A. Aumaitre

New feeds from genetically modified plants: substantial equivalence, nutritional equivalence, digestibility, and safety for animals and the food chain

Abstract The introduction by recombinant DNA technology of new genes into major crops used by animals has raised important questions about the safety of novel feeds. The recently amended European Council Directive 2001/18/EC requires an assessment of risks for human, animals and the environment before viable seeds can be imported or the plant itself can be cultivated in Europe. In addition, the Novel Food and the Novel Food Ingredient Regulation (EC Council Directive, 1997) covers the use of non-viable products of any genetically modified (GM) plant intended for food purposes. The conceptual basis for the analysis of risks remains that of substantial equivalence. In practice, compositional analysis of key nutrients and key toxicants used to compare a GM plant with its conventional counterpart is the major source of data used to establish substantial equivalence. Although laboratory animals are used in toxicological studies of the products of introduced genes, animals are rarely fed the entire transformed plants or their by-products. Despite not being required or recommended by the existing legislation, many new products have been intensively tested with farm animals to measure effects on performance and animal health, digestibility of key nutrients, wholesomeness and feeding value. In this paper, we consider the value of such studies for establishing the safety of GM feedstuffs for the target animals and whether animal feeding studies are always necessary to establish the safety for the consumer of products of animals fed GM material. Compositional analysis has always shown the genetically modified plants to fall within the range of established values. The equivalence in digestible energy and crude protein between isogenic and transformed plants expressing a wide range of modifications (insect resistance, herbicide tolerance, or the barnase/barstar system of sterility/fertility restoration genes) also has been clearly demonstrated in different species. In none of these experiments was animal performance, whether measured as growth rate, feed efficiency and carcass merit in beef cattle, egg mass in laying hens, milk production, composition and quality in dairy cows or digestibility in rabbits, affected by feeding transformed plants compared to animals fed control or isogenic plants. Detection of chloroplasts-specific gene fragments by polymerase chain reaction showed the presence of plant DNA fragments (199 base pairs) in lymphocytes and duodenal juice of the dairy cow, and in muscle, liver, kidney and spleen of broilers. However, tDNA expressing Bt , usually found as a single copy gene, could not be detected in milk, tissues sample or eggs of livestock fed Bt maize and is probably not cause for concern.

Effects of environmental temperature on heat production, energy retention, protein and fat gain in early weaned piglets.

1. Six experiments, each involving two groups of six piglets, were designed to study the influence of environmental temperature on heat production, energy retention and protein and fat gain in early weaned piglets. Immediately after weaning, at a mean age of 25 d, the animals were raised in two open circuit respiratory chambers. Each chamber was equipped with a totally wired cage. The piglets were paired-fed and maintained at environmental temperatures of 20, 24 or 28 degrees. Four replicates were used for each temperature. Metabolizable energy, heat production and nitrogen balance were measured during two consecutive periods (A and B), each of 6 d duration. 2. Heat production was higher at 20 degrees than at 24 and 28 degrees during periods A and B. Energy retention was negative during period A, it was positive during period B and increased with temperature. 3. Protein deposition was always positive and independent of environmental temperature. The net efficiency of protein utilization was 0.77. 4. Body fat was mobilized during period A at a higher rate at 20 degrees than 28 degrees. During period B, fat gain increased with increase in temperature. 5. The calculated ME requirement for maintenance amounted to 411 kJ/kg body-weight 0.75 per d at 28 degrees. 6. The critical temperature of early weaned piglets raised in intensive modern housing and fed at about 90% of the ad lib, intake is close to 28 degrees during the first 12 d after weaning.

Comparative effects of dietary fat and fibre in Alentejano and Large White piglets: Digestibility, digestive enzymes and metabolic data

Abstract An experiment involving 24 Large White (LW) and 24 Alentejano (AL) piglets weaned at 21 days of age was conducted to study the effects of dietary fat and fibre on digestive capacity, and metabolic parameters in both genotypes, according to 2×2×2 factorial arrangement, with two genotypes, two levels of fibre (0 or 15% of wheat bran) and two sources of fat (olive oil or beef tallow). Total tract apparent digestibility (TTAD) was measured and blood samples were taken at fasting and throughout 5 h after meal. Average TTAD in AL and LW piglets, respectively, were 80.2 and 77.9% for energy, 69.4 and 61.4% for fat, 63.0 and 52.6% for NDF, and 39.8 and 13.1% for ADF. Wheat bran reduced TTAD of energy, fat and ADF by 5, 10 and 10 percentage units, respectively, in LW breed, and by 2, 10 and 4 percentage units, respectively, in AL breed. Total activities of pancreatic lipase, trypsin and amylase, and intestinal maltase at 49 d of age were 2.0, 1.5, 5.0 fold and 60% higher, respectively, in Alentejano piglets. For a constant nitrogen intake, daily nitrogen retention was greater in LW than in AL piglets, i.e., 6.7 vs. 5.8 g d −1 , respectively. The maximum serum urea level was observed, 4 h after the meal, for diets containing wheat bran, i.e., 66.1 mg/100 ml and 53.1 mg/100 ml in AL and LW piglets, respectively, but LW breed exhibited higher levels of triglycerides, HDL-cholesterol and LDL-cholesterol.

