Pasture nutritive value: phenotypic contrast level

Nutritive value of pastures based on perennial ryegrass cultivars with contrasting morphologies is presented in Tables 3.19 and 3.20.

Crude protein (CP)

The morphological contrast affected the CP content of pastures only in spring 2013, when CP % was greater in pastures based on dense cultivars than open cultivars (Tables 3.19 and 3.20).

Metabolisable Energy (ME) and Neutral detergent fibre (NDF)

Open cultivars had greater ME density than dense cultivars in all seasons of both years (Tables 3.19 and 3.20). However there was also a significant difference in the ME density of the two cultivars representing the dense phenotype in all seasons; pastures based on Abermagic AR1 had greater ME than pastures based on Prospect AR37. Moreover, in spring 2012 and in summer in both years, the ME content of pastures based on Abermagic AR1 was not significantly different from the ME of pastures based on Base AR37 (one of the open cultivars) (Tables 3.15 and 3.16).

In addition, dense cultivars had greater NDF content than open cultivars in spring in both years (Tables 3.19 and 3.20). Nevertheless, there was also a significant difference in the NDF content of the two cultivars representing the dense phenotype in these seasons; pastures based on Abermagic AR1 had similar NDF content than pastures based on the two cultivars representing the open phenotype, but lower NDF content than pastures based on Prospect AR37 (the other dense cultivar) (Tables 3.15 and 3.16).

This overlap in ME density and NDF content between cultivars within the dense and open contrasts means that robust conclusions regarding the effect of morphology cannot be drawn.

Table 3.19 Nutritive value of pastures based on perennial ryegrass cultivars with contrasting morphology and heading date during 2012 – 13.

Spring 2012 Summer 2012 - 2013 Autumn 2013

Perennial ryegrass contrasts CP (%DM) ME (MJ/kg DM) NDF (%DM) CP (%DM) ME (MJ/kg DM) NDF (%DM) CP (%DM) ME (MJ/kg DM) NDF (%DM)

Morphology Dense 11.8 12.7 45.5 14.8 11.4 52.4 19.8 12.1 45.1

Open 12.2 13.2 42.9 14.5 11.9 51.4 19.8 12.6 44.9

Heading date Mid 11.3 11.9 50.3 15.4 11.0 54.5 20.7 11.7 47.3

Late 12.0 12.7 46.0 14.2 11.5 52.9 20.1 12.1 47.3 SED 0.46 0.07 0.48 0.44 0.07 0.54 0.31 0.06 0.53 P value Morphology 0.386 < 0.001 < 0.001 0.464 < 0.001 0.085 0.888 < 0.001 0.698 Heading date 0.176 < 0.001 < 0.001 < 0.01 < 0.001 < 0.01 0.053 < 0.001 0.898 Morphology x N 0.743 0.561 0.809 0.487 0.397 0.620 0.238 0.425 0.180 Morphology x clover 0.707 0.152 0.202 0.394 0.508 0.859 0.051 0.279 0.309 Heading date x N 0.609 0.669 0.539 0.904 0.309 0.510 0.993 0.494 0.291

Heading date x clover 0.926 0.626 0.105 0.194 < 0.01 < 0.001 0.771 0.052 0.053

Table 3.20 Nutritive value of pastures based on perennial ryegrass cultivars with contrasting morphology and heading date during 2013 – 14.

