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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
451

Produtividade e viabilidade econômica da recria e engorda de bovinos em pastagens adubadas intensivamente com e sem o uso da irrigação. / Productivity and economic viability of beef cattle production at highly fertilazed pastures with and without irrigation.

Fabio Luiz Aires Maya 04 July 2003 (has links)
A pecuária de corte extensiva se mostra incapaz de competir em termos de resultados econômicos com outras alternativas de uso da terra em regiões de terras valorizadas, fato que pode ser comprovado pela substituição gradativa de áreas de pastagens por culturas agrícolas. Nessas regiões, a adubação intensiva de pastagens tem se tornado a opção freqüentemente utilizada para o incremento da produtividade animal que é imprescindível para a viabilização econômica da pecuária frente a demais alternativas de uso da terra. A irrigação aliada à adubação de pastagens cresceu muito desde o final da década de 90 no Brasil Central, crescimento motivado pela expectativa de resultados produtivos elevados como os divulgados por revistas técnicas especializadas. Com o intuito de comparar os resultados produtivos e econômicos de pastagens adubadas intensivamente com e sem o uso da irrigação, foram conduzidos dois experimentos ao longo de um ano em pastagens de Panicum maximum cv tanzânia. Foram avaliados desempenho animal, taxa de lotação e produtividade nos experimentos. A avaliação econômica foi efetuada com a determinação dos indicadores lucro líquido, taxa de retorno sobre o ativo e taxa interna de retorno, por meio de simulações determinísticas e estocásticas. Enquanto no experimento em sequeiro os valores de desempenho animal e de taxa de lotação médios obtidos foram de 0,615 kg GPD e 5,6 UA/ha, respectivamente, no experimento irrigado foram obtidos 0,492 kg GPD e 5,9 UA/ha. A irrigação só foi efetiva no incremento da taxa de lotação na transição entre os períodos de “seca” e “águas”, não confirmando o potencial da irrigação de pastagens no incremento da taxa de lotação. A diferença de produtividade animal entre os experimentos foi minimizada pelo maior desempenho animal do experimento sem irrigação em alguns períodos. Foram obtidas produtividades de 1.628 kg PV/ha no experimento irrigado e 1.672 kg PV/ha no em sequeiro, corroborando o potencial de produtividade de pastagens adubadas intensivamente. A análise de viabilidade sem a consideração de risco apresentou resultados de lucro líquido, taxa de retorno sobre o ativo e taxa interna de retorno, respectivamente de R$ - 164,91 por hectare, - 1,0% e – 6,1%, para o sistema irrigado e R$ 574,90 por hectare, 4,4% e 17,2% para o em sequeiro. Contudo, essa análise subestimou os resultados dos indicadores de viabilidade econômica em ambos sistemas. A análise de risco apontou o sistema irrigado como inviável economicamente, enquanto para o sistema sem irrigação a probabilidade de um resultado econômico que apontasse inviabilidade foi baixa. / Extensive beef production cannot compete with others uses of land for agricultural productions, mainly where land costs are high, therefore a gradual substitution of pasture areas for agricultural crops is occurring. High levels of fertilizer application to pastures have been used for improving beef productivity and, consequently, improve the economic profitability of this activity. Irrigation of pasture increased since 90’s in Central Brazil, motivated by the expectation of high productivities as presented in technical magazines. The objective of this research was to compare the productivity and economic results of highly fertilized pasture, with and without irrigation. Two experiments were conducted for a year in Panicum maximum cv tanzânia pastures. Weight gain, stocking rate and beef productivity were evaluated. In the economic evaluation was determined net margin, simple rate of return and internal rate of return, using deterministic and stochastic simulations. In the non-irrigated experiment the weight gain was 0,615 kg/day and the stocking rate 5,6 AU/ha, and in the irrigated one, 0,492 kg/day and 5,9 AU/ha, respectively. The irrigation only increased the stocking rate in the season transition between dry and rainy period, not confirming the potential for pasture irrigation in the Central South part of Brazil by increasing stocking rate. Productivity difference in irrigated and non-irrigated pastures was minimized by the high weight gain of non-irrigated area in some periods. The animal live weigh gain was 1.628 kg/ha in irrigated experiment, and 1.678 kg/ha in non-irrigated one, indicating high potential for productivity of highly fertilized pasture. The analysis without risk consideration showed results of net margin, simple rate of return and internal rate of return, respectively of R$ -164,91 per hectare, - 1,0% and -6,1% for irrigated system, and R$ 574,90 per hectare, 4,4% and 17,2% for non-irrigated one. Deterministic analysis sub estimated the results of economic viability indicators. Risk analysis showed weak probability of economic viability for irrigated system. Non-irrigated system with high levels of fertilizer application indicated weak probability for not been an economic activity.
452

