J.L.P. Daniel

Aditivos microbiológicos em silagens no Brasil: revisão dos aspectos da ensilagem e do desempenho de animais

O uso de inoculantes microbianos no Brasil vem aumentando nos ultimos anos, embora o numero de trabalhos ainda seja pequeno quando comparado aos observados no exterior, principalmente no que se refere ao desempenho de animais. Nos estudos com silagens de milho e sorgo os inoculantes avaliados foram compostos exclusivamente de bacterias homofermentativas, que tambem representaram a maioria das pesquisas em silagens de capins, enquanto que nas silagens de cana-de-acucar predominou o uso de bacterias heterofermentativas. Em geral, o uso de bacterias homofermentativas apresentou resultados favoraveis apenas para as silagens de milho e capins, traduzidos na maioria das vezes por menores teores de fibra e valor de pH, compensados pelo maior teor de PB. No caso das heterofermentativas foram encontrados bons resultados principalmente para as silagens de cana-de-acucar, com menor pH e teor de compostos fibrosos em face aos aumentos do teor de carboidratos soluveis, associado a maior recuperacao de MS e aumento de estabilidade aerobia. A associacao de bacterias hetero e homofermentativas proporcionou respostas satisfatorias e potencialmente interessantes embora os dados nacionais ainda sejam escassos. Investimentos adicionais na interface forragem:microrganismo podera permitir exploracao de novas perspectivas de aplicacao e consolidacao das recomendacoes desses aditivos.

Performance of dairy cows fed high levels of acetic acid or ethanol

Ethanol and acetic acid are common end products from silages. The main objective of this study was to determine whether high concentrations of ethanol or acetic acid in total mixed ration would affect performance in dairy cows. Thirty mid-lactation Holstein cows were grouped in 10 blocks and fed one of the following diets for 7 wk: (1) control (33% Bermuda hay + 67% concentrates), (2) ethanol [control diet + 5% ethanol, dry matter (DM) basis], or (3) acetic acid (control diet + 5% acetic acid, DM basis). Ethanol and acetic acid were diluted in water (1:2) and sprayed onto total mixed rations twice daily before feeding. An equal amount of water was mixed with the control ration. To adapt animals to these treatments, cows were fed only half of the treatment dose during the first week of study. Cows fed ethanol yielded more milk (37.9 kg/d) than those fed the control (35.8 kg/d) or acetic acid (35.3 kg/d) diets, mainly due to the higher DM intake (DMI; 23.7, 22.2, and 21.6 kg/d, respectively). The significant diet × week interaction for DMI, mainly during wk 2 and 3 (when acetic acid reached the full dose), was related to the decrease in DMI observed for the acetic acid treatment. There was a diet × week interaction in excretion of milk energy per DMI during wk 2 and 3, due to cows fed acetic acid sustained milk yield despite lower DMI. Energy efficiency was similar across diets. Blood metabolites (glucose, insulin, nonesterified fatty acids, ethanol, and γ-glutamyl transferase activity) and sensory characteristics of milk were not affected by these treatments. Animal performance suggested similar energy value for the diet containing ethanol compared with other diets. Rumen conversion of ethanol to acetate and a concomitant increase in methane production might be a plausible explanation for the deviation of the predicted energy value based on the heat of combustion. Therefore, the loss of volatile compounds during the drying process in the laboratory should be considered when calculating energy content of fermented feedstuffs.

Absorption and metabolism of volatile fatty acids by rumen and omasum

A capacidade de absorcao e metabolismo de acidos graxos volateis (AGV) pelo rumen e omaso foi comparada, in vitro. Fragmentos da parede do rumen e das lâminas do omaso foram coletados de oito bovinos mesticos adultos. Um fragmento isolado da mucosa foi colocado em uma câmara de difusao tecidual. Acido valerico e CrEDTA foram adicionados ao fluido ruminal e colocados no compartimento da câmara voltados para a mucosa e uma solucao tampao foi colocada no compartimento voltado para a serosa. As taxas fracionais de absorcao foram medidas pela queda exponencial da relacao VFA:Cr ao longo do tempo. A taxa de metabolismo foi determinada pela diferenca entre a quantidade de AGV absorvida e a detectada no compartimento serosal da câmara. O indice mitotico foi mais alto no epitelio do omaso (0.52%) do que no do rumen (0.28%), bem como a taxa fracional de absorcao, 4.6%/h.cm2 e 0.4%/h.cm2, respectivamente. Acetato, propionato, butirato e valerato tiveram taxas fracionais de absorcoes similares em ambos os compartimentos. As porcentagens do acetato e do propionato metabolizados foram mais baixas do que a do butirato e valerato em ambos os compartimentos. No rumen, a taxa metabolica individual dos AGV foi similar (media de 7.7 mas, no omaso, o valerato (90.0 foi mais metabolizado do que o butirato (59.6 propionato (69.8 e acetato (51.7 . A correlacao entre o metabolismo de AGV e o indice mitotico foi positiva no rumen e no omaso. Concluiu-se que o potencial de metabolismo e de absorcao de AGV por unidade de area do omaso e mais alto do que o do rumen. A variacao da capacidade de absorcao do rumen e do omaso ocorre na mesma direcao e existem indicios de que os fatores capazes de estimular a proliferacao da parede do rumen sao tambem capazes de estimular a parede do omaso.

