Effect of Forage Allowance on Native Pasture Traits, Stocking Rate and Beef Cow Body Condition

Stocking rate is a poor indicator of grazing intensity because, in contrast to forage allowance, it gives no information of feed availability. Forage allowance (FA), measured as kg of forage dry matter (DM) per kg of live weight (LW), is the ratio between forage mass and stocking rate (Sollenberger et al. 2005). Crossbred cows demonstrated higher production efficiency than purebreds in poor and rich quality pastures (Barlow et al. 1994) but few experiments have been conducted under different FA in Campos grasslands with growing beef steers (Maraschin et al. 1997, Soares et al. 2005), and no work has been conducted with beef cows during various gestation-lactation cycles. Also, there have been no studies on FA to test for interations between cow genotype and environment. The objective of this work was to test the effect of two FA and two cow genotypes on pasture traits, stocking rate and body condition score (BCS) of cows

Forage Allowance and Cow Genotype, Tools to Increase Animal Production in Native Pastures

In eight plots (four per block) the effects of two FA per two cow genotypes were tested from August 2007 to March 2010, on a Campos grassland (major species were Axonopus affinis, Oxalis sp., Cyperus sp., Cynodon dactylon, Eryngium nudicaule, Gaudinia fragilis, Chevreulia sarmentosa, Stipa setigera, Paspalum notatum and Coelorhachis selloana) in Uruguay (32º 20` S, 54º 26` W). Forage allowance varied seasonally, in HIGH (5, 3, 4 and 4 kg DM/kg LW) and LOW (3, 3, 2 and 2 kg DM/kg LW) during autumn, winter, spring and summer; respectively. Continuous stocking method was applied throughout the year, with FA adjusted monthly, using the “put and take method” (Mott and Lucas 1952). Thirty PURE (Hereford and Aberdeen Angus) and thirty CROSS (F1 reciprocal Hereford and Angus crosses) multiparous cows, aged four to eight years with normal calving and pregnancies, were randomly assigned to the plots. Cow LW and BCS were measured monthly and in key moments such as calving and at the beginning of the breeding season. BCS was visually assigned on a scale ranking from 1 = very thin to 8 = very fat (Vizcarra et al. 1986). Cows did not breed during summer 2010. Data of cow LW and BCS and calf weight at weaning (94 ± 31 d) were analyzed using the MIXED procedure (SAS Institute, Cary, NC, USA, 2002). The model included FA, cow genotype, year and their interactions as fixed effects, block as random effect, and for cow BCS at the beginning of the breeding season, cow BCS at calving was used as covariate. Tukey–Kramer test were conducted for mean separation (α = 0.05)

Avaliação de painéis de SNP como ferramentas em melhoramento genético de ovinos Corriedale no Uruguai

