Species commonly used to seed California rangelands were sprayed with varying rates of the alkanolamine salt of 2,4-D at a number of vegetative growth stages in two different years. Subclover, hardinggrass, and orchardgrass were not permanently damaged by rates up to 2.0 lb/acre at any of the growth stages tested. Rose clover was tolerant of up to 0.5 lb/acre if sprayed at the proper growth stage but yields were frequently reduced by even low rates at other growth stages.

Thirty-six pastures of crested wheatgrass were grazed in early spring plus early fall; late spring; all spring; early summer; late summer; early fall; and late fall. Summer and fall treatments included grazing with and without supplement. Yearlings made substantial gains in all seasons except during late fall when they lost weight. They finished the entire grazing period with an average gain of 224 lb. Calves gained 249 lb. Yearlings and calves did as well on crested wheatgrass as on forest range, and supplementation provided no additional gain. Cows on supplement gained 125 lb as compared to 50 lb for non-supplemented cows. In years with no fall regrowth, second grazing of crested wheatgrass without supplement produced daily gains in early fall equal to those for single grazing with supplement.

Grass and cattle are an important part of Panama agriculture. Ninety percent of all grassland contains one or more introduced grasses. Brush control, fire control, and improvement in grass and livestock management are major problems. Cattle are grown and finished for market on grass. Low calf crops, disease and parasites, poor dry season feed conditions, and low-quality animals result in a generally low beef production per cow. Improved grazing practices and sound livestock management will result in higher calf crops and increased beef yields. Potential exists for a sound and economically profitable ranching enterprise./Los pastizales y el ganado son una parte muy importante de la agricultura de Panamá. El 90% de las tierras de pastoreo contienen una ó más especies de gramíneas introducidas. El combate de arbustivas, el control de las quemas, y el mejoramiento tanto de las plantas forrajeras como del ganado son de los problemas más importantes. El ganado se cría y se engorda para el mercado en los potreros. Los bajos porcentajes de parición, las enfermedades y los parásitos, el bajo valor nutritivo de los forrajes durante las épocas de sequía, y los animales de calidad inferior traen como consecuencia, por lo general, una baja producción por vaca. Mayores porcentajes de parición y aumentos en el rendimiento de carne podrán lograrse mediante prácticas de pastoreo mejoradas y un manejo adecuado del ganado. La ganadería en Panamá ofrece un buen potencial para establecer empresas remunerativas.

Leaf class (number of leaves per plant) and cutting date were considered as indices of maturity of western wheatgrass. Although some early-season effects of leaf class could be demonstrated, cutting date was a better measure of stage of maturity. Cutting date but not leaf class was shown to affect plant fractions and chemical components. The upper portion of the plant was more digestible than the basal portion. No digestibility effect was demonstrated for topographic location or leaf class. Leaf blades removed from plants under heavy grazing were more digestible in vitro than those from lightly-grazed pastures, probably because of later emergence or shorter height.

Nine legumes, including three strains of variegated alfalfa, were planted in mixture with each of four grasses in the fall of 1950. Alfalfa A-169 was the most productive legume. In 1965 it yielded 100 lb/acre, about 35% more than cicer milkvetch or Ladak alfalfa and 160 lb/acre more than sickle milkvetch or Rhizoma alfalfa. Siberian alfalfa was clearly inferior to all the above. Flat pea, birdsfoot trefoil, and perennial vetch disappeared from the plots early in the study. Intermediate and crested wheatgrasses were more productive than smooth brome, both in combination with legumes and as pure stands. The highest yielding plots in 1965 were those originally sown to mountain brome. This short-lived grass afforded less competition to the legumes which became well established prior to invasion by crested and intermediate wheatgrass or smooth brome grass. The use of a legume with the grass, on the average, increased production by 144 lb/acre.

Diurnal and seasonal differences, as well as site features of slope aspect and shading, were found to be significant variables related to forage moisture content on a mountain summer range in northern Utah. These variations, if ignored in range analysis, can have considerable practical consequence. Therefore, improvements on wet to dry-weight conversion factors have been suggested.

The diet and forage preferences of the black-tailed jackrabbit (Lepus californicus) were studied by stomach content analysis to determine the degree of competition between cattle and jackrabbits on sandhill rangeland. Grasses were most important in the diet in early spring and summer. Forbs were important during summer and fall and shrubs were eaten in fall and winter. Competition for forage between jackrabbits and cattle was greatest in early spring and least in late fall and winter. Jackrabbits influence the longevity of reseeded forage stands and the secondary succession on old fields. A thorough knowledge of diet and forage preferences of jackrabbits permits the land manager to make better decisions for efficient range use.

Stored carbohydrates of sand reedgrass increased from a low in late May and early June to a maximum in late September and early October. Starch was the major stored carbohydrate. The concentration of starch in the roots decreased slightly with increased grazing intensity. The results of this study combined with information on the morphological development, extent of root system, and other physiological aspects of sand reedgrass can be used in developing grazing management systems for sand reedgrass.

Statistical decision theory offers northern Nevada cattle producers an opportunity to increase their income by aiding in making adjustments in livestock numbers according to expected forage production. It is necessary for cattlemen to determine the number of cattle to carry through the winter before knowledge of forage supply for the coming year is available. Statistical decision theory provides a simple tool whereby ranchers may use observed information on precipitation to select the appropriate number of cattle to be wintered. Ninety-five years of weather data were used to evaluate this technique under ranch conditions in northern Nevada. Results indicate that statistical decision theory offers promise as a technique for maximizing the long-run average income of ranchers while making provision for protection of the range resource./Para ejemplificar este modelo bajo probabilidades a priori y a posteriori, se empleó una operación combinada de pié de cría (venta de crías al destete) y de pié de cría-engorda (venta de crías como añojos). Esta organización tiene muy buena flexibilidad para ajustarse a niveles de producción forrajera tanto abajo como arriba de lo normal. Por lo tanto, el valor del modelo expuesto fué más bien limitado para este sistema. El modelo resultó de mayor valor bajo el sistema menos flexible de una operación pié de cría. Aunque los aumentos en los ingresos fueron modestos con el modelo, la técnica ofrece ciertas promesas para trabajar en este campo. La técnica puede aparecer complicada al principio, pero es más bien simple. Los resultados pueden presentarse en una forma sencilla, como aparecen en el cuadro 6, para aquellos no interesados en profundizarse en suposiciones y mayores datos. Este modelo fué desarrollado para ayudar a los ganaderos a utilizar los reducidos datos disponibles en el otoño con el fin de predecir la cantidad de forraje disponible para el año siguiente. El modelo está planeado simplemente para tratar de obtener los máximos ingresos a largo plazo. Podría modificarse fácilmente para reflejar otras cosas tales como diferentes grados de utilización de forraje aceptable, niveles de ingreso mímimo anual, ó cualquier otra medida de importancia en el manejo del recurso pastizal. Esta es otra herramienta que puede ayudar al ganadero a aumentar sus ingresos y a la vez sirve para mejorar la utilización de un pastizal.