Produção de cordeiros em pastagem tropical : dos aspectos bioquímicos da pastagem ao comportamento ingestivo animal / Lamb production in tropical pasture : from the biochemical aspects of pasture to animal ingestive behavior

Tontini, Jalise Fabíola January 2018 (has links)
As pastagens que cobrem uma importante área no território mundial apresentam elevado potencial de produtividade e suas características bioquímicas podem gerar relevante impacto na produção de ruminantes. Porém, poucos trabalhos relatam a concentração de compostos bioquímicos em pastagens tropicais comumente usadas na produção animal. Diante deste fato, o capítulo II desta tese teve como objetivo elucidar e determinar a concentração de taninos condensados e tocoferol, bem como avaliar a produção e os valores nutritivos de espécies forrageiras tropicais normalmente usadas em sistemas de pastejo. Com este estudo foi possível constatar que algumas espécies de gramíneas e leguminosas se destacam não apenas pela sua capacidade de produção de biomassa e qualidade nutricional, mas também pela concentração de compostos bioquímicos, como a gramínea tifton que teve elevada concentração de α-tocoferol (202.3 ± 116.5 mg/kg matéria verde, MV). As leguminosas amendoim forrageiro (15.7 ± 5.2 g/kg matéria seca, MS) e feijão guandu (8.7 ± 0.8 g/kg MS) apresentaram boa concentração de taninos condensados, mas o grande destaque foi para a leguminosa nativa pega-pega (66.5 ± 13.8 g/kg MS) que além da alta concentração de taninos, esses apresentaram potencial para atividade biológica (PPF = 60.1 g/kg MS) Aliado as características bioquímicas, as espécies que irão compor o sistema de produção podem influenciar na biologia de vida livre dos nematoides parasitas do trato gastrintestinal (NGI) e no comportamento ingestivo dos animais. O capítulo III e IV avaliam três diferentes sistemas de alimentação de cordeiros em pastagens tropicais. O capítulo III traz como objetivo avaliar a distribuição de larvas infectantes (L3) em diferentes perfis de pastagem tropical (gramíneas e leguminosas) e o impacto da contaminação da pastagem na carga parasitária e desempenho de cordeiros. Onde, a inclusão da leguminosa tropical alterou a concentração de larvas infectantes na pastagem e a contaminação dos animais. No capítulo IV é apresentado o trabalho que teve como objetivo avaliar o comportamento ingestivo de cordeiros em condições de pastejo contínuo submetidos a diferentes sistemas de alimentação com a presença de leguminosa tropical contendo taninos condensados. Apesar da diferença estrutural e concentração de taninos condensados, de modo geral essas características da pastagem não alteraram o comportamento ingestivo dos cordeiros. / Pastures covering an important area in the world territory present high production potential and their biochemical characteristics can generate a significant impact on the production of ruminants. However, few studies report the concentration of biochemical compounds in tropical pastures commonly used in animal production. Facing this fact, chapter II of this thesis had as objective to elucidate and to determine the concentration of condensed tannins and tocopherol, as well as to evaluate the production and nutritional values of tropical forage species normally used in grazing systems. In this study, it was possible to verify that some species of grasses and legumes stand out not only for their mass production capacity and nutritional quality, but also for the concentration of secondary compounds, such as tifton grass, which had a high α-tocopherol concentration (202.3 ± 116.5 mg / kg green matter, GM). The forage peanut legumes (15.7 ± 5.2 g / kg dry matter, DM) and pigeon pea (8.7 ± 0.8 g / kg DM) had an excellent concentration of condensed tannins, but the main highlight was the native legume Desmodium incunum (66.5 ± 13.8 g / kg DM) that in addition to the high concentration of tannins, these had potential for biological activity (PPP = 60.1 g / kg DM) In addition to the biochemical characteristics, the species that will make up the production system can influence the ecology of the free-living stages of endoparasite of the gastrointestinal tract (NGI) and the ingestive behavior of the animals. Chapter III and IV evaluate three different feeding systems of lambs in tropical pastures. Chapter III aims to evaluate L3 distribution in different tropical pasture (grass and legume) profiles and the impact of pasture contamination on lamb parasitic loads and production performance. Where the inclusion of the tropical legume changed the concentration of infective larvae in the pasture and the contamination of the animals. Chapter IV presents the work that aimed to evaluate the ingestive behavior of lambs under continuous grazing conditions submitted to different feeding systems with the presence of tropical legume containing condensed tannins. Despite the structural difference and concentration of condensed tannins, in general these pasture characteristics did not alter the ingestive behavior of the lambs.
453

