Effects of increasing alfalfa (Medicago sativa) leaf levels on the fattening and slaughtering performance of organic broilers.

A feeding trial was conducted to evaluate the effects of increasing alfalfa leaf levels on the performance of organic broilers. The impact of drying temperature on the nutritional value of alfalfa leaves and thereby on broiler performance was studied using alfalfa leaves dried at either low (alfalfa leaves low temperature (ALLT)) or high temperatures (alfalfa leaves (AL)). Six hundred male Hubbard JA-757 broilers were divided into five feeding groups (Control (C), AL2, AL3, AL4 and ALLT5). Alfalfa leaf content was increased in each of the three fattening phases by 5% (C: 0%-0%-0%; AL2: 0%-5%-10%; AL3: 5%-10%-15%; AL4: 10%-15%-20%; and ALLT5: 10%-15%-20%). At the end of the experiment, broilers in group C had the highest body and carcass weights. Groups AL3, AL4 and ALLT5 showed the lowest body and carcass weights. In particular, the early introduction of alfalfa leaves (5% in phase 1) and high alfalfa leaf content (15%-20%) significantly decreased performance. Antinutritional substances such as saponins occur in alfalfa. In fact, the saponin analysis showed high contents of 3-Glc-Glc-28-Ara-Rha-medicagenic acid and HexA-dHex-Pen-Pen-Pen-zanhic acid in both high- and low-temperature alfalfa leaves.

Optimizing the fluorometric ß-glucuronidase assay in ruminant milk for a more precise determination of mastitis.

Activity of the enzyme ß-glucuronidase (EC 3.2.1.31) is found in milk from ruminants with mastitis. However, the use of this enzymic activity as an indicator of mastitis has gained little attention possibly because of its low activity when compared with other mastitis indicators. The determination may therefore be less precise and the analytical procedure very time consuming and labour intensive. The present study optimized the fluorometric determination of the ß-glucuronidase activity with respect to substrate concentration, pH, incubation time etc., validated the assay, and developed it into large scale analyses. The assay performance is satisfactory regarding precision, linearity etc., and it appears comparable to analogous fluorometric assays for mastitis indicators in milk. From a local dairy herd, 825 milk samples were analysed for potential mastitis indicators, i.e. ß-glucuronidase, lactate dehydrogenase (LDH), alkaline phosphatase (AP), and N-acetyl-ß-d-glucosaminidase (NAGase) activity, and for somatic cell counts (SCC) and the variables were compared. Activity of ß-glucuronidase was moderately but significantly correlated to SCC (r=0·21; n=768) as well as the other mentioned variables (r=0·25-0·43; n=825). Simple indices based on ß-glucuronidase and LDH or NAGase activity were tested as indicators of mastitis (SCC), but were not found to improve the diagnostic value. Future studies may further verify whether ß-glucuronidase can compete with well-established indicators of mastitis in cows such as LDH or NAGase as well as determine whether ß-glucuronidase activity, in combination with other indicators of mastitis, has an advantage. Nineteen milk samples from subclinical and latent cases of mastitis (individual quarters) were identified for specific pathogens (PCR method) and measured for ß-glucuronidase activity. The activity was tested at four different pH levels (5·5, 6·0, 6·5 and 7·0) in order to investigate the possibility of discrimination between pathogens. However, all milk samples (strains of pathogens) had the same pH optimum for ß-glucuronidase activity; this may indicate that enzymic activity from mammary tissue and leucocytes dominates over enzyme activity from bacterial cells.

Animal nutrition with feeds from genetically modified plants.

Plant breeders have made and will continue to make important contributions toward meeting the need for more and better feed and food. The use of new techniques to modify the genetic makeup of plants to improve their properties has led to a new generation of crops, grains and their by-products for feed. The use of ingredients and products from genetically modified plants (GMP) in animal nutrition properly raises many questions and issues, such as the role of a nutritional assessment of the modified feed or feed additive as part of safety assessment, the possible influence of genetically modified (GM) products on animal health and product quality and the persistence of the recombinant DNA and of the 'novel' protein in the digestive tract and tissues of food-producing animals. During the last few years many studies have determined the nutrient value of GM feeds compared to their conventional counterparts and some have additionally followed the fate of DNA and novel protein. The results available to date are reassuring and reveal no significant differences in the safety and nutritional value of feedstuffs containing material derived from the so-called 1st generation of genetically modified plants (those with unchanged gross composition) in comparison with non-GM varieties. In addition, no residues of recombinant DNA or novel proteins have been found in any organ or tissue samples obtained from animals fed with GMP. These results indicate that for compositionally equivalent GMP routine-feeding studies with target species generally add little to nutritional and safety assessment. However, the strategies devised for the nutritional and safety assessment of the 1st generation products will be much more difficult to apply to 2nd generation GMP in which significant changes in constituents have been deliberately introduced (e.g., increased fatty acids or amino acids content or a reduced concentration of undesirable constituents). It is suggested that studies made with animals will play a much more important role in insuring the safety of these 2nd generation constructs.

