A safety evaluation of genetically modified feedstuffs for livestock production; the fate of transgenic DNA and proteins

dTwo genetic constructs used to confer improved agronomic characteristics, namely herbicide tolerance (HT) in maize and soyabean and insect resistance (Bt) in maize, are considered in respect of feeding to farm livestock, animal performance and the nutritional value and safety of animal products. A review of nucleic acid (DNA) and protein digestion in farm livestock concludes that the frequency of intact transgenic DNA and proteins of GM and non-GM crops being absorbed is minimal/non existent, although there is some evidence of the presence of short fragments of rubisco DNA of non-GM soya in animal tissues. It has been established that feed processing (especially heat) prior to feeding causes significant disruption of plant DNA. Studies with ruminant and non-ruminant farm livestock offered GM feeds demonstrated that animal performance and product composition are unaffected and that there is no evidence of transgenic DNA or proteins of current GM in the products of animals consuming such feeds. On this evidence, current HT and Bt constructs represent no threat to the health of animals, or humans consuming the products of such animals. However as new GM constructs become available it will be necessary to subject these to rigorous evaluation.

Survival of Mycobacterium bovis on Feedstuffs Commonly Used as Supplemental Feed for White-tailed Deer (Odocoileus virginianus)

Mycobacterium bovis, the causative agent of bovine tuberculosis, has become established in free-ranging white-tailed deer Odocoileus virginianus in northeastern Michigan. The practice of supplemental feeding of white-tailed deer during the winter is believed to contribute to transmission of M. bovis between deer. The current study was conducted to determine the ability of M. bovis to survive on various feedstuffs commonly used as supplemental feed for deer in northeast Michigan (i.e., apples, corn, carrots, sugar beets, potatoes, and hay) and the effect of maintenance at 220 C, 8 C, and 23 C on survival. Mycobacterium bovis survived on all feedstuffs at all temperatures tested for at least 7 days. At 23 C, M. bovis could still be isolated from samples of apples, corn and potatoes at 112 days. This study suggests that contamination of feedstuffs by M. bovis-infected deer could act as a source of indirect transmission between deer because M. bovis is able to survive in temperatures similar to those recorded during winter months in northeastern Michigan. Current efforts to ban or control supplemental feeding of deer should have a positive effect on decreasing transmission of M. bovis among deer.

Effects of the ruminal comminution rate and microbial contamination of particles on accuracy of in situ estimates of ruminal degradability and intestinal digestibility of feedstuffs.

Effects of considering the comminution rate -kc- and the correction of microbial contamination -using 15N techniques- of particles in the rumen on estimates of ruminally undegraded fractions and their intestinal digestibility were examined generating composite samples -from rumen-incubated residues- representative of the undegraded feed rumen outflow. The study used sunflower meal -SFM- and Italian ryegrass hay -RGH- and three rumen and duodenum cannulated wethers fed with a 40:60 RGH to concentrate diet -75 g DM/kgBW0.75-. Transit studies up to the duodenum with Yb-SFM and Eu-RGH marked samples showed higher kc values -/h- in SFM than in RGH -0.577 vs. 0.0892, p = 0.034-, whereas similar values occurred for the rumen passage rate -kp-. Estimates of ruminally undegraded and intestinal digestibility of all tested fractions decreased when kc was considered and also applying microbial correction. Thus, microbial uncorrected kp-based proportions of intestinal digested undegraded crude protein overestimated those corrected and kc-kp-based by 39% in SFM -0.146 vs. 0.105- and 761% in RGH -0.373 vs. 0.0433-. Results show that both kc and microbial contamination correction should be considered to obtain accurate in situ estimates in grasses, whereas in protein concentrates not considering kc is an important source of error.

Quantification of soluble fibre in feedstuffs for rabbits and evaluation of the interference between the determinations of soluble fibre and intestinal mucin.

