ALBERT

Notes: Two experiments were carried out with grass silages cut at a leafy (Experiment 1) and a more mature (Experiment 2) stage of growth to evaluate the effect of wilting and chop length on silage intake and performance of store lambs. In each experiment, the herbage was cut with a rotary mower and was either ensiled within 24 h as unwilled silage (U) or wilted for 1–3 d (W). Each silage type was harvested with either a double-chop harvester (D) or a precision-chop harvester (P). All silages were treated with formic acid at 3 1 t−1 and were well preserved. The silages were fed ad libitum to Suffolk crossbred store lambs (twenty-four lambs per treatment) without any supplement over a period of 8 or 9 weeks.Wilting of the silages had little effect on silage intake (797 vs. 809g dry matter (DM) d−1) or on lamb performance in Experiment 1. In Experiment 2, wilting of the D silage increased silage DM intake (589 vs. 534 g DM d−1; +10%) and reduced the extent of liveweight losses. Wilting of the P silage reduced silage intake (770 vs. 791g DM d−1; -3%) and reduced liveweight gains.In Experiment 1 intakes of the D silages were 650–667g DM d−1 and just maintained lamb live weights. Intakes of the P silages were 39–49% higher than the D silages (927–968 g DM d−1) and increased liveweight gains. In Experiment 2 intakes of the D silages were 534–589 g DM d−1 and resulted in a loss in lamb live weight. Precision-chopping increased silage intakes by 31–48% (770–791 DM d−1)in Experiment 2 and improved lamb liveweight gains. Lamb performance was higher on the UP silage than on the WP silage.The rumen retention lime (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake before slaughter, was much shorter for the lambs fed on the P silages (12.6–20.6 h) than those fed on the D silages (21.4–29.3 h) in each experiment.Silage intake and liveweight gain were positively related to silage in vivo DM digestibility (DMD), whereas RRT was negatively related to DMD. However, there were distinct differences between the P and D silages in the elevation and, to a lesser extent, in the slope of the regression lines, indicating that intake of D silage was limited by factors other than the digestibility of the silageThe results of this study show that the chop length of grass silage had a far greater effect on intake and on lamb performance than silage digestibility, whereas wilting had little or no effect.

Notes: A perennial ryegrass sward was cut at a leafy stage of growth and harvested with different harvesters to produce silages differing in chop length to evaluate the effect of silage chop length on silage intake and on the performance of store Iambs when silage was fed as the sole diet. The silage was harvested in late May either as long silage (L), single-chopped (S). double-chopped (D). long precision-chopped (LP) or medium precision-chopped (MP) silage with (he appropriate machinery. The silages were treated with formic acid at 2.5 1 t−1. were well preserved (pH 3.7–3.8) and were of high dry-matter digestibility [749–810 g DMD kg−1 dry-matter (DM)]. The silages were fed ad libitum as the sole diet to Suffolk crossbred store lambs over a period of 11 weeks.Silage intake and lamb performance progressively increased as silage chop length declined from 32.4 cm (L) to 6.8 cm (MP). Silage intakes were 572, 661, 750, 893 and 1129 (± 21) g DM d−1 for silages L, S, D, LP and MP respectively. The corresponding daily liveweight gains were -3, 40, 53, 85 and 151 (± 7.6) g d−l. Similar increases in empty body weight gain and carcass weight gain were obtained as silage chop length declined.Rumen retention time (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake in the week before slaughter, was much shorter for silages LP and MP compared with silages L or S. Silage intake was negatively related to RRT(b= -24.5 ± 6.1 gDM h−l RRT).The results of this study showed that high intakes of grass silage and liveweight gains were achieved when grass was cut at a leafy stage of growth and harvested with a precision-chop harvester set to produce a moderate chop length (7 cm). The feeding of long or flail-chopped silages resulted in lower intakes and lower liveweight gains.

Notes: An experiment was carried out to study the effect of silage chop length and barley supplementation on silage intake and the performance of store lambs. The silages were cut from a perennial ryegrass regrowth at a relatively mature stage of growth in early July. Different types of harvester were used to produce a long silage (L), single-chopped (S), double-chopped (D), medium precision-chopped (MP) or a short precision-chopped (SP) silage. The chop length of the silages averaged 37.4, 12.4, 8.4, 7.0 and 2.9 cm respectively. All silages were treated with formic acid at 2.51 t−1grass. They were well preserved and of a good quality with a dry-matter (DM) digestibility of 720–760 g kg−1 DM. The silages were fed ad libitum to Suffolk crossbred store lambs over a period of 10 weeks. Each silage was fed either alone or was supplemented with whole barley at 400 g lamb−1 d−1.When offered silage alone, intakes were 738, 679, 773, 980 and 910 (± 30) g DM d−1 for silages L, S, D, MP and SP respectively. Similar relative differences in intakes between the silages were evident when supplemented with barley. Liveweight gain on silage alone was higher on the precision-chopped silages (85–93 g d−1) than the long or flail-chopped silages (28–49 g d−1). Liveweight gain on the precision-chopped silages was also better when supplemented with barley (150 vs. 90–112 (± 90) g d−1). Silage intake and lamb performance were similar for the MP and SP silages, despite the difference in chop length.Barley supplementation reduced silage intake to a similar extent for all silages (-9%) and increased total DM intake (+ 30%) and metabolizable energy intake (+ 37%). The substitution rates of silage for barley were similar for all silages and averaged 0.24 g silage DM g−l barley DM. The response in weight gain per 100g of barley fed was similar for all silages and averaged 20.0 g liveweight gain and 13.4 g carcass gain. Feed conversion efficiency of the total diet was similar for the Mail-chopped and precision-chopped silages but was less for the long silage.The results of this study show that the benefit in weight gain due to the higher intake of precision-chopped silage was maintained when the silage was supplemented with a moderate level of barley. Such silage required supplementation with barley (400 g d−l) to achieve a rate of liveweight gain of 150g d−1.

Notes: A dairy system simulator, Dairy_sim, was designed to assess the interactions between climate and management in spring-calving milk production systems based on the grazing of grass pastures. The simulator comprises three main components: a grass herbage growth model, an intake and grazing behaviour model, and a nutrient demand model. The simulator was initially parameterized using the Irish National Dairy Blueprint. Sensitivity analysis indicated that the simulator was most sensitive to stocking rate, milk output per cow and nitrogen fertilizer inputs, but less sensitive to other variables. Field data from four grazing systems were used to test the simulator and it was concluded that Dairy_sim was suitable for evaluating the interaction of climate and management for rotational grazing dairy systems based on perennial ryegrass pastures with Friesian cows. The simulator, Dairy_sim, was then used to evaluate the effects of the regional climates of Ireland on system management. The results indicated that, between regions, herbage production at the same input of nitrogen may vary proportionally by 0·10 and that the length of the grazing season may vary by 0·25. It was concluded that the simulator could be a useful tool for developing region-specific dairy production blueprints.

Notes: Coordinate-independent formulations are derived for the conditions satisfied by the elastic modulus tensor of materials with trigonal, hexagonal, and cubic symmetry. Analogous results for two-dimensional modulus tensors are also derived.