Short communication: Influence of various proteolytic sources during fermentation of reconstituted corn grain silages

The objective of this study was to determine the contribution of corn kernel enzymes, bacteria, fungi, and fermentation end-products (main acids and ethanol) to protein solubilization during fermentation of reconstituted corn grain silage. Flint corn kernels were ground (5-mm sieve), rehydrated to 32% of moisture, and treated with no additives (control), gamma irradiation (32 kGy), gamma irradiation + fermentation end-products (1% of lactic acid, 0.3% of acetic acid, and 0.7% of ethanol, as fed), and natamycin (1% as fed). Treated grains were ensiled in nylon-polyethylene bags and stored for 90 d. Protein solubilization was calculated for each treatment and the contributions of proteolytic sources were determined. Bacterial activity was the main contributor to proteolysis (60%) followed by corn kernel enzymes (30%), whereas fungi and fermentation end-products had only minor contributions (∼5% each).

Exchanging physically effective neutral detergent fiber does not affect chewing activity and performance of late-lactation dairy cows fed corn and sugarcane silages.

The objective of this study was to determine whether replacing the physically effective neutral detergent fiber (peNDF) of corn silage with sugarcane silage peNDF would affect performance in dairy cows. Twenty-four late-lactation Holstein cows were assigned to eight 3 × 3 Latin squares with 21-d periods. The dietary treatments were (1) 25% peNDF of corn silage, (2) 25% peNDF of sugarcane silage, and (3) 12.5% peNDF of corn silage + 12.5% peNDF of sugarcane silage. The physical effectiveness factors (pef) were assumed to be 1 for corn silage and 1.2 for sugarcane silage, as measured previously by bioassay. Thus, peNDF was calculated as neutral detergent fiber (NDF) × pef. The concentrate ingredients were finely ground corn, soybean meal, pelleted citrus pulp, and mineral-vitamin premix. Dry matter intake (22.5 ± 0.63 kg/d), 3.5% fat-corrected milk yield (28.8 ± 1.13 kg/d), milk composition (fat, protein, lactose, urea, casein, free fatty acids, and somatic cell count), and blood metabolites (glucose, insulin, and nonesterified fatty acids) were unaffected by the treatments. The time spent eating, ruminating, or chewing was also similar among the diets, as was particle-sorting behavior. By contrast, chewing per kilogram of forage NDF intake was higher for the sugarcane silage (137 min/kg) than the corn silage diet (116 min/kg), indicating the greater physical effectiveness of sugarcane fiber. Based on chewing behavior (min/d), the estimated pef of sugarcane silage NDF were 1.28 in the corn silage plus sugarcane silage diet and 1.29 in the sugarcane silage diet. Formulating dairy rations of equal peNDF content allows similar performance if corn and sugarcane silages are exchanged.

The influence of covering methods on the nutritive value of corn silage for lactating dairy cows

The objective of this study was to evaluate the effect of covering methods on the nutritive value of corn silage and performance of dairy cows. Whole-plant corn was harvested at 340 g/kg of dry matter (DM) and ensiled for 135 d in horizontal silos covered with one of the following methods: oxygen barrier film (45-µm thick) + white-on-black polyethylene film (200-µm thick) over the oxygen barrier film (OB+WB); white-on-black polyethylene film (200-µm thick) (WB); black polyethylene film (200-µm thick) (B); or recycled black polyethylene film (200-µm thick) covered with a layer of 10 cm of sugarcane bagasse (RB+SB). Nutrient composition, fermentation profile, and yeast and mold counts in edible silages were similar across treatments. Silage temperature during the storage period was 24.6, 28.7, 28.4 and 33.1 °C for RB+SB, OB+WB, WB and B, respectively, and the proportion of spoiled silage ranged from 28.7 (for the RB+SB treatment) to 74.2 g/kg DM (for the B treatment). Dry matter intake was similar across treatments and averaged 21.9 kg/d. Milk production was higher for cows fed corn silage covered with RB+SB (34.4 kg/d) compared with those fed corn silage covered with B (30.4 kg/d), resulting in higher feed efficiency for RB+SB treatment. Silages covered with OB+WB and WB had intermediate values. In vivo digestibility of organic matter was higher for cows fed corn silage covered with RB+SB compared with those fed corn silage covered with WB and B, but were similar to those fed corn silage covered with OB+WB. The utilization of oxygen barrier films and the protection of polyethylene film with sugarcane bagasse are effective strategies to increase the recovery of digestible nutrients and, consequently, to enhance production efficiency of lactating dairy cows.

Avaliação morfológica do abomaso e ceco-cólon de bovinos

A morfofisiologia relacionada a absorcao de acidos graxos volateis (AGV) ao longo do trato gastrintestinal de ruminantes nao e totalmente caracterizada. Desse modo, os objetivos deste trabalho foram mensurar a extensao da superficie de absorcao e determinar o indice mitotico (IM) do abomaso, do ceco e da alca proximal do colon ascendente (APCA). Dez bovinos mesticos adultos tiveram seu estomago e intestino grosso removidos imediatamente apos o abate. A area total da superficie de absorcao foi mensurada por meio de digitalizacao e analise de imagens. Cortes histologicos foram feitos para determinacao do IM. A superficie absortiva do abomaso, 0,58m2, foi menor (P<0,01) do que a do rumen, 6,53m2, e a do omaso, 2,31m2. A superficie absortiva do ceco e da APCA, 0,23m2, correspondeu a 3,5% da superficie do rumen e a 10% da superficie do omaso. O IM observado foi 0,48%; 0,14%; 0,36% e 0,41% para as regioes de pregas espirais, pilorica, ceco e APCA, respectivamente. Observou-se correlacao positiva entre a massa tecidual do abomaso e a area de superficie de absorcao, aspecto tambem observado no ceco-APCA. Foi possivel estabelecer regressoes para facilitar a mensuracao da superficie absortiva do abomaso e do ceco-APCA.