One control strategy for gastrointestinal nematodes (GIN) is genetic selection. This study´s objective was to compare eggs per gram of feces (FEC) and fiber diameter (FD) estimated breeding values (EBV) and genomic EBV (GEBV) in Corriedale breed. Analysis included 19547 lambs with data, and 454, 711 and 383 genotypes from 170, 507 and 50K SNP chips, respectively. A univariate animal model was used for EBV and GEBV estimation, which included contemporary group, type of birth and dam age as fixed effects, and age at recording as covariate. Differential weights (α) were considered in the genomic relationship matrix (G), and the best fit models were identified using Akaike´s Information Criterion (AIC), which were later used for GEBV and accuracies estimation. The use of α only impacted on low density SNP chips. No differences were observed in mean accuracies for the whole population. However, in the genotyped subgroup accuracies increased by 2% with the 170 SNP chip (α=0.25), and by 5% (α=0.5) and 14% (α=0.75) with the 507 SNP chip. No differences were observed in FD EBV and GEBV mean accuracies. These results show that it is possible to increase GEBV accuracies despite the use of low-density chips.Una alternativa para el control de los nematodos gastrointestinales (NGI) es la selección genética. El objetivo de este trabajo fue comparar las precisiones de los valores de cría (EBV) y los EBV genómicos (GEBV) del recuento de huevos por gramo en heces (HPG) y diámetro de fibra (DF) en la raza Corriedale. El análisis incluyó 19547 corderos con datos fenotípicos y 454, 711 y 383 genotipados con paneles o chips de 170, 507 y 50K SNP, respectivamente. Los EBV y GEBV se estimaron con un modelo animal univariado que incluyó los efectos fijos: grupo contemporáneo, tipo de nacimiento y edad de la madre, y edad al registro como covariable. Se consideraron pesos diferenciales (α) en la matriz de relaciones genómicas, identificándose los modelos con mejor ajuste con el criterio de información de Akaike (AIC), que fueron utilizados para la estimación de los GEBV y sus precisiones. El uso de α solo impactó en el ajuste con paneles de baja densidad. No se encontraron diferencias en las precisiones promedio de la población total. En cambio, en el subgrupo de animales genotipados las precisiones aumentaron 2% con 170 SNP (α=0.25), y con 507 SNP 5% (α=0.5) y 14% (α=0.75). No hubo diferencias en precisiones de los EBV y los GEBV de DF. Los resultados muestran que es posible aumentar las precisiones de los GEBV aun con paneles de baja densidad.Uma alternativa para o controle de nematóides gastrointestinais (NGI) é a seleção genética. O objetivo deste trabalho foi comparar as precisões dos valores genéticos estimados (EBV) e dos EBVs genômicos (GEBV) da contagem de ovos por grama de fezes (OPG) e diâmetro de fibra (DF) na raça Corriedale. A análise incluiu 19547 cordeiros com dados e 454, 711 e 383 genotipados de 170, 507 e 50K SNPs, respectivamente. Foram estimados os EBV e GEBV com um modelo animal univariado que incluiu efeitos fixos de grupo contemporâneo, tipo de nascimento e idade da mãe e idade no registro (covariável). Pesos diferenciais (α) foram considerados na matriz de relações genômicas, identificando os modelos com melhor ajuste via critério de informação de Akaike (AIC), os quais foram utilizados para estimar o GEBV e suas precisões. O uso de α somente impactou no ajuste com painéis de baixa densidade. Não foram encontradas diferenças na precisão média da população total. Em contraste, no subgrupo de animais genotipados as precisões aumentaram 2% com 170 SNPs (α = 0.25), e com 507 SNPs 5% (α = 0.5) e 14% (α = 0.75). Não houve diferenças na precisão de EBV e GEBV de DF. Os resultados mostram que é possível aumentar a precisão de GEBVs mesmo que se utilizem painéis de baixa densidade

Nutritional strategies to improve reproductive performance in beef cows

Latin America has approximately 25% of the world population of cattle (Scherf, 1997) and countries with an exporting emphasis coexist, Brazil, the world's leading exporter, Argentina, 4th, Uruguay, 7th, among others, and importers. However, in all of them, the production of bovine meat is an important item of the livestock sector and the breeding is carried out mainly in pastoral systems without subsidies. The region shares low reproductive efficiency, manifested by the low production of weaned calves, and the main problems identified as responsible for this situation: the advanced age at first calving and the long postpartum anestrus of our herds or herds. Uruguay is not the exception, historical records indicate that the national average of the percentage of weaning has been maintained in the last 20 years at around 63% with the cows of the first calf presenting the lowest percentages of pregnancy and weaning (DI. CO. SE). The fluctuations between years would mainly reflect the influence of the climate on forage and energy production, the main limiting nutrient in the breeding process. Therefore, one of the priorities of the Uruguayan breeding system, like that of most Latin American countries, is the improvement of the weaning percentage with low-cost alternatives and easy application. Any option to achieve this objective must bear in mind that beef farming in Uruguay is part of the export sector, therefore these practices must be compatible with the production of meat with the designation of origin and friendly to the environment

Patrones electromiográficos de la “Virada por Avante” en regatistas de clase “Optimist”

Se realizó un estudio piloto sobre los músculos implicados en la “virada por avante” en dos regatistas de clase “Optimist”, de diferente edad y experiencia, al fin de elaborar sugerencias para un plan de entrenamiento físico. Las pruebas se realizaron en piscina, donde fue posible medir cuantitativamente, a través de técnicas de electromiografía y análisis de video, la activación de siete músculos durante la maniobra. Fue posible reconocer diferencias en los picos de activación y patrones de activación muscular. Los resultados fueron afectados por la edad y las condiciones de viento. Sugerimos que el entrenamiento se enfoque sobre la prevención de lesiones lumbares, y en la técnica.UY-MoUC

Intake, Energy Expenditure and Methane Emissions of Grazing Dairy Cows at Two Pre-Grazing Herbage Masses

