Experimental Brucella ovis infection in pregnant ewes.

Forty yearling Brucella-free ewes were inoculated with Brucella ovis by the conjunctival route in mid or late first pregnancy. Only a few ewes excreted B ovis during pregnancy and gave birth to stillborn lambs, but most of them excreted the organism at lambing or during lactation. One of the 11 lambs which were born alive but died before they were weaned was found to be infected postmortem. In contrast, none of the 46 surviving lambs which were reared in isolation until adulthood, was found to be infected. At weaning, the 40 ewes were mated again with five Brucella-free rams. Although many of the ewes excreted B ovis, none of the rams was found to be infected when necropsied after mating. Most of the ewes that became pregnant, all having excreted B ovis during their first pregnancy, cleared the infection during the second pregnancy. However, three remained persistently infected and excreted B ovis in their milk throughout the second lactation. None of the lambs born to these three ewes was found to be infected when necropsied at weaning.     

Iodine application affects nitrogen-use efficiency of lettuce plants (Lactuca sativa L.)

Abstract

The main objective of this work was to determine whether nitrogen-use efficiency was affected by the application of different forms (iodide vs iodate) and dosages (20, 40 and 80 µM) of iodine, to ascertain the influence of this trace element in a biofortification programme in lettuce plants. The parameters analysed were root and shoot biomass, nitrate concentration, and organic and total nitrogen as well as those defining nitrogen-use efficiency in plants: total nitrogen content, total nitrogen accumulation, nitrogen-uptake efficiency and nitrogen-utilization efficiency. In addition to decreasing shoot biomass, iodide treatments reduced leaf levels of nitrates, organic nitrogen, and total nitrogen content. Iodate treatments did not affect the concentration of nitrogen in its different forms. The application of iodide caused total nitrogen accumulation and nitrogen-uptake efficiency to decrease, iodate application improved the latter. Both iodide and iodate applications significantly improved nitrogen-utilization efficiency in comparison to the control. The results obtained show that iodate application rates of 40 µM or lower significantly improved all nitrogen parameters analysed, making it possible to increase lettuce productivity and quality.     

Correlated response in litter size components in rabbits selected for litter size variability

A divergent selection experiment for the environmental variability of litter size (Ve) over seven generations was carried out in rabbits at the University Miguel Hernández of Elche. The Ve was estimated as the phenotypic variance within the female, after correcting for year‐season and parity‐lactation status. The aim of this study was to analyse the correlated responses to selection in litter size components. The ovulation rate (OR) and number of implanted embryos (IE) in females were measured by laparoscopy at 12 day of the second gestation. At the end of the second gestation, the total number of kits born was measured (TB). Embryonic (ES), foetal (FS) and prenatal (PS) survival were computed as IE/OR, TB/IE and TB/OR, respectively. A total of 405 laparoscopies were performed. Data were analysed using Bayesian methodology. The correlated response to selection for litter size environmental variability in terms of the litter size components was estimated as either genetic trends, estimated by computing the average estimated breeding values for each generation and each line, or the phenotypic differences between lines. The OR was similar in both lines. However, after seven generations of selection, the homogenous line showed more IE (1.09 embryos for genetic means and 1.23 embryos for phenotypic means) and higher ES than the heterogeneous one (0.07 for genetic means and 0.08 for phenotypic means). The probability of the phenotypic differences between lines being higher than zero (p) was 1.00 and .99, respectively. A higher uterine overcrowding of embryos in the homogeneous line did not penalize FS; as a result, this line continued to show a greater TB (1.01 kits for genetic means and 1.30 kits for phenotypic means, p = .99, in the seventh generation). In conclusion, a decrease in litter size variability showed a favourable effect on ES and led to a higher litter size at birth.     

Fate of plasma glucose in tissues of brown trout in vivo: effects of fasting and glucose loading

We report the fate of glucose, both as a source of energy and as a temporary store, in the tissues of brown trout (Salmo trutta) in control, fasted and glucose-loaded fish. Tissue glucose utilization (³H-2-deoxyglucose phosphorylation) and storage (conversion of ¹⁴C-glucose into glycogen, protein, and lipid) were measured in immature brown trout, and the oxidation rate was calculated as glucose utilization minus storage and ¹⁴C-ionic metabolites remaining in the tissue. The glucose utilization rate is tissue-specific, the highest values being found in spleen, kidney, hindgut, brain, and gill. All these tissues also showed a highly active glycolytic pathway. The lowest utilization indices were observed in white and red muscles, skin, stomach and caeca, which also presented the largest proportion of glucose converted into stores (mainly protein and glycogen). Fasting reduced the glucose disappearance rate by 24%, although there were no significant variations in glucose utilization indices or distribution profile. After a glucose load, plasma glucose and insulin levels rose and the rates of glucose utilization, storage, and oxidation also increased in all tissues (from 1.5- to 4-fold). The relative importance of each tissue in glucose disposal was similar to that in normoglycaemia. In liver, only glucose storage was measured reliably; the conversion of glucose to glycogen was higher than in other tissues, and rose markedly (35-fold) in glucose-loaded fish. In most tissues glucose flux into lipids, glycogen and protein increased. The distribution of glucose may not be a merely substrate-mediated process because fasting in glucose-loaded fish caused lower tissue glucose utilization, particularly in gut, red muscle and gills. Conversion of glucose to tissue stores was reduced, lipids being the most affected.     

