Effect of monensin on in vitro fermentation of silages and microbial protein synthesis.

The objective of the study was to investigate the effects of monensin on silage fermentation and microbial net protein synthesis. In Experiment 1, monensin (0.5, 1, 2, 4, 6, or 10 µg) was added to syringes that contained 120 mg of grass silage (GS), grass silage and concentrate (GS + C), or maize silage (MS), resulting in concentrations of 4.2, 8.3, 16.7, 33.3, 50.0 and 83.3 mg monensin/kg feed. Samples were incubated for 24 h to determine the monensin concentration that resulted in the maximum reduction in methane production without effects on the total gas production. In Experiment 2, GS and GS + C were incubated in a rumen simulation technique (Rusitec) to assess the monensin effects (133 and 266 mg/kg feed) on the production of total gas, methane and volatile fatty acids (VFA), degradation of nutrients and microbial net protein synthesis. In Experiment 1, methane production was reduced without significant effects on the total gas production; the reductions were 17% (GS), 10% (GS + C) and 13% (MS) with 16.7 (GS), 50.0 (GS + C) and 33.3 (MS) mg monensin/kg feed. Monensin reduced the total gas and methane production in GS and GS + C in Experiment 2. Propionate production was enhanced by monensin, accompanied by a decrease in acetate production. Along with a reduction in crude protein (CP) degradation, monensin reduced the ammonia nitrogen concentration in the effluent of both treatments. While the protein produced by liquid-associated microbes increased with monensin, protein production by solid-associated microbes was reduced. Total microbial net protein synthesis increased in the presence of monensin. Monensin influenced the production of total gas, methane and VFA from the silages without an effect on the degradation of organic matter (OM). Different microbial fractions were affected differently by monensin supplementation. If monensin is used as a tool to reduce methane emission, the supplementation level must be carefully chosen to avoid negative effects on overall fermentation in the rumen.

Changes in fatty acid composition of various full fat crushed oilseeds and their free oils when incubated with rumen liquor in vitro.

The fatty acid pattern of dietary lipids can be modified during rumen biohydrogenation (BH). The objective of the present study was to assess changes in the FA pattern of different oilseed products supplied either as crushed full fat oilseed or as free oil after in vitro incubation with buffered rumen liquor. The FA patterns were determined at the beginning and compared with those measured after 24 h of incubation. The contents of fatty acids (FA) < C18 increased (p < 0.05) in nearly all treatments, eventually due to microbial de novo synthesis and fermentation of carbohydrates and proteins during incubation. In contrast, the contents of the dominating C18 FA, (oleic acid - C18:1c9, linoleic acid - C18:2c9,12, linolenic acid - C18:3c9,12,15) were reduced due to BH, resulting in the accumulation of characteristic BH intermediates, such as conjugated linoleic acid (CLA) isomer C18:2c9t11 (rumenic acid). However, both for crushed full fat oilseeds and their free oils the process of BH was not completed at the end of incubation. The disappearance was highest for C18:3c9,12,15, followed by C18:2c9,12 and C18:1c9. The rate of BH of unsaturated FA was higher in the crushed form compared to the oil form. Higher amounts of BH intermediates accumulated in the crushed form. Obviously, the physical form affects the degree of BH in vitro. The current results suggest that feeding crushed full fat seeds instead of their free oils to dairy cows might stimulate the formation of beneficial BH intermediates such as CLA in the rumen.

Occurrence and distribution of 13 trichothecene toxins in naturally contaminated maize plants in Germany.

