Interaction of early lactation pasture allowance and duration on cumulative milk production

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Interaction of early lactation pasture allowance and duration on cumulative milk production

E. Kennedy, Luc Delaby, J.R. Roche, Brendan Horan, E. Lewis

To cite this version:

E. Kennedy, Luc Delaby, J.R. Roche, Brendan Horan, E. Lewis. Interaction of early lactation pas-

ture allowance and duration on cumulative milk production. 27. General meeting of the European

Grassland Federation (EGF), Jun 2018, Cork, Ireland. �hal-01827930�

Grassland Science in Europe, Vol. 23 – Sustainable meat and milk production from grasslands 455

Interaction of early lactation pasture allowance and duration on cumulative milk production

Kennedy E. ¹ , Delaby L. ² , Roche J.R. ³ , Horan B. ¹ and Lewis E. ⁴

1 Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland;

2 INRA, AgroCampus Ouest, UMR Pegase, 35590 Saint-Gilles, France; ³ Down to Earth Advice Ltd, P.O.

Box 12520, Chartwell, Hamilton, New Zealand; ⁴ Devonish, Lagan House, 19 Clarendon Road, Belfast, BT1 3BG, Northern Ireland, UK

Abstract

Fluctuations in spring grass growth can create deficits in grass supply during the early lactation period in Irish dairy production systems. The objective of this experiment was to investigate if different pasture allowances offered to early lactation grazing dairy cows for varying time durations influenced cumulative milk yield and composition produced during the first 33 weeks of the experiment. The two-year experiment offered cows one of four pasture allowances (PA; 60, 80, 100 or 120% of calculated intake capacity) for either two or six weeks. Once the two- and six-week time durations had elapsed, all cows were offered 100% of intake capacity. Data were analysed using mixed models in PROC MIXED (SAS;

v9.4). There was a tendency (P = 0.06) for an interaction between duration and PA for cumulative milk yield. Offering 120% for six weeks increased milk yield (4,270 kg cow ^-1 ) compared to 80 × 2, 100 × 2, 60

× 6 and 80 × 6. All cows other than the 120 × 6 were similar (3,957 kg cow ^-1 ). There was no effect of PA or duration on milk fat, protein and lactose content. This suggests that when cows are offered more than they require to achieve IC for a six-week period (120 × 6), cumulative milk yield is higher compared to those offered a restricted PA for an extended period of time (six weeks).

Keywords: pasture allowance, early lactation, dairy cow

Introduction

Overcoming fluctuations in milk price to help maintain farm profitability can be achieved by maximising utilisation of grazed pasture, the cheapest feed available in temperate climates (Finneran et al., 2012). However, pasture availability deficits in Ireland can arise due to low early spring growth.

This is compounded by increasing herd size and more compact calving patterns (ICBF, 2017) creating a higher demand for pasture in the early spring period. A 10-week restriction of pasture allowance (PA) in early lactation has previously been shown to reduce immediate milk production but cumulative milk production was unaffected (Ganche et al., 2013). However, fluctuations in pasture availability are more likely to occur for shorter periods of time in spring. The objective of this experiment was to investigate if different pasture allowances offered to early lactation grazing dairy cows for either two or six weeks influenced cumulative milk production produced during the 33 week long experiment.

Materials and methods

Ninety six dairy cows were assigned to a randomised complete block design with a 4 × 2 factorial arrangement of treatments in an experiment which was repeated over two years (25 March to 27 November 2014 and 9 March to 23 November 2015). Cows (41 primiparous and 55 multiparous in year one (Y1); 24 primiparous and 72 multiparous in year two (Y2)) were balanced on calving date (17 February, s.d. 15.5 d, Y1; 9 February, s.d. 8.4 d; Y2), breed (Holstein-Friesian, n = 52; Jersey × Holstein- Friesian, n = 38; Norwegian Red, n = 6, Y1; Holstein-Friesian, n = 43; Jersey × Holstein-Friesian, n = 34; Norwegian Red, n = 19, Y2), lactation number (2.4, s.d. 1.61, Y1; 2.6, s.d. 1.50, Y2) and production variables from the two weeks prior to the start of the experiment: milk yield (22.6, s.d. 4.20 kg d ^-1 , Y1;

25.2, s.d. 3.88 kg d ^-1 , Y2), milk fat (55.8, s.d. 9.18 g kg ^-1 , Y1; 51.7, s.d. 7.10 g kg ^-1 , Y1), milk protein

456 Grassland Science in Europe, Vol. 23 – Sustainable meat and milk production from grasslands (34.5, s.d. 3.00 g kg ^-1 Y1; 34.8, s.d. 2.42 g kg ^-1 Y2) and milk lactose (46.9, s.d. 1.87 g kg ^-1 , Y1; 47.0, s.d.

1.34 g kg ^-1 , Y2) concentration, milk solids yield (2.03, s.d. 0.408 kg d ^-1 Y1; 2.17, s.d. 0.350 kg d ^-1 Y2), bodyweight (BW; 469, s.d. 68.2 kg, Y1; 523, s.d. 58.1 kg, Y2) and body condition score (BCS; 3.09, s.d.

