Newsletter

GMOs and Agriculture: Genetically engineered (GE) or genetically modified (GM) crops and animals remain in the daily news. The U.S. Congress has been considering legislation to label foods containing GE or GM ingredients. This topic remains undecided and a public debate on the safety of GE or GM foods.

In a discussion paper published in 2013, Dr. Alison Van Eenenaam (University of California, Davis) goes into great depth in discussing research on the global adaption of GM crops; short and long-term animal studies designed to demonstrate safety of GM crops; molecular and biological changes from consuming GM products; studies to identify molecular compounds (recombinants DNA or proteins decoding for rDNA) in meat, milk and eggs from animals fed GE feeds; and estimates on the cost/benefit of GM crops. The review publication references 133 technical papers on the topic and develops the following conclusion:

“Hundreds of peer-reviewed animal feeding studies have repeatedly shown that GE plants can safely be used in feed, and rDNA fragments have never been detected in products (e.g. milk, meat, eggs) derived from animals that consumed GE feed. Given the 15 year history of safe use and absence of scientific evidence to suggest GE is associated with unique risks, whole food/feed animal feeding studies on GE crops should be reserved for GE crops where the novel phenotype results in a reasonable food safety concern that remains unanswered following all other analyses. Indiscriminately requiring long-term and target animal feeding studies based on a GE process-based trigger is not scientifically justified and will have an inhibitory effect on the development and commercialization of potentially beneficial GE feed crops in the future. World-wide GE regulations have disproportionately focused only on the potential risks associated with GE technology and commercialization of GE crops has been associated with a high regulatory compliance expense which has slowed adoption, particularly in small and poor developing countries. It is time for regulatory frameworks to consider the benefits in addition to any unique risks associated with GE technology. There are many current (increased yields, reduced insecticide use, improved feed quality) and potential future benefits of GE including feed crops with enhanced nutritional characteristics and durability. Regulatory frameworks should formally evaluate the reasonable and unique risks and benefits associated with the use of both GE plants and animals in agricultural systems, and weigh them against those associated with existing systems, and the opportunity costs associated with regulatory inaction.”

A technical writer for the Pork Network investigated whether pig feed with higher levels of soybean meal makes good economic sense with the recent lower corn and soybean meal ingredient prices. Soybean meal use is normally related to its price, composition, availability and anticipated production expectations. There is a trend to include higher levels of SBM in rations for younger animals that have greater need for amino acids. The writer discusses SBM’s advantage in providing levels of digestible amino acids that complement cereal gains needed for optimum pig performance and interest in determining if extra SBM could further improve performance.

The article referred to four research trials conducted by Hubbard Feeds that looked at performance of pigs feed higher levels of properly processed SBM. The research trials demonstrated that pigs fed the higher levels of SBM did not experience adverse performance. In fact, average daily gains were increased slightly in three of the four trails and the feed required per daily gain was essentially the same for the four trials. The writer concluded that a better understanding of soybean processing and how it affects nutrient digestibility has led to a more consistent SBM with higher protein, lysine an amino acid digestibility. She also cited advances in wet chemistry and NIR technologies have contributed to better feed formulation to achieve optimum pig performance.

The digestibility of different oilseed protein sources and the effects of increasing canola meal (CM) in rations of growing pigs was studied by a team of Chinese researchers. In first experiment, four pigs weighing about 15.5 kg were fitted with simple T-cannula at terminal ileum and were fed four diets following repeated 4 × 4 Latin square design after having an adoption period of 7 days. Diet 1 was nitrogen-free diet containing corn starch. Diets 2, 3, and 4 were the basal diet supplemented with soybean meal (SBM), rapeseed meal (RSM), and domestic canola (CM). The composition of the oilseed protein meals tested is found in Table 1. SBM has higher levels of crude protein, indispensable and dispensable amino acids and lower amounts of crude fiber compared to RSM and CM.

The apparent ileal digestibility (AID) of crude protein and amino dietary indispensable acids of the experimental diets are presented in Table 2. Few of the amino acids and crude protein has shown significant responses (P ‹ 0.05) in the AID for the three protein ingredients. The AID of crude protein was lower in RSM but does not differ in CM in comparison to SBM Amino acid digestibility values were lower in diets supplemented with RSM for lysine, methionine, phenylalanine, alanine, aspartic acid, and proline compared to SBM.

Table 1. Proximate and amino acid composition of the protein sources used for ileal digestibility

Table 2. Standardized ileal digestibility of protein sources in pigs (*)

The standardized ileal digestibility (SID) of amino acids for the experimental diets containing the three different protein sources is presented in Table 3. The SID of dietary indispensable amino acids did not differ in the dietary treatments, but the SID of some of the dietary dispensable amino acids varied between protein supplements.

