Marcos Neves Pereira

Ruminal degradability of hard or soft texture corn grain at three maturity stages

The predominance of vitreous endosperm in hard texture flint corn (Zea mays L.) can decrease ruminal starch digestion comparatively to the farinaceous endosperm of dent corn, reducing energy content of the grain. The objective of this experiment was to evaluate the effects of texture and maturity stage on ruminal degradability of corn grain. Two dent and two flint hybrids were harvested at the early dent, half milk line, and black layer stages. The proportion of vitreous endosperm (vitreousness) in dent hybrids was 44.3%, while in flint it was 67.0%. There was a linear increase in vitreousness with advancing maturity. Flint hybrids at the early dent stage were more vitreous than dent at the black layer stage. The increase in vitreousness per maturation day was greater for flint hybrids. Grains were incubated in situ in the rumen of 6 cows. The 24-hour ruminal dry matter degradation was 63.3% for dent corn and 52.4% for flint corn. The 72-hour incubation residues of dent and flint hybrids were 7.6% and 15.6%, respectively. Ruminal degradability was similar between hybrids at the early dent and half milk line stages. There was a marked texture effect on ruminal degradability at the black layer stage (quadratic effect of maturity stage and interaction between texture and maturity stage). Use of dent hybrids, compared to flint hybrids, may result in smaller relative reduction in ruminal starch digestion in situations of late grain harvesting.

Rumen morphometrics and the effect of digesta pH and volume on volatile fatty acid absorption1

The effects of rumen digesta volume and pH on VFA absorption and its relation to rumen wall morphology were evaluated. Nine rumen cannulated cows formed 3 groups based on desired variation in rumen morphology: The High group was formed by Holsteins yielding 25.9 kg milk/d and fed on a high-grain total mixed ration (TMR); the Medium group by Holstein-Zebu crossbreds yielding 12.3 kg milk/d and fed on corn silage, tropical pasture, and a commercial concentrate; and the Dry group by nonlactating grazing Jerseys fed exclusively on tropical pasture. Within each group, a sequence of 3 ruminal conditions was induced on each cow in 3 × 3 Latin Squares, with 7-d periods: high digesta volume and high pH (HVHP), low volume and high pH (LVHP), and low volume and low pH (LVLP). Rumen mucosa was biopsied on the first day of Period 1. Ruminal morphometric variables evaluated were mitotic index, absorptive surface and papillae number per square centimeter of wall, area per papillae, papillae area as a percentage of absorptive surface, and epithelium, keratinized layer, and nonkeratinized layer thickness. There was marked variation in rumen morphology among the groups of cows. Grazing Jerseys had decreased rumen wall absorptive surface area and basal cells mitotic index, and increased thickness of the epithelium and of the keratin layer compared with cows receiving concentrates. Mean rumen pH throughout the 4 h sampling period was: 6.78 for HVHP, 7.08 for LVHP, and 5.90 for LVLP (P < 0.01). The capacity of the rumen wall to absorb VFA was estimated by the Valerate/CrEDTA technique. The fractional exponential decay rate for the ratio of valeric acid to Cr (k Val/Cr) was determined by rumen digesta sampling at 20-min intervals during 4 h, after the mixing of markers and the return of the evacuated ruminal content. The k Val/Cr values for treatments HVHP, LVHP, and LVLP were, respectively: 19.6, 23.9, and 35.0 %/h (SEM = 2.01; P = 0.21 for contrast HVHP vs. LVHP and P < 0.01 for contrast LVHP vs. LVLP). The k Val/Cr was faster under low pH, but decreasing digesta volume under high pH did not elicit such a response. The correlation between the absorptive surface area per square centimeter of rumen wall and the mean of the 3 k Val/Cr values of each cow was 0.90 (P < 0.01). Cows capable of maintaining a less-acidic rumen environment had greater inflow of water into the digestive cavity, had a more developed rumen mucosa, and were more efficient VFA absorbers.

