ABSTRACT Several empirical models were proposed to predict feed intake (FI) of growingfinishing pigs reared under high environmental temperatures. However, these models have not been evaluated under conditions different from those in which they were developed. Twelve empirical models were evaluated using a database built after systematic literature review (observed data: 28 studies in which the FI was evaluated in pigs under high environmental temperatures). Model accuracy was assessed using the mean squared of prediction error (MSPE). Analyses were performed considering two scenarios: (1) general population, where all observed data were used in the simulation; (2) reference population, where data were filtered in order to simulate only scenarios with environment (temperature range) and animals (body weight and sex) similar to that used in the model development. Six models estimated FI values similar (p > 0.05) to those observed in the general population, while four models produced estimates similar to the observed values in the reference populations. Most models were more accurate when they were simulated using the reference population than when the simulation considered the general database. Moving the simulation from the general database to the reference population reduced up to 98 % of the MSPE, depending on the equation. Empirical models allow to accurately predict FI of growing-finishing pigs exposed to high environmental temperatures, especially in scenarios similar to the ones used for model development. Thus, population characteristics (body weight and sex) and environment (temperature range) must be considered in the model assessment.

ABSTRACT A nitrogen balance test was performed to evaluate the individual responses of growing pigs to threonine intake. Eight commercial barrows were used (body weight ranging from 15 to 20 kg). A dose-response study was performed, in which the threonine supply increased in seven equidistant steps (the seven dietary threonine levels ranged from 50 to 120% of the requirements) every three days for each pig. The levels of all other amino acids were 20% higher than the tested amino acid. Nitrogen retention as a function of threonine intake was calculated per individual and per group (NLIN and NLMixed, respectively) using a linear plateau model. The highest break point value was 42.42 g of threonine intake (the most demanding individual), whereas the lowest value was 34.16 g (the least demanding individual), corresponding to a difference of 19%. In terms of N retention, the highest plateau value was 66.71 g and the lowest was 49.48 g, with a difference of 25%. There was no significant correlation between slope and plateau values or between slope and break point values. When using the model in which all parameters were random effects, the variations in threonine intake and nitrogen retention were 1.68±1.30 and 0.01±0.10 g, respectively, and no variance in the slope of the curve was detected. The average daily threonine intake values for the maximum response obtained in the group, as calculated by the NLIN and NLMixed procedures, were 13.96 and 14.02 g/day, respectively. The threonine intake for the maximum N retention between individuals ranged from 34.16 to 42.42 g, corresponding to a difference of 19%. The current recommended intake to optimize N retention is 14.02 g/day. The group responses obtained by the NLMixed procedures are very similar to those estimated by the NLIN procedure (all individuals).

ABSTRACT Little is known about the toxicity of concomitantly occurring mycotoxins in pig diets. This study was conducted to evaluate, through meta-analysis, the individual and the combined effects of mycotoxins on pig performance. The meta-analysis followed three sequential analyses (graphical, correlation, and variance-covariance) based on a database composed of 85 published papers, 1,012 treatments and 13,196 animals. Contamination of diets with individual mycotoxins reduced (p < 0.05) feed intake by 14 % and weight gain by 17 %, while combined mycotoxins reduced the same responses by 42 % and 45 %, respectively, in comparison with the non-challenged group. The correlation (p < 0.05) between reduction in weight gain (ΔG) and reduction in feed intake (ΔFI) was 0.67 in individual challenges and 0.93 in combined challenges. The estimated ΔG was –6 % in individual challenges and –7 % in combined challenges when ΔFI was zero, suggesting an increase in the maintenance requirements of challenged animals. Most of ΔG (58 % in individual challenges and 84 % in combined challenges) was attributed to the changes in feed efficiency. The association of mycotoxins enhances individual toxic effects and the ΔFI is important in explaining the deleterious effects on the growth of challenged pigs.

Broilers are traditionally managed with feeding programs that often consist of three or four phases. In this study we investigated whether a multiphase feeding program (14 phases) of broilers based on the optimal mix of two feeds could replace a traditional four phase system while maintaining broiler performance. To evaluate this prposed program we measured variables of performance, carcass yield, and nitrogen excretion. In addition, we determined if the multiphase feeding program (14 phases) would be equally effective regardless of bird gender. A total of 480 day-old Cobb chicks were used, with an average weight of 44.74 ± 0.16 g (females) and 44.71 ± 0.11 g (males). The birds were distributed in a completely randomized 2 × 2 factorial design. Each treatment consisted of six replicates with 20 animals per experimental unit. Results were analyzed separately in two periods (1–21 and 22–42 days) as determined by slaughter date, as well as for the entire growth period (1–42 days). The multiphase program led to improvements in final body weight and average daily weight gain, in addition to an increase in breast yield.

Uma meta-análise foi realizada para avaliar o desempenho e a qualidade de carcaça e carne de suínos em função do sistema de alojamento nas fases de crescimento/terminação. Foram selecionadas publicações indexadas com resultados de experimentos comparando variáveis de desempenho e de pós-abate de suínos alojados em sistemas intensivos convencionais ou ao ar livre. A base de dados contemplou 27 artigos publicados entre 1997 e 2009. Ao total, foram considerados 2.985 animais e 701 médias na análise de dados. A meta-análise foi realizada através de duas análises sequenciais: gráfica e de variância-covariância. O sistema de criação de suínos ao ar livre aumentou em 9% (P<0,05) o consumo de ração, reduziu em 2% (P<0,01) o ganho de peso diário e piorou em 3% (P<0,05) a conversão alimentar dos animais em relação ao sistema confinado. As características de carcaça (peso de carcaça quente, rendimento, espessura de toucinho e percentual de carne magra) e de carne no Longissimus dorsi (perda por gotejamento e cozimento, pH, temperatura inicial, força de cisalhamento, marmoreio dureza, maciez e suculência) não foram influenciadas (P>0,05) pelo sistema de alojamento dos suínos. Concluiu-se que o sistema de criação influencia no desempenho dos suínos, mas não interfere nas características de carcaça e carne estudadas.

A meta-analysis was carried out to study performance and characteristics of carcass and meat in pigs in function of housing system during the growing/finishing period. Indexed publications with results of experiments comparing performance and post-slaughter variables of pigs housed in outdoor or conventional intensive systems were selected. In total, 2.985 animals and 701 averages were considered in the data analysis. Meta-analysis followed two sequential analyses: graphic and variance. The outdoor productive system increased in 9% (P<0.05) feed intake, reduced in 2% (P<0.01) daily weight gain and worsened in 3% (P<0.05) feed conversion ratio of pigs in comparison to animals in the confined system. Characteristics of carcass (hot carcass weight, yield, backfat thickness and lean meat percentage) and Longissimus dorsi meat (drip and cooking loss, pH, the initial temperature, shear force, marbling, hardness, juiciness and tenderness) were not affected (P>0.05) by the housing system. It is concluded that the housing system influences the pig performance, but does not interfere in characteristics of carcass and meat.