Life Sciences Commons^™

Growth Analysis Of Tall Fescue Genotypes Differing In Yield And Leaf Photosynthesis, Wallace Wilhelm, C. J. Nelson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Leaf growth, dry matter distribution , and carbohydrate content of four tall fescue (Festuca arundinacea Schreb.) genotypes selected for high and low net C02 exchange (NCE) and forage yield were studied in controlled environments t o evaluate the leaf NCE-yield relationship. High yield genotypes produced greater amounts of all plant parts and carbohydrate than the low yield genotypes. Within each yield level the high NCE genotypes produced more dry matter and carbohxdrate. Leaf growth of all genotypes was linear throughout light and dark periods, but rates were 50% greater for high yield genotypes, RGR was similar for all genotypes. NAR …

Nitrate Reductase Activity In Tall Fescue, D. D. Randall, Wallace Wilhelm, R. F. Feuers, C. J. Nelson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

An in vitro assay for tall fescue leaf nitrate reductase activity (NRA) was established that required either O.5 % casein or polyvinylpyrrolidone in the extraction medium for maximal activity. Leaf NRA was proportional to light intensity and fertility levels. Mature tissue and high temperature decreased NRA. NRA showed significant genetic variability in broadly based genotypes and genotypes selected for photosynthetic rates and forage yields. However, progeny of the latter did not show significant genetic variability. High coefficients of variation (30-50%) among the heterogeneous progeny may have masked true genetic differences. No significant correlations were found between NRA and photosynthesis or …

Bacteria In The Air Of Housed Swine Units, L.F. Elliot, T.M. Mccalla, J.A. Deshazer

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Two housed, swine-growing-finishing units were studied for numbers of total bacteria, fecal coliforms, Staphylococcus, and Salmonella in the air. At 30.5 and 122 cm from the floor, total colony-forming particles, as tested, averaged 3.4 x 10) and 1.3 x 105/m³ of air, respectively; whereas fecal coliform counts averaged 24 x 103 and 1.9 x 103/m³ of air, respectively. Only 41% of the organisms growing on Staphylococcus 110 medium tested as Staphylococcus. Of 458 Staphylococcus isolates, 5 were coagulase-positive. No Salmonella were detected in the air of the units tested.

Relationship Between Physiological And Morphological Characteristics And Yield Of Nondormant Alfalfa Clones, A. L. Foutz, Wallace Wilhelm, A. K. Dobrenz

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Alfalfa (Medicago sativa L.) breeders are constantly striving to improve the productivity of alfalfa. Yields have been increased primarily through the selection of plant materials resistant to insects and diseases. The objective of this study was to evaluate physiological characteristics which might be used as selection criteria in alfalfa improvement. Alfalfa clones were grown under field conditions on a Mojave clay loam soil. Carbon dioxide flux was evaluated in a closed system using an infrared gas analyzer. The physiological variables measured in these studies did not account for the varialion in yield among the clones. Apparent photosynthetic rates, dark …

Luteinizing Hormone, Testosterone, Growth And Carcass Responses To Sexual Alteration In The Ram, B. D. Schanbacher, J. J. Ford

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A total of 130 ram lambs were used in a study to determine the effects of sex alteration on serum hormone levels, growth rate and carcass traits. Sex alteration included no treatment (intact rams), scrotal ablation to alter normal testicular secretion (short scrotum rams) and castration to completely remove influences derived from the testes (wethers). Although these data suggest that scrotal ablation at birth did not produce complete azoospermia in Finn-crossbred rams, reduction (P<.01) in testicular weight did produce significant results. Serum testosterone in short scrotum and intact rams was similar, whereas castration resulted in considerably lower concentrations of this steroid (P<.01). On the other hand, serum luteinizing hormone was increased (P<.01) threefold in short scrotum rams and 12-fold in wethers as compared to that of intact rams. Because these results cannot be fully explained by changes in serum testosterone, it is speculated that changes in secretory products of the testis which accompany degeneration of the germinal epithelium are responsible for elevated luteinizing hormone. Post-weaning average daily gain (P<.01) and feed efficiency were highest in intact and short scrotum rams indicating that testosterone (or testis) may be beneficial. Although dressing percentage and adjusted backfat were highest (P<.01) in wethers, carcass weight and yield grade were advantageous (P<.01) in short scrotum and intact rams. Quality grades were similar; all animals reached average choice.

Seasonal Changes In Sexual Activity And Serum Levels Of Lh And Testosterone In Finnish Landrace And Suffolk Rams, B. D. Schanbacher, D. D. Lunstra

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A procedure for assessing sexual activity (libido) in individual rams is described. Mating activity measured by this procedure and serum levels of luteinizing hormone (LH) and testosterone in Finnish Landrace and Suffolk rams was determined at 8-week intervals from October, 1974 through October, 1975. Seasonal changes were observed for serum LH, testosterone and libido index scores. Mating activity in rams was highest for both breeds during the peak breeding season (October) and declined 50% by late spring and summer before it increased the next October.

Serum LH concentrations were lowest in May (.54 ng/ml) and increased abruptly in July ( …