A grazing experiment was undertaken to assess the effects of two levels of herbage mass (HM) on herbage DM intake (DMI), fat and protein corrected milk yield (FPCM), grazing behaviour, energy expenditure (HP), and methane emissions (CH4) of grazing dairy cows in spring. Treatments were a low HM (1447 kg DM/ha; LHM) or a high HM (1859 kg DM/ha; HHM). Pasture was composed mainly of cocksfoot (Dactylis glomerata) and lucerne (Medicago sativa), offered at a daily herbage allowance of 30 kg DM/cow, above 5 cm. Eight multiparous Holstein cows were used in a 2 × 2 Latin Square design in two 10-day periods. Despite the differences in pre-grazing HM between treatments, OM digestibility was not different (P = 0.28). Herbage mass did not affect DMI or FPCM. Grazing time was not different between treatments, but cows had a greater bite rate when grazing on LHM swards. However, HP did not differ between treatments. Daily methane emission (per cow), methane emission intensity (per kg FPCM) and methane yield (as percentage of gross energy intake) were not different. The lack of effect of the amount of pre-grazing HM on energy intake, confirms that the difference between HM treatments was beyond the limits that impose extra energy expenditure during grazing.Fil: Loza, Cecilia. Universidad de la República; UruguayFil: Gere, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; ArgentinaFil: Orcasberro, María Soledad. Universidad de la República; UruguayFil: Casal, Alberto. Universidad de la República; UruguayFil: Carriquiry, Mariana. Universidad de la República; UruguayFil: Juliarena, María Paula. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Ramírez-Bribiesca, Efren. Colegio de Postgraduados; MéxicoFil: Astigarraga, Laura. Universidad de la República; Urugua

Influences of nutrition and metabolism on reproduction of the female ruminant

Beef cows and ewes grazing native pastures are exposed to cycles of undernutrition that reflect the seasonal variations of biomass production. In grazing dairy cows, the physiological undernutrition during early lactation due to increased demands for lactation and low dry matter intake is exacerbated by the need to get sufficient intake from pasture and the extra grazing energy costs. Undernutrition has profound impacts on reproduction by affecting multiple reproductive processes at different levels of the reproductive axis. The objective of this paper is to review the influence of undernutrition on reproductive events of the adult female ruminant, with emphasis on both grassland and mixed rain-fed grazing farming systems. The comparative endocrinology and reproductive biology among ewes, beef and dairy cows may provide a comprehensive knowledge of the metabolic and reproductive adaptation to feed restriction. Understanding the critical underlying physiological mechanisms by which nutrition affects reproduction is the base of focus feeding strategy to improve the reproductive performance of the female ruminan

Metabolic and endocrine profiles and reproductive parameters in dairy cows under grazing conditions: effect of polymorphisms in somatotropic axis genes

<p>Abstract</p> <p>Background</p> <p>The present study hypothesized that GH-AluI and IGF-I-SnabI polymorphisms do change the metabolic/endocrine profiles in Holstein cows during the transition period, which in turn are associated with productive and reproductive parameters.</p> <p>Methods</p> <p>Holstein cows (Farm 1, primiparous cows, n = 110, and Farm 2, multiparous cows, n = 76) under grazing conditions were selected and GH and IGF-I genotypes were determined. Blood samples for metabolic/endocrine determinations were taken during the transition period and early lactation in both farms. Data was analyzed by farm using a repeated measures analyses including GH and IGF-I genotypes, days and interactions as fixed effects, sire and cow as random effects and calving date as covariate.</p> <p>Results and Discussion</p> <p>Frequencies of GH and IGF-I alleles were L:0.84, V:0.16 and A:0.60, B:0.40, respectively. The GH genotype was not associated with productive or reproductive variables, but interaction with days affected FCM yield in multiparous (farm 2) cows (LL yielded more than LV cows) in early lactation. The GH genotype affected NEFA and IGF-I concentrations in farm 1 (LV had higher NEFA and lower IGF-I than LL cows) suggesting a better energy status of LL cows.</p> <p>There was no effect of IGF-I genotype on productive variables, but a trend was found for FCM in farm 2 (AB cows yielded more than AA cows). IGF-I genotype affected calving first service interval in farm 1, and the interaction with days tended to affect FCM yield (AB cows had a shorter interval and yielded more FCM than BB cows). IGF-I genotype affected BHB, NEFA, and insulin concentrations in farm 1: primiparous BB cows had lower NEFA and BHB and higher insulin concentrations. In farm 2, there was no effect of IGF-I genotype, but there was an interaction with days on IGF-I concentration, suggesting a greater uncoupling somatropic axis in AB and BB than AA cows, being in accordance with greater FCM yield in AB cows.</p> <p>Conclusion</p> <p>The GH and IGF-I genotypes had no substantial effect on productive parameters, although IGF-I genotype affected calving-first service interval in primiparous cows. Besides, these genotypes may modify the endocrine/metabolic profiles of the transition dairy cow under grazing conditions.</p