Search

The aim of this study was to evaluate the effects of the association between red clover (RC;Trifolium pratense) and a tropical grass (kikuyu grass) on the proteolysis of ensiled material andthe in vitro degradation of protein and organic matter. Red clover and kikuyu grass were ensiledin the following proportions: 0:1000, 250:750, 500:500, 750:250, and 1000:0 g/kg of dry matter(DM). The fraction of rapidly degradable protein, the ammonia nitrogen (NH3-N) content of thesilo, the in vitro protein degradation, and the degradation rate decreased linearly (P < 0.001) asthe RC content in the ensiled material increased. Cumulative gas production after 24 h incubationshowed a positive quadratic effect when RC was increased to 500 g/kg (P < 0.001). The silageswith the highest RC content reduced proteolysis more effectively during ensiling and ruminalfermentation. Inter-species synergistic effects positively affected in vitro gas production, whichwas optimal when RC and kikuyu grass were ensiled in the same proportions as that of total DM.

International audience; The feeding value of forage mixtures from permanent and temporary multi-species grasslands cannot always be precisely defined. Indeed, the digestibility and feed intake of a combination of forages can differ from the balanced median values calculated from forages considered separately. In order to present an overview of the associative effects between forages on digestion and intake, a literature study was carried out. The associative effects can be studied in a complementary way in vitro to test digestive interactions of a large number of mixtures and to carry out explanatory experiments, and in vivo to investigate intake and digestion at the whole animal scale. We identified three main situations in which interactions between forages can lead to associative effects on intake and digestion: (i) increased intake that can be observed with grass and legume association can be explained by fast digestion of the soluble fraction of legumes, and a higher rate of particle breakdown and passage through the rumen, (ii) increased digestion when a poor forage is supplemented by a high nitrogen content plant can be explained by stimulation of the microbial activity and (iii) modification of digestive processes in the rumen, including proteolysis and methane production when certain bioactive secondary metabolites such as tannins, saponins or polyphenol oxidase are present. According to the type and concentration of these compounds in the diet, the effects can be favourable or unfavourable on intake and digestive parameters. Reported associative effects between forages show a large variability among studies. This reflects the complexity and multiplicity of nutritional situations affecting intake and the rumen function in a given animal. In order to provide more reliable information, further accumulation of data combining in vitro and in vivo studies is required. A better understanding of the associative effects between forages could help to optimise feed use efficiency, resulting in greater productivity, a reduction of the environmental impact of animal emissions and more sustainable animal production.

Phenotypes expressed in a social context are not only a function of the individual, but can also be shaped by the phenotypes of social partners. These social effects may play a major role in the evolution of cooperative breeding if social partners differ in the quality of care they provide and if individual carers adjust their effort in relation to that of other carers. When applying social effects models to wild study systems, it is also important to explore sources of individual plasticity that could masquerade as social effects. We studied offspring provisioning rates of parents and helpers in a wild population of long-tailed tits Aegithalos caudatus using a quantitative genetic framework to identify these social effects and partition them into genetic, permanent environment and current environment components. Controlling for other effects, individuals were consistent in their provisioning effort at a given nest, but adjusted their effort based on who was in their social group, indicating the presence of social effects. However, these social effects differed between years and social contexts, indicating a current environment effect, rather than indicating a genetic or permanent environment effect. While this study reveals the importance of examining environmental and genetic sources of social effects, the framework we present is entirely general, enabling a greater understanding of potentially important social effects within any ecological population.

Foram avaliados os efeitos da suplementação com diferentes relações proteína: carboidrato sobre a composição corporal, características de carcaça e eficiência de deposição de proteína e energia em tourinhos. Utilizou-se 24 bezerros Nelore (132,5 ± 5,5 kg e 90-150 dias de idade) em pastagem por um período experimental de 430 dias. Os tratamentos foram: Controle = mistura mineral ; HPHC = suplemento com alta proteína e alto carboidrato; HPLC = suplemento com alta proteína e baixo carboidrato; LPHC = suplemento com baixa proteína e alto carboidrato; LPLC = suplemento com baixa proteína e baixo carboidrato. foram abatidos quatro animais no início do experimento e 20 animais no final do experimento para avaliar a composição da carcaça. Os tourinhos controle apresentaram o menor (p < 0,05) consumo de EM (9,8 Mcal dia^-1) não havendo diferenças (p > 0,05) entre os tourinhos suplementados (13 Mcal dia^-1). Embora os tourinhos não suplementados tivessem menor (p 0,05) entre os touros suplementados. Suplementos com alto carboidrato foram associados com maior (p < 0,05) ER (596,2 Mcal) do que os suplementos de baixo carboidrato (515,5 Mcal). Não houve diferenças (p > 0,05) na eficiência energética entre os grupos. Portanto, a suplementação aumenta a ingestão e retenção de proteína e energia, sem alterar a eficiência de retenção. The effects of supplementation with different protein: carbohydrate ratios on body composition, carcass characteristics and protein and energy deposition efficiency of young were assessed. Twenty-four Nellore calves (132.5 ± 5.5 kg and 90-150 days of age) were kept on pasture for a 430 day experimental period. The treatments were: Control = mineral mixture only; HPHC = high-protein and high-carbohydrate supplement; HPLC = high-protein and low-carbohydrate supplement; LPHC = low-protein and high-carbohydrate supplement; LPLC = low-protein and low-carbohydrate supplement. Four animals at begning and 20 animal at end of experiment were slaughtered to evaluate the carcass composition. Control bulls had the lowest (p < 0.05) intake of ME (9.8 Mcal day^-1) with no difference (p > 0.05) between supplemented bulls (13 Mcal day^-1). Although non-supplemented bulls had less (p < 0.05) retained protein, retained energy (RE), body weight gain and dressing percentage, differences were not observed (p > 0.05) between supplemented bulls. High-carbohydrate supplements were associated with more (p < 0.05) RE (596.2 Mcal) than low-carbohydrate supplements (515.5 Mcal). Differences were not found (p > 0.05) in the energy efficiency between the groups. Therefore, supplementation increases the intake and retention of protein and energy without changing the retention efficiency.