In second experiment, 192 growing pigs weighing about 25 kg were randomly allotted to four dietary treatments with increasing levels of CM (0, 3.75, 7.50, and 11.25 %). Diets were fed in meal form for 35 days. The experimental rations and pig performance are shown in Table 4.

Table 3. Standardized ileal digestibility of protein sources in pigs

Table 4. Effects of supplementation of canola meal on growth performance in growing pigs

In this experiment, increasing CM levels in growing pig diets had no effect on growth performance and apparent total tract digestibility of nutrients and energy P › 0.05). Total weight gain, total feed intake, and feed per unit of gain were not affected by increasing levels of CM in diets. (Editor’s note- Again, the choice of feed ingredient is based on availability, composition and price.)

A Soybean Meal Digestibility Study experiment was conducted to evaluate apparent (AID) and standardized (SID) ileal digestibilities of crude protein and amino acids with six soybean products in weaning pigs. A total of 14 weaning barrows with an initial body weight about 6.5 kg were fitted with T-cannula at the distal ileum and allotted to seven diets containing various soybean products. The soybean products used in the experiment were conventional soybean meal, four fermented SBMs and a soy protein concentrate. Six corn-based diets were formulated containing 5.0 g/kg of chromic oxide as an indigestible indicator and an N-free diet was used to measure basal endogenous losses of crude protein and amino acids.

The research team indicated that ileal crude protein digestibility did not differ by different soybean products. However, the results suggested that SIDs of some amino acids could be improved by the supplementation of fermented soybean products in the diet. They also reported that probiotics supplementation and UV-sterilization had no effects on chemical composition and ileal AA digestibility.

A Feed Form, Particle Size experiment was conducted to evaluate the effect of feed form and particle size of feed supplemented with L- threonine on growth performance, carcass characteristic and blood biochemical parameters of broiler chickens. The experimental design was a 2 × 2 × 2 factorial arrangement of treatments evaluating two feed forms (pellet or mash), two feed particle sizes (fine or course), and two inclusion rates of dietary L-threonine (with or without). The results showed that the effect of feed form on body weight gain and feed intake fed during the experiment was significant (P ‹ 0.05). Broilers fed pelleted diets had more weight gain than the mash group. Growth performance parameters were not affected by feed particle size and dietary L-threonine supplementation in the experimental period (P › 0.05).

Soy isoflavones are structurally similar to mammalian estrogens and therefore may act as estrogen agonists or antagonists. However, it has not been determined if they have any negative effects on reproductive parameters in male livestock. Therefore, the objective of this study was to evaluate the effects of soybean isoflavones on male reproduction using Chinese mini-pig boars as a model. Fifty Xiang boars were randomly divided into five groups and fed diets containing 0, 125, 250, or 500 ppm soybean isoflavones or 0.5 ppm diethylstilbestrol for 60 days.

The results of including high levels of soy isoflavones is the adult pig diets produced several metabolic responses, however, consuming soy isoflavones at dietary levels up to 250 ppm did not adversely affect reproductive parameters in Chinese mini-pig boars whereas higher levels of soy isoflavones may adversely affect male reproduction. Editor’s Note: The level of isoflavones in SBM is highly variable depending on soybean variety, the growing season environment and other unknown factors. However, it is known at the level of isoflavones in swine diets is insignificant and not a factor in determining performance.

Alternative Protein Sources for Salmon: The potential for alternative plant protein sources to replace limited marine ingredients in fish feeds is important for the future of the fish farming industry. However, plant ingredients in fish feeds contain antinutritional factors that can promote gut inflammation (enteritis) and compromise fish health. It is unknown whether enteritis induced by plant materials is characterized by common or distinct gene expression patterns, and how using feeds with single vs mixed plant proteins may affect the gut transcriptome and fish performance. In this experiment, Atlantic salmon were used to investigate the transcriptome responses of distal gut to varying dietary levels (0–45 %) of soy protein concentrate (SPC) and faba bean (Vicia faba) protein concentrate (BPC) following an 8-week feeding trial. Soybean meal (SBM) and fish meal (FM) were used as positive and negative controls for enteritis, respectively. Gene expression profiling was performed using a microarray platform developed and validated for Atlantic salmon.

The results indicated that the different plant protein materials (SPC, BPC and SBM) generated substantially different gut gene expression profiles, with relatively few transcriptomic alterations common for all plant proteins used. When SPC and BPC were included together in the diet, they induced less extensive alterations of gut transcriptome than diets with either SPC or BPC singly, probably due to reduced levels of individual anti nutritional factors. The mixed plant protein diets were also associated with improved body composition of fish relative to the single plant protein diets, which may provide evidence for a link between the magnitude of changes in gut transcriptome and whole-animal performance.