Phenotypically divergent classification of preweaned heifer calves for feed efficiency indexes and their correlations with heat production and thermography.

The aims of this study were (1) to assess if there is phenotypical divergence for feed efficiency (FE) during the preweaning phase; (2) if FE is correlated with heat production (HP) measured by the face mask method or (3) by surface skin temperature via thermography, and (4) whether these methods are applicable to preweaned calves. Holstein × Gyr heifer calves (n = 36, birth body weight = 32.4 ± 6.6 kg) were enrolled and on trial between 4 and 12 wk of age and were classified into 2 residual feed intake (RFI) and residual body weight gain (RG) groups: high efficiency (HE; RFI, n = 10; and RG, n = 9) and low efficiency (LE; RFI, n = 10; and RG, n = 8). Calves were fed milk (6 L/d) and solid feed (95% starter and 5% chopped Tifton 85 hay, as fed). Growth was monitored weekly and feed intake (milk and solid feed) daily, during the whole period. Gas exchanges (O2 consumption and production of CO2 and CH4) were obtained using a face mask at 45 ± 5 d of age and HP was estimated. Maximum temperatures were measured at 7 sites with an infrared camera at 62 ± 7 d of age. There was divergence in RFI and RG. Respectively, HE and LE calves had RFI of -0.14 and 0.13 kg/d, and RG of 0.05 and -0.07 kg/d. Dry matter intake was 15% lower in HE-RFI compared with LE-RFI, but no differences were observed in average daily weight gain. Within the RG test, no differences were observed in dry matter intake or average daily gain. The HE-RFI calves consumed less O2 (L/d) and produced less CO2 (L/d). Heart rate and HP were lower for HE-RFI calves compared with LE-RFI. Residual feed intake was correlated with HP (r = 0.48), O2 consumption (r = 0.48), CO2 production (r = 0.48), and heart rate (r = 0.40). No differences were observed in HP and gas exchanges between RG groups. Methane production was null in both groups. Eye temperature measured by thermography was 0.5°C greater in HE-RG than LE-RG calves. Differences in skin temperature between HE and LE calves were not observed at the other sites. These results support the hypothesis that calves are divergent for RFI, RG, and FE during preweaning and divergence tests are applicable during this phase. The face mask method described here is a useful tool for estimating differences in HP among phenotypically divergent RFI calves. Eye temperature measured by infrared thermography may have potential to screen phenotypically divergent RG calves.

Ganho compensatório no desempenho e eficiência econômica de novilhos Nelore submetidos a diferentes regimes alimentares / Compensatory gain in performance and economic efficiency of Nellore steers under different feeding regimes

Avaliaram-se o efeito do ganho compensatório no desempenho produtivo e a eficiência econômica de novilhos submetidos a diferentes estratégias de suplementação alimentar na fase de recria e engorda. Cinquenta e quatro bezerros, com peso médio inicial de 169,6±16,7kg, foram divididos em oito tratamentos, sendo cada tratamento uma estratégia de suplementação alimentar. No período da seca, os animais receberam suplemento proteico-energético-mineral (SP), com ingestão média diária de 0,1 ou 0,2% do peso vivo. No período das águas, os novilhos receberam SP com ingestão média diária de 0,5% do peso vivo ou suplementação mineral (SM). No período de terminação, os animais receberam SP com ingestão média diária de 1,4% do peso vivo ou foram confinados. Os animais que receberam SM não tiveram ganho compensatório. Animais que receberam SP nas águas (0,51±0,07kg/dia) tiveram ganho compensatório em relação ao período anterior e obtiveram ganho adicional diário de 123g quando comparados com SM (0,39±0,07kg/dia), entretanto não obtiveram ganho compensatório na fase de terminação. O efeito do ganho compensatório é muito pequeno ou até mesmo nulo no sistema de recria e engorda precoce com terminação em confinamento. A suplementação com menor ingestão de proteína, energia e mineral durante a primeira seca e águas, pós-desmame, da vida de novilhos pode ser compensada com o uso do confinamento na fase de terminação desses animais com resultados econômicos positivos.

