Chemical and physical analysis of wheat samples
The chemical and physical analyses of the wheat samples are summarized in
Table 1 and
2. Specific weight (SW) ranged from 59 kg/hl (Equinox, Crossnacreevy, 1998) to 78 kg/hl (Buster 78 kg/hl SW, 1998/99). Wheat from the 2004 harvest had the highest mean SW values (73.0 kg/hl) of all NI wheat and the 1998 harvest the lowest (68.3 kg/hl). The high N wheat from the 2005 harvest had similar mean values (72.2 kg/hl) when compared with low nitrogen wheats (70.7 kg/hl). The high nitrogen and fungicide wheat samples from HGCA Project 2979 had slightly higher mean SW values (72.8 and 74.3 kg/hl, respectively) than those without (70.8 and 68.0 kg/hl). Wheat from Rosemaund and Plough had similar mean SW (72.5 kg/hl) to those from Terrington (71.4 kg/hl) or High Mowthorpe (71.1 kg/hl). SW was similar for wheat samples with seed rate of 160 (72.9 kg/hl), 40 (71.4 kg/hl) and 640 (71.3 kg/hl). Of all the sources of wheat samples, the commercial wheat from GB had the greatest mean SW value (73.3 kg/hl) and 1998 NI wheat the lowest (68.3 kg/hl).
Thousand grain weight (TG) ranged from 21.7 g (Acbarrie, Manitoba, plot 26, Canadian wheat) to 60.8 g (Riband, 2004). For NI, mean TG was highest for the 2004 harvest (57.5 g) and lowest for the 2005 harvest (42.3 g). The mean TG of the high and low N wheat from the 2005 harvest were identical (42.3 g). The high N and fungicide wheat samples from HGCA Project 2979 had greater mean TG values (43.6 and 43.4 g respectively) than those without (42.6 and 33.7 g, respectively). Wheat samples from Plough had greater mean TG (48.2 g), than Rosemaund (45.0 g), Terrington (41.4 g) or High Mowthorpe (40.8 g). As expected, the lowest seed rate of 40 gave the highest mean TG (50.3 g) and the highest seed rate of 640 gave the lowest (43.9 g). The wheat samples obtained from the 2004 NI harvest gave the highest mean TG (57.5 g) and the Canadian wheat samples the lowest (32.5 g).
In vitro viscosity (IVV) ranged from 3.2 cp (Acbarrie, Manitoba, plot 26, Canadian wheat) to 44 cp (Haven 71, 1998/99). Of the NI samples, wheat harvested in 1998 had the highest mean IVV (17.2 cp) and 2005 the lowest (9.9 cp). The high nitrogen wheat from the 2005 harvest had similar mean IVV (10.3) than the low nitrogen (9.4 cp). The “with N” wheat samples from HGCA Project 2979 had similar mean IVV (7.5 cp) than those without (6.6 cp), while the “with fungicide” wheat samples had slightly lower mean IVV (8.6 cp) than those without (9.8 cp). Wheat samples from Plough had greater mean IVV (13.8 cp), than Rosemaund (11.4 cp), High Mowthorpe (8.5 cp) or Terrington (5.2 cp). The wheats with the higher seed rates of 640 and 160 had slightly greater mean IVV (14.6 cp) than those with the lower seed rate (12.1 cp). Overall, wheat sourced from the 1998 NI harvest had the highest mean IVV (17.2 cp) and the Canadian wheats the lowest (6.2 cp).
