Physiological processes associated with salinity tolerance in an alfalfa half‐sib family

We previously reported an alfalfa half‐sib family, HS‐B, with improved salt tolerance, compared to parental plants, P‐B. In this study, we conducted additional experiments to address potential physiological mechanisms that may contribute to salt tolerance in HS‐B. Vegetatively propagated HS‐B and P‐B plants were treated with a nutrient solution (control) or a nutrient solution containing NaCl (EC = 12 dS/m). Shoots and roots were harvested at various time points after treatment for quantification of proline, soluble sugar, and H₂O₂ using spectrophotometers. Subcellular localization and quantification of Na in roots were conducted using a Na⁺‐specific dye under a confocal microscope. HS‐B produced 86 and 89% greater shoot and root dry biomass, respectively, compared to parental plants, P‐B, under salinity in the greenhouse. Under saline conditions the HS‐B shoots accumulated 115% and roots 55% more soluble sugars than P‐B counterparts. The non‐saline HS‐B shoots, however, showed 72% less soluble sugars than the non‐saline P‐B plants. Under saline conditions HS‐B accumulated 39% less proline in shoots, while roots accumulated 56% more proline, compared to their P‐B parents. HS‐B plants also showed a greater reduction of stomatal conductance under mild saline stress. HS‐B shoots and roots contained 3–4 times less reactive oxygen species (H₂O₂) after salt treatment compared to P‐B plants. Sodium localization and distribution analysis using Na⁺‐specific dye revealed HS‐B plants accumulated 88% and 48% less Na⁺ in stele and xylem vessels compared to P‐B. The study provides insights into the potential mechanisms that may contribute to salt tolerance in HS‐B: maintaining RWC by accumulating soluble sugars while reducing transpiration, maintaining healthy status by reducing oxidative stresses, and preventing salt toxicity by reducing accumulation of Na⁺ inside root cells and xylem.     

Validation of the periodicity of growth zone formation in the otoliths of four fish species from the Upper Zambezi ecoregion,southern Africa

In the Upper Zambezi and Okavango ecoregions, Brycinus lateralis, Hepsetus cuvieri, Schilbe intermedius and Serranochromis macrocephalus are important in subsistence fisheries, while S. intermedius and S. macrocephalus are often caught in commercial catches. Despite their importance, there is little information on their age and growth and age validation. Growth zone deposition rate in otoliths of B. lateralis, H. cuvieri, S. intermedius and S. macrocephalus was validated as annual using edge analysis in this study. Annual deposition of growth zones was corroborated by a fluorochrome marking experiment. Both methods demonstrated that one growth zone was deposited annually. Edge analysis demonstrated that the highest proportion of opaque zones was detected between August and December, most likely as a result of slow growth during lower temperature water during the preceding winter. With growth zone deposition validated as annual, future research should focus on determining the growth, maturity and mortality rates of these species, parameters which are important for their management.     

Tall fescue forage mass in a grass-legume mixture: predicted efficiency of indirect selection

High fertilizer prices and improved environmental stewardship have increased interest in grass-legume mixed pastures. It has been hypothesized, but not validated, that the ecological combining ability between grasses and legumes can be improved by breeding specifically for mixture performance. This experiment examined the predicted efficiency of selection in a grass monoculture environment to indirectly improve tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) forage mass in a grass-legume mixture. Heritability, genetic and rank correlations, and selection efficiencies were estimated for forage mass in a tall fescue half-sib population grown as spaced-plants overseeded with either turf-type tall fescue (monoculture) or alfalfa (mixture). Heritability for tall fescue forage mass in monoculture ranged from 0.32 to 0.70 and were always similar or greater than those in mixture (range 0.27–0.55) for four successive harvests and annual total. Genetic correlations between monoculture and mixture tall fescue forage mass varied with values of 0.48, 0.92, ?0.31, 0.70, and 0.25 in June, July, August, October, and annual total, respectively. Indirect selection efficiencies exceeded or approached direct selection for mixtures only in July and October (1.29, and 0.73, respectively). Whereas, indirect selection efficiencies were low in June, August, and annual forage mass (0.58, ?0.31, and 0.28, respectively). Moreover, low Spearman’s rank correlations (?0.03 to 0.35) indicated differing half-sib family performance between the monoculture and mixture environments. Results indicate that direct selection should be used to improve tall fescue forage mass in a grass-legume mixture, and support the hypothesis of increasing ecological combining ability by breeding for mixtures per se.     

Successful treatment of traumatic oesophageal rupture with severe cellulitis in a mare

A five-year-old standardbred mare suffered a cervical oesophageal rupture subsequent to a kick. Marked cellulitis and extensive soft tissue damage resulted. Treatment consisted of creating an oesophageal fistula, local debridement and systemic antibiotics. The mare made a long but successful recovery. Treatment of oesophageal rupture in the horse is discussed.     

A STUDY OF THE NUMBER AND PHAGE PATTERNS OF STAPHYLOCOCCUS AUREUS IN AN ABATTOIR

Two hundred and forty-seven samples were taken from various areas within an abattoir and the levels of Staphylococcus aureus determined. Sixty-one phage patterns were found in the 141 samples containing coagulase-positive staphylococci. The incidence of coagulase positive staphylococci increased as processing progressed. Articles such as mesh gloves, hands and aprons which were either difficult to effectively clean or maintained at elevated temperatures harboured the greatest numbers of staphylococci. Over 50% of the positive samples contained multiple phage patterns of staphylococci.     

