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A long-term study over 25 months was conducted to evaluate the effects of genetically modified corn on performance of lactating dairy cows. Thirty-six dairy cows were assigned to two feeding groups and fed with diets based on whole-crop silage, kernels and whole-crop cobs from Bt-corn (Bt-MON810) or its isogenic not genetically modified counterpart (CON) as main components. The study included two consecutive lactations. There were no differences in the chemical composition and estimated net energy content of Bt-MON810 and CON corn components and diets. CON feed samples were negative for the presence of Cry1Ab protein, while in Bt-MON810 feed samples the Cry1Ab protein was detected. Cows fed Bt-MON810 corn had a daily Cry1Ab protein intake of 6.0 mg in the first lactation and 6.1 mg in the second lactation of the trial. Dry matter intake (DMI) was 18.8 and 20.7 kg/cow per day in the first and the second lactation of the trial, with no treatment differences. Similarly, milk yield (23.8 and 29.0 kg/cow per day in the first and the second lactation of the trial) was not affected by dietary treatment. There were no consistent effects of feeding MON810 or its isogenic CON on milk composition or body condition. Thus, the present long-term study demonstrated the compositional and nutritional equivalence of Bt-MON810 and its isogenic CON.

-Maize silage was produced from two different varieties (SG: "stay-green" and DD: "dry down") at two different stages of maturity (target: 30-32 and 38-42% DM). Dry matter and nutrients of plant fractions and silages, fermentation parameters of silages and digestibility in sheep were determined. Furthermore a feeding trial was conducted in which the effect of the maize silage on feed intake and performance of dairy cows was studied. This trial series (TS 1) was replicated in the following year (TS 2). In both years, variety SG had higher ear (dehusked) dry matter content and lower residual plant dry matter content (58.9% and 23.7%) than variety DD (54.9% and 26.7%) and a slightly lower ear (dehusked) proportion. The constituents of the ear (dehusked) and residual plants were affected by maturity stage but not by variety. The maize silages of variety DD had slightly lower crude ash, crude fat and crude fibre contents and a higher starch content than SG. In TS 1, the digestibility of the organic matter averaged about 77% for variety SG and 80% for variety DD; in TS 2 this value was uniform at about 77%. While the maize variety had little effect on the average daily feed intake over both feeding trials (SG 17.2 kg DM per cow and DD 16.9 kg DM per cow), the stage of maturity had a significant effect. Maturity stage 2 increased the total daily feed intake from 16.4 to 17.8 kg DM per cow relative to maturity stage 1. The daily milk yield, which averaged 24.9 kg (TS 1) and 25.2 kg per cow (TS 2) was not significantly affected either by the variety or the maturity status, although there was a slight quantitative advantage of 1.1 kg (TS 1) and 0.7 kg (TS 2) milk per cow and day in favour of variety SG over variety DD.dairy cow / maize silage / variety / maturity / feeding value / stay-green Résumé -Influence de la variété du maïs, récoltée à différents stades de maturité, sur la valeur alimentaire de la plante et sur les performances des vaches laitières. lequel ont été étudiées la prise alimentaire et les performances des vaches laitières, a également été mis en place. Cette série d'essais a été réalisée sur deux années consécutives, respectivement, TS 1 et TS 2. Les résultats ont montré que, sur les deux années, les épis (sans spathes) de la variété SG ont eu une teneur en matière sèche plus élevée, et les fractions végétales résiduelles une teneur en matière sèche plus faible (58,9 % et 23,7 %) que celles de la variété DD (54,9 % et 26,7 %). La proportion d'épis (sans spathes) a été légèrement inférieure pour la variété SG. La composition des fractions vé-gétales a été affectée par le stade de maturité mais pas par la variété. Pour les ensilages, ceux de la variété DD ont eu une teneur en matières minérales, en matière grasse et en fibres brutes légèrement plus faible et une teneur en amidon plus élevée que les ensilages de la variété SG. Lors de la première année (TS 1), la digestibilité de la matière organique a été en moyenne de 77 % pour la variété SG et de 80% pour la variété DD ; l'année suivante (TS 2)...

Two experiments were conducted to investigate the iron bioavailability of different sources and supply levels in piglets. In experiment 1, the influence of feeding an iron deficient basal diet or the basal diet supplemented with 28 ppm Fe either in form of Fe-chelate, crystalline Fe-glycinate, or Fe-sulphate on apparent iron digestibility and on blood parameters was determined. In experiment 2, a dose-response approach was used to determine the effects of supplementing an iron-deficient basal diet with 30, 60, or 90 ppm of Fe either in form of crystalline Fe-glycinate or Fe-sulphate on digestibility of Fe, growth and blood parameters. In experiment 1, comparison of iron sources revealed a tendency (0.05 < p < 0.1) for a higher Fe digestibility from Fe-glycinate (40.9%) compared with Fe-chelate (30.8%) or Fe-sulphate (30.7%). Fe-balance was higher (p < 0.05) for Fe-glycinate compared with Fe-sulphate but iron balance was similar for iron sulphate and iron chelate. Those results, however, were not reflected in data of blood parameters. In experiment 2, iron digestibility, blood parameters and performance were significantly (p < 0.05) influenced by iron supply. Effects of iron source on digestibility of iron were lower than observed in the first experiment.

