Agricultural Science Commons^™

Testosterone Regulation Of Luteinizing Hormone And Follicle Stimulating Hormone Secretion In Young Male Lambs, B. D. Schanbacher

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

Polydimethylsiloxane (Silastic) capsules containing crystalline testosterone were implanted subcutaneously in castrate lambs and evaluated for their ability to (1) provide stable, physiological concentrations of serum testosterone and (2) regulate secretion of LH and FSH. Testosterone was nondectable (<.2 ng/ml) between 12 and 24 weeks of age in the serum of castrate lambs implanted with empty capsules but was increased at those ages in Iambs implanted with 20 cm (1.2 ± .1 and .5 ± .1 ng/ml), 60 cm (2.8 ± .1 and .9 ± .1 ng/ml) and 180 cm (6.6 ± .3 and 1.9 ± .2 ng/ml) of testosterone-filled Silastic tubing. Serum concentrations of LH and FSH were suppressed by exogenous testosterone and did not exceed concentrations in intact control rams as long as serum testosterone concentrations were greater than 1 ng/ml. In conclusion, simultaneous suppression of serum LH and FSH by concentrations of testosterone that cause a dose-dependent stimulatory effect on accessory sex gland weights indicates that testosterone is a physiological regulator of gonadotropin secretion in ram lambs. Although testosterone per se may not be directly responsible for negative feedback on LH and FSH secretion, the results presented herein question the need for a nonsteroidal "inhibin-like" testicular hormone to regulate FSH in lambs.

Androgen Response Of Cryptorchid And Intact Rams To Ovine Lh, B. D. Schanbacher

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

Surgically induced cryptorchidism in rams resulted in elevated serum concentrations of LH but near-normal concentrations of androgen (testosterone and 5α-DHT).Injections of ovine LH (2 × 50μg;2 × 500 μg)resulted in maximal androgen secretion in the intact rams and similar but lower concentrations in cryptorchid rams. Peak concentrations were 14·9and 8·5ng/ml in the intact and cryptorchid rams respectively (P < 0·05).

Relationship Of Daylength And Prolactin To Resumption Of Reproductive Activity In Anestrous Ewes, Bruce Schanbacher

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

Concentrations of prolactin were measured in serum from three groups of Rambouillet ewes for 8 weeks to determine whether changes in prolactin concentrations were important during the transition from anestrus to seasonal breeding. Group I (control ewes) was maintained under conditions of natural daylength;group II (short-day ewes) was exposed abruptly on the longest day of the year to artificially shortened daylengths (8 hr light and 16 hr darkness); group III (CB 154 ewes) was maintained similar to control ewes except each ewe received twice daily im injections of 2-bromo-α-ergocryptine (CB 154). A fertile ram was kept with each group of …

Androgen Secretion And Characteristics Of Testicular Hcg Binding In Cryptorchid Rats, B. D. Schanbacher

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

Response of the cryptorchid testis to gonadotrophic stimulation was assessed by comparison of the androgen production capability in vivo and in vitro with that of the normal scrotal testis. Serum androgen concentrations in cryptorchid rats were similar to those in normal rats, and the incremental increase 60 min after 50 i.u. hCG (i.v.) was about 7-fold for both groups. Basal and hCG-stimulated androgen production in vitro was higher for abdominal testes (557 and 3286 ng/pair) than for scrotal tests (157 and 504 ng/pair). Specific binding of hCG by testicular homogenates was slightly higher (P < 0·05)for cryptorchid testes when expressed per unit weight, but Scatchard analysis indicated that although hCG binding affinities did not differ (Ka = 2×10¹⁰ M^-1), hCG binding …

Bacteriological Quality Of Runoff Water From Pastureland, John W. Doran, D.M. Linn

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

Runoff from a cow-calf pasture in eastern Nebraska was monitored for total coliforms (TC), fecal coliforms (FC), and fecal streptococci (FS) during 1976, 1977, and 1978. Bacteriological counts in runoff from both grazed and ungrazed areas generally exceeded recommended water quality standards. The FC group was the best indicator group of the impact of grazing. Rainfall runoff from the grazed area contained 5 to 10 times more FC than runoff from the fenced, ungrazed area. There was little difference in TC counts between the two areas, but FS counts were higher in runoff from the ungrazed area and reflected the …

Plant Nutrient And Economic Value Of Animal Manures, S. R. Wilkinson

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

Animal manures have economic value as plant nutrient sources and as amendments for soils whose physical properties can be improved by adding organic matter. Their value as fertilizer per metric ton applied is generally inverse to their water and carbon contents. Plant nutrient concentrations in animal manures are highly variable, thereby introducing uncertainty into meeting plant nutrient needs for crop production. Where manure has been applied for several years, however, little or no additional fertilizer phosphorus (P) and potassium (K) are needed for crop production. Animal manures were ranked in decreasing order as to replacement fertilizer value (dollars) as follows: …