Spring 2013 Summer 2013 - 2014 Autumn 2014

Perennial ryegrass contrasts CP (%DM) ME (MJ/kg DM) NDF (%DM) CP (%DM) ME (MJ/kg DM) NDF (%DM) CP (%DM) ME (MJ/kg DM) NDF (%DM)

Morphology Dense 18.7 12.5 47.9 15.9 12.3 47.0 25.3 12.2 48.0

Open 17.8 12.9 46.7 15.6 12.6 46.8 25.6 12.6 47.3

Heading date Mid 17.4 12.3 50.0 18.0 11.8 49.1 26.8 11.9 48.2

Late 18.3 12.6 47.9 15.6 12.3 48.1 25.4 12.1 49.2 SED 0.41 0.05 0.45 0.52 0.05 0.43 0.33 0.07 0.49 P value Morphology < 0.05 < 0.001 < 0.01 0.616 < 0.001 0.702 0.375 < 0.001 0.134 Heading date < 0.05 < 0.001 < 0.001 < 0.001 < 0.001 < 0.05 < 0.001 < 0.01 < 0.05 Morphology x N 0.279 0.861 0.948 0.244 0.064 0.402 0.216 0.492 0.691 Morphology x clover 0.626 0.493 0.399 0.923 0.210 0.874 0.579 0.981 0.281 Heading date x N 0.550 0.136 0.457 0.357 0.984 0.138 0.424 0.671 0.774

Heading date x clover 0.655 0.554 0.127 < 0.05 < 0.01 0.077 0.836 0.556 0.756

Heading date contrast

Nutritive value of pastures based on perennial ryegrass cultivars with contrasting heading dates is presented in Tables 3.19 and 3.20.

Crude protein (CP)

During summer in both years, and in autumn 2014, pastures based on mid heading cultivars had greater CP% than pastures based on late heading cultivars, while the opposite occurred in spring 2013 (Tables 3.19 and 3.20). However, in summer 2013 – 14 there was a significant interaction (P < 0.05) between heading date and clover treatment. The CP content of pastures based on both heading dates were not significantly different when sown with clover, but it was greater for mid heading cultivars than for late heading cultivars in the absence of clover (Table 3.21).

Table 3.21 CP (%DM) content of pastures based on cultivars with contrasting heading date and sown with or without clover.

Summer 2013 - 14

+ clover - clover

Mid heading 19.5 a 16.6 a

Late heading 18.3 _a 13.0 _b

SED within clover treatment 0.73 SED between clover treatments 0.83 Different letters within a column indicate statistical differences.

Metabolisable energy (ME)

Late heading cultivars had greater ME density than mid heading cultivars in all seasons of both years (Tables 3.19 and 3.20).

Significant interactions between heading date and clover treatment were detected in both summers. In summer 2012 – 13, the presence of clover increased significantly the ME density of both heading date contrasts, but this increment was greater for mid than for late heading cultivars. Meanwhile, in summer of the second year, ME density only increased in pastures based on mid heading date cultivars when grown in association with clover (Table 3.22).

Table 3.22 ME density (MJ/kg DM) of pastures based on cultivars with contrasting heading date and sown with or without white clover

Summer 2012 - 13 Summer 2013 - 14 + clover - clover + clover - clover Mid heading 11.3 b 10.6 b 12.0 b 11.7 b Late heading 11.6 a 11.3 a 12.3 a 12.3 a SED within clover treatment 0.10 0.07

SED between clover treatments 0.11 0.08

Neutral detergent fibre (NDF)

In spring in both years, pastures based on mid heading cultivars had greater NDF content than pastures based on late cultivars (Tables 3.19 and 3.20).

In summer in both years, mean NDF content of pastures based on mid heading cultivars (Commando AR37 and Kamo AR37) was also greater than for pastures based on late cultivars (Alto AR37 and One50 AR37). However, in summer 2012 – 13, the NDF content of pastures based on Alto AR37 was not significantly different from the NDF of pastures based on Commando AR37 and Kamo AR37, but it was greater than from pastures based on One50 AR37. Meanwhile, in summer 2013 – 14, the NDF content of pastures based on Kamo AR37 was greater than the NDF content of pastures based on Commando AR37, One50 AR37 and Alto AR37 (Tables 3.15 and 3.16). This confounding effect is also present when considering the interaction with clover treatment in summer 2012 – 13.

In autumn 2014, late cultivars had greater NDF content than mid cultivars (P = 0.031).