The objective of this study, which was part of a larger grazing‐systems experiment, was to investigate the cumulative impact of three levels of grazing intensity on sward production, utilization and structural characteristics. Pastures were grazed by rotational stocking with Holstein–Friesian dairy cows from 10 February to 18 November 2009. Target post‐grazing heights were 4·5 to 5 cm (high; H), 4 to 4·5 cm (intermediate; I) and 3·5 to 4 cm (low; L). Detailed sward measurement were undertaken on 0·08 of each farmlet area. There were no significant treatment differences in herbage accumulated or in herbage harvested [mean 11·3 and 11·2 t dry matter (DM) ha−1 respectively]. Above the 3·5 cm horizon, H, I and L swards had 0·56, 0·62 and 0·67 of DM as leaf and 0·30, 0·23 and 0·21 of DM as stem respectively. As grazing severity increased, tiller density of grass species other than perennial ryegrass (PRG) decreased (from 3,350 to 2,780 and to 1771 tillers m−2 for H, I and L paddocks respectively) and the rejected area decreased (from 0·27 to 0·20 and to 0·10 for H, I and L paddocks respectively). These results indicate the importance of grazing management practice on sward structure and quality and endorse the concept of increased grazing severity as a strategy to maintain high‐quality grass throughout the grazing season. The findings are presented in the context of the need for intensive dairy production systems to provide greater quantities of high‐quality pasture over an extended grazing season, in response to policy changes with the abolition of EU milk quotas.

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A perennial ryegrass (Lolium perenne L.)‐dominated sward on a well‐drained soil (Experiment 1) and a creeping bent (Agrostis stolonifera L.)‐dominated sward on a poorly drained soil (Experiment 2) were subjected to four treading treatments: control (C, no damage), light damage (L), moderate damage (M) or severe damage (S) to quantify the effects on herbage dry‐matter (DM) production and tiller density. In Experiment 1, treading damage was imposed in spring. In Experiment 2, one‐third of the site was damaged in autumn, one‐third in spring and one‐third in both spring and autumn. Both sites were rotationally grazed after treading treatments. Pre‐grazing herbage mass was measured eight times in Experiment 1 and seven times in Experiment 2 on each plot, and tiller density was assessed four times in each experiment. In Experiment 1, pre‐grazing herbage mass was reduced by 30% in S plots at the first harvest after damage, but cumulative pre‐grazing herbage DM production was not different between treatments (12·7 t DM ha−1). In Experiment 2, annual cumulative pre‐grazing herbage mass was reduced by between 14 and 49%, depending on intensity of treading damage event and season when damage occurred. Tiller density was not affected by treatment in either experiment. A perennial ryegrass‐dominated sward on a well‐drained soil was resilient to heavy treading damage. A creeping bent‐dominated sward on poorly drained soil requires a more careful grazing management approach to avoid major losses in cumulative pre‐grazing herbage mass production during wet weather grazing events.

This study showed that MPG given to cows with a low BCS for 6 weeks prior to mating had limited benefits on reproductive outcomes.

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El objetivo fue investigar la influencia de la suplementación dietaria de búfalos con aceite de pescado sobre el ácido linoleico conjugado (ALC) y los ácidos grasos Ω6 y Ω3 en lípidos intramusculares (IM) y grasa de cobertura (GC). Se emplearon veinte animales divididos en dos grupos alimentados sobre <i>Brachiaria brizantha</i> y suplementados con 3 kg de afrecho de arroz, 500 g de maíz y 500 g de pellet de girasol, durante 60 días. El grupo I se mantuvo con esta dieta, el II recibió adicionalmente 100 ml/día de aceite de pescado por animal. Los resultados (expresados en mg/g grasa) indicaron una disminución de ácido palmítico en IM y GC del grupo II (189,05) vs grupo I (206,97) y en II (259,72) vs I (280,84) respectivamente. El ALC se incrementó levemente en IM y GC del grupo II (17,09) vs I (11,56) y en el II (16,80) vs I (11,75) respectivamente. El ácido linoleico (18:2 n6) en IM del grupo II (23,45) disminuyó en relación con el I (38,19) y en GC del grupo II (13,21) se incrementó levemente con relación al I (12,71). El ácido alfa linolénico (18:3 n3) en IM de grupos I y II fue similar (8,37 y 8,69), en cambio el contenido de dicho ácido en GC fue menor en el grupo I (4,70) comparado con el grupo II (6,05). La relación Ω6/Ω3 en IM y GC fue más estrecha en el grupo II (2,69:1) y (2,18:1) con relación al grupo I (4,55:1) y (2,70:1) respectivamente. La suplementación con aceite de pescado produjo disminución del ácido linoleico, mejorando la relación entre Ω6/Ω3. Además causó una leve disminución de los valores de ácido palmítico y un pequeño aumento de ALC.