WEED CONTROL SYSTEMS IN SYNTHETIC AUXIN-RESISTANT SOYBEANS

Connor L Hodgskiss (8932271) 23 June 2020 (has links)
<p>Herbicide-resistant weed populations have become problematic throughout the Eastern Corn Belt, with 18 unique herbicide-resistant weed biotypes confirmed in Indiana alone. In response to these resistant populations, the agricultural chemical industry has responded by developing glyphosate-resistant crops paired with resistance to synthetic auxin herbicides such as dicamba and 2,4-D.</p><p>This research evaluates weed population shifts in cropping systems using row crops that are resistant to synthetic auxin herbicides. Identifying weed population shifts will allow future research to be targeted to weed species that would become more prevalent in cropping systems using synthetic auxin-resistant crops. The use of multiple sites of action will be needed in order to prevent weed shifts in both conventional and no-till corn-soybean production systems. Weed densities and species richness were reduced within field evaluations when six or more herbicide sites of action were implemented with residual herbicides in both corn and soybean years over a seven-year period. Additionally, soil seedbank weed densities and species richness were reduced within 2,4-D-resistant soybean production systems. Additional strategies other than the application of herbicides may be needed to manage weed populations in the future due to the high levels of herbicide-resistant weed populations in the Midwest.</p><p>Off-target movement of these synthetic auxin herbicides, has been a concern, and label-mandated buffer areas are required near sensitive areas. Investigation of whether cover crops can be an effective tactic in managing weeds in these label-mandated buffer areas was conducted. Cover crop utilization in buffer areas has not been investigated in Indiana. Additionally, termination timing is becoming more prominent as farm operators are increasingly terminating cover crops after planting. Our results demonstrate that using cover crops that utilize cereal rye and that are terminated at, or after the time of soybean planting will be beneficial in suppressing waterhemp, grasses, and sometimes horseweed within label-mandated buffer areas, but not for suppression of giant ragweed. However, delaying termination of cover crops can result in soybean yield reductions and caution should be used. Terminating cover crops with glyphosate and auxin and a residual herbicide was more effective than glyphosate alone, but would not be permitted within label-mandated buffer areas.L</p>
454

ASSESSMENT OF POSTHARVEST PEST MANAGEMENT PRACTICES IN NEPAL AND EFFICACY OF HYPOXIA FOR CONTROLLING SITOPHILUS ORYZAE L. (COLEOPTERA: CURCULIONIDAE)

