The relationship between plasma triglyceride concentrations and body fat content in male and female broilers—a basis for selection?

1. The relationship between plasma triglyceride concentrations and body fat content was examined in three groups of male and one of female broiler chickens fed ad libitum on a normal growing diet.

2. Phenotypic correlations between total plasma triglyceride concentration and fat content were + 0.50, + 0.37 and + 0.39 for the three groups of male broilers and +0.33 for the group of females. Triglyceride content of plasma very low density lipoprotein (VLDL) plus low density lipoprotein (LDL) showed similar correlations with fat content.

3. Selection of birds from a flock of 550 male broilers on the basis of high or low plasma VLDL plus LDL triglyceride concentrations produced groups with significant differences in body fat content but little difference in body weight.

4. The results suggest that measurements of plasma triglyceride concentration could be used as an indirect means of selecting for decreased body fat content in broiler breeding programmes.     

Field trials on the retention of potato stocks in England

Summary Field trials done to supplement replicated smallplot trials showed that the incidence of leaf roll and Y viruses in potato crops remained low for several years in many parts of England when the crops were sprayed with insecticide, and in some parts, where aphids were few, without spraying. Four sprays with DDT emulsion at 2 lb. of active ingredient per acre per application, at intervals of 14 days, starting soon after the plants emerged, were enough to check spread from sources within the crop. Insecticides did no prevent viruliferous aphids, coming from outside the crop, from infecting sprayed plants. Although many growers could safely keep potato stocks for several years longer than they do now, others could not because virus Y is introduced by aphids from other crops in the same area. Risk from incoming infective aphids will remain until all potato crops are free from virus, but if all infected crops were sprayed with an efficient aphicide before the summer dispersal flight this should greatly decrease the amount of disease introduced into healthy crops.

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Zusammenfassung Feldversuche, die zur Erg?nzung wiederholter Kleinparzellenversuche durchgeführt wurden, ergaben, da? die H?ufigkeit des Auftretens der Blattroll- und Y-Viren bei Kartoffelbest?nden mehrere Jahre in vielen Teilen Englands gering blieb, wenn die Best?nde mit einem Insektenmittel gespritzt wurden; in manchen Teilen, in denen wenig Blattl?use vorkamen, war dies auch ohne Spritzen der Fall. Viermaliges Spritzen mit DDT-Emulsion zu 2 lb. aktiven Bestandteile pro “acre” pro Applikation in 14t?gigen Intervallen, wobei man bald nach dem Aufgang begann, reichten aus, um die Ausbreitung von Quellen innerhalb der Best?nde zu hemmen. Die Insektizide verhinderten nicht, da? virus-tragende Blattl?use, die von au?erhalb der Best?nde stammten, die gespritzten Pflanzen infizierten. Obwohl manche Züchter ihre Kartoffelbest?nde verschiedene Jahre l?nger halten k?nnten als sie es jetzt tun, würde anderen dies nicht gelingen, weil das Y-Virus von Blattl?usen aus anderen Best?nden des gleichen Gebietes eingeführt wird. Die Gefahr ansteckender Blattl?use wird bestehen bleiben, bis alle Kartoffelbest?nde virusfrei sind; wenn jedoch alle infizierten Best?nde mit einem wirksamen Blattlausmittel vor dem sommerlichen Befallsflug gespritzt würden, w?re der Umfang der Infizierung mit dieser Krankheit von gesunden Pflanzungen bedeutend zu verringern.

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Résumé Des essais en plein champ, effectués pour compléter des essais à différentes reprises sur petites parcelles, ont démontré que l'incidence des virus Y et de l'enroulement dans les cultures de pommes de terre restait faible pendant plusieurs années dans bien des régions d'Angleterre, pourvu que les cultures aient été traitées par pulvérisation d'un insecticide, et dans certaines régions, où les pucerons sont rares, mêmes sans pulvérisations. Quatre pulvérisations d'une émulsion de DDT à la dose de 2 lb. de substance active par “acre” et par pulvérisation, espacées de deux semaines, dont la première est effectuée peu après la levée, suffisaient pour enrayer la propagation à partir de sources situées à l'intérieur de la culture. Les insecticides n'empêchaient pas les pucerons porteurs de virus, venant d'en dehors de la culture, d'infecter les plantes traitées. Si bien des cultivateurs pourraient continuer sans inconvénient la culture de pommes de terre de la même semence pendant plusieurs années de plus que d'ordinaire, d'autres ne le pourraient pas parce que le virus Y est apporté d'autres cultures de la même région par les pucerons. Le risque de pénétration de puccrons infectieux continuera d'exister tant que toutes les cultures ne seront pas exemptes de virus. Mais si toutes les cultures infectées étaient traitées avec un insecticide efficace avant le vol de dispersion en été, il en résulterait une forte diminution de la maladie introduite dans des plantations saines.

