Samples of threespine sticklebacks, Gasterosteus aculeatus (L.), collected in seawater at Halifax, Nova Scotia, were acclimated to six combinations of conditions at 10 and 20C and in 0, 12, and 30‰ salinity (S). Bioassays of 10 000 min were performed at various constant temperatures from 20 to 30C in the diallel combinations of acclimation and salinities of 0, 12, and 30‰. Highest upper lethal temperatures, corresponding to combinations of acclimation, occurred in isosmotic test salinity of 12‰. Upper lethal temperatures ranged in all tests from 28.76 to 21.63C. A 10-degree increase in thermal acclimation resulted in increases in upper lethal temperature ranging from −0.27 to 0.77 degrees in tests conducted at 12‰ S and increases ranging variously from 1.45 to 3.56 degrees in tests conducted at 0 and 30‰ S. Upper lethal temperatures were shifted significantly by the ambient salinity but not by salinity of acclimation. Within the range of total lengths, 30–80 mm, there were no significant differences in mean lengths of dead and surviving fish in relation to acclimation temperatures and test salinities. There was no rank-correlation between order of death and total length in 15 of 18 test combinations.

Sunflower silage (SS) is being promoted as an efficient forage for feeding dairy cattle in the face of shortages of irrigation and erratic rainfall. The objective was to compare, through the in vitro gas production technique, the kinetics of ruminal fermentation of SS and its mixtures with maize silage (MzS) to know its nutritional characteristics before its inclusion in feeding strategies. Five combinations of SS with MzS were assessed (MzS%: SS%); T1) 100:0, T2) 75:25, T3) 50:50, T4) 25:75 y T5) 0:100. Combining MzS with 25% SS decreased neutral detergent fiber and acid detergent fiber contents (P<0.05), which resulted in a digestibility of dry mather, organic matter, neutral detergent fiber and metabolizable energy similar to MzS (P>0.05), and with a CP content not statistically higher than MzS. The MzS had the highest total gas production (GP) but at a lower fermentation rate (P<0.05) when compared to T2 that had a better fermentation rate of 0.0530 %/h, with Lag time of 3.4 h. Before ensiling, sunflower supplies 31.8 % more CP, 11.8 % less metabolizable energy and 11.9 % less in vitro digestibility of organic matter than maize plant. Compared to T1, the T2 supplied 1.6 % more crude protein, 2 % less metabolizable energy and 4.4 % less of in vitro digestibility of organic matter. Therefore it is concluded that sunflower silage could be an alternative to substitute up to 25 % of maize silage as the crude protein and metabolizable energy supply are similar to maize silage.

An accounting analysis was performed on the evolution and performance of productive, economic and marketing strategies implemented by small-scale dairy farmers in the peri-urban area of Texcoco, Mexico. Economic and production records for 1 023 lactation were obtained in two periods, 2000 and 2012. The general cost methodology was used to establish the accounting structures of these production systems, and the re-adjustment of values financial methodology through calculating deflated values based on data from the Mexican National Index of Consumer Prices. Evidence is presented that farmers in Stratum I defined as strategies not hiring temporary or permanent labour, as well as independence in the purchase of inputs (this Stratum produces 90% of its inputs). Stratum II reduced 3 of the main 4 items of the total production cost (feeding, medicines and breeding) and increased the mean profit per litre of milk ($ 2.00 MXN) through selling strategies. Stratum III defined as their strategies increased productivity (59%), a reduction in the cost (29%) of the main input (feed) and taking advantage of their productive scale to obtain a higher receipt of revenues for the farm.

