Two experiments were conducted during the winters of 2012-13 (yr 1) and 2013-14 (yr 2), to evaluate 3 winter feeding systems: (i) field grazing standing whole plant corn (SC) cv. ‘DKC 26-25’ (yr 1, CP = 9.5%, TDN = 66.1%; yr 2, CP = 9%, TDN = 69.8%), (ii) field grazing swathed barley hay (SB) cv. ‘Ranger’ (yr 1, CP = 13.2%, TDN = 56.8%; yr 2, CP = 10%, TDN = 61.9% and (iii) barley hay bales fed in drylot pens (DL) cv. ‘Ranger’ (yr 1, CP = 13.1%, TDN = 53.2%; yr 2, CP = 8.2%, TDN = 55.2%). Forages were allocated on a 3-4 d interval in SC and SB systems. The specific objectives were to compare crop yield and agronomy, beef cow performance, reproductive efficiency and system costs in experiment 1 (EXP 1); and ruminal pH, SCFA and ammonia concentration in experiment 2 (EXP 2). In EXP 1, 60 dry, pregnant Black Angus cows (yr 1, 644 kg ± 72 kg; yr 2, 672 kg ± 66 kg) at mid-gestation, stratified by body weight (BW) were allocated to 1 of 3 replicated (n=2) winter grazing treatments for 77 d in yr 1 and 78 d in yr 2. Increases in rib fat were greater (P = 0.02) for SC cows compared to SB cows (1.6 vs 0.3 mm, respectively). Estimated DMI was lower (P < 0.01) for SC cows (9.1 kg/d) compared to SB and BH cows (14.3 and 13.0 kg/d, respectively) which did not differ (P > 0.05) from each other. Calves born to cows grazing SC were heavier (P ˂ 0.01) at birth compared to calves from SB and BH cows (43, 40 and 40 kg, respectively). Changes in cow BW and average daily gain (ADG) were lower (P < 0.01) and negative in year 2 (BW change, 23.8 and -4.9 kg; ADG, 0.3 and -0.1 kg for yr 1 and 2, respectively). The number of calves born in first 21 d was 44% higher (P < 0.01) in yr 1 compared to yr 2. Economic analysis revealed that total costs were greatest for BH ($2.75/cow/d) compared to SC and SB ($2.06 and $2.00 cow/d, respectively) systems. In EXP 2, 9 cannulated beef heifers were cycled through the 3 winter systems concurrently within EXP 1, in a replicated 3 × 3 Latin square design, for 63 d to evaluate effect of forage type and day of allocation on rumen fermentation. Results from EXP 2 indicated an increase (P < 0.01) in minimum pH of cannulated heifers from d 1 to d 3 of forage allocation in SC and SB systems. Lower (P < 0.01) minimum and mean pH and increased duration and area (P < 0.01) under pH 5.8 were observed in yr 2 in SC and yr 1 in SB. In yr 2, total SCFA, acetate and propionate concentration increased (P < 0.01) in SB heifers, but butyrate concentration increased (P < 0.05) in SC heifers compared to yr 1. Ruminal fermentation was unaffected (P > 0.05) by day of forage allocation and yr of study in BH system. Results from EXP 1 and EXP 2 suggest that both SC and SB systems are cost effective alternatives to BH system, and do not negatively affect cow reproductive performance following winter grazing. However, yearly differences in weather and seeding date of forages can have a profound effect on nutrient composition of forages, and can cause variations in cow performance and rumen metabolism during the period of extensive winter grazing.