The effect of compensatory growth on performance and economical efficiency of steers on different dietary supplementation strategies in the rearing and fattening stages was evaluated. Fifty-four calves with average initial weight of 169.6±16.7kg were divided into eight treatments, each of them being a strategy of food supplementation. During the dry season the animals received protein - energy - mineral supplement (SP) with an average daily intake of 0.1 or 0.2 % of body weight (BW). During the rainy season the animals received SP with an average daily intake of 0.5 % of body weight or mineral supplementation (SM). In the fattening period, the animals received SP with an average daily intake of 1.4 % of body weight or were placed in feedlot. Animals that received SM had no compensatory gain. Animals that received SP during the rainy season (0,51±0,07kg/day) had compensatory growth when compared to the previous period, and obtained additional daily gain of 123g when compared to SM group (0,39±0,07kg/day), however did not obtain compensatory gain during the fattening phase. The effect of compensatory gain becomes minimal or zero in feedlot finished. Supplementation strategies with protein, energy and mineral intake in the first dried and the first water in steer's life can be compensated with the use of these animals in the feedlot finishing phase with positive economic results.

Desempenho e análise econômica de novilhos Nelore submetidos a diferentes estratégias de suplementação alimentar nas fases de recria e engorda / Performance and economic analysis of Nelore submitted to different strategies for supplementary feeding during rearing and fattening

Avaliou-se o desempenho produtivo e a eficiência econômica de diferentes estratégias de suplementação alimentar na fase de recria e engorda de novilhos Nelore. O experimento foi dividido em três períodos, seca, água e terminação. Cinquenta e quatro bezerros com peso médio inicial de 169,6kg foram divididos em oito tratamentos, sendo cada tratamento uma estratégia de suplementação alimentar. No período da seca, os animais receberam suplemento proteico-energético-mineral com ingestão média diária de 0,1% do peso vivo médio (PV) para os tratamentos A, B, C, D, e 0,2 por cento do PV para os tratamentos E, F, G e H. No período das águas, os novilhos dos tratamentos A, B, E e F receberam suplemento proteico-energético-mineral com ingestão média diária de 0,5 por cento do PV, e os novilhos dos tratamentos C, D, G e H receberam suplementação mineral. No período de terminação, os animais dos tratamentos B, D, F e H receberam suplemento proteico-energético-mineral com ingestão média diária de 1,4 por cento do PV, e os animais dos tratamentos A, C, E e G foram engordados em confinamento. Houve diferença estatística (p<0,05) para o peso final acumulado (PF). Os maiores valores de PF foram de 492,0; 475,1 e 473,1kg para os animais dos tratamentos F, B e H, respectivamente. Os animais dos tratamentos que receberam suplemento 1,4 por cento do PV na terminação permaneceram 70 dias a mais do que os animais que foram engordados em confinamento. Todas os tratamentos foram economicamente viáveis, contudo o tratamento G apresentou o maior resultado de caixa, VPL e TIR, sendo eles R$349,00; R$252,10 e 2,45 por cento, respectivamente. A suplementação de proteína, energia e minerais a pasto ou em confinamento reduziu a idade ao abate dos animais e constitui uma alternativa economicamente viável para produção de bovinos de corte.

The aim of this study was to evaluate the production performance and economic efficiency of different strategies of supplementation on the rearing and fattening of Nelore calves. The experiment was divided in to three periods, Drought, Rainy and Finishing. Fifty four calves with average initial weight of 169.6 kg were divided in eight treatments, each treatment with one supplementation strategy. During the dry season the animals were protein-energy and mineral supplemented with an average daily intake of 0.1 percent of body weight (BW) for strategies A, B, C, D and 0.2 percent of BW for strategies E, F, G and H. During the rainy season, animals from strategies A, B, E and F were protein-energy and mineral supplemented with an average daily intake of 0.5 percent of BW and strategies C, D, G and H received only mineral supplementation. During the finishing period, animals from strategies B, D, F and H were protein-energy and mineral supplemented with an average daily intake of 1.4 percent of BW and animals from strategies A, C, E and G were fattened in feedlots. There was statistical difference (p<0.05) for the cumulative final weight (FW). Higher values of FW were 492.0, 475.1 and 473.1kg for animals from strategies F, B and H respectively. Animals from strategies supplemented 1.4 percent of BW remained 70 days more in the termination period than animals fattened in feedlots. All strategies were economically viable, however, strategy G had a major cash result, net present value (NPV) and internal rate of return (IRR), R$ 349.00; R$ 252.10 and 2.45 percent respectively. Protein, energy and mineral supplementation on pasture or feedlot reduces the age at slaughter of animals and is an economically viable alternative for production of beef cattle.

