Post‐grazing cutting management in tall fescue affects the sward structure,forage and liveweight production

Tall fescue is the main perennial grass of the pastures of the temperate region of Argentina. However, after flowering in spring, tall fescue loses productivity and quality. Based on this, the objective of this work was to evaluate the effects of different post‐grazing mechanical cutting managements on the forage mass, leaf proportion, stocking rate, liveweight gain and liveweight production of tall fescue pastures. The treatments were post‐grazing mechanical cutting at anthesis (FC), post‐grazing mechanical cutting throughout spring and summer (SSC), and no post‐grazing mechanical cutting (NC). The experiment was performed from 2011 to 2014 in Argentina. The greatest and lowest forage mass were determined in September–November and May–September respectively. The leaf proportion of the SSC treatment was greater than that of the NC treatment, except in September–November. NC had higher stocking rate and lower liveweight gain than SSC, and neither NC nor SSC differed from FC. The liveweight production of the treatments was characterized by a trade‐off between stocking rate and liveweight gain. We conclude that FC is an attractive management because, with a single post‐grazing cutting, swards remain productive and leafy.     

School food in Mexican children

OBJECTIVE: To establish the school eating habits of Mexican children, who are prone to obesity and later to high rates of adult chronic diseases. DESIGN: Questionnaires for students and parents with staff questionnaires and interviews. SETTING: Randomly sampled schools in a socio-economically representative district of Mexico City. SUBJECTS: Subjects were 1504 adolescents aged 10-19 years attending schools in Mexico City, 27 teachers and seven headmasters, sampled from both public and private schools and from the full range of socio-economic groups. RESULTS: Foods brought from home were of a higher nutritional quality than those purchased at school, where purchases were dominated by crisps, soft drinks and other items with high energy density. Girls were more inclined to purchase inappropriately; those from poorer homes purchased less. Private-school students irrespective of socio-economic grade brought more food from home and purchased more expensive food at school. School policies allowed food and drink vendors to market any products within the schools, which benefited financially from these activities. CONCLUSIONS: Current school food policies are conducive to amplifying the current epidemic of obesity and related adult chronic diseases, and need to change.     

Screening for resistance to Diaporthe toxica in lupins by estimation of phomopsins and glucoseamine in individual plants

Immunological and biochemical assays were developed for screening for resistance to Diaporthe toxica in individual plants of narrow-leafed lupins ( Lupinus angustifolius ). The former was an enzyme-linked immunosorbent assay (ELISA) for measuring phomopsin mycotoxins and the latter gave an estimation of glucoseamine in infected stem pieces. Stems of L. angustifolius seedlings were inoculated with conidia from D. toxica cultures and, as expected with this latent disease, remained symptomless for 21 days after inoculation. At this time, phomopsins were measured in excised stems that had been incubated for 6 or 8 days to allow mycelial growth from latent infection structures, thereby increasing the phomopsins to detectable levels in individual plants. The estimation of glucoseamine was carried out on the same stems that had been assayed for phomopsins. The method was based on the alkaline deacetylation of chitin to chitosan, the glucoseamine residues of which are de-aminated with nitrous acid, yielding an aldehyde which is determined colorimetrically. At six days after excision, both tests clearly distinguished the very resistant, resistant, intermediate and susceptible lines and they may be useful in large-scale resistance screening in lupin breeding programmes. The ELISA of phomopsins is easier to use and would be particularly useful in the elimination of susceptible plants and those plants expressing intermediate levels of resistance during early generations of the breeding programme.     

Lime-induced growth depression in Lupinus species: Are soil pH and bicarbonate involved?

In a series of experiments, the effect of elevated pH on root growth of different lupin genotypes and lime-tolerant Pisum sativum was assessed. Seedlings were cultivated in pH-controlled but unbuffered nutrient or test solutions with pH 5—8 under constant light or constant darkness. Moderately increased solution pH did not affect root elongation. At high pH, root elongation rates were reduced by less than 35%, L. luteus being most sensitive. In a further experiment, effects of 10 mM bicarbonate (HCO₃^-) and organic buffers (MES, TES) were examined. Bicarbonate severely affected root elongation of lupins, sensitivity increasing in the order Lupinus albus < L. angustifolius < L. luteus. Since the reduced root elongation was not accompanied by a decreased root weight, specific root weight was increased. Shoot growth was not affected by HCO₃^-. Addition of organic buffers to alkaline nutrient solution, similarly to HCO₃^-, reduced elongation of main roots, but not that of laterals. Both treatments increased citrate concentrations in roots of sensitive L. luteus, but not of tolerant L. albus. Other carboxylates were not related to growth inhibition. Xylem exudate pH was always below 5.8, indicating that HCO₃^- was probably not translocated to the shoot. It is concluded that HCO₃^- is a key factor for lime-induced growth inhibition of calcifuge lupins, with the roots, not the shoots, being primarily affected.     

Lipid metabolism in juveniles of Yellowtail,Seriola dorsalis,fed different levels of dietary methionine containing a low level of cholesterol: Implication in feed formulation

The involvement of dietary methionine in the lipid metabolism of Seriola dorsalis, at different levels of dietary methionine (Met), and low content of cholesterol was investigated. Four diets containing different Met levels and a low amount of cholesterol (0.23 g/kg diet) were prepared. One hundred and eighty juveniles (16.2 ± 1.5 g) were randomly distributed into each 12 500‐L ponds. After 60 days, the growth in weight (%) significantly increased following the Met supplementation, whereas SGR of all the experimental treatments was higher than the Basal Diet. The expression of the insulin‐like growth factor (IGF‐1) increased significantly (0.2‐fold) and was complemented by significant changes in Mat, BHMT and HMG‐CoA, for fish that were in the low and higher Met levels. The cholesterol content in the whole body and liver increased following methionine supplementation, similarly to that observed for crude lipids, in particular in the whole body and liver tissues. However, the relative amount of most fatty acids remained unchanged. Only the oleic acid increased at a higher amount of Met. Therefore, once the dietary requirement of methionine is met, the methionine is used to synthesize cholesterol. It is recommended to supply a higher amount of methionine to spare energy for growth.