Sheep Updates 2007 - part 5

This session covers six papers from different authors: GENETIC IMPROVEMENT 1. Breech Strike Resistance: Selecting for resistance traits reduces breech strike, Bindi Murray, John Karlsson, Johan Greeff, Department of Agriculture and Food, Western Australia 2. Breeding Merino Sheep for Worm Resistance increases profit in a Mediterranean Environment, John Karlsson and Johan Greeff Department of Agriculture and Food, Western Australia FEEDING 3. Embryo lasses were not increased when Merino ewes that had lost weight were supplemented with lupins, C. Viñoles Gil, B.L. Paganoni, K.M.M. Glover, J.T.B. Milton & G.B. Martin, School of Animal Biology, Faculty of Natural and Agricultural Sciences, University of Western Australia, Crawley, WA 4. Mineral nutrition of sheep grazing dual-purpose wheats, Hugh Dove, CSIRO Plant Industry, Canberra, ACT BEEF PRODUCTIVITY 5. The effect of genetic potential and pre feedlot growth path on beef eating quality, Bill McKiernan and John WilkinsNSW Department of Primary Industries 6. Long-term consequences of growth and nutrition of cattle early in life for beef production, Paul Greenwood and Linda Cafe, Cooperative Research Centre for Beef Genetic Technologies, and NSW Department of Primary Industries Beef Industry Centre of Excellence, University of New England, Armidale NS

Effect of nutrition on follicle development and ovulation rate in the ewe

The general aim of this thesis was to gain further knowledge on the effect of nutrition on endocrine response and follicular dynamics in the cyclic ewe. Paper I presents an investigation of the effect of low and high body condition on follicular dynamics and endocrine profiles in ewes. The study showed that ewes in high body condition had a constant pattern of three follicle waves, while ewes in low body condition developed two or three waves during the cycle. Individual follicle tracking by ultrasonography (US) made it possible to study the growing profile of each follicle in relation to its endocrine milieu. Oestradiol and FSH levels were implicated in the regulation of follicle turnover. Ewes in a high body condition had a higher ovulation rate, which was associated with higher FSH and lower oestradiol concentrations during the follicular phase of the cycle. There was a lack of information regarding the limitations of US to evaluate follicles in different size and ovulation rate, which could replace more invasive techniques. The objective of Paper II was to assess the accuracy of ultrasonography in evaluating the number of follicles and corpora lutea (CL) compared with observations made at post-mortem examination of the ovaries. The predictive value and sensitivity of US was 100% for the presence and 96% for the absence of CL. The sensitivity was 80% for the determination of two CL. The sensitivity was high (90-95%) for follicles ³4 mm. The lower sensitivity (62%) and predictive value (71%) of US for evaluating smaller follicle classes (2 and 3 mm, respectively) may explain inconsistent results found in the literature. Overall, the study demonstrated that US is a good tool for counting the number of CL to evaluate ovulation rate under field conditions. In Paper III we evaluated if a short-term nutritional supplementation before ovulatory wave emergence could increase the number of follicles recruited into this wave, in ewes in low body condition. The supplement increased the proportion of ewes with a three-wave pattern, but neither FSH concentrations nor follicle recruitment were increased. In the short-term supplemented group the higher feed intake induced a decrease in progesterone concentrations, which prolonged the life span of the largest follicle present at the beginning of the nutritional treatment. A field trail was performed to evaluate the effect of the same nutritional treatment on ovulation rate. Ewes in moderate-high body condition had a higher ovulation rate than ewes in low body condition. In conclusion, short-term supplementation of ewes prolonged the life span of the last non-ovulatory follicle and promoted a 3-wave pattern of follicle development during the inter-ovulatory interval. Supplementation also promoted the development of a more active dominant follicle in ewes with a single ovulation. Short-term supplementation from Day 8 to Day 14 of the oestrous cycle increased ovulation rate in ewes with a moderate to high body condition. In Paper IV the hypothesis tested was that glucose, insulin, leptin and IGF-I are increased during a short-term supplementation. Acute changes in the peripheral concentrations of glucose and metabolic hormones related to time of feeding were measured. The results showed that glucose, insulin and leptin increased in the supplemented group on the third day after supplementation commenced. IGF-I concentrations were similar among groups. Thus, the effect of a short-term nutritional supplementation on ovulation rate in the ewe may be mediated through an increase in the concentrations of glucose, insulin and leptin

La consolidación de la generación de conocimiento y difusión de los sistemas silvopastoriles en Uruguay

