Trends in feed evaluation for poultry with emphasis on in vitro techniques

Accurate knowledge of the actual nutritional value of individual feed ingredients and complete diets is critical for efficient and sustainable animal production.For this reason,feed evaluation has always been in the forefront of nutritional research.Feed evaluation for poultry involves several approaches that include chemical analysis,table values,prediction equations,near-infrared reflectance spectroscopy,in vivo data and in vitro digestion techniques.Among these,the use of animals(in vivo)is the most valuable to gain information on nutrient utilization and is more predictive of bird performance.However,in vivo methods are expensive,laborious and time-consuming.It is therefore important to establish in vitro methods that are reliable,rapid and practical to assess the nutritional quality of feed ingredients or complete diets.Accuracy of the technique is crucial,as poor prediction will have a negative impact on bird performance and,increase feed cost and environmental issues.In this review,the relevance and importance of feed evaluation in poultry nutrition will be highlighted and the various approaches to evaluate the feed value of feed ingredients or complete diets will be discussed.Trends in and practical limitations encountered in feed evaluation science,with emphasis on in vitro digestion techniques,will be discussed.

Evaluation on Feed Factors Affecting the Dung Pollutants of Livestock and Poultry

The 30 pairs of feed and dung samples from the livestock and poultry farms with different scales were checked and analyzed. The results showed： a great linear relation existed between the feed factors and 7 pollutants such as ammonia nitrogen, phosphorus, copper, iron, arsenic, mercury, cadmium in livestock and poultry＇s dung. The main affecting factors of feed were respectively nitrogen, phosphorus, copper, and arsenic, which were totally feed ingredient elements. And it indicated that the dung pollutants such as nitrogen, phosphorus, copper, iron, arsenic, mercury, and cadmium could be regulated by controlling the feed ingredients. But the dung nitrogen did not have a linear relation with the feed factors. Reducing the nitrogen in feed did not mean the relative decrease of the dung nitrogen content. Feed consumption rate of unit weight did not have notable performances, and it did not show curve model after curve fitting method. The pollutant index of ammonia nitrogen, phosphorus, copper, and arsenic of the group whose feed consumption rate of unit weight was less than 20 g/kg·d was extremely remarkably lower than those of the 20 -30 g/kg·d group. The pollutant index of mercury, chromium, and cadmium showed the opposite performance. With the increase of feed consumption rate, each pollutant did not act in an increasing trend, of which the pollutant index of ammonia nitrogen and the general phosphorus presented a quadratic model trend. The feed consumption level of unit weight had an extremely remarkable effect on the pollution level rate and the eady warning level rate, showing the thrice model trend, of which the 20 -30 g/kg. d group was the maximal, respectively for 16.67% and 50%, which was the same with the above-mentioned law.

Prediction of net energy of feeds for broiler chickens

Net energy(NE)enables the prediction of more accurate feed energy values by taking into account the heat increment which is approximately 25%of apparent metabolizable energy(AME)in poultry.Nevertheless,application of NE in poultry industry has not been practiced widely.To predict the NE values of broiler diets,23 diets were prepared by using 13 major ingredients(wheat,corn,paddy rice,broken rice,cassava pellets,full-fat soybean,soybean meal,canola meal,animal protein,rice bran,wheat bran,palm kernel meal and palm kernel oil).The diets were formulated in order to meet the birds'requirements and get a wide range of chemical compositions(on DM basis;33.6%to 55.3%for starch;20.8%to 28.4%for CP,2.7%to 10.6%for ether extract[EE]and 7.0%to 17.2%for NDF),with low correlations between these nutrients and low correlations between the inclusion levels of ingredients allowing for the calculation of robust prediction equations of energy values of diets or ingredients.These diets were fed to Ross 308 broilers raised in 12 open-circuit respiratory chambers from 18 to 23 d of age(4 birds per cage)and growth performance,diet AME content and heat production were measured,and dietary NE values were calculated.The trial was conducted on a weekly basis with 12 diets measured each week(1per chamber),1 of the 23 diets(reference diet)being measured each week.Each diet was tested at least 8times.In total,235 energy balance data values were available for the final calculations.Growth performance,AME(15.3 MJ/kg DM on average)and AME/GE(79.4%on average)values were as expected.The NE/AME value averaged 76.6%and was negatively influenced by CP and NDF and positively by EE in connection with efficiencies of AME provided by CP,EE and starch for NE of 73%,87%and 81%,respectively.The best prediction equation was:NE=(0.815×AME)—(0.026×CP)+(0.020×EE)—(0.024×NDF)with NE and AME as MJ/kg DM,and CP,EE and NDF as%of DM.The NE prediction equations from this study agree with other recently reported equations in poultry and are suitable for both ingredients and complete feeds.

Re-evaluation of recent research on metabolic utilization of energy in poultry:Recommendations for a net energy system for broilers

Different energy systems have been proposed for energy evaluation of feeds for domestic animals.The oldest and most commonly used systems take into account the fecal energy loss to obtain digestible energy(DE),and fecal,urinary and fermentation gases energy losses to calculate metabolizable energy(ME).In the case of ruminants and pigs,the net energy(NE)system,which takes into account the heat increment associated with the metabolic utilization of ME,has progressively replaced the DE and ME systems over the last 50 years.For poultry,apparent ME(AME)is used exclusively and NE is not yet used widely.The present paper considers some important methodological points for measuring NE in poultry feeds and summarizes the available knowledge on NE systems for poultry.NE prediction equations based on a common analysis of three recent studies representing a total of 50 complete and balanced diets fed to broilers are proposed;these equations including the AME content and easily available chemical indicators have been validated on another set of 30 diets.The equations are applicable to both ingredients and complete diets.They rely primarily on an accurate and reliable AME value which then represents the first limiting predictor of NE value.Our analysis indicates that NE would be a better predictor of broiler performance than AME and that the hierarchy between feeds is dependent on the energy system with a higher energy value for fat and a lower energy value for protein in an NE system.Practical considerations for implementing such an NE system from the commonly used AME or AMEn(AME adjusted for zero nitrogen balance)systems are presented.In conclusion,there is sufficient information to allow the implementation of the NE concept in order to improve the accuracy of feed formulation in poultry.