Pragya Kandel (10752345) 22 July 2021 (has links)
Farmers in Nepal lose about a third of their harvested grain due to postharvest handling and storage. This has led to food insecurity and economic losses. Despite the importance of postharvest, the grain storage system in Nepal relies on traditional storage structures like bamboo granaries. The incidence of storage pests is reported up to 100% in these structures. To minimize the storage loss, farmers use different grain protection methods including toxic chemicals. Multiple cases of pesticides-related poisoning and deaths have been caused by misuse and overuse of pesticides. To push safer, chemical-free alternatives like hermetic storage it is important to understand current pest challenges and management practices in Nepal. Adaptation of chemical-free pest management strategies like hermetic storage largely depends upon basic and applied laboratory research findings. Determining the baseline adult mortality under various hypoxia levels and subsequent insect emergence will help determine the effectiveness of a low oxygen environment in controlling <i>Sitophilus oryzae</i> (L.). This would increase our understanding of hermetic storage technology and help improve its application to both farmers and commercial users and serve as a possible substitute to traditional or chemical pest control methods. In chapter one, I report the result of the survey conducted in Nepal to understand i) current post-harvest storage practices and (ii) assessment of the best delivery approach for storage innovations. In chapter 2, I report the result from laboratory experiment conducted to understand the lethality of hypoxia at 5% oxygen level and below against <i>Sitophilus oryzae</i> (L.), which is a major storage pest reported by farmers in Nepal.
455

Influence of Mesotrione, ALS-Inhibitor Resistance, and Self-Incompatibility on Giant Ragweed Management in Soybean

Benjamin Clyde Westrich (12468291) 28 April 2022 (has links)
<p>  </p> <p>Giant ragweed (<em>Ambrosia trifida</em> L.) is an annual broadleaf plant capable of emergence throughout the cropping season, opportune colonization of disturbed soil, rapid biomass accumulation, and a propensity to evolve mutations that endow resistance to herbicides, all of which contribute to giant ragweed being one of the most challenging weeds to control in row-crop production. Many soybean growers rely on acetolactate synthase (ALS)-inhibiting herbicides such as cloransulam for control of giant ragweed prior to its emergence, though the spread of biotypes resistant to ALS inhibitors can render these herbicides largely ineffective. Mesotrione inhibits the 4-hydroxyphenylpyruvate dioxygenase (HPPD) enzyme, and applications of this herbicide have recently been approved for use in mesotrione-resistant soybean varieties. Field experiments demonstrated that preemergence applications of mesotrione resulted in greater control of giant ragweed populations segregating for ALS-inhibitor resistance than several other commonly used herbicide combinations. Where mesotrione was applied, giant ragweed biomass was reduced by an average of 84% relative to the nontreated, while treatments without mesotrione increased biomass by an average of 34% by suppressing competition from other weed species. Additionally, both soil- and agar-based bioassays demonstrated that combinations of mesotrione and metribuzin can be synergistic for control of giant ragweed. </p> <p>Cloransulam was shown to result in strong selection for giant ragweed individuals with ALS-inhibitor resistance, increasing the proportion of resistant plants that emerged at one field site from 15% to greater than 90% after a single preemergence application. This selection pressure was reduced when mesotrione was co-applied with cloransulam. However, no herbicide combination, including sequential applications of non-ALS-inhibiting herbicides, consistently resulted in a resistance frequency similar to the baseline if an ALS inhibitor was applied preemergence. Resistance to cloransulam and other ALS inhibitors is expressed in giant ragweed plants possessing at least one mutant (Trp574Leu) <em>ALS</em> allele. The distribution of this allele in one field violated the Hardy-Weinberg Equilibrium, despite the fact that <em>ALS</em> is a nuclear gene and the Trp574Leu mutation does not incur a fitness penalty. We suspected that the inheritance of this mutation may be linked with a gene or genes responsible for self-incompatibility (SI) in giant ragweed, and that linkage drag was disrupting pollination in resistant plants. This research provided evidence that giant ragweed does possess SI, as greater pollen retention, pollen tube growth, and seed set were observed in cross-pollinated plants compared with self-pollinated plants. Non-Mendelian inheritance of the Trp574Leu mutation was documented in crosses between plants from three different giant ragweed populations, indicating that the mutant <em>ALS</em> allele may be linked with an SI allele common to many plants because of a shared resistant ancestor.  In crosses between plants from one population, production of resistant F1 seeds was 33% greater on average compared with the expectation under Mendelian inheritance. </p> <p>Collectively, this research demonstrated that mesotrione may become a highly effective tool for control of giant ragweed in soybean. Applications of mesotrione can also reduce the selection for an increased frequency of ALS inhibitor-resistant biotypes induced by cloransulam, though a more robust weed management strategy may be necessary to maintain the long-term viability of ALS inhibitors.  The need for sound weed management practices is underscored by the impact of the linkage of SI and <em>ALS</em> genes, which may be encouraging a more rapid spread of herbicide-resistance than was previously anticipated.</p>
456

