1. Effect of Lolium perenne L. cultivar on milk performance and DMI in spring to early-summer M. McEvoy 1, M. O’Donovan 1, J.P. Murphy 1, N. Galvin 1 Animal & Grassland Research and Innovation Centre, Teagasc, Moorepark

2. BACKGROUND Limited research on effect of cultivar on animal performance. Why? Cost Belief – between cultivar differences are small and could be predicted from cutting Benefits of animal production trials Detection of anti-quality factors in promising cultivars Test persistency under field conditions (plant pulling/ treading) Identify cultivars which increase animal performance Improve farm profitability

3. …Background Most valuable pasture is that which is converted to milk Farmers want to know superior cultivars before they reseed – not find out afterwards!! Requirement to evaluate cultivars under grazing animals To determine differences in Sward characteristics Nutritive value Intake Animal production Identify sward characteristics which influence animal performance

4. OBJECTIVE To quantify the difference in milk performance and DM intake of lactating dairy cows offered 4 perennial ryegrass cultivars with different sward structures

5. MATERIALS & METHODS 4 perennial ryegrass cultivars were sown in 2009 as monocultures balanced on ploidy and heading date Cv1 (Tetraploid; 24 May) Cv2 (Tetraploid; 31 May) Cv3 (Diploid; 22 May) Cv4 (Diploid; 28 May) Cultivars managed with similar rotation length fertiliser opening and closing dates

6. EXPERIMENTAL DESIGN 4×4 latin square 14 day periods (9 days adaption & 5 days measurement) 24 multiparous lactating Holstein Friesian cows Experimental period – March to May 2011 Offered 16 kg DM herbage cow -1 d -1 (>4 cm) And 1 kg DM concentrate

7. RESULTS

8. RESULTS – SWARD Cv1Cv2Cv3Cv4SEP-value Herbage mass (kg DM ha -1 )1015 a 1099 b 1142 b 1299 c 280.001 Pre height (cm)8.5 a 8.4 a 8.8 ab 9.1 b 0.20.09 Density (kg DM/cm/ha)208 a 246 b 285 c 327 d 100.001 Area (m 2 cow -1 d -1 )193 a 153 b 150 bc 123 c 100.001 Post height (cm)3.7 a 3.9 ab 4.1 b 3.9 ab 0.010.05

9. Leaf, Stem and Dead proportions 0.73 0.74 0.80 0.13 b 0.14 ab 0.23 b 0.20 a 0.07 a 0.12 b 0.04 c Leaf NS Stem P<0.05 Dead P<0.001

10. EXTENDED TILLER AND PSEUDOSTEM HEIGHT – PRE GRAZING 20.4 22.9 19.9 20.1 5.7 ac 6.2 bc 6.4 b 5.4 a

11. RESULTS - ANIMAL 31.4 ab 30.1 b 30.2 b 32.0 a

12. RESULTS - ANIMAL Cv1Cv2Cv3Cv4SECultivar Milk yield (kg/d)31.4 ab 32.0 a 30.2 b 30.1 b 0.80.05 Milk fat (g/kg)46.043.043.745.70.1NS Milk protein (g/kg)33.6 a 32.6 b 33.8 a 0.040.01 Milk lactose (g/kg)47.147.247.347.20.03NS Milk solids (kg/d)2.49 a 2.44 a 2.30 b 2.36 ab 0.10.01 Dry Matter Intake (kg d -1 ) 16.1 a 17.5 b 16.4 a 16.1 a 0.40.05

13. RESULTS - ANIMAL 2.49 a 2.44 a 2.30 b 2.36 ab 31.4 30.1 30.2 32.0

14. SUMMARY Higher density and herbage mass on Cv3 and Cv4  less area offered per day Cultivar did influence intake and animal performance  milk yield – higher on Cv1 & Cv2

15. CONCLUSION Significant differences between cultivars in sward characteristics Cultivars do influence milk production & this cannot be predicted accurately under cutting trials Sward structure appears to be a key driver Higher sheath height/ stem proportion reduces quality Sheath height acts as barrier to intake Resulting decline in animal performance Requirement to evaluate cultivars under animal production studies To determine traits which influence animal peformance

16. ACKNOWLEDGEMENTS Moorepark technical and farm staff for assistance in measurements, laboratory analysis and care of animals Irish Dairy Farmers - Dairy Levy funding

17. Comparison of 2010 and 2011 results 20102011Level of Significance Cv1Cv2Cv3Cv4Cv1Cv2Cv3Cv4YearVarYear * Var Milk yield (kg/d) 23.222.7 21.828.528.827.3 0.001 NS Milk solids (kg/d) 1.781.741.731.672.182.152.032.070.001 0.07