Dimas Estrasulas de Oliveira

Estimating forage intake of lactating dual-purpose cows using chromium oxide and n-alkanes as external markers

Os n-alcanos tem sido utilizados para estimar o consumo de materia seca, a digestibilidade e a composicao da dieta de animais em pastejo. O objetivo desse estudo foi comparar as tecnicas de oxido cromico e n-alcanos usadas para estimar o consumo de forragem. Vinte vacas lactantes cruzas Holandes × Gir recebendo duas fontes de gordura (tratamentos: CLA (acido linoleico conjugado) ou Megalac (controle)) mais 4 kg de concentrado foram dosadas com n-alcanos e oxido cromico para estimar o consumo de estrela-africana (Cynodon nlemfuensis Vanderyst var. nlemfuensis). A digestibilidade in vitro da materia seca da estrela africana e do concentrado foi usada para estimar o valor nutritivo da dieta. Foram quantificados n-alcanos entre C23 e C36 na dieta e fezes. A regressao entre exigencia e o consumo de energia metabolizavel (EMr, Mcal d-1) derivada da materia seca da forragem calculada usando oxido de cromo foi ConsumoCr = 19,1 + 0,62 EMr (R2 = 0,27) e a mesma relacao estimada usando a relacao C35:C36 de n-alcanos foi ConsumoC35:C36 = 9,3 + 0,77 EMr (R2 = 0,52). Houve efeito de tratamento na concentracao fecal de oxido de cromo com variacao diaria e entre turnos. Para tecnica de n-alcanos, houve efeito de tratamento e periodo e efeito linear de dia de coleta nas concentracoes fecais do C35. Para as concentracoes fecais do C36, houve efeito de tratamento e um efeito quadratico de dia de coleta. Nao houve efeito de tratamento na concentracao fecal da relacao C35:C36, mas houve efeito de turno e efeito linear de dia de coleta. As estimativas do consumo de forragem obtidas com os dois marcadores foram diferentes, mas aquela obtida com o par de alcanos C35:C36 foi mais precisa que aquela obtida com o oxido cromico e a digestibilidade in vitro. O manejo dos animais experimentais pode ter influenciado a concentracao dos marcadores nas fezes, determinando variacoes e inconsistencias que explicam parcialmente a falta de acuracia das estimativas.

N-alkanes to estimate voluntary forage intake of cattle using controlled-release capsules

N-alcanos tem sido usados como marcadores internos em ensaios de digestibilidade com ruminantes e nao-ruminantes por mais de 20 anos. Neste estudo dois ensaios foram conduzidos para avaliar: 1) a taxa de liberacao de alcanos de capsulas de liberacao controlada inseridas no rumen de novilhos fistulados em pastejo ou mantidos em gaiolas de metabolismo e; 2) o uso de n-alcanos para estimar o consumo voluntario de forragem dos novilhos mantidos em gaiolas de metabolismo. Seis novilhos Nelore, fistulados no rumen foram colocados individualmente em gaiolas de metabolismo e alimentados com dietas variando a relacao forragem:concentrado (80:20, 60:40 e 40:60, respectivamente). A silagem de milho foi a unica fonte de forragem. No ensaio de pastejo, os animais foram avaliados sob tres regimes de alimentacao (Brachiaria brizantha cv. Marandu sem ou com suplementacao com concentrado na proporcao de 0,3 ou 0,6% do peso vivo, PV). A taxa de liberacao de n-alcanos (mg d-1) foi medida multiplicando-se a distância percorrida pelo embolo da capsula (mm d-1) apos 3, 7, 10, 13 e 17 dias de insercao no rumen, pela concentracao de alcanos dos tabletes das capsulas (mg mm-1). Houve um efeito de dia (P 0,05) do regime de alimentacao ou da interacao regime da alimentacao x dia da medida. Os valores foram 6,9 e 14,8% menores do que o proposto pelo fabricante para o C32 quando os animais foram mantidos em gaiolas de metabolismo e pastejo, respectivamente. Os valores para o C36 foram 15,9 e 23,1% menores para os animais em gaiolas de metabolismo e pastejo, respectivamente. A liberacao media do C32 dentro do rumen foi 372 e 341 mg d-1 para os animais em gaiolas de metabolismo e pastejo, respectivamente. Nao houve diferenca na taxa de liberacao entre os animais em gaiolas de metabolismo e em pastejo e a regressao linear usando os dois conjuntos de dados resultou em uma taxa de liberacao de 345 mg dia-1 do C32. Os consumos estimados de forragem usando o par C33:C32 de alcanos nao diferiu dos consumos observados para os animais em gaiolas de metabolismo. Estes resultados indicam que as capsulas de liberacao controlada podem ser utilizadas para estimar o consumo de forragem em animais estabulados mas a taxa de liberacao e a concentracao de alcanos nas capsulas devem ser medidas para gerar predicoes mais exatas.

Alkanes as markers in nutritional studies with wild ruminant and non-ruminant animals

Knowledge of information relative to the digestibility, intake and botanical and morphological composition of the diet is important in nutritional studies, since it provides the basis for understanding aspects related to the ingestive behavior and selectivity of animals. N-alkanes have been used successfully as markers in studies with many species of animals, particularly domesticated ruminants, most of the times as replacements for conventional markers as chromium oxide for example. However, for wild ruminants and non-ruminant animals information on this technique is still scarce and, as a consequence, its potential for use unknown. This review reports the use of this technique in studies of feed digestibility, intake and diet composition with wild ruminants and non-ruminant animals, summarizing results and inferring on the feasibility and applicability of the technique.

