Comportamento alimentar e avaliação das reservas corporais de ruminantes em pastagens de montanha do Norte da Península Ibérica
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2016
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O sucesso de qualquer estratégia de gestão de sistemas de produção animal assentes em pastoreio depende da compreensão da relação existente entre o animal e a pastagem, no sentido de se obter uma mais eficiente utilização do coberto vegetal, e do conhecimento dos parâmetros de produção animal. Neste sentido, este estudo teve como principais objetivos estudar o comportamento alimentar de bovinos de aptidão mista em pastoreio monoespecífico e misto (com caprinos). Esta avaliação foi realizada por observação direta dos animais em três ocasiões ao longo da época de pastoreio, registando as atividades dos animais a cada quinze minutos durante o período de luz de dois dias consecutivos. Simultaneamente, foram recolhidas amostras representativas dos componentes vegetais e das fezes excretadas por cada animal no sentido de avaliar a composição da dieta selecionada pelos animais, utilizando os n-alcanos como marcadores fecais. Adicionalmente, avaliámos a performance de pequenos ruminantes em áreas de pastagem de montanha ao longo da época de pastoreio (primavera-verão-outono). Os resultados obtidos indicam que os bovinos, independentemente da tipologia de pastoreio (monoespecífico vs. misto), dedicaram a quase totalidade do seu tempo de pastoreio na área de pastagem (7,9 e 7,8 h/dia, respetivamente), quando comparado com o tempo despendido na vegetação arbustiva (1,3 e 0 h/dia, respetivamente). Os resultados da composição de dieta estimada pelos marcadores fecais foram consistentes com os obtidos pela observação direta e indicam que a dieta dos bovinos foi composta quase exclusivamente por vegetação herbácea em todas as épocas de pastoreio (valor médio de 0,957 para as duas tipologias de pastoreio). Os resultados indicam também um maior consumo de vegetação herbácea nos bovinos em pastoreio misto (0,979 vs. 0,935; P=0,0384) como resultado da presença de caprinos no rebanho. Pelo contrário, os caprinos demonstraram possuir uma capacidade para incorporarem na sua grandes quantidades de espécies arbustivas nas suas dietas (cerca de 21,5%), o que sugere que poderão constituir um bom complemento aos bovinos. Em ambas as tipologias de pastoreio as espécies animais rejeitaram a ingestão de Ulex gallii. Para a monitorização das reservas corporais foram efetuadas cinco sessões de Abril a Novembro em caprinos e ovinos nos quais foi determinado o peso vivo (PV), a condição corporal (CC) e medidas de ultrassonografia em tempo real (UTR). As medidas de UTR foram em três pontos anatómicos (na região torácico-lombar, na parede torácica e na região esternal). De uma forma geral, o PV revelou ser um mau estimador das reservas corporais de gordura avaliadas pela CC, com um valor de correlação entre 0,007 (P>0,05) e 0,388 (P<0,01). Já a relação entre a CC e as medidas obtidas por UTR apresentou de forma consistente valores de correlação mais elevados, embora tenha sido observada uma variação muito grande do valor de correlação com o tipo de tecido e com a região avaliada, com um valor de r entre -0,033 (P>0,05) e 0,569 (P<0,01).