Made available in DSpace on 2016-05-17T16:51:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-10. Added 1 bitstream(s) on 2016-05-17T16:54:56Z : No. of bitstreams: 1 000864315.pdf: 1933866 bytes, checksum: 3d5e86a181b0ce722fb5dfee9bb0700e (MD5) / Brazilian livestock consists of animals raised and finished in tropical pastures, most of them established in medium and low fertility soils. The tropical forages, however, are limited in some nutrients, especially in minerals, which can compromise the results of cattle production. Among the minerals, phosphorus (P) occupies an important position due to its role in animals' metabolism and to its cost, which represents most of the mineral supplements costs, so rendering this input the most expensive for the definition of the production costs of cattle raised in grasslands. Often, the farmers do not follow the ideal techniques for the animal's' mineral supplementation and, besides that, practical observations suggest that not always the animal productivity is related to the mineral supplementation techniques or with the P contents of the supplements. Following the hypothesis that the recommended levels of P can be reduced without damaging the animal productivity, the aim of this trial was to check on the effects of reducing the phosphorus supplementation concentrations (from 4% to 1.8%) in a beef cow herd raised on Urochloa decumbens pastures on the productive and reproductive parameters, as well as on the supplementation costs. The study was conducted on the cerrado biome, from 2011 to 2013. Variables analyzed included pregnancy rate, calving interval, weight of calves at weaning and cost of supplementation. No changes were found for the productive and reproductive performance of the herd. However, there was a significant reduction in the supplementation costs when the herd was supplemented with a mineral mixture containing 1.8% phosphorus

Orientador:Elisa Helena Giglio Ponsano / Co-orientador:Pedro Antonio Muniz Malafaia / Banca:Rafael Silva Cipriano / Banca:Antonio Carlos de Laurentiz / Banca:Francisco Leydson Formiga Feitosa / Banca:Max José de Araújo Faria Junior / Resumo:A pecuária brasileira consiste basicamente em animais criados e terminados em pastagens tropicais, com a maior parte delas implantadas em solos de média a baixa fertilidade. As forrageiras tropicais, entretanto, são limitadas em alguns nutrientes, inclusive em minerais, o que pode comprometer os desempenhos dos animais. Dentre os minerais, o fósforo (P) ocupa uma importante posição, por suas funções no metabolismo animal e por seu preço, que representa boa parte do custo dos suplementos minerais, tornando este insumo o de maior relevância na composição dos custos de produção de bovinos criados em pastagens. Nem sempre as recomendações consideradas ideais na suplementação mineral dos animais são seguidas pelos produtores e observações de campo sugerem que a produtividade animal não se relaciona com os esquemas de suplementação mineral ou com os teores de P dos suplementos utilizados. Partindo da hipótese de que as concentrações preconizadas de P podem ser reduzidos sem prejuízo para a produtividade animal, o objetivo deste ensaio foi verificar os efeitos da redução dos níveis de suplementação com P (de 4% para 1,8%) em um rebanho de vacas de corte criadas em pastagens de Urochloa decumbens sobre as características produtivas e reprodutivas do rebanho, bem como sobre os custos de suplementação. O trabalho foi realizado no bioma do cerrado de 2011 a 2013. As variáveis analisadas incluíram taxa de prenhez, intervalo de partos, peso ao desmame e custos com a suplementação. Não foram encontradas alterações nas características produtivas ou reprodutivas do rebanho. Entretanto, houve uma significativa redução nos custos de suplementação quando o rebanho passou a ser suplementado com a mistura mineral contendo 1,8% de P / Abstract:Brazilian livestock consists of animals raised and finished in tropical pastures, most of them established in medium and low fertility soils. The tropical forages, however, are limited in some nutrients, especially in minerals, which can compromise the results of cattle production. Among the minerals, phosphorus (P) occupies an important position due to its role in animals' metabolism and to its cost, which represents most of the mineral supplements costs, so rendering this input the most expensive for the definition of the production costs of cattle raised in grasslands. Often, the farmers do not follow the ideal techniques for the animal's' mineral supplementation and, besides that, practical observations suggest that not always the animal productivity is related to the mineral supplementation techniques or with the P contents of the supplements. Following the hypothesis that the recommended levels of P can be reduced without damaging the animal productivity, the aim of this trial was to check on the effects of reducing the phosphorus supplementation concentrations (from 4% to 1.8%) in a beef cow herd raised on Urochloa decumbens pastures on the productive and reproductive parameters, as well as on the supplementation costs. The study was conducted on the cerrado biome, from 2011 to 2013. Variables analyzed included pregnancy rate, calving interval, weight of calves at weaning and cost of supplementation. No changes were found for the productive and reproductive performance of the herd. However, there was a significant reduction in the supplementation costs when the herd was supplemented with a mineral mixture containing 1.8% phosphorus / Doutor

