A model of the effect of nutrition on litter size and weight in the pregnant ewe

A model has been developed to predict litter size, lamb birthweight, perinatal lamb mortality and ewe weight change during the second part of pregnancy from different nutritional regimes. The model, which can contain 200 ewes, has been tested against field data from experimental flocks of Masham, Finn × Scottish Halfbred and Welsh Mountain ewes. The prediction of litter size from weight at mating is reasonable as is the prediction of mean lamb birthweight for a range of litter sizes. The model currently overestimates the weight of Finn × S. Halfbred singles, and underestimates ewe weight increase in late pregnancy and the mortality of lambs from some litter sizes.The problem of predictive accuracy is discussed and weighed against the task of collecting a great deal of data. The problem with a predictive reproductive model is that reproductive performance is a breed characteristic whereas nutritional demand can be predicted from size and physiological state.     

Genetic parameters relating isoflavone and protein content in soybean seeds

Isoflavones are a class of compounds present in high amounts in soybean seeds, which can be used for prevention and treatment of several chronic diseases. Proteins present in soybean seeds are the basis for the high nutritional value and versatility of this leguminous species in animal and human feeding. The main goals of this work were to estimate heritabilities for isoflavone contents in soybean seeds and the correlation between isoflavone and protein contents. Commercial variety IAC-100 (high isoflavone and normal protein contents) and the line BARC-8 (low isoflavone and high protein contents) were crossed, and one single F₁ plant derived 97 F₂ seeds, which were used to obtain F₃ seeds. A sample of F₃ seeds from each F₂ plant was used for isoflavone determination by HPLC and protein by the Kjeldahl method. Six isoflavone forms were detected: daidzin, genistin, glycitin, malonyldaidzin, malonylgenistin and malonylglycitin. Total isoflavone contents ranged from 427.92 to 965.89 μg per gram of dry seed and the protein content ranged from 45.17 to 34.95% in BARC-8 and IAC-100, respectively. Our results indicate that it is possible to select for high isoflavone content in early breeding generations because the broad sense heritabilities for the contents of the various isoflavone forms were higher than 90%. In addition, high correlation values among the contents of the individual isoflavone forms were observed (between 0.80 and 0.98). However, negative correlation values were obtained between isoflavone and protein contents, ranging from −0.51 to −0.37 for the different isoflavone forms. The correlation value of −0.47 between total isoflavone and protein contents confirmed the negative correlation between these two parameters, as reported by other authors. This revised version was published online in August 2006 with corrections to the Cover Date.     

Bacteriophages with potential for inactivation of fish pathogenic bacteria: survival, host specificity and effect on bacterial community structure

Phage therapy may represent a viable alternative to antibiotics to inactivate fish pathogenic bacteria. Its use, however, requires the awareness of novel kinetics phenomena not applied to conventional drug treatments. The main objective of this work was to isolate bacteriophages with potential to inactivate fish pathogenic bacteria, without major effects on the structure of natural bacterial communities of aquaculture waters. The survival was determined in marine water, through quantification by the soft agar overlay technique. The host specificity was evaluated by cross infection. The ecological impact of phage addition on the structure of the bacterial community was evaluated by DGGE of PCR amplified 16S rRNA gene fragments. The survival period varied between 12 and 91 days, with a higher viability for Aeromonas salmonicida phages. The phages of Vibrio parahaemolyticus and of A. salmonicida infected bacteria of different families with a high efficacy of plating. The specific phages of pathogenic bacteria had no detectable impact on the structure of the bacterial community. In conclusion, V. parahaemolyticus and A. salmonicida phages show good survival time in marine water, have only a moderated impact on the overall bacterial community structure and the desired specificity for host pathogenic bacteria, being potential candidates for therapy of fish infectious diseases in marine aquaculture systems.