Lupinus luteus, Vicia sativa and Lathyrus cicera as protein sources for piglets: ileal and total tract apparent digestibility of amino acids and antigenic effects

Abstract Twenty-four male piglets, weaned at 28 days of age, were used to measure the total and ileal digestibility and serum immune responses to dietary leguminous seeds. The experimental diets consisted of a control starter (C) and three other diets prepared by replacing 30% of the crude protein content of the C diet by the protein of Lupinus luteus (LL), Vicia sativa (VS) or Lathyrus cicera (LC). The total tract apparent digestibility (TTAD) of energy and crude protein (CP) was lowest ( P P L. luteus , vicilin of V. sativa and vicilin of L. cicera were detected 28 days after feeding the diet in the sera of piglets fed on the LL, VS or LC diets, respectively. Conversely, no storage protein was found in the serum of any piglet fed either on LL, VS or LC diets. The presence of antibodies against β-conglutin of lupine, vicilin of V. sativa and vicilin of L. cicera , respectively indicated an immune response in weaned piglets. The absence of residual antigenic proteins may be due to the digestive adaptation of the piglet to the legume-based diets. However, no direct relation between the differences in digestibility coefficients among the legume seeds and their antigenicity was established.

Waxy versus regular maize: Energy value for growing pigs and utilization in piglet diets

Two experiments were performed to determine the feeding value of amylopectin-rich waxy maize. n nA digestibility trial (A) was made with growing pigs (5 castrated Large White males per group) kept in digestibility crates for total collection of excreta for 10 consecutive days. The diets consisted exclusively of Funks G 4384 maize cultivars, either regular (Group 1) or waxy (Group 2), supplemented with minerals, vitamins and essential amino acids. Waxy maize was better utilized than regular maize, the respective values being: digestibility of energy, 90.3 versus 88.4 (P < 0.05); digestible energy, 3980 ± 28 vs. 3914 ± 13 kcal/kg dry matter (P < 0.10); apparent metabolisable energy, 3887 vs. 3832 kcal/kg dry matter (P < 0.10) or corrected ME, 3839 vs. 3787 kcal/kg dry matter (P < 0.10). The utilization of crude protein was slightly in favour of waxy maize; nitrogen digestibility being 86.3 vs. 85.6 (NS) and retained nitrogen, 15.2 vs. 14.2 g/d (P < 0.10). n nIn Trial B, utilization of two types of maize of the same variety, LG 11, which were isogenic except for the waxy gene, was studied with a total of 128 piglets weaned at 5 weeks. The waxy maize (Group 2) or regular maize (Group 1) was introduced at the level of 70% into isonitrogenous diets (20% CP) offered until the age of 9 weeks. In these conditions, a noticeable effect was found in favour of waxy maize. Average daily gain was 470 g (Group 2) versus 434 g (Group 1), a significant increase of 8% (P < 0.05); feed conversion ratio was 1.76 (Group 2) versus 1.84 (Group 1) (P < 0.10). n nThe digestibility in vitro of the two types of maize used in Trial B was also assayed. The rate of hydrolysis of waxy maize starch was more rapid in the presence of piglet pancreatic juice, a fact suggesting that the energy of this type of maize is more available for monogastric animals.

PROXIMATE CHEMICAL ANALYSIS OF FINAL CANE MOLASSES AND EFFECT OF FEEDING 30% MOLASSES ON INTESTINAL SUCRASE AND MALTASE ACTIVITIES IN THE RAT

Abstract The final cane molasses used contained, on an air dry basis, 18.5% moisture, 62.1% alcohol-soluble sugars, 32.2% sucrose, 8.6% glucose and 15% fructose. The nitrogen content was particularly low (0.58%, out of which scarcely half was present as amino acids). The effect of molasses on growth rate and on the activities of intestinal disaccharidases was investigated using three groups of nine weanling rats fed for 21 days on diets containing 30% of either final molasses, sucrose, or maize starch, respectively. Growth rate and food intake were similar in all groups; feed/gain was similar for molasses and maize starch based diets and significantly lower for sucrose. Molasses significantly increased the weight of intestinal tissue and the protein content of intestine. No difference in the total and specific activity of intestinal maltase was found between the treatments. On the contrary, a considerable increase ( P