An experiment was conducted to evaluate the effects of dietary boron (B) on growth performance, bone mechanical properties, and calcium (Ca) and phosphorus (P) metabolism in pigs. Thirty-six barrows were weaned at approximately 21 d of age and randomly assigned to receive one of three dietary treatments. Treatments consisted of 1) low-B basal diet (control), 2) basal + 5 mg B/kg diet, and 3) basal + 15 mg B/kg diet. Boron was supplemented as sodium borate. Barrows remained on their respective experimental diets throughout the nursery (35 d) and growing (30 d) phases of production. Blood samples were obtained from each barrow at the end of each phase. Following the 30-d growing period, eight barrows per treatment were transferred to stainless steel metabolism crates. Barrows had an adjustment period of 7 d, followed by a 7-d total collection of urine and feces. All barrows were fed at 90% of the previous ad libitum grower intake of the control animals during the adjustment and collection periods. At the end of the 7-d collection period, barrows were killed and femurs and fibulas were harvested for the assessment of bone mechanical properties. During the nursery phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.34) feed efficiency during the nursery phase. During the growing phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.97) feed efficiency during the growing phase. Boron did not affect (P = 0.44) bone ash percentage, but B supplementation increased (P < 0.05) bone ash P. Ultimate shear force of the fibula was increased (P < 0.05) in barrows supplemented with 15 mg B/kg diet compared to barrows fed diets supplemented with 5 mg B/kg diet. Apparent absorption and retention of Ca and P were not affected (P > 0.05) by dietary B. These data indicate that B supplementation to pigs can increase growth and bone strength without greatly affecting Ca and P metabolism. 相似文献
Recent Advances in Turkey Science. Edited by C. Nixey and T. C. Grey, Poultry Science Symposium Number 21. London, Butterworths, ISBN 0 408 00971 3
Egg and Eggshell Quality. Sally E. Solomon, 1991, 149 pp., illustrated. London, Wolfe Publishing Ltd., £35.00, ISBN 0 7234 1647 8.
Aleen Cust, Veterinary Surgeon, Britain's First Woman Vet. Connie M. Ford, 1990, 109 pp., £5.99, Bristol, Biopress Ltd., The Orchard, Clanage Road, ISBN 0 948737 11 5.
Avian Incubation. Edited by S. G. Tullett, 1991, xiv + 335 pp., illustrated. London, Butterworth‐Heinemann. £00.00, $00.00. ISBN 0–7506–1002–6.
A Colour Atlas of Diseases & Disorders of the Domestic Fowl & Turkey. Edited by C. J. Randall, second edition, 1991, 175 pages, 432 illustrations in colour. London, Wolfe Publishing Ltd, £35, ISBN 0723416281. 相似文献
We studied the relationships of landscape ecosystems to historical and contemporary fire regimes across 4.3 million hectares in northern lower Michigan (USA). Changes in fire regimes were documented by comparing historical fire rotations in different landscape ecosystems to those occurring between 1985 and 2000. Previously published data and a synthesis of the literature were used to identify six forest-replacement fire regime categories with fire rotations ranging from very short (<100 years) to very long (>1,000 years). We derived spatially-explicit estimates of the susceptibility of landscape ecosystems to fire disturbance using Landtype Association maps as initial units of investigation. Each Landtype Association polygon was assigned to a fire regime category based on associations of ecological factors known to influence fire regimes. Spatial statistics were used to interpolate fire points recorded by the General Land Office. Historical fire rotations were determined by calculating the area burned for each category of fire regime and dividing this area by fifteen (years) to estimate area burned per annum. Modern fire rotations were estimated using data on fire location and size obtained from federal and state agencies. Landtype Associations networked into fire regime categories exhibited differences in both historical and modern fire rotations. Historical rotations varied by 23-fold across all fire rotation categories, and modern forest fire rotations by 13-fold. Modern fire rotations were an order of magnitude longer than historical rotations. The magnitude of these changes has important implications for forest health and understanding of ecological processes in most of the fire rotation categories that we identified.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
Abstract – Standard metabolic rate (SMR, closely related to basal and resting metabolism) varies by up to threefold among juvenile Atlantic salmon, Salmo salar L., of similar size at common temperature. Here, consequences of this variation are predicted by combining empirically derived relationships between SMR, specific dynamic action, energy budgets, water velocity, food level in the environment and food availability to fish. The range of velocities across which growth is predicted to occur is inversely related to a fish’s SMR. Growth is positively related to SMR at high but negatively related to it at low‐food levels. The relationship between food level and the range of velocities over which lower SMR fish can grow but higher SMR fish cannot is asymmetrically bi‐phasic and peaked. It is predicted that maternal manipulation of offspring SMR would generate fitness benefits through bet‐hedging against unpredictability in food level and increases in the overall range of velocities that the family of offspring can occupy and thrive in. 相似文献