     

Plasma protein levels as potential marker traits for resistance to furunculosis

Abstract. The feasibility of including individual records on correlated traits in a family selection programme which aims to increase resistance to furunculosis in Atlantic salmon was studied; markers were selected because of their potential role in the pathogenesis of the disease. Fibrinogen and α₂-antiplasmin both show genetic variation; both are correlated with survival after challenge with Aeromonas salmonicida , the correlation being 0·44 and 0·37 ( P < 0·05), respectively, and it is possible to measure both on a large scale at low costs. Contrary to α₂-antiplasmin, fibrinogen was negatively correlated with survival due to furunculosis within the 10 most resistant families and within the 10 most susceptible families in contrast to an overall positive correlation. This inconsistency could be attributable to the presence of different allelic phases in different families, and of major linked loci influencing survival and fibrinogen levels. Thus, only α₂-antiplasmin fulfils the requirements for a marker trait for resistance to the disease suitable for individual selection at the population level, whereas the use of fibrinogen would be restricted to within family selection. The full statistical model explained 51% of the variation in resistance to furunculosis, and α₂-antiplasmin contributed 15% to this variation when considered as a separate entity. Thus, the additional gain from including individual records on α₂-antiplasmin in a family selection programme could be significant.     

Nutritional effects on the growth and fatness of broilers

1. Broiler chickens given diets high in protein, or choice-fed on a high protein balancer, had much lower abdominal fat contents than those reported in many recent experiments. The values for males were 10.8 g/kg liveweight at 56 d at 2.43 kg liveweight in one experiment in Scotland and 16.0 g/kg liveweight at 42 d at 1.93 kg liveweight in another in South Africa. For females the values were 18.8 g/kg liveweight at 56 d at 2.15 kg liveweight in Scotland and 15.7 g/kg liveweight at 42 d at 1.60 kg in South Africa. 2. The content of abdominal fat was, in general, increased by reducing the protein content of the diet or by dilution of the food with oil or starch. It was, in general, reduced by diluting the food with dietary fibre which also reduced liveweight gain. 3. The results are consistent with the idea that chickens attempt to control their food intake so that they achieve a particular fatness. This level of fatness differs between the sexes and between degrees of maturity.     

Grass Yields Under Clipping and Watering Explain Varied Efficacy of Management Intensive Grazing on Rangelands

Management intensive grazing (MIG) may not maximize plant productivity on rangelands because of morphophysiological traits of grassland vegetation. We examined defoliation and moisture effects on the biomass yield of rhizomatous and caespitose grass pairs that were either phylogenetically similar or of similar agroclimatic adaptation, including two agronomic grasses. From relatively low to high moisture regime adaptation, species pairs included western wheatgrass (Pascopyrum smithii [Rydb.] A. Love) and needle-and-thread (Hesperostipa comata [Trin. & Rupr.] Barkw.), northern wheatgrass (Elymus lanceolatus [Scribn. & J.G. Sm.]) and western porcupine grass (H. curtiseta [Hitchc.] Barkw.), plains and foothills rough fescue (Festuca hallii [Vasey] and F. campestris Rydb.), and smooth and meadow brome (Bromus inermis Leyss. and B. riparius Rehm). Response variables were shoot yield, root-shoot ratio, and water-use efficiency. We hypothesized that caespitose grasses, regardless of their origin or adaptation to agroclimate regime, would respond more determinately in biomass accumulation. Defoliation effects on shoot biomass were more pronounced under high moisture. Low intensity ? high frequency defoliation yielded similarly to deferred controls in all grasses, and the same was true for high-intensity ? low-frequency (HILF) defoliation in 1 rhizomatous grass. Three of the 4 rhizomatous grasses and 1 caespitose grass yielded greater under HILF defoliation compared with high-intensity ? high-frequency defoliation. Caespitose grasses allocated more biomass to roots under low moisture conditions. Water-use efficiency decreased under high moisture conditions and more intense and/or frequent defoliation and peaked in agronomic grasses. Overall, our results suggested that growth patterns corresponded more with phylogenetic similarity as opposed to growth form. A conceptual model from these results showed that across all species, only the introduced bromes generated greater biomass under HILF defoliation, and this may explain why past research consistently concludes that MIG does not enhance plant productivity on rangelands.     

