Effect of exogenous porcine somatotropin administration on nitrogen and energy metabolism in three genotypes of pigs

Effects of exogenous administration of porcine recombinant somatotropin (rpST) on protein gain and metabolic rate were measured in three genotypes (castrated males) of pigs (Pietrain, Duroc and a crossbreed between Dutch Yorkshire and Dutch Landrace). Six pigs of each genotype were assigned at approximately 60 kg to receive pST doses of either 0 (C) or 14 mg (T) administered i.m. twice weekly over 10 wk. Pigs were housed in individual metabolism cages at a room temperature of 20 to 22 degrees C and received feed at 2.6 times maintenance. Protein gain (N x 6.25) was measured over the final 6 wk of the 10-wk test period. For 2 wk in the test period (wk 2 and wk 5), six pigs of each treatment x genotype group were placed in a large respiration chamber and energy balances (in protein and fat) and metabolic rate were measured. Rate of weight gain measured over the final 6 wk of the experimental period increased by 105 g/d (13%) with rpST administration (P less than .01). Daily protein gain over 6 wk was increased by 48 g/animal with application of rpST (P less than .001). There was a genotype x treatment interaction (P less than .01) for protein gain. Daily protein gain in Durocs with pST treatment was increased (39%) more than in crossbreds (31%). Daily fat gain was decreased by 42 g/animal (P less than .001) by T. Daily heat production with rpST was increased by 12 kcal/kg.75, which is comparable to a 12% increase in the maintenance energy requirement.     

Growth rate,feed utilization and energy metabolism of the African catfish,Clarias gariepinus (Burchell, 1822), as affected by dietary protein and energy content

Three feeding experiments were conducted in open circuit balance respirometers, to determine the effect of dietary protein level on growth rate, feed utilization and energy metabolism of Clarias gariepinus (Burchell). The feeding level was 2% of the fresh body weight per day. Three energy levels, 8.4, 12.6 and 16.8 kJ calculated metabolizable energy (ME) per gram of feed, were used, while crude protein levels in the diets were 20, 25, 30, 35 and 40%.Growth rate, heat production, metabolizability (ME as percentage of gross energy intake) and protein gain were maximal at the intermediate energy level. Digested protein per gram of growth was lowest at this energy level (determined ME = 13 kJ/g). Growth rate, metabolizability and protein gain increased as protein intake increased. There was no effect of the different protein levels on heat production. The efficiency of protein gain (% of the digestible protein intake) was highest (45–49%) at the intermediate energy level. Efficiency of protein gain (% of digestible intake) decreased slightly when protein intake increased. ME intake per gram of growth was minimal at the 8.4 kJ energy level and decreased at higher protein intake levels.At the highest energy level, growth rate was reduced compared to the intermediate energy level, but efficiency of energy gain, retention of fat and energy were highest. Much of the dietary fat was deposited as lipid reserves. After 4 weeks the growth rate, digestibility, metabolizability, and efficiency of protein- and energy gain (% of digestible or metabolizable intake respectively) were strongly reduced at this energy level.     

Effects of recombinant porcine somatotropin on metabolic rate in growing pigs

Effects of recombinant porcine somatotropin (rpST) on metabolic rate were studied in two trials with 24 crossbred barrows (Yorkshire x Landrace) in each. The barrows weighed about 80 kg (SE within trials 2.2 kg) at the start of the measurements and in each trial 12 pigs received 4 mg of rpST and 12 received a placebo. The diet contained 2.57 Mcal NE/kg and 20% CP (about 1% lysine). Animals were fed approximately 2.8 times maintenance (280 kcal ME.kg-.75.d-1). Heat production (gaseous exchange of CO2 and O2) and activity were measured continuously. Heat production associated with activity was calculated from the regression of heat production on activity. Animals treated with rpST exceeded controls in rate of gain by 252 g/d (P less than .001) and in metabolic rate by 14.5 kcal.kg-.75.d-1 (P less than .01). The rpST treatment increased rectal (+ .2 degrees C) and surface (+ .8 degrees C) temperatures. Activity-related heat production in treated pigs was increased, but this was only partly related to the increase in metabolic rate with rpST. The daily patterns of total and activity-related heat production were similar between pigs in both experimental treatments.     