Nitrogen content (N) ranged from 12.5 g/kg DM (Zebedee, -N, HGCA Project 2979) to 32.6 g/kg DM (BW252, AAFCWPG, plot 55, Canadian wheat). Of the NI samples, mean N was highest for wheat harvested in 1998 (20.3 g/kg DM) and lowest for that harvested in 2005 (17.2 g/kg DM). As expected, the “high nitrogen” wheat from the 2005 harvest had greater mean N (18.2 g/kg DM) than the low (16.1 g/kg DM). Similarly, the “with N” wheat from HGCA Project 2979 had higher mean N (19.1 g/kg DM) than the “without” (13.9 g/kg DM), while the “with fungicide” wheat had lower mean N (19.9 g/kg DM) than the “without” (22.3 g/kg DM). Wheat samples from Plough had slightly greater mean N (20.3 g/kg DM), than Rosemaund (19.0 g/kg DM), High Mowthorpe (18.5 g/kg DM) or Terrington (16.6 g/kg DM), and the higher the seed rate the lower the N content. Overall, wheat sourced from the 2005 NI harvest had the lowest N (17.2 g/kg DM) and the Canadian wheat the highest (26.9 g/kg DM).
The NDF content of the wheat samples ranged from 101 g/kg DM (Consort 78, 1998/99) to 195 g/kg DM (Sceptre, TL9801, plot 82, Canadian wheat). Of the wheat sourced from NI, the 1998/99 harvest had the lowest mean NDF (132 g/kg DM) and the 2004 harvest the highest (147 g/kg DM). From the wheat sourced from HGCA Project 2979, the “with N” wheat had similar mean NDF content (143 g/kg DM) than the “without” (137 g/kg DM) and the “with fungicide” wheat had lower NDF content (135 g/kg DM) than the “without” (162 g/kg DM). The location to give wheat with the highest mean NDF was Plough (160 g/kg DM) and the lowest was Terrington (138 g/kg DM), and the seed rate to give the highest mean NDF was 40 (158 g/kg DM) and the lowest was 160 (151 g/kg DM). Of all the wheat samples, the Canadian wheat had the greatest mean NDF content (153 g/kg DM) and the 1998/99 wheat the lowest (132 g/kg DM).
Total starch content ranged from 547 g/kg DM (Acbarrie, Manitoba, plot 24, Canadian wheat) to 719 g/kg DM (Consort 78, 1998/99). Of the NI wheat the 2004 harvest had the lowest mean starch content (603 g/kg DM) and 1998/9 the highest (673 g/kg DM). The high N wheat from the 2005 harvest had similar starch content (634 g/kg DM) than the low nitrogen wheat (645 g/kg DM). The “with N” wheat from HGCA Project 2979 had lower starch (639 g/kg DM) than the “without N” wheat (665 g/kg DM), while the “with-fungicide” wheat had greater starch content (623 g/kg DM) than the “without-fungicide” (610 g/kg DM). Wheat samples from Terrington had slightly greater mean starch content (646 g/kg DM), than Rosemaund (637 g/kg DM), High Mowthorpe (636 g/kg DM) or Plough (612 g/kg DM). The wheat from the seed rate of 640 had the similar mean starch content (626 g/kg DM) to the seed rate of 160 (612 g/kg DM). Overall, the Canadian wheat had the lowest mean starch content (579 g/kg DM) and the 1998/99 NI wheat had the highest (673 g/kg DM).
Total non-starch polysaccharides (NSP) ranged from 81.7 g/kg DM (Consort, low N, 2005) to 138.8 g/kg DM (Rialto, Limavady, 1999). The “with N” wheat from HGCA Project 2979 had slightly higher total NSP (100.5 g/kg DM) than the “without N” wheat (97.6 g/kg DM), while the “with-fungicide” wheat had slightly lower total NSP (103.2 g/kg DM) than the “without-fungicide” (111.8 g/kg DM). Wheat samples from Plough had greater mean total NSP (109.1 g/kg DM), than Rosemaund (107.8 g/kg DM), High Mowthorpe (105.0 g/kg DM) or Terrington (96.0 g/kg DM). The wheat with the seed rate of 640 had the lowest mean total NSP content (106.5 g/kg DM) and the seed rate of 160 had the highest (117.6 g/kg DM). Overall, the 2005 NI wheat had the lowest mean total NSP content (101.3 g/kg DM) and the 1998/99 NI wheat had the highest (117.0 g/kg DM).
