In the rapid response (RR) biotype of glyphosate-resistant (GR) giant ragweed (Ambrosia trifida L.), exposure to glyphosate elicits H2O2 production in mature leaves, resulting in foliage loss and reduced glyphosate translocation. When glyphosate is applied with POST herbicides intended to improve control of A. trifida, the RR to glyphosate has the propensity to antagonize these herbicide combinations. This research documents how transient changes in air temperature, soil moisture, and light intensity during a 6-d period surrounding herbicide application regulate induction of the RR and the effect on POST herbicide interactions with glyphosate. Air temperature had the greatest influence on H2O2 accumulation in leaf disks following treatment with glyphosate, as plants at 30 C produced more than twice the amount of H2O2 at 2.5 h after treatment compared with 10 C. Plants under field capacity conditions accumulated nearly 50% more H2O2 than those at one-third field capacity, while those under no shade had only 18% more H2O2 compared with those in a shaded environment. Despite these initial results, dry weight reduction at 21 d after treatment never differed by more than 8% between levels of environmental factors, thus indicating a negligible influence on glyphosate efficacy. The magnitude of glyphosate-induced antagonism was generally greater at 30 C (12% to 21% less than expected control) versus 10 C (11% to 16%) on atrazine, cloransulam, dicamba, and topramezone and was greater at field capacity (20% to 24%) versus one-third field capacity (11% to 15%) on cloransulam and topramezone. These results indicate air temperatures and soil moisture levels conducive to optimal plant growth accelerate the RR to glyphosate, thereby increasing the likelihood of glyphosate-induced antagonism on several translocated herbicides.

The behaviour of cercariae was recorded on video at 10, 20 and 30 °C and a combination of population and individual behavioural patterns studied. Initially cercarial populations were extremely active, individuals alternating between swimming and sinking behaviour. As they aged the percentage sinking and resting increased resulting in the establishment of a vertical distribution in the water column. An increased environmental temperature reduced the active life-span of the parasites. Over time cercarial swimming rates declined. Swimming rates increased with environmental temperature and as a result of a shadow stimulus. As cercariae aged, the duration of swimming events decreased. Post-stimulation swimming periods were significantly longer than pre-stimulation periods. Pre- and post-stimulation swimming distances also declined with age. Post-stimulation swimming distances were significantly longer than pre-stimulation distances. The sinking rates of cercariae decreased with age while sinking periods and distances increased. Data for proportional time spent swimming and the ratio of sinking to swimming events indicated that as cercariae aged, less time was spent swimming. The frequency of swimming/sinking events declined with age. The implications of this behaviour for dispersal and transmission are discussed.

The development and mortality of the eggs of Ancylostoma duodenale and Necator americanus in distilled water were monitored over a range of temperatures between 15 and 35°C. Egg demography was examined within the context of a fourparameter mathematical model of development and mortality. Over the range of temperatures studied, egg mortality (μ) was an increasing exponential function of temperature (T) measured in degrees Celsius. A single model adequately described the mortality of both species (ln [μ] = 0·041*T − 6·87). The minimum time (τ) to hatching was consistently less for A. duodenale (ln [1/T] = −(0·79+53·05*[l/T]) than N. americanus (ln [1/T] = −(0·99 + 53·05*[l/T])). The hatching rate [σ when t > τ) was an increasing function of time and temperature in both cases, but the precise functional relationship was species specific.

New Zealand × Californian rabbit does were offered ad libitum three diets: diet A, with 960 g lucerne per kg dry matter (DM), having 8•7 MJ digestible energy (DE) and 108 g digestible protein (DP) per kg DM; diet AF with 920 g lucerne and 50 g animal fat per kg DM, having 9•6 MJ DE and 105 g DP per kg DM; and diet C, as a control diet having 12•0 MJ DE and 122 g DP per kg DM. Productive parameters were measured for the first five parities, and food intake and milk yield during the first two parities.

In experiment 1, 79 does (342 parities) were housed in a cooled building, litters were standardized to eight kits and weaned at 28 days of age. DM intake during lactation was lower (P < 0•001) but DE intake, milk yield and litter growth were higher for group C. Values for does on diet AF generally were between those of groups A and C. Average results for groups A, AF and C were respectively: 59, 65 and 51 days for the parturition interval; 160, 170 and 193 g for daily milk output in the first two lactations; 3•7, 4•0 and 4•5 kg for litter weight at weaning.

In experiment 2, 64 does (294 parities) were housed in a climatic chamber at a constant temperature of 30oC, litters were standardized to six kits and weaned at 35 days of age. DM intake during lactation was lower (P < 0•001) but milk yield and litter growth were higher (P < 0•001) for C does. Average results for groups A, AF and C were respectively: 70, 70 and 56 days for parturition interval; 106, 128 and 128 g for daily milk output in the first two lactations; 3•7, 4•4 and 4•4 kg for litter weight at weaning. Lucerne-based diets allowed a reasonable performance of reproductive rabbit does in the long term, even under hot conditions.

An experiment was carried out on pigs to provide a test of two current conceptual frameworks available for the understanding and prediction of food intake. Framework 1 assumes that food intake will be that which allows potential (genetic) performance to be achieved. If this is not achieved then it is because intake is being constrained. Framework 2 sees food intake as being a consequence of a process of optimization such that biological efficiency (the ratio of net energy ingested to oxygen consumed) is maximized. Both frameworks predict that a reduction in temperature will increase the intake of a high quality food. For a food of low quality framework 2 predicts that intake will also be increased when temperature is decreased while framework 1 predicts that it will not. This difference between the predictions of the two frameworks allows them to be tested by means of an experiment in which foods of different quality were given to animals at different environmental temperatures.

Forty pigs were randomly allocated to a control (C) food based on micronized wheat with 13·1 MJ digestible energy (DE) and 232 g crude protein (CP) per kg fresh food, or one of two high bulk foods. The high bulk foods contained either 650 g/kg of unmolassed sugar-beet pulp (SBP) or 650 g/kg of wheat bran (WB). Half the pigs were maintained at a thermoneutral temperature of 22ºC for 14 days followed by a cold temperature of 12ºC for 14 days. The other half were maintained at 12ºC for a period of 14 days followed by a temperature of 22ºC for 14 days. Food intake was recorded daily and live weight twice weekly.

There was a highly significant food ✕ temperature interaction ( P < 0·001) for food intake. A reduction in temperature resulted in an increase in food intake on C and WB but had no effect on the intake of SBP. There was a highly significant effect of both temperature and food on intake ( P < 0·001). A reduction in temperature resulted in a significant increase in food intake, intake on WB was higher than that of either C or SBP. There was no overall effect of temperature on live-weight gain although a reduction in temperature resulted in a non-significant increase in the gain of C and reduction in the gain of WB and SBP. There was a highly significant effect of food ( P < 0·001) on live-weight gain, as gain on C was higher than that on either WB or SBP.

The results of the experiment were in agreement with the predictions set forward by the first framework that growing pigs are eating to achieve maximum performance subject to constraints.