Displacement of the lethal temperature of fishes by various metabolic stresses has been described by Brett (1958). Demonstrations of changes in the lethal level for temperature induced by the imposition of osmoregulatory stress began with the finding of Loeb and Wasteneys (1912) that the level of lethal temperature and the resistance time could be altered when an undesignated species ol Fund,ulus (invariably identified as F. heteroclitus in the literature) was exposed to potentially lethal temperatures in media of various salinities. In spite of the obvious significance of those findings to such considerations as adaptation, distribution, and physiologic descriptions, rather little subsequent experimental attention has been alloted to this response. Summaries of the occasional studies of subsequent investigators are presented by Arai et al. (1963) and by Strawn and Dunn (1967).The present study, besides considering the use of lethal temperature as a parameter for physiologic descriptions of the cyprinodontids banded killifish (Fund,ulus diaphanus (LeSueur)) and mummichog (F. heteroclits (L.)), examines the proposition that the lethal temperature for a given level of thermal acclimation is highest in isosmotic medium. Banded killifish occur most commonly in fresh r raters but along the coastal boundary of its range it occasionally frequents estuaries. Mummichog, in contrast, habituate tidal bays, saltmarshes, and estuaries, venturing upstream rather infrequently. To compensate for the inequality in the salinities of the customary habitats, both species were brought to a common acclimation, I4'/oo salinity, the approximate isosmotic level for the blood of Fund,ulus (Doudoroff, 1945). Subsequently, isosmotic baths served as the control medium for lethal tests which were conducted also in fresh water and in sea water, for both species.Method,s. -Quantities of mummichog and banded killifish were collected from various coastal and inland waters of Halifax Co., Bras d'Or Lake on Cape Breton Island, and Kedge Lake, Annapolis Co., Nova Scotia, during Iate summer, 1967. They were maintained, subsequently, in a laboratory at Dalhousie University for several rn'eeks in glass aquaria, the contents of which were maintained at levels of salinity approximately that of previous natural habitats of the several collections. Each aquarium rvas equipped with a conventional aerating aquarium filter. Water was changed at 5-7-day intervals depending on the extent of fouling. Both species were fed a daily surfeit of a prepared diet "Tetramin." The laboratory was illuminated continuously to provide constancy and to promote maximum utilization of food.Three weeks prior to the intended commencement of lethal tests these fish were transferred to water having a level of salinity of I4%0, with intervening levels of 20%o ior mummichog and 8%o for killifish for 5 days. The level ol t4%o 2717

<p><strong>Background: </strong>Small-scale dairy systems are a development option, and in Mexico they represent over 78% of dairy farms providing 37% of milk production. They are a source of employment and income in rural areas that enable dairy families to overcome poverty. However, ruminant production systems emit 17% of world methane, a greenhouse gas that affects climate change. Strategies must be devised to reduce the environmental footprint of dairy systems through increase productivity. <strong>Objective: </strong>The objective was to estimate the methane emission from enteric fermentation in small-scale dairy systems in the highland valleys of central Mexico with four feeding strategies. <strong>Methodology: </strong>Twenty four small-scale farms, with herds between 7 and 18 dairy cows participated in the study, which had implemented different feeding strategies that were assigned to the following groups: (CC) five farms that had a conventional management based on the cut-and-carry of temperate irrigated pastures, use of concentrates and straw, (CC+EM) six farms that use cut-and-carry of pastures plus maize silage in the dry season, (PCI) six farms that manage intensive continuous grazing of pastures, (PCI+EM) seven farms with continuous grazing of pastures, and use maize silage in the dry season. Farms were visited monthly during a whole year to record individual milk yields, milk composition and live weight of cows, to sample feeds for chemical analyses and record amounts of used feed. This information enabled to define a diet type per month, and dry matter and gross energy intakes were estimated subtracting the energy contribution of the supplements from total requirements. Methane emissions were estimated from a model derived by a global meta-analysis that includes variables of feed intake, diet composition, milk composition, and cow live-weight. A hierarchical experimental design was used where 288 records were subjected to analysis of variance to detect differences among the groups (alpha P≤0.05).  <strong>Results</strong>: Farms that implemented grazing of pastures as a source of fresh quality herbage (PCI) in mean generated 10.5% less enteric methane and 13.9% les intensity of emission (P&lt;0.05) compared with those that incorporated cut and carry or implemented corn silage for the dry season. <strong>Implications:</strong> Results show the potential of small-scale dairy systems to reduce their methane emissions and intensity of emissions by implementing grazing of temperate irrigated pastures. <strong>Conclusions:</strong> The implementation of fresh quality herbage through continuous grazing of temperate irrigated pastures with the use of moderate supplementation without incorporation of corn silage is a viable methane mitigation strategy in small-scale dairy systems in the highlands of Mexico.</p>