The effects of rate of inorganic nitrogen (N) fertilization (0, 80 or 160 kg N ha )1 per regrowth), season of harvest (regrowths 1, 2 and 3) and perennial ryegrass (Lolium perenne L.) cultivar [classified as having either a normal or elevated water soluble carbohydrate (WSC) concentration genotype] on in vitro gas production and digestibility were assessed. Increased N fertilizer application significantly decreased total gas production (TGP), methane (CH 4 ) production and organic matter digestibility (OMD). The results suggest that the decreases in TGP and CH 4 production were associated with a restriction in organic matter (OM) fermentation and an altered crude protein (CP) to structural carbohydrate ratio rather than a modification in the stoichiometry of fermentation. Season of harvest only significantly (P < 0AE05) altered in vitro OMD and CH 4 production at 8 h, despite altering the chemical composition of the herbage. Cultivar effects on all measured in vitro parameters were not significant presumably because the elevated WSC concentration trait was not expressed strongly in the study.

In some European countries, the majority of annual enteric methane (CH 4 ) emissions by ruminants occur at pasture -a direct result of the predominance of grazing within ruminant production systems. However, there are only limited data available as to the effect of perennial ryegrass cultivar and season of harvest on CH 4 production. Using the in vitro gas production technique, the effect of perennial ryegrass cultivar on fermentation characteristics and CH 4 production was determined (Experiment 1) and the persistence of these traits throughout the growing season for two cultivars, identified from Experiment 1 as having either a high or low methanogenic potential, was examined (Experiment 2). In Experiment 1, organic matter (OM) digestibility and cumulative total gas production profiles were unaffected by cultivar but, with regard to the kinetics of CH 4 production, the asymptote value (A), cumulative CH 4 yield at 72 h, and the fractional rate (l) of CH 4 production at both time of 0AE5A(T 1 2 )(lCH 4 T 1 2 ) and at 48 h (lCH 4 48h) were significantly (P < 0AE05) different. The amount of digested OM, as a proportion of cumulative CH 4 production (DigOM/CH 4 ) at 24 and 72 h after commencement of inoculation, revealed that the amount of substrate required to produce 1 ml of CH 4 also differed significantly between cultivars (P < 0AE01). In Experiment 2, regrowth number significantly modified the majority of measured samples (P < 0AE01); cultivar effects were limited to the lag phase of the cumulative CH 4 production curve and DigOM/ CH 4 at 8 h only (P < 0AE05). These results suggest that differences exist between cultivars in how OM is partitioned following microbial fermentation and that these differences demonstrate persistency throughout the growing season. In the course of time it may be possible to exploit these differences through cultivar selection and plant breeding programmes, and thereby reduce enteric CH 4 emissions within pastoral production systems.

The effects on growth performance and on some health parameters due to the inclusion of sugar beet pulp in antibioticfree diets for weaned piglets were evaluated on a commercial farm. A conventional diet (C) and one containing 120 g/kg of sugar beet pulp (SBP) were fed to 668 weaned piglets from 21 to 64±3 days of age. Every two weeks, live weight and feed consumption (FC) of the two groups were recorded by pens. Fecal samples were collected from 8 pairs of piglets for each treatment to evaluate the evolution over the time of the apparent digestibility of the nutrients, as well as the volatile fatty acids content and the microbial count in the feces. The dietary treatment did not affect FC. In comparison to C, SBP slightly reduced average daily gain over 36 to 49 (528 vs. 498 g/d; P<0.05) and 50 to 64±3 (677 vs. 631 g/d, respectively; P<0.01) days of age. Digestibility of NDF of diet C increased with age from 441 to 526 g/kg whereas that of diet SBP increased from 465 to 638 g/kg. The differences between diets became significant after 36 days of age (P<0.01). From 29 to 35 days of age higher contents of water (793 vs. 713 g/kg; P<0.01), acetic (322 vs. 206 µmol/g dm; P<0.01) propionic (108 vs. 81 µmol/kg dm; P<0.01) acids and lower counts for fecal-coliforms (6.9 vs. 8.2 log 10 /g; P<0.01), clostridia (1.3 vs. 2.3 log 10 /g; P<0.01) and Staphylococcus spp. (6.7 vs. 8.1 log 10 /g; P<0.01) were found in the feces of the SBP piglets compared to those of C. These differences progressively disappeared with time. Some piglets showed clinical signs of purulent arthritis and meningitis, but no signs of diarrhea were observed. The SBP group showed, with respect to C, a significantly lower number of piglet deaths caused by meningitis (15 vs. 30 ‰, respectively; χ 2 , P<0.05), and a significantly lower number of piglets removed because lack of growth (33 vs. 76 ‰, respectively; χ 2 , P<0.01). No clear evidence to explain this result was found, however it was concluded that the inclusion of 12% of sugar beet pulp in antibiotic-free diets can improve the health status of piglets with little effect on growth performance.

Bittante (2004) Feeding dairy cows with full fat extruded or toasted soybean seeds as replacement of soybean meal and effects on milk yield, fatty acid profile and

Previous studies have identified small but significant differences in in vitro methane (CH4) production between perennial ryegrass cultivars harvested pre-heading date. This raises the possibility that enteric CH4 production could be reduced through cultivar selection. The aim of this study was to assess the effect of harvest date on in vitro CH4 output of two cultivars previously identified as having a high and low methanogenic potential (Lovett et al., 2003).