Effect of selection for growth rate on relative growth in rabbits

The effect of selection for growth rate on relative growth of the rabbit body components was studied. Animals from the 18th generation of a line selected for growth rate were compared with a contemporary control group formed with offspring of embryos that were frozen at the seventh generation of selection of the same line. A total of 313 animals were slaughtered at 4, 9, 13, 20, and 40 wk old. The offal, organs, tissues, and retail cuts were weighed, and several carcass linear measurements were recorded. Huxley's allometric equations relating the weights of the components with respect to BW were fitted. Butterfield's quadratic equations relating the degree of maturity of the components and the degree of maturity of BW were also fitted. In most of the components studied, both models lead to similar patterns of growth. Blood was isometric or early maturing and skin was late maturing or isometric depending on the use of Huxley's or Butterfield's model. Full gastrointestinal tract, liver, kidneys, thoracic viscera, and head were early maturing, and the chilled carcass and reference carcass were late maturing. The retail cuts of the reference carcass showed isometry (forelegs) or late maturing growth (breast and ribs, loin, hind legs, and abdominal walls). Dissectible fat of the carcass and meat of the hind leg had a late development, whereas bone of the hind leg was early maturing. Lumbar circumference length was later maturing than the carcass length and thigh length. Sex did not affect the relative growth of most of the components. Butterfield's model showed that males had an earlier development of full gastrointestinal tract and later growth of kidneys than females. No effect of selection on the relative growth of any of the components studied was found, leading to similar patterns of growth and similar carcass composition at a given degree of maturity after 11 generations of selection for growth rate.     

Predicting the growth of gilthead sea bream (Sparus aurata L.) farmed in marine cages under real production conditions using temperature- and time-dependent models

The growth of gilthead sea bream ( Sparus aurata ) has been studied considering five multiple exponential regression models using data from 20 lots of gilthead sea bream growing in 20 marine cages from a Mediterranean commercial fish farm. The final weight ( W _f) of fish was predicted in relation to the initial weight ( W _i), time ( n ) and temperature ( T ), or the sum of effective temperatures (∑ T _ef). The estimated weight results from the simulation using the five models have been compared with the real final weight values using the mean of the absolute values of the prediction errors in short and long term (the precision value). All models presented a high determination coefficient, above 96%, and good prediction values in the short term. Regression models were tested using data from six new cages. The best models for predicting the growth of sea bream long term were the ones where final weight is expressed in relation to the initial weight and the sum of effective temperature,     and     obtaining long-term prediction errors 12.9% and 10.7% respectively.     

Comparison of different nonlinear functions to describe Nelore cattle growth

This work aims to compare different nonlinear functions for describing the growth curves of Nelore females. The growth curve parameters, their (co)variance components, and environmental and genetic effects were estimated jointly through a Bayesian hierarchical model. In the first stage of the hierarchy, 4 nonlinear functions were compared: Brody, Von Bertalanffy, Gompertz, and logistic. The analyses were carried out using 3 different data sets to check goodness of fit while having animals with few records. Three different assumptions about SD of fitting errors were considered: constancy throughout the trajectory, linear increasing until 3 yr of age and constancy thereafter, and variation following the nonlinear function applied in the first stage of the hierarchy. Comparisons of the overall goodness of fit were based on Akaike information criterion, the Bayesian information criterion, and the deviance information criterion. Goodness of fit at different points of the growth curve was compared applying the Gelfand's check function. The posterior means of adult BW ranged from 531.78 to 586.89 kg. Greater estimates of adult BW were observed when the fitting error variance was considered constant along the trajectory. The models were not suitable to describe the SD of fitting errors at the beginning of the growth curve. All functions provided less accurate predictions at the beginning of growth, and predictions were more accurate after 48 mo of age. The prediction of adult BW using nonlinear functions can be accurate when growth curve parameters and their (co)variance components are estimated jointly. The hierarchical model used in the present study can be applied to the prediction of mature BW in herds in which a portion of the animals are culled before adult age. Gompertz, Von Bertalanffy, and Brody functions were adequate to establish mean growth patterns and to predict the adult BW of Nelore females. The Brody model was more accurate in predicting the birth weight of these animals and presented the best overall goodness of fit.     

Analysis of beef cattle longitudinal data applying a nonlinear model

The objective of this work was to evaluate the Nelore beef cattle, growth curve parameters using the Von Bertalanffy function in a nested Bayesian procedure that allowed estimation of the joint posterior distribution of growth curve parameters, their (co)variance components, and the environmental and additive genetic components affecting them. A hierarchical model was applied; each individual had a growth trajectory described by the nonlinear function, and each parameter of this function was considered to be affected by genetic and environmental effects that were described by an animal model. Random samples of the posterior distributions were drawn using Gibbs sampling and Metropolis-Hastings algorithms. The data set consisted of a total of 145,961 BW recorded from 15,386 animals. Even though the curve parameters were estimated for animals with few records, given that the information from related animals and the structure of systematic effects were considered in the curve fitting, all mature BW predicted were suitable. A large additive genetic variance for mature BW was observed. The parameter a of growth curves, which represents asymptotic adult BW, could be used as a selection criterion to control increases in adult BW when selecting for growth rate. The effect of maternal environment on growth was carried through to maturity and should be considered when evaluating adult BW. Other growth curve parameters showed small additive genetic and maternal effects. Mature BW and parameter k, related to the slope of the curve, presented a large, positive genetic correlation. The results indicated that selection for growth rate would increase adult BW without substantially changing the shape of the growth curve. Selection to change the slope of the growth curve without modifying adult BW would be inefficient because their genetic correlation is large. However, adult BW could be considered in a selection index with its corresponding economic weight to improve the overall efficiency of beef cattle production.