Persistência da lactação e composição do leite em ovelhas leiteiras das raças Lacaune e East Friesian

The objective of this study was to evaluate the lactation persistency and milk composition in East Friesian and Lacaune dairy ewes. Twenty one East Friesian and forty six Lacaune ewes on 44±7.2 days in milk (DIM) were used in a rotational system grazing paddocks of Panicum maximum jacq. cv. ‘Aruana’. Milk yield (MY) was measured every four days throughout the experiment (92 days). Milk samples for composition analysis were collected on days 1, 25, 50, 75, and 92. The best fi t prediction equations for MY were MY=1.42-0.02* DIM, r²=0.20 for East Friesian; and MY=2.03-0.08* DIM, r²=0.22 for Lacaune. At the beginning of the experimental period Lacaune MY was 30% higher. Lacaune ewes showed lower persistency and higher milk yield (1.67 vs. 1.35kg day-1, P<0.001), milk fat yield (114.80 vs. 102.85g day -1 , P<0.001) and protein yield (82.82 vs. 73.10g day -1 , P < 0.001). East Friesian ewes had greater milk fat (7.31 vs. 6.86%, P<0.0008) and protein concentrations (5.18 vs. 4.93%, P<0.001). Overall, the East Friesian ewes showed more persistency than Lacaune, but the milk yield and milk yield composition was greater in Lacaune.

Green leaf allowance and dairy ewe performance grazing on tropical pasture.

The objective of this study was to explain the influence of green leaf allowance levels on the performance of dairy ewes grazing a tropical grass. Seventy-two lactating ewes grazed Aruana guineagrass (Panicum maximum Jacq. cv. Aruana) for 80 d. The treatments were 4 daily levels of green leaf allowance (GLA) on a DM basis corresponding to 4, 7, 10, and 13 kg DM/100 kg BW, which were named low, medium-low, medium-high, and high level, respectively. The experimental design was completely randomized with 3 replications. During the experimental period, 4 grazing cycles were evaluated in a rotational stocking grazing method (4 d of grazing and 16 d of rest). There was a linear effect of GLA on forage mass, and increasing GLA resulted in increased total leaf mass, reaching an asymptotic plateau around the medium-high GLA level. The stem mass increased with increased GLA, and a pronounced increase was observed between medium-high and high GLAs. Increasing GLA increased both forage disappearance rate and postgrazing forage mass. Leaf proportion increased with GLA, peaking at the medium-high level, and the opposite occurred for stem proportions, which reduced until medium-high GLA level, followed by an increase on high GLA. Forage CP decreased linearly with GLA, and increasing GLA from low to high reduced CP content by 31%. On the other hand, NDF increased 14% and ADF increased 26%, both linearly in response to greater GLA levels. Total digestible nutrients decreased linearly by 8% when GLA increased from low to high level. Milk yield increased, peaking at medium-high GLA (1.75 kg ewe(-1) d(-1)) and decreased at high GLA level (1.40 kg ewe(-1) d(-1)). Milk composition was not affected by the GLA levels. There was a reduction in stocking rate from 72 to 43 ewes/ha when GLA increased from low to high level. Productivity (milk yield kg ha(-1) d(-1)) increased as GLA increased, peaking at medium-low level (115 kg ha(-1) d(-1)). Although this tropical grass showed the same pattern in responses to GLA levels as reported in the literature with temperate pastures, the magnitude of the process changed and the maximum response in milk yield from lactating dairy ewes grazing a tropical pasture would be achieved with higher forage allowances than in temperate pastures. Overall, Aruana guineagrass grazed by lactating dairy ewes should be managed to provide 7 to 10 GLA in kg DM/100 kg BW according to the production goals.

Different herbage allowances and milk yield in crossbred Holstein x Gir

The objective of this study was to evaluate different herbage allowances in stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis), on the herbage disappearance rate (HDR) and milk yield in crossbred Holstein x Gir cows. Thirty animals were assigned to three different herbage allowances (HA), ranging from 10.0, 12.5 and 15.0% BW. There was effect of HA on the HDR (P<0.001). Increasing the HA in one unit had effect on the HDR increasing by 140.0kg ha-1 day-1. There was effect of leaf:stem ratio on milk yield (P<0.05). The increasing in supplying herbage allowances did not resulted in increased milk yield because the management for herbage allowance and herbage growth.

Comparing plastic syringes and disposable columns to extract n-alkanes in forage and concentrate feeds

N-alcanos foram extraidos de alimentos, sobras e fezes de bovinos com a utilizacao de seringas plasticas descartaveis de 5mL como um material alternativo as colunas descartaveis que sao normalmente utilizadas para a fase de extracao liquido-solido. Para ambos os metodos, os n-alcanos (cadeias de carbono entre 31 e 36 atomos) foram identificados usando cromatografia gasosa. As regressoes lineares entre metodos foram: 1) fezes: coluna Alcano=2,63+0,92×seringa Alcano [r2=0,94, raiz do quadrado medio do erro (RMSE)=13,7mg kg-1, n=30], em que o intercepto e o coeficiente angular nao diferiram simultaneamente de zero e um (P>0,05), respectivamente; 2) alimentos: coluna Alcano=0,36+1,12×seringa Alcano (r2=0,85, RMSE=1,9mg kg-1, n=21), em que o intercepto e o coeficiente angular nao diferiram simultaneamente de zero e um (P>0,05), respectivamente; 3) sobras: coluna Alcano=0,49+0,92×seringa Alcano (r2=0,98, RMSE=1,2mg kg-1, n=15), em que o intercepto e o coeficiente angular nao diferiram simultaneamente de zero e um (P>0,05), respectivamente. Materiais com baixas concentracoes de alcanos podem afetar os valores obtidos em ambos os metodos de extracao. Esses resultados sugerem que as seringas plasticas descartaveis podem ser uma alternativa viavel as colunas, reduzindo o custo analitico.