0.193, Y1; 3.17, s.d. 0.167, Y2). Cows were then randomly assigned to one of four PA (60, 80, 100 or 120% of intake capacity; IC) for either two or six weeks. Once the two- and six-week time durations had elapsed, all cows were offered 100% of IC. Intake capacity was calculated using the equation of Faverdin et al. (2011) based on age, parity, days in milk, BW, BCS and potential milk yield. Pasture allowance (>

3.5 cm) for the 60, 80 and 120% treatments were calculated based on the IC of the 100×6 treatment.

Treatment groups grazed adjacent to each other to ensure similar HM was offered. Herbage mass (HM;

> 3.5 cm) was measured twice weekly by cutting 6 strips (120 m ² ) per grazing area. As HM was similar between treatments daily area allocations differed. Pre- and post-grazing sward heights were measured daily using a rising plate meter. Fresh pasture areas were offered after each milking while treatments were being imposed and on a 24-hour basis thereafter. Milk yield was recorded daily, individual cows daily yields were summed to calculate cumulative milk yield following the 33-week experimental period. Data were analysed using covariate analysis and mixed models in SAS v9.4. Terms for year, parity, breed, PA, duration and the interaction of PA and duration were included. Pre-experimental values were used as covariates in the model.

Results and discussion

There was a tendency (P = 0.06) for an interaction between duration and PA for cumulative milk yield (Figure 1). Cows assigned to the 120 × 6 treatment had a higher cumulative milk yield (4,270 kg cow ^-1 ) than the 80 × 2, 100 × 2, 60 × 6 and 80 × 6 treatments. All cows other than the 120 × 6 were similar (3,957 kg cow ^-1 ). Following the first ten weeks of the experiment (six weeks when different PA were imposed and four weeks when 100% IC was offered) the 120×6 treatment produced more milk (+ 44 kg cow ^-1 ) than all other treatments during this period. This was due to their higher dry matter intake; in this study there was a linear response to PA when DMI was measured at weeks two and six of the experiment;

for every 10% increase in PA, DMI increased by 0.65 and 0.56 kg cow ^-1 day ^-1 , respectively (Kennedy et al., 2018). However, a six-week period is relatively short in the context of a 33 week long experiment;

consequently it gave the other treatments an opportunity to increase their milk production when IC was restored to 100%. Nevertheless, a six-week PA restriction (60 × 6 and 80 × 6) in early lactation did

3,500 3,600 3,700 3,800 3,900 4,000 4,100 4,200 4,300 4,400

60x2 80x2 100x2 120x2 60x6 80x6 100x6 120x6

kg cow

Treatment

ab ab

a

a

a

a

ab

b

Figure 1. Effect of early lactation treatment on 33-week milk yield (P = 0.06).

Grassland Science in Europe, Vol. 23 – Sustainable meat and milk production from grasslands 457 reduce cumulative milk yield in comparison to offering 120% IC however, cumulative milk yield of these treatments was similar to the control treatment (100 × 6). As the 100 × 6 and 120 × 6 treatments were similar it suggests that there was no advantage in offering additional grass over and above cows IC in early lactation. There was no effect of PA or duration on 33-week average milk fat (4.75%), protein (3.61%) and lactose (4.71%) content.

Conclusion

The results of this experiment suggest that when cows are offered more than they require to achieve IC for a six-week period (120×6), cumulative milk yield is higher compared to those offered a restricted PA for an extended period of time (six weeks). However, decisions on feeding the early lactation dairy cow need to incorporate effects on animal behaviour and welfare as well as production.

Acknowledgements

The authors wish to thank the Moorepark farm staff and technicians for their care of the experimental animals and assistance with experimental measurements. This experiment was funded by Teagasc Core Funding and the Irish Dairy Levy.

References

Faverdin P., Baratte C., Delagarde R., and Peyraud J.L. (2011) GrazeIn: a model of herbage intake and milk production for grazing dairy cows. 1. Prediction of intake capacity, voluntary intake and milk production during lactation. Grass and Forage Science 66: 29-44.

Finnernan, E., P. Crossan, P. O’Kiely, L. Shalloo, D. Forristal, and M. Wallace (2012) Stochastic simulation of the cost of home- produced feeds for ruminant livestock systems. Journal of Agricultural Science, Cambridge. 150: 123-139.

Ganche E., Delaby L., O’Donovan M., Boland T.M., and Kennedy E. (2013) Direct and carryover effect of post-grazing sward height on total lactation dairy cow performance. Animal 7: 1390-1400.

Kennedy E., Delaby L., Roche J.R., Horan B. and Lewis E. (2018) Interaction of early lactation pasture allowance and duration

on dry matter intake. Proceedings of the 27

General Meeting of the European Grassland Federation, Cork, Ireland, 17-21 June,

2018 (this volume).