Efecto del aporte de ensilaje de sorgo a la dieta de vaquillonas que pastorean verdeo de trigo

Coria, María Lucía 27 September 2010 (has links)
The objetive of this study was to evaluate the association between wheat pasture (WP) and sorghum silage (SS), from a nutritional and production viewpoint, to optimize the use of both resources. Three experiments were performed: I. Consumption, digestibility of DM, N and use of forage fiber; II. Mass of WP, weight and growth performance: average daily gain (ADG) and beef production/ha and, III. Estimation of voluntary intake by an external marker, LIPE. WP nutritional quality, %: June: 25.6, 18.1, 18.0, 88.9, 36.2, 15.6, July: 38.4, 18.2 , 17.1, 88, 8; 36, 3, 15.7, August 8: 45.6, 14.0, 16.6, 78.9, 42.1, 19 7, August 24: 41.7, 16.7, 14.7, 73.2, 52.4, 21.0, September: 25 0, 18.6, 9.7, 71.4, 60.0 and 26.5 for dry matter (DM), crude protein (CP), non-structural carbohydrates (CNES), in vitro DM digestibility (DMD), neutral detergent fiber (NDF) and acid detergent fiber (ADF), respectively. The values for the same quality parameters of SS were 30.4, 51.2, 7.8, 61.3, 35.3, 2.5, 18.9 and 1.9. In Experiment I, 24 lambs of 38+4.4 kg of body weight (BW) were placed in individual metabolism cages. The treatments were: WP ad libitum, SS ad libitum, 800WP (800g WP + SS), 600WP (600g WP + SS), 400WP (400g WP + SS) and 200WP (200g WP + SS). Total diet intake was determined by the difference between offered and rejected feed. Total fecal output (FO), as well as marker technique (LIPE) were used to estimate in vivo DMD. Other determinations included: NDF, ADF, IVDMD, NDF digestibility, ADF digestibility and balance of nitrogen (N). The Experiment II lasted 101 days (from 11/06 to 19/09, 2007). 60 heifers of 8 months of age and 200 +24.7 kg BW were used, which were distributed in six treatments in a factorial arrangement of two alternatives for availability (WP and WP + SS) and three intensities (A, M and B) with two replications. In Experiment III, 24 heifers were used. The treatments evaluated were the same as in Experiment II. SS intake was estimated by the difference between offered and rejected, and total intake of feed by an external marker, LIPE. The DMD was determined in vitro. In experiment I there was effect of diet (p <0.01) on NDF, IVDMD FDA, DIVFDA, N content in the diet, urine and N retained. Increasing WP allowances to SS basal diet showed no differences between them, nor against the pure diets, with the total DM intake in lambs. Animals that consumed WP, could replace up to 75% of this ingredient from SS, without to lower the consumption of MSD. Only in the ad libitum diet of WP N maintenance requirements of the lambs were covered, with negative balance in the other treatments. In experiment II there were differences (p <0.0001) between diets, and interaction D x I (p <0.05) for total C in WP and IVDMD. The total C was higher in WP without the addition of SS (A, M and B) for the three I with a substitution effect with depressed in consumption of WP in SS treatments. In experiment III, there were no significant differences for availability of WP between treatments (p = 0.9391 for D and p= 0.4171 for I), there was differences between dates sampling (DS) and interactions between I x DS and between I x DS x D. The average forage availability for WP was 800 kgDM/ ha. The ADG and AW differ significantly (p <0.0001) between weighing dates. The receptivity of WP increased by 83% (p ≤ 0.01) by the use of SS for AS and 69% for MS, the effect was not significant for BS (31%). There was variation in the relationship PB: CNES between diets with SS respect to the diets based only on WP, however AG of the heifers did not differ between treatments. The use of high grazing intensities of WP would not affect the ADG in heifers, which would increase the stocking rate or extend the grazing period of WP without affecting production. The enclosure for 20 h in SS and grazing WP for 4 h in growing heifers increases the receptivity of WP, may improve the stability of the productive results and thus increase the benefits of farms. / El objetivo de este trabajo fue evaluar las