The effect of stoking rate and calving date on the dry matter intake and feed efficiency of three pasture based systems of milk production

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The effect of stoking rate and calving date on the dry matter intake and feed efficiency of three pasture based

systems of milk production

J. Mccarthy, B Mccarthy, K. M. Pierce, Luc Delaby, Norann Galvin, A.

Brennan, Brendan Horan

To cite this version:

J. Mccarthy, B Mccarthy, K. M. Pierce, Luc Delaby, Norann Galvin, et al.. The effect of stoking

rate and calving date on the dry matter intake and feed efficiency of three pasture based systems of

milk production. Agricultural Research Forum 2013, 2013, Tullamore, Ireland. Agricultural Research

Forum, 2013, Proceedings of the Agricultural Research Forum. �hal-01210848�

The effect of stoking rate and calving date on the dry matter intake and feed efficiency of three pasture based systems of milk production.

J. McCarthy

, B. McCarthy

, K.M. Pierce

, L.

Delaby

, N. Galvin

, A. Brennan

and B. Horan

*Animal and Grassland Research and Innovation Centre, Teagasc Moorepark, Fermoy, Co. Cork.

School of Agriculture, Food Science & Veterinary Medicine, UCD, Belfield, Dublin 4.

INRA, AgroCampus Ouest, UMR 1348, Physiologie, Environnement et Génétique pour l'Animal et les Systèmes d'Elevage, F-35590 Saint-Gilles, France.

Introduction

The efficiency of milk production in Ireland is dependent on systems based upon the extensive use of cheap high quality grazed grass (Horan et al., 2005). At a national level, such systems would be greatly enhanced through a combination of higher stocking rates and an earlier and more compact calving pattern to maximise grass utilisation (McCarthy et al., 2012). The primary objective of the study was to quantify the impact of stocking rate (SR) and calving date (CD) on the dry matter (DM) intake of spring calving pasture-fed dairy cattle.

Materials and Methods

In each of 3 years (2009, 2010 and 2011), 138 spring calving HF dairy cows with an average Economic Breeding Index of €148 were randomly assigned to one of two mean calving date treatments: Early calving (mean calving date: 14

of February) and Late calving (mean calving date: 1

of March). Within each calving group, a total of 46 animals were allocated to one of three SR treatments, Low (2.51 cows/ha), Medium (2.92 cows/ha) and High (3.28 cows/ha). In total there were 6 individual farmlets in each year, with 23 cows in each.

Once allocated, all animals remained on the same treatment for the duration of the study. Cows were turned out to pasture in early February with SR treatments managed separately and calving date treatments within each SR managed similarly. Different grazing intensities were imposed on each SR, with target post-grazing residual heights of 4.5-5.0, 4.0-4.5, and 3.5-4.0 for the low, medium and high SR respectively. Individual animal intakes were estimated using the n-alkane technique (Mayes et al., 1986) on three occasions in each year at pasture; in April, May and September. During each intake period, all cows

were dosed twice daily for a 12 day period with 500 mg of C32. Faecal grab samples were collected twice daily from each cow in the last 6 days of each period and bulked for analysis. Herbage samples were collected manually to represent herbage grazed after both the morning and evening milking on day 6 to 11 of each measurement period. The ratio of herbage C33 to dosed C32 was used to estimate intake. Milk yield was recorded each day during the study and live-weight weekly. The animal production data for the measurement periods were analysed using PROC Mixed of SAS (SAS, 2002). Cow was included as a random effect while year, stocking rate, calving date, and period were included as fixed effects.

Results and Discussion

There was a significant effect of stocking rate on milk production, bodyweight and DM intake (Table 1). The Low SR treatment achieved the highest daily milk and MS yield and also had a higher daily grass and total DM intake while the High SR was lowest and the Medium SR was intermediate. Calving date also had a significant effect on milk production and approached significance for grass and total DM intake. The late calving date group achieved higher milk and milk solids yields per cow. The interaction of SR and calving group for grass and total DM intake approached significance due to the comparably higher intakes of the Medium and High SR treatments in the late calving group.

Conclusions

This study shows that in a grass-based system, milk production and individual animal bodyweight will be reduced as stocking rate increases due to a reduction in grass DM intake. The presence of a SR by calving group interaction for grass and total DM intake also indicates that the reduction in individual animal intake and milk production performance at higher SR can be effectively reduced by delaying calving date.

References

Horan, B., Faverdin P., Delaby L., Buckley F., Rath M.

and Dillon P. (2006) Animal 82: 435-444.

Mayes, R.W. Lamb, C.S. and Colgrove, P.M. J. (1986) Agric Sci, 107: 161-170.

McCarthy, B., Pierce, K.M., Delaby, L., Brennan, A., Fleming, C. and B. Horan. (In press) Grass & Forage Sci.

Statistical Analysis Systems Institute. 2002.

Cary, NC, USA.

Table 1. Effect of stocking rate and herd mean calving date on milk production and DM intake.

Calving group Early Late Significance

Stocking rate Low Medium High Low Medium High SE

SR CD SR x CD Milk yield (kg/cow/d) 21.8 19.5 19.3 22.7 20.7 20.9 0.31 *** ***

MS

yield (kg/cow/d) 1.6 1.5 1.5 1.7 1.6 1.5 1.57 *** * Bodyweight (kg) 515 496 494 514 506 500 4.0 *** 0.13

Daily intake (DM/cow)

Concentrate 1.0 1.0 1.0 1.0 1.0 1.0

Grass 14.9 14.3 12.8 14.9 14.3 13.5 0.21 *** 0.12 0.13

Total 15.9 15.3 13.8 15.9 15.3 14.5 0.19 *** † 0.10

1

Significance: ***= P<0.001, **= P<0.01, *=P<0.05, †=P<0.10.

2

s.e. – standard error,

3

MS = Milk solids (fat plus protein)

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