| Popis: |
The objective of the study was to reduce the amount of imported grain in fattening diets based on maize silage by the use of high ear content varieties of maize and by abandoning the lower, less nutritious 60 cm of the stover. Maize of the local Halamish hybrid (HS) and of the US J × 180 hybrid was grown under drip irrigation. Hybrid HS was planted 14 days earlier than J × 180 in order to be harvested on the same day. The HS yielded 24.38 t and J × 180 yielded 19.25 t dry matter (DM) ha −1 , with 44 and 51% ears in DM, respectively. Hybrid J × 180 was cut at 7 cm (L) and 60 cm above ground surface (H); there were thus three silages: HS, J × 180 L and J × 180 H. The DM content of the fresh material at harvest time was 30.3, 38.3 and 38.3%, respectively. The mean composition of the silages (%) was: DM, 30.8, 39.6 and 37.5; crude protein, 8.7, 8.0 and 8.4; NDF, 57.5, 53.1 and 49.7; ADF, 33.9, 28.3 and 27.2; and ash in ADF 2.8, 1.8 and 1.5 in DM for HS, J × 180 L and J × 180 H, respectively. Total sugar, glucose, Ca, P, VFA, lactic acid, aerobic bacteria, yeasts and moulds in the fresh material and in the silage were determined. Ensiling losses of DM were 5.2, 0.5 and 0.5% for HS, J × 180 L and J × 180 H, respectively. The silages were examined in a digestion trial with 6 replicates and in a 130-day feeding trial in which maize silage comprised 50%, vetch hay 10% and cottonseed 17% of the diet on a DM basis. There were 14 Friesian and 14 beef breed bulls in each treatment group. The digestibility coefficients of organic matter of the three silages and consequently their calculated ME content did not differ (70.8, 69.9 and 70.4%; 10.7, 10.6 and 10.8 MJ kg −1 DM for HS, J × 180 L and J × 180 H silages, respectively). This may be attributed to the higher digestibility of fibre components, and a significantly lower percentage of ingested grain excreted on the HS silage diet (2.9, 11.6 and 7.0 for HS, J × 180 L and J × 180 H silages, respectively). In the feeding trial, DM intake per 100 kg live weight for Friesians was 2.26, 2.15 and 2.10 kg; ADG was 1.18, 1.09 and 1.23 kg; and ME intake per kg liveweight gain was 88.0, 88.6 and 78.9 MJ for HS, J × 180 L and J × 180 H silage diets, respectively. The corresponding values for beef breed bulls were, in the same order: 2.26, 2.24 and 2.07 kg; 1.29, 1.24 and 1.18 kg; 73.2, 75.9 and 73.9 MJ. A fourth diet containing only 40% silage did not differ significantly from the other diets. Most of the differences in performance were not significant. |
