THE UTILIZATION OF GRASS FED INDOORS TO YOUNG BEEF CATTLE, WITH OR WITHOUT SUPPLEMENTARY BARLEY

An experiment was carried out in which grass was cut and fed indoors, with or without supplementary barley. Seven animals were allocated to each of the following treatments: (1) grass ad lib . without supplementary barley; (2) grass ad lib . with supplementary barley at the rate of 0.5 lb/100 lb bodyweight; (3) grass ad lib . with supplementary barley at the rate of 1 lb/100 lb bodyweight. Supplementary barley increased total dry-matter intake and improved daily liveweight gain and food conversion rate. The mean daily liveweight gains for the 17-week experimental period were 1.60, 1.91 and 2.20 lb and the corresponding feed dry-matter conversion ratios were 6.18, 5.67 and 5.55 for Treatments 1, 2 and 3, respectively.
The dry-matter digestibility of the diets was slightly higher when the grass was supplemented with barley than when grass alone was given. Although barley depressed the digestibility of protein, the absolute and the proportionate retention of nitrogen was increased. This was particularly marked on Treatment 3, presumably because of the higher net energy value of the diet containing the greater amount of barley. The N-retention data corresponded to the rates of liveweight gain obtained.     

The breeding systems and some interspecific relations of a number of African Trifolium spp.

The breeding systems of 12 species and varieties of Trifolium from Africa were investigated. One annual and the three perennial species were allogamous and self-incompatible, the other annuals were autogamous.The effect of temperature on pollen germination and growth was variable. In some species high temperatures (30°C) adversely affected pollen germination and low temperatures (20°C) in others. A high humidity (93–98% R.H.) was essential for good pollen germination and growth.Approach grafts indicated that these species were closely related, however, this method of grafting may not be as reliable as the cleft graft for assessing species relations. From hybridization attempts between seven species, it appears that some interspecific hybrids may be possible within this group.     

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.

     

Freshwater mussel assemblage structure in a regulated river in the Lower Mississippi River Alluvial Basin,USA

• 1. This paper documents a diverse, reproducing freshwater mussel community (20 species) in Lower Lake — an impounded, regulated portion of the Little Tallahatchie River below Sardis Dam in Panola Co., Mississippi, USA.
• 2. Despite being regulated and impounded, the lake has a heterogeneous array of habitats that differ markedly in mussel community attributes. Four distinct habitat types were identified based on current velocity and substrate characteristics, representing a gradient from habitats having lotic characteristics to lentic habitats. All four habitat types supported mussels, but habitats most resembling unimpounded, lotic situations (relatively higher current velocity and coarser substrate) had the highest mussel abundance and species density (10.1 mussels m^?2, 1.8 species m^?2, respectively). Lentic habitats (no flow, fine substrate) were characterized by lower abundance and species density (2.0 mussels m^?2, 0.8 species m^?2, respectively), but supported mussel assemblages distinctive from lotic habitats.
• 3. Evidence of strong recent recruitment was observed for most species in the lake and was observed in all four habitat types.
• 4. Although impounded and regulated, Lower Lake represents one of the few areas of stable large‐stream habitat in the region. The presence of a diverse, healthy mussel community in this highly modified habitat suggests that a large component of the regional mussel fauna is relatively resilient and adaptable and is limited primarily by the absence of stable river reaches. Management actions that increase stream stability are likely to result in expansion of the mussel fauna and restoration of a valuable component of ecosystem function in this region.

Published in 2006 by John Wiley & Sons, Ltd.