Development of bio-assays and screening for resistance to beet armyworm (Spodoptera Exigua Hübner) in Allium cepa L. and its wild relatives

The beet armyworm (Spodoptera exigua Hübner)is the most important pest in tropical Alliumcultivations. All shallot (Allium cepa L. group Aggregatum) cultivars are susceptible to this pest. Therefore accessions from three wild Alliumspecies, namely A. galanthum Kar. et Kir., A. fistulosum L. and A. royleiStearn, next to A. cepa L. were used to screen for resistance. First of all, a reliable bio-assay had to be developed. To this end transparent plastic cages with in total 5 plants of one accession per cage were placed on per lite in a heated greenhouse. Five 3-day old larvae were inoculated on each plant. Eight days after inoculation the number of surviving larvae per cage and the mean fresh weightper larva was determined. The lowest larval survival (36%) was found on A. roylei. This was not, however, significantly different from other Allium accessions. Significant differences were found in the fresh weight per larva fed on different Allium accessions. The larvae survived on A. roylei had a very low fresh weight (10.3 mg per larva), while those on an accession of A. fistulosum had the highest fresh weight (45.1 mg per larva). The larval fresh weight on A. roylei was lower than all the other accessions except from the tropical shallot cultivar Bawang Bali. To check whether or not a toxic compound was involved in the resistance present in A. roylei, tenaccessions from four Allium species were screened. Five 3-day old larvae were inoculated on regularly replaced leaf material of each accession ofAllium species. No significant differences were found in mean fresh weight per larva and mean survival of larvae among different accessions. There were also no significant differences in pupal weight and developmental time. All larvae became pupae 10 days after inoculation. The data indicate that there is no toxic compound present in A. roylei. These results are underlined by the observation in the greenhouse bio-assay that A. roylei plants were equally damaged by the beet armyworm compared to otherAllium species. The results obtained so far therefore suggest that introduction of resistance to S. exigua via the exploitation of variation for resistance to the beet armyworm in A. roylei is unclear and that genetic engineering using Cry sequences could provide a way forward. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nine years of practical experience with phenylamide resistance in Phytophthora infestans in the Netherlands

Resistance to phenylamide fungicides in thePhytophthora infestans population in the Netherlands decreased from a level of 77% of the samples containing resistant strains in 1980 to 0% in 1986 with decreasing use of metalaxyl, the only phenylamide fungicide registered for use against late blight in this country. Use of metalaxyl decreased because the fungicide alone and combinations of metalaxyl with preventive late blight fungicides were not commercially available from 1981 through the first part of the potato growing season of 1984. When metalaxyl was made available again in August 1984 in a mixture with mancozeb and from 1985 in a mixture with almost full rates of maneb and fentinacetate its use remained limited because growers were advised to apply the combination only two times per season in critical situations only to control the severe late blight epidemics of 1984 and 1985. Moreover application on seed potato crops was not allowed. In 1986 the combination was hardly used because the mild epidemic was easily controlled by preventive compounds only.In 1987 and 1988 phenylamide resistance increased to 16 and 42%, respectively, inherent to a general use of the combination in both years in most potato growing regions of up to two applications to combat a very severe epidemic.In lots of seed potatoes harvested in 1988 the percentage of blighted tubers yielding resistant isolates significantly differed from 13% for regions where seed potatoes are predominantly grown for table and processing crops to 41% for a region where predominantly starch potatoes are grown, both as seed and production crops. The more intensive use of metalaxyl combinations in the latter area through the years as compared to the other areas is assumed to be responsible for the higher incidence of resistance.In most years application of the combination induced a significant shift in the population to resistance as is indicated by the higher frequency at which resistant isolates were present in leaf samples taken from treated fields or tuber samples from the harvested crop.The strategy adopted by Dutch potato growers to combat phenylamide resistance in late blight, involving limited use of metalaxyl mixtures to a maximum of two times in critical situations only, has kept up to now resistance in the population at a level at which metalaxyl still significantly contributes to the efficacy of the combination in controlling the disease. Never-theless the observed increase in resistance in the population of 1988 after two consecutive late blight years indicates that this may change if severe epidemics occur each year.     