Soluble NSP ranged from 8.4 g/kg DM (Soissons 2003) to 38.0 g/kg DM (Haven 60, 1998/99). Of the wheat sourced from NI, the 2003 harvest had the lowest soluble NSP content (19.6 g/kg DM) and the 1998/99 harvests the highest (26.7 g/kg DM). The high N wheat from the 2005 harvest had similar mean soluble NSP content (21.5 g/kg DM) than the low N wheat (20.7 g/kg DM) and the “with N” wheat from HGCA Project 2979 also had similar mean soluble NSP content (23.4 g/kg DM) than the “without” (20.6 g/kg DM). The “with-fungicide” wheat had lower mean soluble NSP content (20.4 g/kg DM) when compared to the wheat “without” (23.4 g/kg DM) and wheat from Rosemaund had the greatest mean soluble NSP content (23.6 g/kg DM) of all the HGCA Project sites, and Terrington had the least (21.2 g/kg DM). A seed rate of 160 produced wheat with similar mean soluble NSP content (24.8 g/kg DM) to a seed rate of 40 (23.3 g/kg DM).
Gross energy (GE) ranged from 18.06 MJ/kg DM (Zebedee, -N, HGCA Project 2979) to 18.84 MJ/kg DM (BW252, AAFCWPG, plot 55, Canadian wheat). Of the NI wheat, the 2003 and 2005 harvests had similar mean GE (18.30 MJ/kg) to 1998/99 (18.40 MJ/kg). The high N wheat from the 2005 NI harvest had slightly higher mean GE (18.35 MJ/kg) than the low (18.26 MJ/kg) and the “with N” wheat from HGCA Project 2979 had higher mean GE (18.40 MJ/kg) than the “without N” wheat (18.18 MJ/kg), while the “with-fungicide” wheat had lower mean GE (18.33 MJ/kg) than the “without-fungicide” (18.51 MJ/kg). Wheat samples from Rosemaund had greatest mean GE (18.48 MJ/kg), then Plough (18.47 MJ/kg), then High Mowthorpe (18.33 MJ/kg) and finally Terrington (18.24 MJ/kg). The wheat with the seed rate of 40 had the greatest mean GE content (18.52 MJ/kg) and the seed rate of 640 had the lowest (18.43 MJ/kg). Overall, the Canadian wheat had the highest mean GE (18.66 MJ/kg) and the 2005 NI wheat had the lowest (18.30 MJ/kg).
Amylose content ranged from 115 g/kg starch (Tanker, high N, 2005) to 211 g/kg (Consort, 2004). Of the wheat sourced from NI the 2005 harvest had the lowest mean amylose content (154 g/kg starch) and the 2004 harvest the highest (173 g/kg starch). The low N wheat from the 2005 harvest had greater mean amylose content (166 g/kg starch) than the high nitrogen wheat (142 g/kg starch). From the wheat sourced from HGCA Project 2979, the “with N” wheat had lower mean amylose content (158 g/kg starch) than the “without” (168 g/kg starch) and the “with-fungicide” wheat had similar amylose content (149 g/kg starch) to the “without” (148 g/kg starch). The location to give wheat with the highest mean amylose content was Terrington (168 g/kg starch) and the lowest was High Mowthorpe (152 g/kg starch), and the seed rate to give the highest mean amylose was 640 (159 g/kg starch) and the lowest was 40 (155 g/kg starch). Of all the wheat samples, the GB commercial wheat had the greatest mean amylose content (168 g/kg starch) and the 2003 NI wheat the lowest (152 g/kg starch).
Hardness ranged from 8.41 (Napier, Rosemaund S/R 640) to 66.65 (Hussar, Limavady, 1998 NI wheat) using the older SKCS method. Using the more recent SKCS method hardness ranged from −2.94 (Riband, −N, Rosemaund) to 74.11 (Malacca, high N, 2005 NI wheat). Unfortunately, problems occurred with both these methods. The first method could not incorporate all the wheat samples as they were not available and also more recent and accurate methods are available. For the second method, the SKCS NIRS equation, which was developed at CCFRA, was skewed and biased in order to predict samples scanned at AFBI. However, we cannot be certain that the results obtained from the adjusted SKCS equation are correct as the H value (Mahalabonis distance) is not affected by skewing and biasing, only the predicted results. Therefore, the H value was large (average H value of 35.04). Normally, the H value should be less than three, indicating that the samples are similar to those in the sample database.