La adopción de sistemas silvopastoriles (SSP) en Uruguay ha tenido un fuerte impulso en los últimos años. La generación de conocimiento en situaciones planificadas para explotar las sinergias entre los distintos componentes empiezan a consolidarse y los primeros resultados permiten ubicar a Uruguay en un punto de destaque en la temática. La creación de redes interinstitucionales estratégicas para diseñar experimentos de largo plazo, permitirá una mejor comprensión de las interacciones bióticas y abióticas de los SSP.Agencia Nacional de Investigación e Innovació

Simulación de sombra para una plantación silvopastoril de eucalipto híbrido según orientación de plantación: NS o E-O

La planificación del marco de plantación arbóreo en sistemas silvopastorileses un aspecto central para alcanzar el equilibrio productivo entre los distintos componentes. La radiación solar constituye un recurso crítico parala sustentabilidad productiva del sotobosque, sobretodo en lugares de latitudes altas y medias. El uso de modelos de simulación de sombras permite auxiliar la toma de decisiones en la planificación y manejo posterior del componente forestal de los sistemas silvopastoriles. El objetivo de este trabajo es estimar la superficie de sombreado de una plantación real de un híbrido de E. grandis x E. camaldulensis de 11 años de edad con diseño silvopastoril de filas simples con callejones de 20 m en dos orientaciones de plantación (N-S y E-O), localizada en la ciudad de Fraile Muerto,departamento de Cerro Largo Uruguay. Se caracterizaron los individuos arbóreos, colectando datos mediante trabajo de campo de las variables dasométricas: forma de copa, densidad de follaje, ancho de copa, longitud de la copa, altura del tronco, altura total y diámetro a la altura del pecho (DAP). Los árboles presentaron valores promedio de 31cm de DAP, 31 m de altura total (Ht), 9 m de altura de tronco, 22 m de longitud de copa viva y 6 m de ancho de copa. Se efectuaron 24 simulaciones estáticas de sombreado en 2 parcelas de 50 m x 50 m (2500 m2) con el software ShadeMotion v.4.0® (CATIE, 2017). Las simulaciones se realizaron en el día 21 de cada uno de los meses del año, a las 12PM. En todos los árboles se asumió una densidad de copa constante de 80% y pendiente 0°del terreno. Las simulaciones según las variables mencionadas indican quela parcela N-S presentó un rango anual de superficie de sombreado entre 29% y 34 %, y la parcela E-O de 29 % y 92 %, respectivamente para los solsticios de verano y de invierno. El promedio anual de superficie sombrada a las12PM fue de 33% para N-S y de 63% para la orientación E-O. En Uruguay estos resultados primarios permiten inferir que sistemas silvopastoriles establecidos en callejones con orientación N-S presentan menor variabilidad durante el año y mayor radiación acumulada a nivel de sotobosque. Estos resultados son coincidentes con lo reportado por otros autores, en donde se establece que la orientación N-S permite mayor incidencia de radiación para lugares de latitudes medias. No obstante, es fundamental mejorar la478comprensión de las variaciones espaciales y temporales de la radiación solaren distintos momentos del turno forestal, para posibilitar la planificación del manejo silvícola y permitir niveles de radiación adecuados para el desarrollo de especies que crecen en el sotobosque.Agencia Nacional de Investigación e Innovació

Sheep Updates 2007 - part 5

This session covers six papers from different authors: GENETIC IMPROVEMENT 1. Breech Strike Resistance: Selecting for resistance traits reduces breech strike, Bindi Murray, John Karlsson, Johan Greeff, Department of Agriculture and Food, Western Australia 2. Breeding Merino Sheep for Worm Resistance increases profit in a Mediterranean Environment, John Karlsson and Johan Greeff Department of Agriculture and Food, Western Australia FEEDING 3. Embryo lasses were not increased when Merino ewes that had lost weight were supplemented with lupins, C. Viñoles Gil, B.L. Paganoni, K.M.M. Glover, J.T.B. Milton & G.B. Martin, School of Animal Biology, Faculty of Natural and Agricultural Sciences, University of Western Australia, Crawley, WA 4. Mineral nutrition of sheep grazing dual-purpose wheats, Hugh Dove, CSIRO Plant Industry, Canberra, ACT BEEF PRODUCTIVITY 5. The effect of genetic potential and pre feedlot growth path on beef eating quality, Bill McKiernan and John WilkinsNSW Department of Primary Industries 6. Long-term consequences of growth and nutrition of cattle early in life for beef production, Paul Greenwood and Linda Cafe, Cooperative Research Centre for Beef Genetic Technologies, and NSW Department of Primary Industries Beef Industry Centre of Excellence, University of New England, Armidale NS