interacciones entre el verdeo de trigo (VT) y el silaje de sorgo (SS), desde el punto de vista nutricional y productivo, para optimizar el aprovechamiento de ambos recursos. Para esto se realizaron tres experimentos: I. Consumo, digestibilidad de la MS, uso del N y de la fibra del alimento; II. Disponibilidad del verdeo, peso vivo y respuesta productiva: ganancia diaria de peso y peso acumulado por hectárea; y III. Estimación del consumo voluntario por medio de un marcador externo, LIPE. Calidad nutritiva del VT en %: junio: 25,6; 18,1; 18,0; 88,9; 36,2; 15,6; julio: 38,4; 18,2; 17,1; 88,8 36;3; 15,7; 08 de agosto: 45,6; 14,0; 16,6; 78,9; 42,1; 19,7; 24 de agosto: 41,7; 16,7; 14,7; 73,2; 52,4; 21,0; septiembre: 25,0; 18,6; 9,7; 71,4; 60,0 y 26,5 para materia seca (MS), proteína bruta (PB), carbohidratos no estructurales (CNES), digestibilidad de la MS (DIVMS), fibra detergente neutro (FDN) y fibra detergente ácido (FDA), respectivamente. Los valores para los mismos parámetros de calidad del SS fueron: 30,4; 51,2; 7,8; 61,3; 35,3; 2,5; 18,9 y 1.9. En el Experimento I se utilizaron 24 corderos de 38+4.4 kg de peso vivo (PV), que se ubicaron en jaulas de metabolismo individuales. Las dietas evaluadas fueron: VT ad libitum, SS ad libitum, 800VT (800g de VT+SS), 600VT (600g de VT+SS), 400VT (400g de VT+SS) y 200VT (200g de VT+SS). Mediciones: consumo de MS (C) de SS y VT por oferta y rechazo y con el marcador, FDN, FDA, DIVMS, DIVFDN (digestibilidad de la FDN) y DIVFDA (digestibilidad de la FDA); producción de heces (PH) y balance de nitrógeno (N). El Experimento II duró 101 días (del 11/06 a 19/09 de 2007). Se utilizaron 60 vaquillonas de 8 meses de edad y de 200 +24,7 kg PV, que se distribuyeron en 6 tratamientos en un arreglo factorial de dos alternativas de Disponibilidad (VT y VT+SS) y tres Intensidades (A, M y B), con dos repeticiones. En el Experimento III se utilizaron 24 vaquillonas. Los tratamientos fueron los mismos que en el Experimento II. Se estimó el C de SS por oferta y rechazo y C total con un marcador externo, LIPE. La digestibilidad se determinó in vitro. En el Experimento I hubo efectos de dieta (p<0.01) sobre contenido de FDN, FDA DIVMS, DIVFDA, contenido de N en la dieta, en la orina y retenido. Asignaciones crecientes de VT a una dieta basal de SS no mostraron diferencias entre sí, ni tampoco frente a las dietas puras, en el consumo de MS total con corderos. Animales que consumieron VT, pudieron reemplazar hasta un 75% de este ingrediente por SS, sin que decayera el consumo de MSD. Solamente en la dieta de VT ad libitum se cubrieron los requerimientos de mantenimiento de N de los corderos, siendo el balance negativo en los demás tratamientos. En el Experimento II, no hubo diferencias significativas para disponibilidad de VT entre los tratamientos (p= 0,9391 para D y p= 0,4171 para I), sí hubo entre fechas (F) de muestreo y para las interacciones entre I*F y entre I*F*T. La disponibilidad promedio del VT fue de 800 kgMS/ha. La GP y el ADP presentaron diferencias significativas (p<0,0001) entre fechas de pesadas. La receptividad del verdeo aumentó en 83% (p≤ 0,01) por el uso de SS para AS y un 69% para MS, no siendo significativo el efecto para BS (31%). En el Experimento III hubo diferencias (p<0.0001) entre D, y para la interacción D x I (p<0.05) para C total, de VT y para DIVMS. El C total fue mayor en VT sin aporte de SS (A, M y B) para las tres I, con un efecto de sustitución con depresión del consumo del VT en los tratamientos con SS. Hubo variación en la relación PB:CNES entre las dietas a base de SS con VT respecto a las dietas basadas únicamente en VT sin embargo las GP de las vaquillonas no difirieron entre tratamientos. La utilización de altas intensidades de pastoreo de VT no afectarían las GP en vaquillonas, lo cual permitiría aumentar la carga animal o prolongar el período de pastoreo del VT sin afectar la producción. El encierre durante 20 horas en SS y pastoreo de 4 horas en VT en recría de vaquillonas aumenta la receptividad del mismo, pudiendo mejorar la estabilidad de los resultados productivos y aumentar de esta forma los beneficios de la explotación.
457