Using the in vitro rate of starch digestion results, starch was classified as described in the method section of the report. The rate constant was greatest for Buster 67, 1998/99 wheat (4.352% degradation/h) and lowest for Teal, PSC, plot 46 Canadian wheat (1.326% degradation/h).
Protein profiles were classified as described in the method section of the report. The proportion of protein in the high molecular weight (HMW) -glutenin subunits band (Band 1) ranged from 2.1 (Haven 60, 1998/9 NI wheat) to 7.9% (Soissons, 2003), the proportion in the larger low molecular weight (LMW) -glutenin and ω-gliadin subunits (Band 2) ranged from 9.1 (Haven 60, 1998/9 NI wheat) to 18.8% (Robigus, +F, High Mowthorpe, HGCA Project 2979 wheat), the proportion in the smaller LMW-glutenin and ω-gliadin subunits (Band 3) ranged from 10.2 (Aardvark, Downpatrick, 1998/9 NI wheat) to 23.6% (Arklow Sky, GB commercial wheat), the proportion in the α-, β-, γ-gliadin subunits (Band 4) ranged from 24.3 (Spark –N, Terrington, HGCA Project 2979 wheat) to 48.1% (Rialto, Downpatrick, 1998/9 NI wheat) and the proportion of protein in the albumins and globulins band (Band 5) ranged from 20.9 (Robigus, +F, High Mowthorpe, HGCA Project 2979 wheat) to 37.4% (Haven 60, 1998/9 NI wheat).
Animal trials
It was found that there were very highly significant (p<0.001) differences between diet treatments for all the measured parameters (total DMI, LWG and gain:feed,
in vivo viscosity, ME:GE, AME content, ME:Gain, DM retention, ileal dry matter, starch and protein digestibility). Total DMI ranged from 61.6 (Ambrosia, -F, HM) to 85.7 g/d (Buster 71, 1998/99), with fertilizer and fungicide application and seed rate having no significant effect (p>0.05) (
Table 3). Total LWG ranged from 41.9 (Ambrosia, -F, HM) to 64.2 g/d (Buster 71, 1998/99), with wheat treated with fungicide being significantly (p<0.05) greater (10%) than that without. Total gain:feed ranged from 0.67 (Predator, -N, Terr) to 0.82 (Riband, 2004), with significant differences between high and low N levels and seed rate (p<0.05 and 0.01 respectively).
In vivo viscosity ranged from 3.3 (Riband, 2003) to 13.0 (Malacca, high N, 2005), with high N wheat having increased mean viscosity over low (8.6 cps compared with 6.9 cps, p<0.001). Both ME:GE (0.67 (Buster 67, 1998/99) to 0.78 (Predator, -N, HM)) and AME content (12.67 (Buster 67, 1998/9) to 14.71 MJ/kg (Malacca, high N, 2005)) were significantly (p<0.05) affected by high and low N treatments. ME:gain ranged from 16.75 (Soissons, high N, 2005) to 20.65 MJ/kg (Zebedee -N, Terr), with fertilizer and fungicide application and seed rate having no significant effect. DM retention ranged from 0.697 (Napier, S/R 640, Rose) to 0.753 (Napier, high N, 2005), with -N diets giving significantly (p<0.05) higher (0.730) values than +N (0.719). Neither ileal dry matter (0.627 (Claire, high N, 2005) to 0.756 (Consort, 2003)) nor starch digestibility (0.832 (Aardvark, 2004) to 0.972 (Goodwood, low N, 2005)) were significantly (p>0.05) affected by fertilizer and fungicide application and seed rate (
Table 4). However, ileal protein digestibility, which ranged from 0.703 (Consort, high N, 2005) to 0.832 (Savannah, 2004), was significantly (p<0.05) affected by seed rate.