The objective of the present study was to monitor the occurrence and distribution of a spectrum of trichothecene toxins in different parts of maize plants. Therefore maize plants were sampled randomly from 13 fields in southwest Germany and the fractions kernels, cobs, husks, stalks, leaves and rudimentary ears were analyzed for eight A-type and five B-type trichothecenes. Each of the toxins was found in at least three of the total of 78 samples. The study revealed that both A-type and B-type trichothecenes may be present in all parts of the maize plant but may be unevenly distributed. For the contents of deoxynivalenol, 3- and 15-acetyldeoxynivalenol, nivalenol, scirpentriol, 15-monoacetoxyscirpenol, HT-2 and T-2 toxin significant differences (p < 0.05) were found between different parts of the maize plants whereas no significant differences were observed for fusarenon-X, 4,15-diacetoxyscirpenol, neosolaniol, T-2 triol and T-2 tetraol. Up to twelve toxins co-occurring in one sample were detected. As a group B-type trichothecenes dominated over A-type trichothecenes concerning incidences and levels. Contamination was strongest with rudimentary ears based on incidence and mean and maximum contents; mean contents with few exceptions tended towards a higher level than in other fractions with significant (p < 0.05) differences compared to leaves for seven toxins.

Response of imidazolinone-tolerant and -susceptible volunteer oilseed rape (Brassica napus L.) to ALS inhibitors and alternative herbicides.

BACKGROUND: Imidazolinone-tolerant oilseed rape (Brassica napus L.) varieties are currently grown in Canada, North America, Chile and Australia with high acreage. A Europe-wide introduction has started and will be pushed further for both spring and winter varieties. The primary aim of this study was to evaluate the impact of imidazolinone tolerance for future volunteer oilseed rape control in subsequent crops, particularly winter wheat. RESULTS: A greenhouse bioassay showed cross-tolerance of imidazolinone-tolerant oilseed rape towards sulfonylureas, triazolopyrimidines and sulfonylaminocarbonyltriazolinones (resistance factors between 5 and 775), with a homozygous variety expressing a much higher tolerance level compared with a heterozygous variety. Calculated ED90 values suitable for controlling tolerant plants were always much higher than the recommended herbicide dose. Generally, results were confirmed under field conditions, but with higher efficacies than expected in some cases (e.g. florasulam). Herbicides with an alternative mode of action were found to be effective in controlling imidazolinone-tolerant volunteers in subsequent winter wheat crops. CONCLUSION: Herbicide strategies have to be adjusted for volunteer control in subsequent crops if imidazolinone-tolerant oilseed rape varieties are to be grown. However, agronomic tools (harvest date, harvest technique, tillage) should be used conscientiously in the first place to keep volunteer oilseed rape densities at the lowest possible level.

Effect of weaning age on feed intake and ruminal fermentation patterns of calves fed a dry total mixed ration with ad libitum access to grass hay.

To study the effect of weaning age on average daily gain (ADG), dry matter intake (DMI) and ruminal fermentation, 10 rumen-cannulated male Holstein calves were randomly assigned to one of two treatments: (i) early weaned at 8 weeks of age (235 l milk); (ii) conventionally weaned at 12 weeks of age (347 l milk). Twice daily grass hay (9.0 MJ ME x kg(-1) DM) and a dry total mixed ration (TMR) (11.6 MJ ME x kg(-1) DM) containing 15% alfalfa hay and 85% concentrates were offered separately. Water was available ad libitum. Ruminal fluid was collected via cannulas at weeks 9, 11, 13 and 15, twice weekly just prior to as well as 1, 3, 5 and 7 h after morning feeding. Calves of both treatments achieved adequate ADG (947 vs. 959 g; p > 0.05). Just-weaned calves rapidly increased DMI (1.1-2.5 kg TMR and 2.4-3.6 kg TMR for early- and conventionally-weaned calves, respectively). From weeks 10-12 early-weaned calves consumed significantly more dry feed than conventionally-weaned calves (week 10: 2.5 vs. 1.6 kg/d; week 12: 3.4 vs. 2.4 kg/d). Early weaning stimulates DMI supporting ruminal fermentation intensity, indicated by lower ruminal pH. After weaning, only early-weaned calves achieved critical average ruminal pH (week 9: 5.7 vs. 6.0, p = 0.017; week 11: 5.9 vs. 6.2, p = 0.007). Experimental treatment did not affect the concentration of ruminal short-chain fatty acids (SCFA). For all calves, the effects of the concentrate-rich TMR were shown by a high SCFA level (daily average: 137-152 mmol x l(-1)) and an acetate to propionate to butyrate ratio between 51:36:9 and 54:33:10.