and ethical aspects as a basis for the existence of future generations. Sustainability in the production of food of animal origin or edible protein necessitates efficient production. Efficiency calculations should not be limited to only the food chain links ‘feed—animal—food of animal origin’, but should include the entire food chain. A system has the highest efficiency or the greatest sustainability if it is impossible to improve one parameter without deterioration of one or more of the other parameters. The present review is divided into two parts. In the first, the authors define the term sustainability and the objective of the paper. Protein of animal origin is the main topic and is the focus of the chapters regarding resource inputs in the form of arable land, water, fuel, etc., and outputs in form of animal yields and emissions such as carbon dioxide, methane and laughing gas. Carbon Footprints (CF) as an ‘overall measure of emissions’ are defined.
This part describes challenges to improving sustainability during the production of food of animal origin. Some potential advancements in the sustainability of producing food of animal origin, such as feeds that do not compete with human nutrition, plant and animal breeding, trends in animal nutrition, potential alternative protein sources, alternatives of animal products in nutrition, including lower food losses, are discussed in the paper. The potential for reducing gaseous emissions is also an important chapter in this contribution. Complex calculations employing parameters of efficient use of limited resources and reduction of emissions seem to be helpful in finding optimums in production of food of animal origin.
Feed-efficient ruminant production is a key topic in the further development of ruminant husbandry all over the world. Ruminants contribute substantially to human nutrition by production of milk and meat. They are also extremely useful for mankind by providing other important products and labour, such as skins, clothing, bones, dung, heating material, and working as draft animals, etc. The microorganisms in the rumen of ruminants are able to process lignocellulose from low quality roughage into volatile fatty acids and energy, to transfer non-protein nitrogen, such as urea, into microbial protein, and to synthesize B vitamins. Therefore, ruminants are able to produce food of animal origin without competition for feed with non-ruminants and man. On the other hand, gas methane (CH4 ) with a high greenhouse gas potential is an unavoidable by-product of rumen fermentation. Furthermore, growing ruminants are characterized by a low growing potential (daily yield in edible protein < 0.05% of body weight). The objectives of ruminant breeding, nutrition and keeping/management should, therefore, be to maximize/optimize the advantages of ruminants and to minimize their disadvantages. Feed-efficient ruminant production is viewed as a complex system starting with plant and animal breeding. More systemic approaches are considered necessary to understand interactions and to find acceptable solutions for complex relationships in the context of food security, resource efficiency, as well environmental, social and economic aspects.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.