Digestibility and ruminal digestion kinetics of corn silage

A degradabilidade in situ da matéria seca (MS) de silagens de milho em dois estados de maturidade (grão leitoso e meia linha de leite), de conhecida digestibilidade in vivo e in vitro, foi determinada com o propósito principal de comparar valores de digestibilidade com a degradabilidade no rúmen após 24 e 48h de incubação. Também foi analisada a cinética da digestão no rúmen, pelo modelo exponencial de McDonald, e foi calculada a degradabilidade efetiva, assumindo uma taxa de passagem de 4%/h. Dados de digestibilidade in vivo, in vitro e de degradabilidade in situ a 24 e 48h foram analisados com um modelo linear que incluiu o efeito do estado de maturação e metodologia de avaliação. Houve efeito significativo (P<0,05) da metodologia na estimação da digestibilidade, mas não foi encontrado efeito da maturação ou da interação maturação x metodologia. A digestibilidade in vivo (52,9%) não foi diferente da degradabilidade in situ a 24h (55,6%), e apresentou valores numéricos na amplitude dos valores da degradabilidade efetiva. A digestibilidade in vitro (61,6%) não foi diferente da degradabilidade in situ a 48h (61,9%), e ambas as alternativas foram maiores do que a digestilidade in vivo. A degradabilidade in situ a 24h de incubação é um bom preditor da digestibilidade in vivo da silagem de milho. Este parâmetro foi superestimado em 15-20% pela digestibilidade in vitro e pela degradabilidade in situ a 48h de incubação.

rrn operons in Haemophilus parainfluenzae and mosaicism of conserved and species-specific sequences in the 16S-23S rDNA long spacer.

The mosaic organisation of short-sequence boxes was analysed in the cloned and sequenced long ribosomal spacer (547 bp) of Haemophilus parainfluenzae GR. Comparison and alignment of both the long and the short spacer were performed in H. parainfluenzae and H. influenzae Rd. The long spacer contained two tRNA genes (tRNA(Ala) and tRNA(Ile)) which are highly homologous to the corresponding genes found in the spacers of other species, such as Haemophilus spp., Actinobacillus spp., and Plesiomonas shigelloides. At the 3' end of tRNA(Ala) a putative ribosomal spacer loop was found, showing a strong secondary structure. Pulsed field gel electrophoresis (PFGE) analysis after restriction of the genome of H. parainfluenzae GR with I-Ceu I and subsequent polymerase chain reaction (PCR) analysis of PFGE-separated DNA fragments demonstrated that the H. parainfluenzae genome contained six operons and that the long spacer was present in three copies of them. Two short DNA segments were identified as being species-specific, allowing us to design PCR primers which were useful in the molecular identification of H. parainfluenzae isolates.

Energy expenditure due to forage intake and walking of grazing cattle

The relative increment in daily maintenance requirement by physical activity was estimated in free-grazing cattle. The effects of forage harvesting and walking were measured and expressed as an index in relation to the value of energy expenditure of animals in corrals. All indices were obtained from experiments conducted in Balcarce (Argentina) from 1993 to 1995. Energy expenditure of Aberdeen Angus steers was estimated by the l4C-entry rate technique, on animals standing still in a corral, grazing at two different biting rates or walking at four different speeds. Information on time spent on grazing and distance traveled was obtained from the literature. These estimations indicate that the maintenance cost of cattle in corrals could be increased on pastures by a factor of 1.08 to 1.30, depending upon the grazing conditions. It was observed that grazing at high biting rate was the variable of highest effect on maintenance energy cost, and that walking or grazing at moderate biting rate was of lower incidence

[Clonal diffusion and evolution of mecA and Tn554 polymorphisms in methicillin-resistant Staphylococcus aureus in Italy]. / Diffusione clonale ed evoluzione dei polimorfirsmi di mecA e Tn554 in Staphylococcus aureus meticillino-resistente in Italia.

The purposes of the present study were to track the geographic spread of 69 MRSA strains in Italy recovered from 7 hospitals in four towns; to detect the clonal identities among the isolates by a combination of multiple genomic typing methods and to measure temporal trends in clonal types between 1984 and 1998. Our results showed the spread of three major clones among the MRSA isolates of 1984-1995 period: the most represented MRSA clone carried the PFGE pattern A, the mecA polymorph II and had no homology with Tn554 (II::NH::A); most of these isolates were susceptible to the macrolides,being similar to the historically " archaic" MRSA strains; the clone typed I::E::A, carried the PFGE pattern A, the mecA polymorph I and Tn554E commonly defined as "Iberian clone"; unique clone, showing an uncommon PFGE pattern E. the mecA polymorph II and the Tn554 E (II::E::E) and were characterized by a uniform susceptibility to tetracycline and rifampin. During 1997-98 the representation of this clone increased instead of the classical "Iberian clone". A new multi-resistant MRSA strain, carrying the PFGE pattern B (or B'), the mecA polymorph XI and Tn554 polymorph B (XI::B::B), called "Brazilian clone", increased from being absent (1984-95) to 48%. Our molecular data show an Italian MRSA "scenario" far from the common European trends and clearly documented the spread of an archaic clonal type (II::NH::A) in 1984-95, the arrival and rapid increase of Brazilian done in 1997-98 and the chronological and geographical spread of a unique (H::E::E) called "Italian clone", instead of the widely spread Iberian MRSA clone.

[Heparin and ischemic stroke]. / Eparina e stroke ischemico.

In absence of careful controlled trials, heparin therapy of ischemic stroke is based today on the clinical experience and personal belief of the physicians. Moreover, the incomplete knowledge of physiopathogenesis of ischemic stroke adds further confusion on those nosographic conditions treatable with heparin. This work aims to report the opinions prevalent in the literature, together with personal convictions, so to supply the reader with a complete view of the scientific discussion on this argument.

Relative contributions of hyperplasia and hypertrophy to growth in cattle.

The relationship between postweaning DNA accumulation and body weight was calculated for a reference growing steer. Accumulation of DNA (hyperplasia) was calculated from patterns of protein accretion derived from literature data and protein-to-DNA ratios (Pro/DNA) measured in samples of muscles from chuck, round and plate, hides, intestines, rumens and livers of steers slaughtered at body weights ranging from 150 to 700 kg. Amounts of protein relative to DNA found in muscles from chuck, round and plate were used to estimate Pro/DNA changes in carcass. Corresponding values from intestines, rumen and liver were used to estimate Pro/DNA patterns for viscera. This ratio increased in carcass until animals reached body weights of approximately 300 kg and leveled off thereafter. No cell enlargement was evident in viscera. Thus, postweaning protein accretion in carcass results from both cell enlargement (hypertrophy) and DNA accumulation (hyperplasia) until body weights of 300 kg are attained, subsequent growth appeared to be hyperplastic in nature. In viscera, hyperplasia was the primary determinant of protein accretion.