The aim of the present study was to investigate whether pigs prefer diets varying in Trp content and whether these preferences change with time. To that end, a feeding trial was carried out over a 6-wk period. Piglets (equal proportion of males and females) with an initial BW of 8.20 +/- 0.90 kg were randomly subdivided into four groups of 12 pigs each. Two reference groups were fed (as-fed basis) either 0.11% Trp (Trp-deficient) or 0.20% Trp (Trp-adequate) diets. Two other groups had a choice of two diets containing either 0.11 or 0.16% Trp (Trp-choice 1), or 0.11 or 0.20% Trp (Trp-choice 2). Average daily feed intake reached 335 and 366 g in pigs fed Trp-deficient and Trp-choice 1 diets, respectively. For Trp-choice 2 and Trp-adequate diets, a higher (P < 0.05) feed intake of 589 and 645 g/d, respectively, was observed. Piglets on Trp-choice 1 and Trp-choice 2, respectively, selected 87 and 93% of the higher Trp diet. Resulting Trp contents of total diets were 0.15 and 0.19% (as-fed basis) in Trp-choice 1 and Trp-choice 2, respectively. In wk 1, pigs on Trp-choice 2 chose lower proportions of the Trp-deficient feed (31% of total diet) than did pigs on Trp-choice 1 (44%), but at the end of the experiment, pigs of both groups almost exclusively chose the feed with the higher Trp content (96 and 98% for Trp-choice 1 and 2). Pigs on Trp-choice 1 had an ADG of 218 g, which was only slightly above the ADG of Trp-deficient pigs (198 g). Pigs on Trp-choice 2 and Trp-adequate diets had ADG of 404 and 458 g, respectively, which were higher (P < 0.05) than those observed for Trp-deficient and Trp-choice 1 groups. Plasma Trp concentrations in Trp-choice 2 and Trp-adequate groups (9.21 and 9.01 micromol/mL, respectively) were higher (P < 0.05) than in Trp-deficient and Trp-choice 1 groups (5.88 and 4.96 micromol/mL, respectively). Conversely, the sum of essential AA showed a higher (P < 0.05) concentration in plasma from pigs on the Trp-deficient and Trp-choice 1 diets than in plasma from pigs on Trp-choice 2 and Trp-adequate diets. Nutritional depletion of Trp influences the food selection behavior of piglets. Results of growth performance and the dietary preferences suggest that piglets are able to detect Trp-deficiency-induced metabolic changes and respond with an aversion against the Trp-deficient diet.

The study aimed to investigate the effects of insoluble dietary fibre differing in lignin content on performance and parameters of gut microbiology in 48 weanling piglets (8.5 kg mean body weight) fed common diets ad libitum. Fibre sources tested were wheat bran (low lignin) and pollen from Chinese Masson pine (Pinus massoniana) as model of fibre rich in lignin, added to diets as follows: no addition (control), 3.0% wheat bran, 1.27% pine pollen and 2.55% pine pollen. In colonic chyme, bacterial colony counts remained unaffected by treatment, but ammonia contents were reduced by fibre additions (up to -38%). The effects on ammonia were best explained by added cellulose and lignin. Fibre additions reduced apparent (faecal) digestibility of dry matter (DM) and crude protein (CP) up to -3.5 and -4.3% units with cellulose and lignin being the major determinants for changes in CP digestibility.

The aim of the present study was to investigate whether pigs prefer diets varying in Trp content and whether these preferences change with time. To that end, a feeding trial was carried out over a 6-wk period. Piglets (equal proportion of males and females) with an initial BW of 8.20 +/- 0.90 kg were randomly subdivided into four groups of 12 pigs each. Two reference groups were fed (as-fed basis) either 0.11% Trp (Trp-deficient) or 0.20% Trp (Trp-adequate) diets. Two other groups had a choice of two diets containing either 0.11 or 0.16% Trp (Trp-choice 1), or 0.11 or 0.20% Trp (Trp-choice 2). Average daily feed intake reached 335 and 366 g in pigs fed Trp-deficient and Trp-choice 1 diets, respectively. For Trp-choice 2 and Trp-adequate diets, a higher (P < 0.05) feed intake of 589 and 645 g/d, respectively, was observed. Piglets on Trp-choice 1 and Trp-choice 2, respectively, selected 87 and 93% of the higher Trp diet. Resulting Trp contents of total diets were 0.15 and 0.19% (as-fed basis) in Trp-choice 1 and Trp-choice 2, respectively. In wk 1, pigs on Trp-choice 2 chose lower proportions of the Trp-deficient feed (31% of total diet) than did pigs on Trp-choice 1 (44%), but at the end of the experiment, pigs of both groups almost exclusively chose the feed with the higher Trp content (96 and 98% for Trp-choice 1 and 2). Pigs on Trp-choice 1 had an ADG of 218 g, which was only slightly above the ADG of Trp-deficient pigs (198 g). Pigs on Trp-choice 2 and Trp-adequate diets had ADG of 404 and 458 g, respectively, which were higher (P < 0.05) than those observed for Trp-deficient and Trp-choice 1 groups. Plasma Trp concentrations in Trp-choice 2 and Trp-adequate groups (9.21 and 9.01 micromol/mL, respectively) were higher (P < 0.05) than in Trp-deficient and Trp-choice 1 groups (5.88 and 4.96 micromol/mL, respectively). Conversely, the sum of essential AA showed a higher (P < 0.05) concentration in plasma from pigs on the Trp-deficient and Trp-choice 1 diets than in plasma from pigs on Trp-choice 2 and Trp-adequate diets. Nutritional depletion of Trp influences the food selection behavior of piglets. Results of growth performance and the dietary preferences suggest that piglets are able to detect Trp-deficiency-induced metabolic changes and respond with an aversion against the Trp-deficient diet.