L’objectif principal de la thèse était de caractériser les impacts de différents types de gestion pastorale (bovins, équins, caprins) sur les communautés végétales de « nouveaux écosystèmes » fortement anthropisés que sont les digues et remblais de la réserve de Donzère-Mondragon dans la basse vallée du Rhône. Différents outils ont été utilisés (relevés de végétation, analyses de sols, analyses minérales des herbages, télédétection, SIG, etc.) à des échelles spatiales différentes afin de dégager les interrelations entre les différents niveaux d’organisation et fonctionnalités de la végétation. En effet, l’émergence des « nouveaux écosystèmes » oblige les gestionnaires à reconsidérer les principes initiaux de la gestion conservatoire. Dans notre étude, il a pu être démontré que les systèmes de pâturage faisant appel à des troupeaux d’herbivores dont l’organisation est adaptée pour maintenir l’ouverture des milieux, augmentent la richesse spécifique, la diversité et l’hétérogénéité de la végétation à court terme (3-5 années) par rapport à l’absence de gestion ou aux interventions mécaniques. Les analyses montrent également que les espèces annuelles qui apparaissent sont appétentes et contribuent à augmenter la valeur fourragère de certains faciès du site pâturé par les chevaux. Ces herbivores ont également un impact sur la banque de graines permanente du sol en augmentant son hétérogénéité et la densité de graines viables sous les faciès les plus pâturés. Le pâturage des vaches et des chevaux confirme une corrélation entre l’indice de végétation (NDVI) obtenu après l’analyse de photographies aériennes, la biomasse et la richesse en espèces végétales. Les estimations d’indices de consommation de la ronce sous SIG ont permis d’apprécier l’efficacité de l’action des chèvres. Ces différents résultats, pour les modalités testées, correspondent bien à ceux déjà obtenus lors d’applications de systèmes pastoraux en milieux naturels. Des expérimentations devraient également être menées à l’avenir via des systèmes de pâturage mixtes notamment bovin-caprin et équin-caprin pour accroître l’effet de la restauration aux dépens de la colonisation d’arbustes compétitifs dont la ronce. La gestion pastorale appliquée devrait néanmoins être pensée sur le moyen terme, si possible via des contrats pluriannuels, favorisant la durabilité de cette méthode de gestion et de ses effets dans le temps. / The main objective of the thesis was to characterize the impacts of different types of pastoral management (cattle, horses, goats) on "new ecosystems" plant communities. Our experimentations were conducted in highly anthropized dykes and embankments of the Donzère-Mondragon reserve in the lower Rhone valley. Various tools were used (i.e. vegetation surveys, soil analyzes, grassland mineral analyzes, remote sensing, GIS, etc.), and at different spatial scales in order to identify the interrelationships between the different levels of vegetation organization and functions. Indeed, the emergence of "new ecosystems" requires managers to reconsider the initial principles of conservation management. Our study showed that, in the short term (3-5 years), grazing systems using herds of herbivores, whose organization is adapted to maintain open habitats, increase species richness, diversity and heterogeneity of plant communities compared to lack of management or mechanical interventions. Moreover, the annual species that appear are appetizing and contribute to increase the forage value of the site grazed by horses. These herbivores also have an impact on the permanent seed bank by increasing both its heterogeneity and the density of viable seeds under the most grazed patches. Grazing of cattle and horses confirm a correlation between the vegetation index (NDVI), biomass and plant species richness. Finally, we evaluated the efficacy of goats’ action on bramble via consumption indices calculated using GIS. Our different results are in the line with those already obtained in natural environments. Future experiments should test the effects of mixed grazing systems, particularly cattle, goats and horses, on the colonization dynamic of competitive shrubs such as brambles. Applied pastoral management should be considered in the medium term, via multi-year contracts to promote the sustainability of this management method and its effects over time.