The success of any animal production management system that lies on grazing depends on the understanding of the existing relation between animal and pasture, in order to obtain a more efficient usage of the ground cover, and on the knowledge of animal production parameters. As such, this study had as primary objectives the study of feeding behaviors in cattles when in monospecific grazing and mixed grazing (with goats). This evaluation was made by direct observation of the animals in 3 occasions along the grazing season, with animal activity being registered every 15 minutes during light period for two consecutive days. Simultaneously, samples were gathered from vegetation and animal feces excreted by each animal in order to evaluate the animal selected diet composition, using n-alkanes as fecal markers. Additionally, small ruminant performances were evaluated in mountain pasture areas along the grazing season (Spring – Summer – Autumn). Results indicate that cattles, regardless of grazing typology (monospecific or mixed), have spent almost all of their grazing time in the pasture area (7.9 and 7.8 h/day, respectably), when compared with the time spent on shrubby vegetation (1.3 and 0 h/day, respectably). Results from diet composition estimated by fecal markers were consistent with direct observation and indicate that bovine diet was almost exclusively composed by herbaceous vegetation in all grazing seasons (means value of 0,957 for both grazing typologies). Results also indicate a larger consumption of herbaceous vegetation in cattles in mixed grazing (0,979 vs. 0,935; P=0.0384) as a result of the presence of goats on the flock. On the contrary, goats showed to have the ability to incorporate on their diets large quantities of shrubby vegetation (about 21.5%), what suggests they might be a good complement to cattles. In both grazing types, both species rejected the ingestion of Ulex gallii. In order to monitor the body reserves in goats and sheep five sessions where carried out between April and November, in which live weight (LW), body condition (BC) and real time ultrasonography measures (RTU) were determined. RTU measurements were made in three anatomical points (thoracic-lumbar region, thoracic wall and sternal region). Generally, LW revealed to be a bad estimate for body fat reserves evaluated by BC with an r value between 0.007 (P>0.05) and 0.388 (P<0.01). Meanwhile, the relation between BC and the measures obtained with RTU showed consistently higher correlation values, although it was reported a great variation of the correlation value with tissue type and evaluated region with an r value between –0.333 (P>0.05) and 0.569 (P<0.01).
The success of any animal production management system that lies on grazing depends on the understanding of the existing relation between animal and pasture, in order to obtain a more efficient usage of the ground cover, and on the knowledge of animal production parameters. As such, this study had as primary objectives the study of feeding behaviors in cattles when in monospecific grazing and mixed grazing (with goats). This evaluation was made by direct observation of the animals in 3 occasions along the grazing season, with animal activity being registered every 15 minutes during light period for two consecutive days. Simultaneously, samples were gathered from vegetation and animal feces excreted by each animal in order to evaluate the animal selected diet composition, using n-alkanes as fecal markers. Additionally, small ruminant performances were evaluated in mountain pasture areas along the grazing season (Spring – Summer – Autumn). Results indicate that cattles, regardless of grazing typology (monospecific or mixed), have spent almost all of their grazing time in the pasture area (7.9 and 7.8 h/day, respectably), when compared with the time spent on shrubby vegetation (1.3 and 0 h/day, respectably). Results from diet composition estimated by fecal markers were consistent with direct observation and indicate that bovine diet was almost exclusively composed by herbaceous vegetation in all grazing seasons (means value of 0,957 for both grazing typologies). Results also indicate a larger consumption of herbaceous vegetation in cattles in mixed grazing (0,979 vs. 0,935; P=0.0384) as a result of the presence of goats on the flock. On the contrary, goats showed to have the ability to incorporate on their diets large quantities of shrubby vegetation (about 21.5%), what suggests they might be a good complement to cattles. In both grazing types, both species rejected the ingestion of Ulex gallii. In order to monitor the body reserves in goats and sheep five sessions where carried out between April and November, in which live weight (LW), body condition (BC) and real time ultrasonography measures (RTU) were determined. RTU measurements were made in three anatomical points (thoracic-lumbar region, thoracic wall and sternal region). Generally, LW revealed to be a bad estimate for body fat reserves evaluated by BC with an r value between 0.007 (P>0.05) and 0.388 (P<0.01). Meanwhile, the relation between BC and the measures obtained with RTU showed consistently higher correlation values, although it was reported a great variation of the correlation value with tissue type and evaluated region with an r value between –0.333 (P>0.05) and 0.569 (P<0.01).
Descrição
Dissertação de Mestrado em Engenharia Zootécnica
Palavras-chave
Ruminante , Hábito alimentar , Pastagem de montanha , Gestão de pastagens , Tecido adiposo , Monitorização , Ultrassonografia