Proceedings Of The 6th Annual Meeting, Southern Soybean Disease Workers (March 13-15, 1979, Hot Springs, Arkansas): Healthy Beans, A Key To Profit

Southern Soybean Disease Workers: Conference Proceedings

Contents

Schedule, Committees, Officers

The Gold That Grows, John Stephens

IPM Program, Joe Good

The Role of the Ag Consultant - Dick Jensen

Seed Quality, Ron Hager

Nematode-Economic Threshold, Don Schmitt

Problems of Marketing Foliar Fungicides, Gordon Elliott and Nic Thomas

Results of Point System in Determining Application Time, Billy Moore

Disease Loss Report, R. V. Sturgeon

Seed Treatment Report, M. C. McDaniel

SSDW Financial Status Report, Sid Stephens

Update of FIFRA and RPAR, Curtis L. Mason

Needs and Effects of a Foliar Fungicide - B. C. Smale

The Effect of Bean Pod Mottle, Soybean Mosaic and Bean Yellow Mosaic …

Relationship Of In Vitro Gonadotropin Binding To Bovine Testes And The Onset Of Spermatogenesis, B. D. Schanbacher

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

Concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined in serum of crossbred beef bulls during pubertal development. Serum LH ranged between .5 and 2.0 ng/ml with highest concentrations observed as 12 months of age. Serum FSH varied considerably among individuals but mean concentrations were within the normal range (50 to 100 ng/ml). Neither LH nor FSH increased at the time when testosterone increased or spermatogenesis entered meiosis.

Specific binding of ^{1 2 5} I-labeled human chorionic gonadotropin (hCG) and ^{1 2 5} I-labeled FSH to the bovine testis was demonstrated by autoradiographic localization techniques. Binding of …

Transmission Of Sarcocystis Suihominis From Humans To Swine To Nonhuman Primates (Pan Troglodytes, Macaca Mulatta, Macaca Irus), R. Fayer, A. O. Heydorn, A. J. Johnson, R. G. Leek

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

Sporocysts of Sarcocystis suihominis obtained from human feces were used to infect swine. Heart, tongue, and skeletal muscle from experimentally infected and noninfected control swine were fed via stomach tube to nonhuman primates including chimpanzees (Pan troglodytes), rhesus monkeys (Macaca mulatta), and cynomolgus monkeys (Macaca irus). All primates fed infected swine tissues shed sporocysts beginning 13 to 15 days postinfection and were still shedding sporocysts at the conclusion of the experiment, 30 days postinfection. Rhesus and cynomolgus monkeys were fed infected swine tissues a second time and shed sporocysts. All primates remained in good …

Fertilizing Capacity And Ultrastructure Of Fowl And Turkey Spermatozoa Before And After Freezing, M. R. Bakst, T. J. Sexton

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

The fertilizing capacity, motility and ultrastructure of fowl and turkey spermatozoa were examined at various stages of the freezing process. For both species, fertility and motility were depressed after equilibration with dimethylsulphoxide at 5 °C. After freezing, motility was maintained at 55% for fowl spermatozoa and 40% for turkey spermatozoa; however, fertility was 55% for the fowl and 0% for the turkey. Qualitatively, the damage to the spermatozoa of both species was nearly identical, as revealed by scanning and transmission electron microscopy. The plasmalemma was the primary site of damage. 'Bent' spermatozoa, coiled tails and swollen mitochondria were also present. …

Uterine Blood Flow Of Cows During The Oestrous Cycle And Early Pregnancy: Effect Of The Conceptus On The Uterine Blood Supply, S. P. Ford, J. R. Chenault, S. E. Echternkamp

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

Blood flow to each uterine horn of cows during the oestrous cycle and early pregnancy was determined daily by use of electromagnetic blood flow probes placed around both middle uterine arteries. The pattern of blood flow to uteri of pregnant and non-pregnant cows was similar until Day 14 after mating or oestrus. Between Days 14 and 18 of pregnancy blood flow to the uterine horn containing the conceptus increased (P < 0.01) 2- to 3-fold, whereas blood flow to the non-gravid uterine horn in these cows remained constant. No corresponding increase in blood flow to the uterine horn ipsilateral to the ovary bearing the CL was observed in non-pregnant cows during this 4-day period. By Day 19 of pregnancy, blood flow to the gravid uterine horn had returned to a level similar to that observed on Day 13. Blood flow to both uterine horns of pregnant cows remained constant from Days 19 to 25 and then increased to the gravid horn (P < 0.01) markedly until Day 30 whereas blood flow to the non-gravid horn remained low. Uterine blood flow during the oestrous cycle of non-pregnant cows was positively correlated (P < 0.01) with systemic concentrations of oestradiol and the ratio of oestradiol (pg/ml) to progesterone (ng/ml). There was no association between oestradiol concentrations and blood flow to the gravid uterine horn. These data indicate local control of uterine blood flow by the bovine conceptus which may function to create optimal conditions for the continuation of pregnancy.