BACTERIAL PENETRATION IN FLOOR AND NEST BOX EGGS FROM MEAT AND LAYER BIRDS

A method similar to that used by Board and Board (1967) was used to determine the numbers of eggs penetrated by bacteria on 3 poultry farms in south-east Queensland. Significant differences in the percentages of penetrated eggs between the eggs of layer birds (9.7%) and the eggs of meat birds (16.1%) and between nest eggs (10.5%) and floor eggs (15.3%) were detected. The distribution of the numbers of penetration points was similar for nest and floor eggs for both types of bird and was independent of shell surface area or thickness.     

Determinants of herbaceous plant species composition on a number of ranches in the north‐western Transvaal

Herbaceous plant species composition was measured on ranches in the Thabazimbi district, Transvaal, to obtain veld composition scores and to quantify the relations between such scores and certain determinants considered important in influencing species composition. Determinants investigated were mean annual rainfall and herbivory (stocking rate). The survey was undertaken on seven game and cattle ranches in Combretum apiculatum woodland of the Mixed Bushveld (Acocks 18) of the north‐western Transvaal. Rainfall for the season preceding the vegetation survey and bulk and selective grazer stocking rates had a significant effect on veld composition scores. The recommended agricultural grazer stocking rate for the survey area is 12.5 LSU 100 ha"¹ a"¹. Under the present conditions and in view of the findings of this survey, it is suggested that a grazer stocking rate of 6.25 LSU 100 ha^?1 a^?1 be implemented.     

Perspective article: The evolving use of stocking rate indices currently based on animal number and type in semi‐arid heterogeneous landscapes and complex land‐use systems

Abstract

Methods of determining stocking rate based on metabolic mass, animal type and biomass are reviewed in the context of equilibrial/disequilibrial paradigms. In South Africa, the calculation of ‘carrying capacity’ is based on conversion of animal species to metabolic mass equivalents. This assumes homogenous systems that tend to some point of equilibrium. It is applied widely in commercial livestock systems involving one or two species. Examination of a case study in the Lowveld of the Northern Province, South Africa, showed that the determination of ‘stocking rate’ in this multi‐herbivore and heterogenous system, overestimated the ‘carrying capacity’ of the reserve over 20 years. The actual animal numbers in the system dropped by approximately 4 000 kg km^?2 after a drought in the early period of the study into the bounds as determined by a model incorporating rainfall and animal biomass. An approach to determine stocking density using animal type, biomass, rainfall and vegetation parameters is suggested. The development of this as a coarse‐scale (regional) and ranch‐specific model to cover a range of scales and heterogeneity in key resources is advocated.     

Evaluation of the dose–response relationship of oral robenacoxib in urate crystal‐induced acute stifle synovitis in dogs

The objective of the study was to establish the dose–response relationship for robenacoxib, a selective cyclooxygenase (COX)‐2 inhibitor, in a urate crystal model of acute synovitis. In a randomized partial Latin square design trial, 12 beagle dogs were administered orally single doses of robenacoxib (0.5, 1, 2, 4 and 8 mg/kg), placebo and the positive control meloxicam (0.1 mg/kg), 3 h after injection of sodium urate crystals into a stifle joint. Dogs were assessed for weight bearing on a force plate and by subjective clinical orthopaedic observations. Robenacoxib produced dose‐dependent improvement in weight bearing, and decreased pain on palpation and joint swelling, over the dose range 0.5–2 mg/kg with no further increase in effect over the range 2–8 mg/kg. For weight bearing on the force plate, the ED₅₀ of robenacoxib was 0.6–0.8 mg/kg. The onset of action and time to peak effect of robenacoxib were faster (respectively, 2–2.5 h and 3–5 h) than for meloxicam (respectively, 3 h and 6 h). Robenacoxib significantly inhibited COX‐2 at all doses, with dose‐related activity. Robenacoxib did not inhibit COX‐1 over the dose range 0.5–4 mg/kg, but produced transient inhibition at 8 mg/kg. In conclusion, oral administration of robenacoxib over the dose range 0.5–8 mg/kg demonstrated significant analgesic and anti‐inflammatory efficacy in dogs.     

Establishment of warm‐season grasses in summer and damage in winter under supplementary irrigation in a semi‐arid environment at high elevation in western United States of America

As with other areas of the world, herbage production of cool‐season grasses in irrigated semi‐arid areas of the western USA at high elevation declines during summer. The use of warm‐season grasses during this period could be a possible way to ameliorate this decline in herbage production. The ability of twenty‐one grass cultivars, representing seven warm‐season grass species, to establish in the summer of 2005, as measured by stand frequency and herbage production, the potential for damage in winter under irrigated conditions in 2005–2006 and the stand frequency in 2006 at two sites in semi‐arid environments of the western USA was compared with that of a cultivar of each of six cool‐season grass species. Some warm‐season grass species, including switchgrass (Panicum virgatum), showed potential for use in this environment, based on their similar herbage production in 2005 and similar values of stand frequency in 2005 and 2006 to that of cool‐season grasses. All the cultivars of the warm‐season grass species suffered greater winter damage than did the cultivars of the cool‐season species. The higher winter damage to the species of warm‐season grasses did not correspond with a lower stand frequency in the second year.