Diet digestibility and performance of dairy cows supplemented with live yeast

A suplementacao com levedura pode melhorar a eficiencia digestiva de ruminantes. Entretanto, a resposta depende da cepa de levedura e da composicao da dieta. Silagem de milho e polpa citrica sao fontes frequentes de carboidratos para vacas leiteiras no Sudeste do Brasil. Avaliou-se a suplementacao de vacas leiteiras alimentadas com dieta baseada em silagem de milho e polpa citrica com Saccharomyces cerevisiae cepa CNCM I1077 (Lallemand SAS, Toulouse, Franca). Vinte vacas Holandesas multiparas em meio de lactacao foram alocadas a uma sequencia de dois tratamentos em delineamento de reversao simples. Os tratamentos foram: 10 g de levedura viva em farinha de ostra para fornecer um minimo diario de 1 × 1010 ufc por vaca ou farinha de ostra fornecidos sobre a refeicao matinal. A dieta continha (% da materia seca): 16,8% de proteina bruta, 30,9% de fibra em detergente neutro, 43,9% de silagem de milho, 2% de feno de tifton, 14,4% de milho floculado, 16,9% de polpa citrica e 21,7% de farelo de soja. A suplementacao com levedura aumentou as producoes diarias de leite (29,4 vs. 28,5 kg, p = 0,11), proteina (0,939 vs. 0,908 kg, p = 0,05) e lactose (1,264 vs. 1,241 kg, p = 0,06), e nao teve efeito sobre a gordura do leite (p = 0,53). O consumo diario de materia seca foi 21,4 kg com levedura e 20,7 no controle (p = 0,11). A digestibilidade aparente da fibra em detergente neutro no trato digestivo total foi 48,1% com levedura e 43,2% para o controle (p = 0,08). Houve tendencia de aumento no consumo de materia orgânica digestivel com a suplementacao de levedura (p = 0,07). A resposta positiva em secrecao de proteina do leite a suplementacao com levedura parece ter sido resultado do aumento na digestibilidade da fibra, mas o mecanismo para a resposta nao pode ser elucidado.

Resposta de vacas leiteiras à substituição total de milho por polpa cítrica e à suplementação com microminerais orgânicos I: consumo e digestão

Avaliou-se a resposta de vacas leiteiras a substituicao total de milho maduro finamente moido por polpa citrica peletizada. O teor dietetico do milho foi 10% e o de polpa 24% nos tratamentos com milho, e o de polpa foi 33% nas dietas exclusivas com polpa. Simultaneamente, foi avaliada a substituicao total de fontes inorgânicas de Cu, Mn, Se, Zn e Cr por fontes orgânicas. Quatro dietas baseadas em silagem de milho foram geradas por arranjo fatorial dos dois fatores. Dezesseis vacas receberam os tratamentos em quadrado latino 4x4. O efeito da substituicao de fontes inorgânicas por fontes orgânicas de microminerais nao foi conclusivo. O consumo diario de materia seca foi 19,4kg na polpa e 20,5kg na dieta com milho (P=0,03). O consumo de materia orgânica digestivel foi maior nas dietas com milho (P<0,01). Houve tendencia de queda na taxa fracional de degradacao ruminal in situ da MS da silagem de milho (P=0,11) e de aumento no tamanho da fracao indigestivel (P=0,15) nas dietas com milho, sugerindo que a degradacao de forragens nao determinou o menor consumo nas dietas com polpa. A substituicao total de milho por polpa citrica pode reduzir o consumo e a digestibilidade.

Resposta de vacas leiteiras à substituição parcial de farelo de soja por ureia encapsulada

Avaliou-se a substituicao parcial de farelo de soja na dieta-controle por ureia encapsulada ou por ureia, ambos acrescidos de polpa citrica. Dezoito vacas foram alocadas a uma sequencia de tres tratamentos, em seis quadrados latinos 3x3, com periodos de 21 dias. O teor de proteina bruta nas dietas foi 15,5%, cerca de 1,5% oriundo de nitrogenio nao proteico (NNP). O uso de NNP reduziu o consumo diario de materia seca em 0,8kg (P=0,04), sem influenciar a producao de leite (31,5kg, P=0,98). A conversao do alimento em leite foi menor na dieta-controle (P<0,09). As fontes de NNP aumentaram o teor de N-ureico no plasma (NUP) duas horas apos a alimentacao da manha (P=0,06). A frequencia de NUP acima de 22,0mg/dL foi maior com ureia (P<0,01), similarmente ao observado para o teor e a secrecao diaria de N-ureico no leite (P<0,01). A substituicao de farelo de soja por NNP e polpa citrica melhorou a eficiencia alimentar, sem afetar o balanco de nitrogenio.