Increased Lamb Production With Rams Exposed To Short Daylengths During The Nonbreeding Season, B. D. Schanbacher

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

Exposure of rams during the nonbreeding season (anestrous period) to short daylengths will initiate a new sexual cycle characterized by testicular growth, increased mating activity and improved semen quality. Lambing results accumulated from 300 potential matings indicate that rams exposed to artificial photoperiods of 8 hr light and 16 hr darkness for 10 weeks (referred to as rams on short-days) are more fertile than control rams maintained under the relatively long days of spring. When five control rams were penned individually with 30 ewes synchronized with progestogen and PMSG, 67% of the ewes were mated. Eighty-nine percent of the ewes …

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

Relationships between leaf photosynthesis and yield have not been well defined in forage grasses. Therefore, leaf growth, dry matter distribution, carbohydrate concentration, and growth analysis of four genotypes of tall fescue (Festuca mundinacea Schreb.) were examined. Genotypes, selected in the field for high and low CO₂ exchange rate (CER) in combination with high and low yield, were compared in an attempt to study the relationship between photosynthesis and yield.

In the vegetative growth stage, high yielding genotypes produced greater amounts of all plant parts (leaves, stem bases, and roots) than did low yielding genotypes; however, low yielding genotypes …

Leaf Growth, Leaf Aging, And Photosynthetic Rate Of Tall Fescue Genotypes, Wallace Wilhelm, C. J. Nelson

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

Leaf growth and leaf aging both influence the total amount of CO, fixed by a particular leaf in the canopy during its photosynthetically productive life. Four genotypes of tall fescue (Festuca arundinacea Schreb.) were selected for all combinations of high and low COB exchange rates (CER) and yield. The purpose of this study was to determine CER during aging and leaf growth rates of tall fescue genotypes in growth chambers and in the field on a Mexico silt loam (Udollic Ochraqualfs; fine, montmarillonitic, mesic). Leaf growth of vegetative tillers in controlled environments was continuous throughout the day for all …

Irradiance Response Of Tall Fescue Genotypes With Contrasting Levels Of Photosynthesis And Yield, Wallace Wilhelm, C. J. Nelson

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

The purpose of this study was to determine if genotype by irradiance interactions or genetic variation in diurnal trends of CO, exchange rate (CER) influenced the CER-yield relationship in tall fescue (Festuca mundinucea Schreb.). Genotypes were selected in the field for high CER-high yield, high CER-low yield, low CER-high yield, and low CER-low yield. Responses of CER to photosynthetic photon flux density (PPFD) of these genotypes were determined using both growth chamber- and field-grown material. The shapes of the PPFD response curves were similar for all genotypes, and saturation occurred at approximately 1,200 μE m^-2 sec^-1 (400 …

Proceedings Of The 5th Annual Meeting, Southern Soybean Disease Workers (March 21-23, 1978, Fort Walton Beach, Florida): 3 P'S In A Pod - Policies, Protection, Production

Southern Soybean Disease Workers: Conference Proceedings

Contents

Farm Policies, Weldon Barton (Assistant US Secretary of Agriculture)

World Soybean Problems, Glen Whitney, Dick Ford, and Frank Ray

Interrelation of Governmental Agencies with Industry, University, and Soybean Producers
EPA: Relationship and Responsibility to Agriculture and the Public, Nathan Chandler
EPA: Problems and Requirements of Registration, Herb Harrison
State: Pesticide Impact Program, Charles Smith
Industry: View on Benefit and Risk of the Pesticide Business, Charles Gilbert
University: Role of Land Grant University in Pesticide Development, James Martin
Producer: What's Needed, "Profit or Perish," Peter Myers

DBCP Status Report and Other Nematicides
Shell Chemical, Max Sckerl
Dow Chemical, Walter Miller …

Testicular Steroid Secretion In Response To Gnrh-Mediated Lh And Fsh Release In Bulls, B. D. Schanbacher, S. E. Echternkamp

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

Assay of frequently collected blood samples in four mature Hereford bulls indicated the existence of a tonic mechanism for the secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH), i.e., their episodic release was not observed. Increased plasma concentrations of LH and FSH, however, were obtained in response to an intravenous injection of 500 µg of gonadotropin releasing hormone (GnRH). These gonadotropins showed similar secretory profiles after GnRH, but the relative magnitude of the LH response (30-fold) was considerably greater than that of the FSH response (sevenfold).