Desempenho de bovinos Tabapuã e seus cruzados em pastagens de braquiária no estado da Bahia / Performance of straightbred and crossbred Tabapuã cattle on brachiaria pasture in Bahia state

Comparou-se o desempenho de bovinos de diferentes grupos genéticos quanto a algumas características produtivas da desmama até o abate. Os dados são referentes a 827 bovinos machos oriundos do cruzamento de vacas Tabapuã com touros Tabapuã (TAB), Red Angus (REDTAB), Santa Gertrudis (STATAB), e das fêmeas TabapuãxRed Angus com touros Santa Gertrudis (STAREDTAB) (nascidos entre 1999 e 2001 e criados em pastagens de braquiária, no Estado da Bahia). Foram analisados o peso à desmama ajustado aos 205 dias (PD205), o peso ao abate (PA), o ganho médio diário da desmama ao abate (GMD) e a idade ao abate (IA). O grupo contemporâneo (GC), o grupo genético (GG) e a interação entre GC e GG influenciaram as características avaliadas (P<0,05). O REDTAB apresentou superioridade entre os GG para GMD no primeiro ano do GC (1GC), com média de 0,552kg (P<0,05). Os cruzados STATAB e STAREDTAB não apresentaram diferenças significativas para as médias de GMD (P>0,05); entretanto, apresentaram médias inferiores às do grupo REDTAB e TAB. Em condição de ambiente mais favorável, o REDTAB pode ser mais precoce, obtendo maior GMD e PA com menor IA, sendo superior ao Tabapuã e aos cruzados da segunda geração (F2). Os cruzados F2 não demonstraram vantagem em relação ao cruzado F1 e à raça pura.

The aim of this study was to compare the different genetic groups performances from weaning to slaughter. The d ata are referred to 827 male calves of Tabapuã c ows crossed with Red Angus (REDTAB) and Santa Gertrudis sires and from Tabapuã x Red Angus cows crossed with Santa Gertrudis sires , born from 1999 to 2001 and raised in Brachiaria pastures, in Bahia state , Brazil. The w eaning weight was adjusted to 205 day s (WW205), slaughter weight (SW ), average daily gain from weaning to slaughter (ADG) and age slaughter (AG), were analyzed. The contemporary group (CG), genetic group (GG) and the interaction between CG and GG influenced the parameters (P<0.05). The REDTAB showed superiority between GG for ADG in 1CG, with an average of 0.522 kg (P<0.05). The cro s sbreed STATAB and STAREDTAB weren 't different to ADG (P>0.05), however, ha d lower averages than REDTAB and TAB. In more favorable environment al conditions, REDTAB s hould get higher ADG and SW and lower AG , being superior than Tabapuã and to the second generation's crossbr ed (F2). The crossbr ed F2 show ed no advantage over F1crossbr ed and straightbred.

Further improvements in the application of high-performance liquid chromatography, capillary electrophoresis and capillary electrochromatography to the analysis of algal toxins in the aquatic environment.

The presence of algal toxins in the aquatic environment represents an important socioeconomic concern in many places worldwide, due to the toxicity that these compounds can induce in seafood or freshwater organisms at very low levels. Several analytical alternatives have been proposed over the last years for the control of these contaminants, which acute or chronic toxicity requires low detection levels and demands for the search of sensitive methods for their detection and determination. HPLC has been widely used for this purpose, although several alternatives such as CE or capillary electrochromatography (CEC) are being lately developed with this aim. In this work we report on the application of improved HPLC, as well as CE and CEC, for the analysis of diarrhetic shellfish poisoning toxins, amnesic shellfish poisoning (ASP) toxins and microcystins (MCs) present in different matrices such as water, shellfish or algae. Improvements in sample preparation for increasing sensitivity and selectivity are also shown. While UV and fluorimetric detection are the detection methods generally used, mass spectrometric detection was also applied for ASP toxins and MCs, especially for confirmatory purposes. From the results obtained it can be concluded that both HPLC and CE offer a good potential for a sensitive and selective determination of these algal toxins in such complex matrices. The results obtained for CEC allow also to conclude that this technique can result in a promising technique for such application.

