Impact of drying on in vitro gas prodution and voluntary dry matter intake of rice plants, and feeding experiences with double sliced rice straw
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2009
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Devido a rápida expansão das indústrias de etanol, as forragens são cada vez mais escassas para o sector leiteiro em todo o mundo e em particular na Califórnia, USA, também o custo e mais elevado devido ao aumento de preço dos combustíveis. Para além disso, devido a actual crise no sector leiteiro, há falta de alimentos fibrosos a baixo preço no mercado.
Na Califórnia, como a lei proíbe a combustão da palha de arroz, os produtores de arroz estão pressionados devido á grande quantidade de palha que têm que retirar dos campos. Por isso, a palha de arroz pode ser uma oportunidade para os produtores de leite obterem uma forragem a baixo custo.
No âmbito desta Tese, foram realizadas três experiências tendo como objectivo principal identificar e quantificar factores que podem condicionar a digestibilidade de palhas de arroz e, consequentemente, a sua ingestão voluntária.
Na experiência I, a palha de arroz foi macerada mas não houve impacto na digestão in vitro da fibra de detergente neutro ao fim de 36 h de incubação (dNDF30; 407.1 versus 405.6 g/kg NDF; P =0.63). A hipótese de que a maceração poderia aumentar o valor nutricional da palha de arroz não obteve confirmação neste estudo.
Na experiência II, foi medida a produção de gás in vitro de plantas de arroz em três estádios diferentes (i.e., em verde, durante a secagem e seca). A produção de gás observada foi maior para as plantas em verde (132 versus 115 versus 112 ml/g MS as 24h; P < 0.01), sendo a diferença observada, relativamente aos valores obtidos para os outros dois tratamentos difícil de explicar com base em metodologias convencionais de determinação da composição química.
Devido ao facto de na experiência anterior ter havido efeito do estádio na fermentação das plantas, na experiência III foi medida a ingestão voluntária de matéria seca (MS) de plantas de arroz nos mesmos três estádios (i.e., em verde, durante a secagem e seca). Os resultados foram consistentes com a experiência anterior, tendo sido a ingestão de MS de plantas em verde aproximadamente 30% mais elevada (5.14 versus 4.13 versus 3.69 kg MS/dia; P < 0.01).
Uma demonstração no campo foi conduzida para avaliar a opinião dos produtores de leite relativamente a uma nova técnica de cortar e enfardar a palha de arroz. A técnica ‘double sliced’ tem em vista minimizar os aspectos negativos da palha de arroz que são a sua resistência e extrema maleabilidade. A palha de arroz foi introduzida na dieta de acordo com a preferência dos nutricionistas/proprietários, após o período de distribuição da palha foi feito um inquérito aos nutricionistas/proprietários relativamente à experiência com esta palha de arroz. O resultado foi bastante positivo, pois não foi necessário tempo adicional para obter uma mistura homogénea da dieta total (total mixed ratio; TMR) com a palha de arroz e no houve rejeição da palha por parte dos animais em dietas com 0.7 a 1.4 kg/dia de palha de arroz.
Embora a maceração não tenha melhorado o valor nutricional da palha de arroz na experiência I, houve uma maior produção de gás pelas plantas em verde e a ingestão de MS foi também mais elevada para as plantas em verde indicando que a investigação deverá focar-se nas diferenças que ocorrem entre plantas em verde e secas. Estes resultados também indicam que o desenvolvimento de uma técnica não dispendiosa e capaz de preservar o valor nutricional da planta em verde poderá contribuir para aumentar a incorporação de palha de arroz, nas dietas dos ruminantes, mesmo naqueles que apresentam maior grau de exigências nutricionais.
