The objective of this experiment was to determine the effects of replacing corn with soybean hulls (SH) or Bermudagrass tifton hay (TH) on performance of sheep fed cactus-based diets. Three ruminally fistulated sheep were used in a 3 x 3 Latin square experiment with 21-day periods. All diets contained 75% spineless cactus (dry matter basis, DM) and formulated to be isonitrogenous. Fiber source had no influence on nutrient intakes except for the intake of neutral detergent fiber (NDF) which was lower (p<0.05) for animals fed corn relative to those fed SH or TH. Time expended in rumination and total chewing time were higher (p<0.05) for animals fed TH than those fed SH or corn. In vivo nutrient digestibilities were similar for all dietary treatments and averaged 69.6%, 74.8%, 69.9%, and 61.8% for DM, organic matter, crude protein, and NDF, respectively. Feeding SH relative to TH and corn decreased ruminal pH (p<0.05) and increased concentration of total volatile fatty acids (p<0.05). However, ruminal NH3-N concentration was higher (p<0.05) for animal fed TH than for those fed SH or corn. Abdominal distension and ruminal biofilm production were greater (p<0.05) in animals fed corn or SH than in those fed TH. It was concluded that replacing corn with SH or TH up to 15% of the diet DM in a cactus-based diet had no effect on nutrient intakes or total tract nutrient utilization. Changes in ruminal fermentation parameters reflected differences in ruminal degradability between the two fiber sources. Bermudagrass tifton hay was more effective than SH in reducing the risk of bloat associated with feeding high levels of spineless cactus to ruminants.

RESUMOAvaliaram-se a viabilidade técnica e a rentabilidade de um sistema de produção de leite com gado mestiço, mediante análise de custos e receitas da atividade e avaliação da rentabilidade. Os dados foram obtidos de uma unidade experimental da EPAMIG, situada no município de Felixlândia, MG, e referemse a dois períodos iguais de um ano cada. As variáveis analisadas foram: rentabilidade nos períodos de análise, custo de cria do bezerro e sua importância sobre a receita da atividade. A viabilidade do sistema foi demonstrada pela rentabilidade de 20,2% no ano 1 e 37,6% no ano 2; a venda dos bezerros à desmama representou 25% da receita total.Palavras-chave: gado de leite, sistema de produção, F 1 , rentabilidade ABSTRACTThe economic viability of a milk production system with crossbred (F 1 INTRODUÇÃOAs mudanças econômicas ocorridas desde o início da década de 1990 vêm exigindo rápidos ajustes estratégicos e estruturais do setor agroindustrial do leite. A desregulamentação do mercado do leite, posterior à abertura comercial da economia brasileira, resultou em um mercado bastante competitivo exigindo produtividade, qualidade e escala de produção (Reis et al., 2001). A abertura do mercado interno à competição internacional colocou o produtor brasileiro de leite em embate com fortes concorrentes, entre os quais se destacam a Nova Zelândia e a Argentina (Schiffler, 1998).

The objective of this study was to detect Mycoplasma agalactiae (Ma) and the Mycoplasma mycoides cluster (Mmcluster) in 373 goat milk samples of different breeds from herds located in Pernambuco and Paraíba states, as well as to evaluate somatic cell count (SCC) and milk composition from positive animals. For this, DNA extraction from milk samples was carried out, followed by generic and species-specific amplification by Polymerase Chain Reaction (PCR). Milk constituents were determined by medium infrared spectrometry and SCC by flow cytometry. Analyses of variance and tests of comparison of means verified the effects of positivity on the evaluated characteristics. The frequencies for Ma and Mmcluster were 43.21 and 5.70%, respectively. In all genetic groups, Ma was detected in all positive samples, whereas Mmcluster was only observed in samples from Moxotó, Parda Sertaneja, and that without a defined racial pattern. Statistical difference was observed (p < 0.05) between mean values of protein, casein and SCC in positive and negative Ma samples. In terms of Mmcluster there was only a statistically significant difference in the SCC parameter. The detection of Mycoplasma in samples of goat milk suggests an introduction of infected animals into the evaluated herds, as well as possible contact with the etiological agents at fairs and exhibitions.

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