Long term feeding of Bt-corn--a ten-generation study with quails.

A ten-generation experiment with growing and laying quails were carried out to test diets with 40 (starter) or 50% (grower, layer) isogenic or transgenic (Bt 176) corn. Feeding of diets containing genetically-modified corn did not significantly influence health and performance of quails nor did it affect DNA-transfer and quality of meat and eggs of quails compared with the isogenic counterpart.

Assessment of novel foods in animal nutrition.

Composition of feeds from GMO crops were determined as well as digestion and feeding experiments were carried out with broilers (Bt-corn), layers (Bt-Corn, Pat-corn), pigs (Bt-corn, Pat-sugar beet, soybeans), sheep (Bt-corn silage, Pat-corn silage), growing bulls (Bt-corn silage) and fistulated cows (Bt-corn silage). Up to now, no significant differences in nutritional value between feeds from isogenic and transgenic plants of the first generation were observed. The so-called substantial equivalence, but also the nutritional equivalence of transgenic hybrids could be demonstrated. Recombinant plant DNA constructs were not detected in animal tissues samples. In the future, long term feeding experiments for nutritional assessment of novel feeds should be combined with risk assessment studies. Proposal for discussion has been submitted.

Investigations on genetically modified maize (Bt-maize) in pig nutrition: fattening performance and slaughtering results.

A grower finisher performance trial with forty-eight pigs was designed to compare the growth performance of pigs fed diets containing either genetically modified (GM) Bt-maize (NX6262) or its parental maize (Prelude) line. During the experiment, the pigs were fed with a grower and a finisher diet both containing 70% maize investigated in a previously study which showed that they contained similar ME values and digestibility of crude nutrients. The pigs with an initial live weight of 23.9 +/- 3.0 kg were allotted to single boxes. During a 91 days growing period the pigs of both groups recorded equal performance in daily weight gain (AW) 815 +/- 93 vs. 804 +/- 64 g/d depending on equal amounts of feed intake 1.95 +/- 0.15 vs. 1.94 +/- 0.15 kg/d (parental vs. transgenic). The results confirm equal performance among growing-finishing pigs fed parental or genetically modified maize containing diets. For slaughtering the pigs were divided into 4 groups with a different duration of the finishing period. After slaughtering the carcass characteristic were registered.

Investigations on genetically modified maize (Bt-maize) in pig nutrition: chemical composition and nutritional evaluation.

The objective of the present study was to determine the composition and the nutritional value of parental and transgenic maize seeds fed to pigs. The parental maize line was genetically modified to incorporate a gene from Bacillus thuringiensis (Bt) expressing a toxin against the European corn borer (Ostrinia nubilalis). Both (parental and transgenic) maize lines were analyzed for crude nutrients, starch, sugar, non-starch polysaccharides (NSP), amino acids, fatty acids, as well as for selected minerals. Furthermore, four complete diets were mixed and were analyzed for the same nutrients and some selected ingredients. The diets contained 70% maize to attain a high effect level. To evaluate the feeding value of one variety of genetically modified maize (transgenic) compared to the feeding value of the unmodified maize (parental) line, a balance study with twelve pigs was designed. Three collecting periods were used for each maize line each with six animals. The collected faeces were analyzed for crude nutrients. All measured parameters were virtually the same (e.g. crude protein 11.59% vs. 11.06% in DM), especially the digestibility of crude protein (85.8 +/- 2.3% vs. 86.1 +/- 1.8%), the amount of nitrogen-free-extract (92.8 +/- 0.6% vs. 93.2 +/- 0.6%) and the metabolizable energy (15.7 +/- 0.2% vs. 15.8 +/- 0.2% MJ/kg DM) for both maize lines. Compared to the parental line, the chemical composition and digestibility of crude nutrients and energy content were not significantly affected by the genetic modification of maize. Therefore, from the view of a nutritional assessment, the genetically modified maize can be regarded as substantially equivalent to the parental maize line.