HPLC and HPCE analysis of microcystins RR, LR and YR present in cyanobacteria and water by using immunoaffinity extraction.

Microcystins, which have their origin in species of cyanobacteria present in freshwaters, have recently been found to be important contaminants of the aquatic environment at trace levels. HPLC and HPCE with UV detection have been applied in the determination of such toxic compounds. Immunoaffinity chromatography for the selective extraction and clean-up of microcystins has been successfully applied to different matrices. Simple protocols for unambiguous determination of these toxins are presented and the immunoaffinity clean-up is compared with conventionally used solid phase extraction procedures. The development and optimisation of an on-line preconcentration procedure based on field amplified sample stacking for the analysis of microcystins by HPCE in the micellar electrokinetic chromatography mode is also described, using borate buffer with the anionic surfactant SDS, as separation electrolyte. Results indicate that sub-nanogram/gram content of microcystins can be detected in water samples, while sub-microgram/gram concentrations can be determined in algae samples.

Further studies on the analysis of DSP toxin profiles in galician mussels.

Further studies on mussel samples from Galicia, Spain, have revealed the presence of okadaic acid (OA), dinophysistoxin 2 (DTX2), and the fatty acid acyl esters of both of these toxins as the "DTX3" complex. Measurements were performed with an improved in situ method for the formation of 9-anthryldiazomethane (ADAM) derivatives followed by liquid chromatography with fluorescence detection. Base hydrolysis of DTX3 toxins gave free OA and DTX2, which were determined following ADAM derivatization. Results were confirmed by liquid chromatography/mass spectrometry analyses, and in most of the samples, free DTX2 was the most abundant toxin. However, the OA/DTX2 ratio in the DTX3 conjugated form was different, with OA being the most abundant in all cases. This difference could be due to different rates of metabolism of OA and DTX2 to the acyl esters or due to contamination of the shellfish by the two toxins at different points in time, resulting in less acyl ester formation for one toxin versus the other. The second possibility would be reasonable if two different source organisms were producing the toxins.

Capillary electrophoresis with diode array detection as an alternative analytical method for paralytic and amnesic shellfish toxins.

In recent years the marine environment has been seriously damaged by the presence of several toxic phytoplanktonic species, such as dinoflagellates and other toxic algae, which contaminate shellfish and other marine products. Amnesic and paralytic shellfish toxins are examples of these contaminants. The search for sensitive methodologies for the analysis of such compounds is one of the aims of researchers working in the marine environment. High-performance liquid chromatographic methods have been used for this purpose, allowing the detection of very low levels of these toxins. Recently, capillary electrophoresis (CE) has been used as an alternative for the separation and analysis of these compounds. In this paper, we report the optimization of CE procedures for their analysis. Due to the complexity of the matrix, clean-up procedures are required for removing interferences which affect the electrophoretic resolution. The influences of electrophoretic parameters such as voltage, buffer concentrations and organic modifiers, were studied in order to optimize the electrophoretic system to achieve high resolution as well as an accurate quantitation. Extraction and other steps such as clean-up of samples prior to the electrophoretic analysis have been also studied. Different buffers and organic modifiers were used in order to improve the separation of the toxic components, and consequently to obtain accurate quantitative information about the amount of toxins present in the contaminated samples.

Solid-phase extraction and high-performance liquid chromatography procedures for the analysis of paralytic shellfish toxins.

Paralytic shellfish poisoning (PSP) toxins are produced by certain dinoflagellate species such as Gymnodinium catenatum and Alexandrium tamarensis, during certain periods of the year influenced by several environmental factors, affecting the aquaculture industry and mainly bivalve molluscs. HPLC with fluorescence detection is a powerful analytical technique for the analysis of such toxins; several HPLC alternatives have been developed in order to improve the liquid chromatographic analysis, but due to the complexity of the sample matrix, important work has been focused recently on the clean-up of samples prior to HPLC analysis. Solid-phase extraction procedures offer advantages for this clean-up. In this work we focus on the study of three different clean-up methods prior to HPLC with fluorescence detection analysis of PSP toxin present in contaminated mussel samples; by spiking uncontaminated mussel samples with two different PSP toxin standards and by calculating the recovery values for these experiments. These recoveries must be taken into account in order to quantify the exact amount of PSP toxins present in the contaminated samples.