Alterações morfológicas induzidas por butirato, propionato e lactato sobre a mucosa ruminal e epiderme de bezerros: II. Aspectos ultra-estruturais

The effect of volatile fatty acids (VFA) on rumen wall, epidermis of nasolabial surface, perioplum, and epicera of calves was evaluated. The experiment also aimed to validate the procedure of tegument biopsies as indicators of ruminal mucosa alterations. Seventeen neonatal calves with foley catheters received intraruminal infusions of VFA or saline, during 37 days. At 89-day-old, the animals were slaughtered and tissue samples were collected from rumen, nasolabial surface, epicera, and perioplum from face and hindquarters. VFA infusion increased total epithelium area and metabolically active ruminal cell area; although butirate did not induce the papilar development. The effect of nasolabial surface VFA infusion was the opposite to that observed in the rumen. No histological lesion was observed on nasolabial surface, epicera, and perioplum, demonstrating that these are consequences of VFA direct effect on ruminal epithelium. Butyrate and lactate induced more alterations on the ruminal epithelium. Indirect and direct VFA effects on keratinized epithelium tissues morphology were not identical. Tegumentary biopsies may be useful as indicators of morphological alterations of ruminal mucosa.

Ruminal silage degradability and productivity of forage and grain-type sorghum cultivars

Forrageiras para alimentacao de vacas leiteiras devem conciliar a alta producao de materia seca por area, maximizando a taxa de lotacao animal, com o alto valor nutritivo, capaz de reduzir a necessidade de alimentos concentrados por litro de leite produzido. Dezoito cultivares de sorgo foram cultivados com espacamento de 0,70 m e 12 plantas por metro linear. As plantas colhidas ao atingirem o estadio leitoso-pastoso foram ensiladas em laboratorio. Onze caracteristicas agronomicas e quimicas foram avaliadas. As silagens foram incubadas in situ e a degradabilidade efetiva da materia seca no rumen (DEF) foi calculada assumindo uma taxa de passagem de -0,04 h-1. A producao de materia seca foi 13,0 ± 2,3 (media ± D.P.) t ha-1. O teor de fibra em detergente neutro foi 50,3 ± 3,8 e a DEF foi 48,8 ± 2,8 (% da materia seca). A DEF media do sorgo foi 84% da DEF de uma amostra composta de 60 cultivares de milho simultaneamente cultivados, ensilados e incubados no rumen. Os 12 cultivares do tipo forrageiro foram mais altos, produtivos e fibrosos e tiveram menor DEF que os 6 cultivares graniferos e de duplo proposito. O teor de fibra em detergente acido foi a caracteristica mais correlacionada a DEF (r=-0,64). O modelo linear correlacionando a DEF a produtividade foi: DEF=54,69 - 0,4449 x t de materia seca ha-1 (r2=0,14). Apesar de existirem cultivares com alta produtividade e digestibilidade, pode ser dificil conciliar o maximo valor nutritivo com a maxima produtividade na planta de sorgo.

Response of lactating cows to live yeast supplementation during summer.