An in vitro rumen fermentation was performed, where two sources of slowly fermentable fibre (milk thistle, MT; pure cellulose, CE) and three of rapidly fermentable fibre (tomato peels without seeds, TP; citrus pulp, CI; pectin, PE) were incubated alone or as 75:25 or 25:75 mixtures (MT:TP, MT:CI, MT:PE, CE:TP, CE:CI, CE: PE ), to detect associative effects among substrates. Substrates or mixtures (0.5 g) were incubated with 75 ml of buffered rumen fluid into individual bottles at 39°C for 96 h. Differences among measured and expected GP were analysed by ANOVA. In mixtures containing MT, positive associative effects were detected within first 24 h. Only the combination of 75% MT and 25% TP showed negative interactions. In the mixtures of MT:CI and MT:PE positive associative effects were detected respectively at 24 and 12 h (P

The effect of the forage source on ruminal fermentation in vitro was investigated for fine (F) and coarse (C) milled diets, using a modified Hohenheim gas production test and a semi-continuous rumen simulation technique (Rusitec). It was hypothesised that the replacement of maize silage by grass silage might lead to associative effects and that interactions related to particle size variation could occur. Five diets with a maize silage to grass silage ratio of 100 : 0, 79 : 21, 52 : 48, 24 : 76 and 0 : 100 differed in their content of CP and carbohydrate fractions, as well as digestible crude nutrients, derived from a digestibility trial with wether sheep. For in vitro investigations, the diets were ground to pass a sieve of either 1 mm (F) or 4 mm (C) perforation. Cumulative gas production was recorded during 93 h of incubation and its capacity decreased with increasing proportion of grass silage in the diet. Across all diets, gas production was delayed in C treatments compared with F treatments. Degradation of crude nutrients and detergent fibre fractions was determined in a Rusitec system. Daily amounts of NH3-N and short-chain fatty acids (SCFA) were measured in the effluent. Degradation of organic matter (OM) and fibre fractions, as well as amounts of NH3-N, increased with stepwise replacement of maize silage by grass silage. Degradability of CP was unaffected by diet composition, as well as total SCFA production. In contrast to the results of the gas production test, degradation of OM and CP was higher in C than in F treatments, accompanied by higher amounts of NH3-N and SCFA. Interactions of silage ratio and particle size were rare. It was concluded that the stepwise replacement of maize silage by grass silage might lead to a linear response of most fermentation characteristics in vitro. This linear effect was also supported by total tract digestibility data. However, further investigations with silages of variable quality seem to be necessary.

Selection for improved host response to infectious disease offers a desirable alternative to chemical treatment but has proven difficult in practice, due to low heritability estimates of disease traits. Disease data from field studies is often binary, indicating whether an individual has become infected or not following exposure to an infectious disease. Numerous studies have shown that from this data one can infer genetic variation in individuals’ underlying susceptibility. In a previous study, we showed that with an indirect genetic effect (IGE) model it is possible to capture some genetic variation in infectivity, if present, as well as in susceptibility. Infectivity is the propensity of transmitting infection upon contact with a susceptible individual. It is an important factor determining the severity of an epidemic. However, there are severe shortcomings with the Standard IGE models as they do not accommodate the dynamic nature of disease data. Here we adjust the Standard IGE model to (1) make expression of infectivity dependent on the individuals’ disease status (Case Model) and (2) to include timing of infection (Case-ordered Model). The models are evaluated by comparing impact of selection, bias, and accuracy of each model using simulated binary disease data. These were generated for populations with known variation in susceptibility and infectivity thus allowing comparisons between estimated and true breeding values. Overall the Case Model provided better estimates for host genetic susceptibility and infectivity compared to the Standard Model in terms of bias, impact, and accuracy. Furthermore, these estimates were strongly influenced by epidemiological characteristics. However, surprisingly, the Case-Ordered model performed considerably worse than the Standard and the Case Models, pointing toward limitations in incorporating disease dynamics into conventional variance component estimation methodology and software used in animal breeding. - See more at: http://journal.frontiersin.org/Journal/10.3389/fgene.2012.00215/full#h1