With accelerated expansion of ethanol industry, forage supplies are much tighter to dairy sector, in addition, forage is more expensive due to increased fuel costs. In the actual milk crisis circumstances there is a need for inexpensive fiber products. Environmental restrictions to burn rice straw in California are struggling rice producers with high amounts of rice straw in the fields to be removed. Thus, rice straw is an opportunity for dairy producers to acquire an inexpensive source of fiber. In this thesis, three experiments were conducted to identify and quantify ways to increase digestibility of rice straw increasing consequently dry matter (DM) intake of rice straw. On Experiment I, rice straw was macerated but there was no effect on in vitro dNDF30 (407.1 versus 405.6 g/kg NDF; P = 0.63). The supposition that maceration would increase nutritional value of rice straw failed to be effective. On Experiment II, it was measured the in vitro gas production of rice plants in three different stages (i.e., fresh, during dry down and dry rice plants). There was a significant higher gas production of fresh plants (132 versus 115 versus 112 ml/g DM at 24h; P < 0.01). On Experiment III, since on previous experiment there was an effect of stage on fermentability of plants, it was measure the DM intake of rice plant in the same three stages (i.e., fresh, dry down and dry rice plants). Results were consistent to Experiment II, DM intake of fresh plants was approximately 30 % higher (5.14 versus 4.13 versus 3.69 kg DM/day; P < 0.01). A demonstration was conducted to evaluate dairy producers’ judgment relative to double sliced rice straw, a new technique able to minimize toughness and malleable characteristics of rice straw. Rice straw was fed at nutritionists/managers’ decision and after the feeding period a series of questions was asked to managers mainly regarding to their experience with the double sliced rice straw. Overall, the output was very positive, rice straw did mix properly and with no extra time, TMR feed was homogenous and no sorting behavior by the cows was observed at feeding levels from 0.7 to 1.4 kg/day. Although maceration did not improve nutritional value of rice straw, fresh plants produced more gas than dry plants and cows also ate more of fresh than dry rice plants indicating that research should be focus on differences between fresh and dry plants. These results also indicate that there is potential to increase DM intake of rice straw worldwide, if, a non-expensive technique to “stagnate” the nutritional status of the fresh plant will be developed.
With accelerated expansion of ethanol industry, forage supplies are much tighter to dairy sector, in addition, forage is more expensive due to increased fuel costs. In the actual milk crisis circumstances there is a need for inexpensive fiber products. Environmental restrictions to burn rice straw in California are struggling rice producers with high amounts of rice straw in the fields to be removed. Thus, rice straw is an opportunity for dairy producers to acquire an inexpensive source of fiber. In this thesis, three experiments were conducted to identify and quantify ways to increase digestibility of rice straw increasing consequently dry matter (DM) intake of rice straw. On Experiment I, rice straw was macerated but there was no effect on in vitro dNDF30 (407.1 versus 405.6 g/kg NDF; P = 0.63). The supposition that maceration would increase nutritional value of rice straw failed to be effective. On Experiment II, it was measured the in vitro gas production of rice plants in three different stages (i.e., fresh, during dry down and dry rice plants). There was a significant higher gas production of fresh plants (132 versus 115 versus 112 ml/g DM at 24h; P < 0.01). On Experiment III, since on previous experiment there was an effect of stage on fermentability of plants, it was measure the DM intake of rice plant in the same three stages (i.e., fresh, dry down and dry rice plants). Results were consistent to Experiment II, DM intake of fresh plants was approximately 30 % higher (5.14 versus 4.13 versus 3.69 kg DM/day; P < 0.01). A demonstration was conducted to evaluate dairy producers’ judgment relative to double sliced rice straw, a new technique able to minimize toughness and malleable characteristics of rice straw. Rice straw was fed at nutritionists/managers’ decision and after the feeding period a series of questions was asked to managers mainly regarding to their experience with the double sliced rice straw. Overall, the output was very positive, rice straw did mix properly and with no extra time, TMR feed was homogenous and no sorting behavior by the cows was observed at feeding levels from 0.7 to 1.4 kg/day. Although maceration did not improve nutritional value of rice straw, fresh plants produced more gas than dry plants and cows also ate more of fresh than dry rice plants indicating that research should be focus on differences between fresh and dry plants. These results also indicate that there is potential to increase DM intake of rice straw worldwide, if, a non-expensive technique to “stagnate” the nutritional status of the fresh plant will be developed.
Descrição
Dissertação de Mestrado em Engenharia Zootécnica
Palavras-chave
Palha de arroz , Digestibilidade , Maceração