This work compared the quantification of soluble fibre in feeds using different chemical and in vitro approaches, and studied the potential interference between soluble fibre and mucin determinations. Six ingredients: sugar beet pulp (SBP), SBP pectins, insoluble SBP, wheat straw, sunflower hulls and lignocellulose, and seven rabbit diets, differing in soluble fibre content, were evaluated. In experiment 1, ingredients and diets were analyzed for total dietary fibre (TDF), insoluble dietary fibre (IDF), soluble dietary fibre (SDF), aNDFom (corrected for protein, aNDFom-cp) and 2-step pepsin/pancreatin in vitro DM indigestibility (corrected for ash and protein, ivDMi2). Soluble fibre was estimated by difference using three procedures: TDF?IDF (SDFIDF), TDF?ivDMi2 (SDFivDMi2), and TDF?aNDFom-cp (SDFaNDFom-cp). Soluble fibre determined directly (SDF) or by difference as SDFivDMi2 were not different (109 g/kg DM, on average). However, when it was calculated as SDFaNDFom-cp the value was 40% higher (153 g/kg DM, P menor que 0.05), whereas SDFIDF (124 g/kg DM) did not differ from any of the other methods. The correlation between the four methods was high (r ? 0.96; P ? 0.001; n = 13), but it decreased or even disappeared when SBP pectins and SBP were excluded and a lower and more narrow range of variation of soluble fibre was used. In experiment 2, the ivDMi2 using crucibles (reference method) were compared to those made using individual or collective ankom bags in order to simplify the determination of SDFivDMi2. The ivDMi2 was not different when using crucibles or individual or collective ankom bags. In experiment 3, the potential interference between soluble fibre and intestinal mucin determinations was studied using rabbit intestinal raw mucus, digesta and SBP pectins, lignocelluloses and a rabbit diet. An interference was observed between the determinations of soluble fibre and crude mucin, as contents of TDF and apparent crude mucin were high in SBP pectins (994 and 709 g/kg DM) and rabbit intestinal raw mucus (571 and 739 g/kg DM). After a pectinase treatment, the coefficient of apparent mucin recovery of SBP pectins was close to zero, whereas that of rabbit mucus was not modified. An estimation of the crude mucin carbohydrates retained in digesta TDF is proposed to correct TDF and soluble fibre digestibility. In conclusion, the values of soluble fibre depend on the methodology used. The contamination of crude mucin with soluble fibre is avoided using pectinase.

The handbook of feedstuffs; production, formulation, medication,

Includes bibliographies.

USDA weekly feedstuffs report.

Mode of access: Internet.

Tryptophan determination in proteins and feedstuffs by ion exchange chromatography

A chromatographic method was developed for the determination of tryptophan content in food and feed proteins. The method involves separation and quantitation of tryptophan (released from protein by alkaline hydrolysis with NaOH) by isocratic ion-exchange chromatography with O-phthalaldehyde derivatization followed by fluorescence detection. In this procedure, chromatographic separation of the tryptophan and alpha-methyl tryptophan, the internal standard, was complete in 15 min, without any interference from other compounds. The precision of the method was 1-4%, relative standard deviation. Accuracy was validated by agreement with the value for chicken egg white lysozyme, a sequenced protein, and by quantitative recoveries after spiking with lysozyme. The method allows determination in a range of feed proteins, containing varied concentrations of tryptophan, and is applicable to systems used for routine amino acid analysis by ion-exchange chromatography. (C) 2004 Elsevier Ltd. All rights reserved.

Total and ileal digestible tryptophan contents of feedstuffs for broiler chickens

Reliable values of total and digestible tryptophan in components of feed formulation matrices are needed because tryptophan is often the third limiting amino acid in practical poultry diets. However, tryptophan is oxidatively destroyed during acid hydrolysis in routine amino acid analysis and its determination requires a separate analytical procedure. The variability in contents and apparent ileal digestibility for 6-week-old broiler chickens of tryptophan in 74 samples representing 24 feedstuffs are presented in this paper. The average ileal tryptophan digestibility coefficient in wheat was 0.83, in sorghum and triticale 0.75, maize 0.71, soybean meal 0.84, sunflower meal 0.81, canola meal 0.78 and cottonseed meal 0.75. Among the grain legumes, tryptophan in lupins was better digested than that in chickpeas, fababeans and field peas. Among the animal protein meals, the tryptophan digestibility coefficients in fish meal (0.77) and blood meal (0.84) were substantially higher than those in meat meal (0.64), meat-and-bone meal (0.63) and feather meal (0.52). Marked variations in tryptophan digestibility were also observed among samples of fish meal, meat-and-bone meal and meat meal, highlighting significant batch-to-batch differences. For most feedstuffs, considerable variability was observed in the tryptophan concentrations, but such variations were not reflected in digestibility coefficients. (c) 2006 Society of Chemical Industry.