Heat balance characteristics of limit-fed growing pigs of several breeds kept in groups at and below thermal neutrality

The lower critical temperature (Tcr) and thermoregulatory heat production below Tcr were studied in Norwegian Landrace (N), Finnish Landrace (F), Dutch Landrace (D), and Great Yorkshire (Y) barrows. Animals, weighing 26 kg at the start, were kept in groups for 18, 2-d periods in climate respiration chambers at environmental temperatures (Tenv) between 11 and 26 degrees C. Feeding level of animals in a group was 93 g.kg-.75.d-1 (2.5 times maintenance) and based on mean BW. Great Yorkshire pigs had a higher growth rate and a lower feed to gain ratio than Landrace pigs. Production characteristics of Landrace breeds were similar. The derived Tcr of the breeds was between 18.0 and 20.4 degrees C, the lower value associated with Y pigs and the higher value with F pigs. Thermoregulatory heat production was 6.4 to 11.9 kJ.kg-.75.d-1.degrees C-1 and did not differ between breeds. Radiant surface temperature (Trs) of pigs increased by .4C degrees (= bTrs) when Tenv was raised by 1.0 C degrees between 11 and 26 degrees C. In D pigs, bTrs was higher than in other pigs. Radiant surface temperature was related to backfat thickness; bTrs was increased with greater backfat thickness.     

Required thermal thresholds during transport of animals

Summary

Conditions (total complex of stressors) during the transport of animals vary strongly between and within transports. Adverse climatic conditions are stressors that animals have to face during transport. The thermoregulation of animals is discussed with respect to threshold values for optimal climatic conditions. These thermal thresholds depend on animal related factors and environmental conditions. The specific impact of transport conditions, such as food and water deprivation, high stocking density, high humidity and high air velocity, on thermal thresholds are described.     

Use of zoospores of Polymyxa betae in screening beet seedlings for resistance to beet necrotic yellow vein virus

A system to culture viruliferousPolymyxa betae and to produce zoospores is described. The zoo spores were used for inoculation of beet seedlings, grown in nutrient solution, in tests for resistance to beet necrotic yellow vein virus (BNYVV). On most occasions in a time course experiment, and with various zoospore cultures, the partially resistant cultivar Rima and the accession Holly-1–4 had virus concentrations similar to the susceptible cultivar Regina, but the virus concentration inBeta vulgaris ssp.maritima accession WB42 was significantly lower (P<0.05). ‘Regina’ could be distinguished from various resistant accessions by a significantly higher virus concentration (P<0.05) shortly after inoculation, or after transplanting the seedlings from the nutrient solution into sand. Results of screening for resistance to BNYVV, using zoospores for inoculation, did not correspond with results of a test in which infested soil was used.Tests in which seedlings are grown in nutrient solution and inoculated with zoospores are suitable for the detection of accessions with a high level of resistance to BNYVV. To obtain virus infection in all plants, the optimal density of the zoospore suspension should first be determined and plants should be assayed shortly after inoculation.     

A greenhouse test for screening sugar-beet (Beta vulgaris) for resistance to beet necrotic yellow vein virus (BNYVV)

Small differences in activity between batches of purified beet necrotic yellow vein virus (BNYVV) were observed in ELISA. A four-parameter modelled dose-response curve of purified BNYVV was used for the conversion of ELISA values to virus concentrations. Seedlings of the susceptible cultivar Regina and the partially resistant cultivars Nymphe and Rima were tested for resistance to BNYVV in a mixture of sand and infested soil. Plants were grown in a green-house with low nutrient supply and at temperatures below the optimum of both the vectorPolymyxa betae and BNYVV. Root systems were small and consisted mainly of lateral roots. Significant differences in average virus concentrations were found between cultivars, both when using the complete root systems and when using either the top or the bottom part of the root systems. Average virus concentrations in Regina were always significantly higher than in Rima and higher than in Nymphe on all occasions except one (P<0.05). Differences between Nymphe and Rima were less evident. Variation between plants was greatest within Rima. The test described in this paper can be used for the discrimination of different cultivars and for the identification of individual plants with resistance to BNYVV.     

Expression in vitro of resistance to Heterodera schachtii in hairy roots of an alien monotelosomic addition plant of Beta vulgaris,transformed by Agrobacterium rhizogenes

Summary Hairy roots, induced by Agrobacterium rhizogenes, were obtained of nematode susceptible beet plants (Beta vulgaris) and of the nematode resistant alien monotelosomic addition AN5, carrying a telosome from B. patellaris. The additional telosome was found to be stably present in vitro in the roots of AN5. The hairy root cultures were inoculated with larvae of the beet cyst nematode Heterodera schachtii. On the root culture of AN5 significantly less cysts developed than on the other root cultures. These results indicate that the resistance to the beet cyst nematode is expressed in the roots after transformation and can be monitored under in vitro conditions.