Forty-eight Pelibuey×Katahdin male intact lambs (23.87±2.84 kg) were used in an 84-d feeding trial, with six pens per treatment in a 2×2 factorial design arrangement. The aim of the study was to evaluate the interaction of two dietary energy levels (3.05 and 2.83 Mcal/kg ME) and two dietary protein levels (17.5% and 14.5%) on growth performance, dietary energetics and carcass traits. The dietary treatments used were: i) High protein-high energy (HP-HE); ii) High protein-low energy (HP-LE); iii) Low protein-high energy (LP-HE), and iv) Low protein-low energy (LP-LE). With a high-energy level, dry matter intake (DMI) values were 6.1% lower in the low-protein diets, while with low-energy, the DMI values did not differ between the dietary protein levels. Energy levels did not influence the final weight and average daily gain (ADG), but resulted in lower DMI values and higher gain efficiencies. No effects of protein level were detected on growth performance. The observed dietary net energy (NE) ratio and observed DMI were closer than expected in all treatments and were not affected by the different treatments. There was an interaction (p<0.03) between energy and protein level for kidney-pelvic and heart fat (KPH), KPH was higher in lambs fed high energy and high protein diet but not in high energy and low protein diet. The KPH was increased (20.2%, p = 0.01) in high-energy diets, while fat thickness was increased (21.7%, p = 0.02) in high-protein diets. Therefore, it is concluded that dietary energy levels play a more important role in feed efficiency than protein levels in finishing lambs with a high-energy diet (>2.80 Mcal/kg ME). Providing a level of protein above 14.5% does not improves growth-performance, dietary energetics or carcass dressing percentage.

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Rios Rinch, F.G., Barreras-Serrano, A., Estrada-Angdo, A., Obregon, J.F., Plascencia-Jorquera, A., PortilloLoera, J.J. and Zinn, R.A. 2010. Effect of level of dietary zilpaterol hydrochloride (P,-agonist) on performance, carcass characteristics and visceral organ mass in hairy lambs fed all-concentrate diets. J. Appl

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Comparison of efficiency and reproductive aptitude indexes between a reference and field strains of the cattle tickRhipicephalus (Boophilus) microplus, in Sinaloa, Mexico AbstractThe objective of this work was to study the reproductive behavior of two strains of R. (B.) microplus, one wild-caught (Native) and one reference strain (Media Joya) for two years, measuring the reproductive efficiency index (REI) and reproductive aptitude index (RAI). Engorged ticks from each strain were collected monthly from February 2002 to February 2004. These were weighed and kept in the laboratory until egg-laying. Oogenic masses were individually weighed and incubated until larvae emergence. REI and RAI were calculated from each sample, grouping ticks by weight in 100 mg range classes. An analysis of variance and Duncan's multiple rank tests were carried out on the data (P < 0.05). Pearson's correlation coefficients were estimated (P < 0.01) in order to determine the relationship between engorgement weight and the weight and number of laid and hatched eggs. The Native strain showed a higher engorgement weight than Media Joya strain. In both strains REI and RAI were similar in all weight classes; with a quadratic tendency in Media Joya and linear-quadratic in the Native strain (P < 0.05). Significant differences where observed when REI and RAI of both strains were compared along the duration of the study (P < 0.01) with the Native strain performing better in both indexes, including better performance during the dry season. All parameters studied showed highly significant correlation; eggs laid and eggs hatched were notably highly correlated, 0.94 and 0.91, for Media Joya strain and Native strain respectively. ResumoO objetivo deste trabalho foi estudar a conduta reprodutiva de duas cepas de R. (B.) microplus, uma coletada no campo (Nativa) e outra de referência (Média Jóia), por dois anos, calculando o índice de eficiência reprodutiva (REI) e o índice de aptidão reprodutiva (RAI). Foram coletados mensalmente carrapatos fêmeas engurgitadas de cada cepa no período de Fevereiro de 2002 a Fevereiro de 2004. Estas foram pesadas e conservadas no laboratório até ovipositar. As massas de ovos foram pesadas individualmente e incubadas até a eclosão das larvas. O REI e o RAI foram calculados para cada coleta, agrupando os carrapatos em classe de peso de 100 mg. Os dados foram submetidos a uma análise de variância e prova de classe múltipla de Duncan (P < 0,05). Foram calculados os coeficientes de correlação de Pearson (P < 0,01) para estimar a associação entre o peso dos carrapatos engurgitados e o peso e número de ovos postos e eclosionados. A cepa Nativa mostrou um peso ao engurgitamento mais alto do que a cepa Média Jóia. Os valores de REI e de RAI em ambas cepas foram similares em todos as classes de peso, mostrando tendência cuadrática na Média Jóia e linear-cuadrática na cepa Nativa (P < 0,05). Ambos os índices por classe de peso no engurgitamento foram sempre mais altos na cepa Nativa (P < 0,05). Os valores de REI e de RAI de amba...