Divergent effects of defoliation intensity and frequency on tiller growth and production dynamics of Pascopyrum smithii and Hesperostipa comata

Rotational stocking theoretically enables regrazing of regrowth, but regrowth may be limited in xerophytic vegetation. We tested the hypothesis that regrowth would be slow and fixed in Hesperostipa comata (a caespitose, drought‐tolerant grass), while growth would be flexible in Pascopyrum smithii (a rhizomatous, less drought‐tolerant grass) under increasing defoliation and moisture, by assessing tiller growth rates, population dynamics and plant yield on marked plants in a Dry Mixed Grass prairie. Plots were clipped in late summer to simulate a deferred control, or intermittently during the growing season (May–August) at high intensity–low frequency (HILF), low intensity–high frequency (LIHF) or high intensity–high frequency and crossed with two water treatments (ambient and addition) in both a xeric upland and a mesic lowland. Growing season defoliation increased tiller growth rates of P. smithii in the upland, whereas HILF and LIHF reduced growth in the lowland. All defoliation regimes increased tiller growth for H. comata. Tiller populations of H. comata increased with frequent defoliation, while tiller populations of P. smithii decreased regardless of defoliation regime. Frequent defoliation, regardless of intensity, reduced yield relative to the deferred control for both grasses. While water addition consistently increased growth rates and reduced differences in tiller number among defoliation treatments, the regrowth of both grasses remained similar under varied defoliation with ambient moisture. High moisture conditions also promoted regrowth more in P. smithii compared to H. comata. In summary, neither grass species displayed an inherently fixed or flexible tiller or plant yield response in response to defoliation or moisture.     

Efficiency of nitrogen uptake by potatoes

White Rose potatoes were fertilized with isotopically labeled ammonium sulfate at rates of 67, 134, 202 and 270 kg N/ha to evaluate N uptake efficiency. All N application increased yields above the control, however the 3 higher N rates produced the same yields statistically. All N rates which maximized yields maintained petiole levels of total N above 600 ppm. Rapid changes in petiole inorganic N occurred during the growing season. Fertilizer derived inorganic N decreased at rates ranging from 67 to 518 ppm/day during the third month after planting. Total inorganic N in petioles during the same period dropped at rates ranging from 500 to 880 ppm/ day. Tubers grown in N-fertilized plots assimilated total N in a nearly linear pattern during the period 82 to 125 days after planting. Uptake of total N ranged from 142 to 233 kg/ha. In assessing N utilization by 3 methods, good agreement was achieved between the isotope and difference method in the first and third (last) samplings, however, agreement was poor between the two in the second sampling. With N rates to 202 kg/ha the uptake efficiency was about 57% but dropped to 39% with application of 270 kg N/ha. When uptake efficiency was measured by dry matter production in relation to units of N fertilizer, the 67 kg N rate was superior to other rates. Inorganic N levels in the surface meter of soil were higher before planting and fertilizer application than after harvest. Following harvest the control plots had more N below 1.5 m than did the N fertilized plots. In control plots, the total inorganic N between 1.5 and 2.5 m depths was equivalent to 170 kg N/ha. Virtually none of the accumulated N below 1 m was due to labeled N applied in the experiment. Using 134 kg N/ha as the optimum rate, tubers removed 178 kg N/ha of which 78 kg was derived from the applied fertilizer. With total N input of 191 kg/ha (57 kg N/ha from irrigation water) the N rate required for maximum yield would pose no risk of nitrate pollution since it represents only 13 kg more than crop removal (191 vs 178 kg N/ha).