Concentrations of testosterone in jugular and spermatic vein blood were increased sevenfold …

The Welfare Effects Of Erosion Controls, Banning Pesticides, And Limiting Fertilizer Application In The Corn Belt: Comment, Clayton Ogg

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

The recent Journal work by C. Robert Taylor and Klaus Frohberg was an impressive study from the standpoint of both the energy and imagination that must have gone into the model and the practical implications concerning the welfare effects of nonpoint pollution abatement. Yet, it appears that costs of nutrient management were considerably overestimated in the light of a number of experiments using techniques for controlling nutrient losses through proper timing of nitrogen fertilizer applications. Therefore. the model may have failed to represent the most cost effective techniques for reducing nitrogen pollution.

Acute And Chronic Effects Of Gonadotropin Releasing Hormone On Reproductive Characteristics Of Rams During The Nonbreeding Season, B. D. Schanbacher, D. D. Lunstra

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

Acute and chronic effects of gonadotropin releasing hormone (GnRH) administration on reproductive characteristics of 32 rams have been assessed during the nonbreeding season. Rams injected intramuscularly with 50 µg of GnRH had elevated (P<.01)concentrations of serum testosterone and noticeably higher (60%) mating activities when compared to control animals injected with saline. Daily injections of GnRH resulted not only in higher testosterone concentrations and mating activity, but also in increased testes size (P<.05). The apparent change in testicular function may account for the improvement in semen quality which was observed in these animals. Although benefits were only slight for percentages of live sperm, normal sperm and sperm with normal acrosomes, sperm motility was markedly increased (P<.05).

These data suggest that reproductive performance in rams is related to testicular androgen secretion and that a spring decline in those characteristics normally associated with high fertility in the male can be lessened by chronic treatment with GnRH.

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 ( …

Isolation And Identification Of Mycoplasma Agalactiae Subsp. Bovis From Arthritic Cattle In Iowa And Nebraska, O.H. V. Stalheim, S.S. Stone

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

Two strains of Mycoplasma were isolated from synovial fluids of arthritic feeder cattle and were identified as Mycoplasma agalactiae subsp. bovis by growth inhibition and fluorescent antibody tests. The strains (Iowa 1136 and Nebraska 2) could not be distinguished from known strains (Donetta and California 01) by immunoelectrophoresis or by agar gel precipitation.

Isolation And Identification Of Mycoplasma Agalactiae Subsp. Bovis From Arthritic Cattle In Iowa And Nebraska, O. H. V. Stalheim, S. S. Stone

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

Two strains of Mycoplasma were isolated from synovial fluids of arthritic feeder cattle and were identified as Mycoplasma agalactiae subsp. bovis by growth inhibition and fluorescent antibody tests. The strains (Iowa 1136 and Nebraska 2) could not be distinguished from known strains (Donetta and California 01) by immunoelectrophoresis or by agar gel precipitation.

Isolation And Identification Of Mycoplasma Agalactiae Subsp. Bovis From Arthritic Cattle In Iowa And Nebraska, O. H. V. Stalheim, S. S. Stone

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

Two strains of Mycoplasma were isolated from synovial fluids of arthritic feeder cattle and were identified as Mycoplasma agalactiae subsp. bovis by growth inhibition and fluorescent antibody tests. The strains (Iowa 1136 and Nebraska 2) could not be distinguished from known strains (Donetta and California 01) by immunoelectrophoresis or by agar gel precipitation.

Lysimetric Calibration Of The Bowen Ratio-Energy Balance Method For Evapotranspiration Estimation In The Central Great Plains, Blaine L. Blad, Norman J. Rosenberg

Department of Agronomy and Horticulture: Faculty Publications

Most reports show good agreement between evapotranspiration (ET) rates estimated by Bowen Ratio-Energy Balance (BREB) method and rates measured with lysimeters, although underestimation by the BREB model has occasionally been reported. This study was conducted to evaluate the performance of the BREB technique in the climatic conditions characteristic of the central Great Plains, a region where a significant proportion of the energy consumed by evapotranspiration is supplied from advected sensible heat.

Agreement between the BREB method and lysimetric measurements of ET is good during non-advective periods but during advective periods the BREB model underestimates ET by about 20%. Data collected …

Developmental Changes In Spermatogenesis, Testicular Carnitine Acetyltransferase Activity And Serum Testosterone In The Ram, B. D. Schanbacher, W. R. Gomes, N. L. Vandemark

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

Total of 73 crossbred rams was used to determine spermatogenic and steroidogenic changes in the testis of the growing animal. Testicular weight increased slowly until 80 days of age, then increased tenfold during the following 3 months. Spermatogenesis began in rams at 60 to 70 days of age and was qualitatively complete by 120 days. Although testicular levels of the enzyme carnitine acetyltransferase (CAT) increased in growing rams, CAT did not appear to be uniquely associated with any particular cell type. Therefore, this enzyme was judged to be unsatisfactory as a cell "marker" in studying spermatogenesis in this species. Serum …