Dietary lysine requirement of juvenile pacu Piaractus mesopotamicus (Holmberg, 1887)

Lysine is the reference essential amino acid in fish feeds and usually the most limiting amino acid in feedstuffs. The dietary lysine requirement of juvenile pacu Piaractus mesopotamicus (4.3 g) was determined using five isonitrogenous (32% CP) test diets containing graded levels of lysine (0.9, 1.17, 1.44, 1.69 and 1.96% of dry diet) fed three times a day to four groups of 18 fish for 74 days. Growth, body composition, nutrient retention and hematological parameters of pacu were analyzed. Analysis of variance showed that all growth performance parameters were significantly affected by dietary treatments. The lysine requirements estimated using regression analysis for maximum weight gain and feed efficiency were 1.45 and 1.51% of dry diet, respectively. Nitrogen retention efficiency increased with increasing levels of dietary lysine up to 1.43% (p<0.05). Whole-body protein increased (p<0.05) and whole-body lipid decreased (p<0.05) with increasing dietary lysine level. Thus, the lysine requirement of juvenile pacu was estimated as being 1.4-1.5% of dry diet or 4.4-4.7% of dietary protein. (c) 2009 Elsevier B.V. All rights reserved.

Practical and economic advantages of choice feeding systems for laying poultry

Poultry can be managed under different feeding systems, depending on the husbandry skills and the feed available. These systems include the following: (1) a complete dry feed offered as a mash ad libitum; (2) the same feed offered as pellets or crumbles ad libitum; (3) a complete feed with added whole grain; (4) a complete wet feed given once or twice a day; (5) a complete feed offered on a restricted basis; (6) choice feeding. Of all these, an interesting alternative to offering complete diets is choice feeding which can be applied on both a small or large commercial scale. Under choice feeding or free-choice feeding birds are usually offered a choice between three types of feedstuffs: (a) an energy source (e.g. maize, rice bran, sorghum or wheat); (b) a protein source (e.g. soyabean meal, meat meal, fish meal or coconut meal) plus vitamins and minerals and (c), in the case of laying hens, calcium in granular form (i.e. oyster-shell grit). This system differs from the modern commercial practice of offering a complete diet comprising energy and protein sources, ground and mixed together. Under the complete diet system, birds are mainly only able to exercise their appetite for energy. When the environmental temperature varies, the birds either over- or under-consume protein and calcium. The basic principle behind practising choice feeding with laying hens is that individual hens are able to select from the various feed ingredients on offer and compose their own diet, according to their actual needs and production capacity. A choice-feeding system is of particular importance to small poultry producers in developing countries, such as Indonesia, because it can substantially reduce the cost of feed. The system is flexible and can be constructed in such a way that the various needs of a flock of different breeds, including village chickens, under different climates can be met. The system also offers a more effective way to use home-produced grain, such as maize, and by-products, such as rice bran, in developing countries. Because oyster-shell grit is readily available in developing countries at lower cost than limestone, the use of cheaper oyster-shell grit can further benefit small-holders in these countries. These benefits apart, simpler equipment suffices when designing and building a feed mixer on the farm, and transport costs are lower. If whole (unground) grain is used, the intake of which is accompanied by increased efficiency of feed utilisation, the costs of grinding, mixing and many of the handling procedures associated with mash and pellet preparation are eliminated. The choice feedstuffs can all be offered in the current feed distribution systems, either by mixing the ingredients first or by using a bulk bin divided into three compartments.