Integrated Agronomic Management Practices for Tall Fescue in Mississippi

Slusher, Patton J 14 August 2015 (has links)
Tall fescue (Schedonorus arundinaceus), is a cool season perennial that provides grazing into the early summer months for southern livestock. Grazing the tall fescue variety, Kentucky-31, has negative effects on animal health, particularly after jointing. Two studies were arranged as randomized complete blocks in a split-plot design, with three replicates to compare: the effect of ten herbicides on seedhead suppression, or the effect of inter-seeding legumes [white clover (Trifolium repens) or alfafla (Medicago sativa)] coupled with nitrogen supplementation on fescue yield and forage nutritive value. The herbicides imazethapyr + 2,4-D and without, metsulfuron + chlorsulfuron, reduced seedheads emergence, but not yield compared to the control. Kentucky-31 inter-seeded with white clover and fertilized with 11 kg N ha-1 produced greater biomass than tall fescue fertilized with 11 kg N ha-1. The inter-seeding of white clover produced composite forage samples with greater in vitro dry matter disappearance than nitrogen supplemented alfalfa.
458

Evaluation of heat abatement use, vaginal temperature, and activity of pregnant, lactating Holstein cows housed on pasture with or without the choice between shade and sprinklers for heat abatement.

Braman, Kevin M. 08 August 2023 (has links) (PDF)
The objective of this thesis was to determine how pregnant, lactating Holstein cows on pasture interact with shade and sprinklers when offered a choice or no-choice between methods. Authors hypothesized that cows would use shade more then sprinklers, but sprinklers would be more effective at cooling cows. Additionally, authors predicted cows using shade more would have decreased lying bouts and steps and an increase in time lying, compared to cows choosing sprinkler. Results indicate cows will use both methods when offered alone or together. However, cows will choose to be exposed or in shade at lower temperature humidity index values, but as the heat load increases, cows will shift to using sprinkler just as much as shade, and decrease overall time exposed. Overall, sprinklers were more effective at reducing vaginal temperature in heat stressed cows on pasture. Cows in shade had decreased lying bouts and steps, and increased time lying.
459

Arthropod community response to high-intensity, low-frequency cattle grazing events and pasture succession

Bankroff, Timothy J. 03 December 2014 (has links)
No description available.
460

The Effect of Environment and Social Dynamics on Lamb Behavior

Pullin, Allison Nicole 27 June 2017 (has links)
No description available.

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