Dairy cows experiencing heat stress have reduced intake and increased reliance on glucose, making feeding strategies capable of improving diet digestibility plausible for improving postrumen nutrient flow and performance. The effect of yeast on digestion and performance of lactating cows during the warm summer months of southeastern Brazil was evaluated. Cows were individually fed in tie stalls and temperature-humidity index was above 68 during 75.6% of the experiment. Twenty-eight Holstein cows (207±87 d in milk) received a standard diet for 14 d and then a treatment for 70 d, in a covariate-adjusted, randomized block design with repeated measures over time. Treatments were yeast (Saccharomyces cerevisiae) or control. Yeast was top dressed to the diet in the morning, equivalent to 25×10(10) cfu of live cells and 5×10(10) cfu of dead cells. The diet contained corn silage (37.7%), Tifton silage (7.1%), raw soybeans (4.1%), soybean meal (16.5%), finely ground corn (20.7%), and citrus pulp (11.9%). Yeast increased milk (26.7 vs. 25.4 kg/d) and solids yield (3.06 vs. 2.92 kg/d), especially lactose. Response in milk yield was consistent over time and started at d 5. The daily intake of digestible OM, total-tract digestibility of nutrients, urinary allantoin excretion, chewing pattern throughout the day, and dry matter intake did not respond to yeast. A trend was observed for increased plasma glucose with yeast (62.9 vs. 57.3mg/dL), lowered respiratory frequency (48 vs. 56 breaths/min), and increased plasma niacin content (1.31 vs. 1.22 µg/mL), though cows had similar rectal temperature. Ruminal lactate and butyrate as proportions of ruminal organic acids were reduced by yeast, but no effects on other organic acids, ruminal pH, or protozoa content were detected. Plasma urea N over 24h was increased by yeast. On d 72 to 74, citrus pulp was abruptly replaced with finely ground corn to induce acidosis. The increased load of starch increased dry matter intake between 0700 and 1300 h, jugular blood partial pressure of CO2, HCO3-, and base excess, and decreased blood pH for both treatments. The yeast treatment had a higher blood pH compared with the control, 7.34, and 7.31, respectively. Yeast supplementation improved lactation performance of dairy cows under heat stress. Improvement in lactation performance apparently involved the regulation of body homeothermia, rather than improved digestibility.

Botulismo em bovinos leiteiros no Sul de Minas Gerais, Brasil

An outbreak of bovine botulism in a dairy herd caused by ingestion of contaminated maize, in southern Minas Gerais, Brazil is described. The herd was composed by 148 lactating cows of high milk production fed with diet based on maize ensilage and concentrate in a free stall system. Thirty eight cows were affected, with 100% of fatality rate. Samples from intestine, rumen and liver of necropsied cattle and drinking water and maize were submitted to the mouse bioassay and soroneutralization tests for detection of Clostridium botulinum toxins. Types C and D toxins were detected in samples from intestinal and rumen contents and maize. The reporter of an outbreak of botulism in cattle associated with an unusual source of toxin, shows that stocked maize in inadequate conditions is a factor of risk for the occurrence of the botulism in dairy cattle.

Avaliação de híbridos de milho obtidos do cruzamento entre linhagens com diferentes níveis de degradabilidade da matéria seca

Na recomendacao de um hibrido para producao de silagem, nao basta apenas considerar a producao de materia seca; e necessario tambem que a silagem tenha alta degradabilidade efetiva (DEF) da materia seca da planta inteira. O objetivo deste trabalho foi avaliar as caracteristicas agronomicas, bromatologicas e de degradabilidade ruminal da materia seca de hibridos comerciais de milho recomendados para a producao de silagem e de hibridos experimentais provenientes do cruzamento entre linhagens de alta e baixa degradabilidade. Foi avaliado o desempenho de 23 hibridos de milho, sendo dezoito hibridos experimentais e cinco comerciais, indicados para silagem. O experimento foi instalado no ano agricola 2003/2004, com delineamento experimental de blocos casualizados, com tres repeticoes e a parcela experimental constituida de quatro linhas de 5,0 metros. As plantas foram colhidas a 20 cm do solo, no estadio da linha de leite na metade do grao (farinaceo/duro). As silagens foram incubadas in situ por 0, 6, 12, 24 e 96 horas, no rumen de tres vacas fistuladas e a degradabilidade efetiva foi calculada assumindo taxa de passagem de -0,05%/hora. Foi observado que entre as cultivares avaliadas, ha hibridos com grande potencial para a producao de silagem de qualidade com alta degradabilidade da materia seca de planta inteira (DEF), independentemente da textura do grao; e correto o uso da estrategia de sintetizar hibridos visando a alta degradabilidade efetiva da materia seca da planta inteira (DEF) utilizando linhagens que apresentam alta DEF. A baixa correlacao da degradabilidade efetiva com caracteristicas agronomicas e bromatologicas, evidencia a necessidade de maior utilizacao da DEF na selecao de hibridos de milho, visando a producao de silagem de qualidade.