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The effect of opening farm cover on early lactation milk and milk solids production
A. Claffey, Luc Delaby, T.M. Boland, M. Egan
To cite this version:
A. Claffey, Luc Delaby, T.M. Boland, M. Egan. The effect of opening farm cover on early lactation
milk and milk solids production. 27. General meeting of the European Grassland Federation (EGF),
Jun 2018, Cork, Ireland. �hal-01827925�
Grassland Science in Europe, Vol. 23 – Sustainable meat and milk production from grasslands 133
The effect of opening farm cover on early lactation milk and milk solids production
Claffey A.
1,2, Delaby L.
3, Boland T.M.
2and Egan M.
11
Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland;
2
School of Agriculture and Food Science, University College Dublin, Ireland;
3INRA, AgroCampus Ouest, UMR Pegase, 35590 Saint-Gilles, France
Abstract
Grass availability in spring is highly variable. Including grazed grass in the diet of early lactation dairy cows can result in improved animal performance. The objective of this experiment was to determine if a high opening farm cover (OFC) can impact on early lactation milk production in a spring calving system. In spring 2017 (6 February – 25 April), 45 cows were randomly assigned to one of three (n = 15) OFC; High (H) (974 kg DM ha
-1), Medium (M) (863 kg DM ha
-1) and Low (L) (624 kg DM ha
-1). All cows were allocated an equal daily grazing area. Post-grazing sward height and daily herbage allowance (DHA) were measured daily and pre-grazing herbage mass (> 3.5 cm) twice weekly. Milk yield was recorded daily and composition once weekly. There was a significant effect of treatment on daily milk yield (P < 0.05); the H treatment had greater production than the M treatment (+1.9 kg cow
-1). Milk composition did not differ with treatment. Daily herbage allowance was greater (P > 0.05) on the H treatment than the L treatment, with the M treatment intermediate. Higher OFC increases grass availability on the farm which increases DHA, resulting in increased milk production performance.
Keywords: herbage allowance, pasture availability, early lactation, milk production
Introduction
The supply of feed in the form of grazed grass generally exceeds the feed demand of spring-calving dairy cows from mid-April to mid-September. There is, however, little grass growth from November to February (Dillon et al., 1995), resulting in low grass availability in early spring when a significant quantity of milk is produced in spring calving milk production systems. Positive effects of including grazed grass in the diet of early lactation cows on animal and sward productivity have been reported (Kennedy et al., 2007, McEvoy et al., 2008). Dry matter intake (DMI) in early lactation is a critical factor influencing animal performance and increasing daily herbage allowance (DHA) can result in increased milk production (Kennedy et al., 2007). The increase in DMI post calving to peak intake capacity occurs at a vulnerable period in the grazing season. As a result, it is essential to ensure adequate herbage is available to support DMI requirements until grass growth equals animal demand on farm. If grass is not available in adequate supply in early spring, concentrate supplementation is required in conjunction with grass silage to achieve similar production to cows on a high grass DHA (Kennedy et al., 2005). In recent years data from Pasturebase Ireland (Hanrahan et al., 2017) has shown that farms in Ireland do not have sufficient herbage amassed at turnout in spring (opening farm cover; OFC) to meet feed demand, particularly as herd size increases and this warrants an investigation into the effect of OFC on the early lactation milk production of a spring calving dairy cow.
Materials and methods
An experiment was established at Teagasc, Animal and Grassland Research Innovation Centre,
Moorepark, Fermoy, Co. Cork, Ireland in 2017. Opening farm cover, the average grass available on per
hectare basis on 1 February prior to the commencement of grazing, was visually quantified using the farm
cover technique described by O’Donovan et al. (2002). A range of OFC’s was established by imposing
three closing management treatments during autumn 2016. A proportion of the farm was closed each day
using the autumn rotation planner (Teagasc, 2009) from (1) 25 September to 9 November to achieve a
134 Grassland Science in Europe, Vol. 23 – Sustainable meat and milk production from grasslands high OFC (H); (2) 10 October to 24 November to achieve a medium OFC (M); and (3) 24 October to 9 December to achieve a low OFC (L). In spring (6 February – April), 45 (12 primiparous and 33 multiparous) spring calving dairy cows were selected and blocked according to calving date, lactation number, breed, pre-experimental milk production variables (day three to eight), pre-experimental body weight and body condition score and randomly assigned to one of three treatments (H, M and L) (n = 15).
All treatments were stocked at 2.9 cows ha
-1. All cows were allocated a fixed daily area as specified by the spring rotation planner (Teagasc, 2009). Fresh pasture was allocated after each milking and on-off grazing (Kennedy et al., 2011) was used as a management tool to graze in inclement weather. Pre- (PreGSH) and post-grazing sward height (PostGSH) were measured daily using a rising plate meter (Jenquip, Feilding, New Zealand). Herbage mass (> 3.5 cm; HM) was measured twice weekly by cutting two strips from each paddock to be grazed next with an Etesia mower (Etesia UK Ltd., Warwick, UK). Daily herbage allowance was calculated using the measured herbage mass and the area allocated to the cows to determine kg grass DM offered per cow. All treatment groups were offered the same quantity of concentrates per cow and the quantity fed on a daily basis was determined by the requirement of the M treatment to maintain a grazing residual ≥ 3.5 cm. All cows received a total of 215 kg concentrate over the experimental period. Silage was supplemented to an individual treatment when PostGSH dropped below 3 cm. Milk yield was recorded daily (Dairymaster, Causeway, Co. Kerry, Ireland) and milk composition (fat and protein concentrations) was measured weekly using MilkoScan 203 (DK-3400, Foss Electric, Hillerød, Denmark). Milk solids (MS) yield was calculated as the sum of milk fat and protein yield. Milk production variables were analysed using PROC MIXED in SAS version 9.4 (SAS Institute Inc., Cary, NC, USA). Terms used in the model included treatment, breed, parity, days on experiment and pre-experimental milk production variables.
Herbage variables were analysed using PROC MIXED. The terms included in the model were treatment, week and rotation.
Results and discussion
The OFC on 1 February was 974, 863 and 624 kg DM ha
-1for the H, M and L treatments, respectively.
Treatment had a significant effect (P < 0.05) on daily milk yield. The H treatment had a greater daily milk yield (23.5 kg cow
-1) compared to M (21.6 kg cow
-1), with the L intermediate (22.3 kg cow
-1) (Table 1).
There was, however, no significant effect of treatment on milk solids yield (H = 1.89, M= 1.82 and L = 1.81 kg MS cow
-1daily). Milk composition was similar for all treatments (fat = 47.7 g kg
-1and protein = 34.3 g kg
-1). In the current study DHA was significantly greater for the H compared to the L treatment (P
< 0.05; +3.2 kg DM cow
-1). A total of 77, 89 and 99 kg silage DM cow
-1were offered to the H, M and L treatments, respectively. There were also significant differences in total DMI (grass + silage + concentrate) (P < 0.05); H had a daily intake of 16 kg DM cow
-1while the L had a daily DMI of 12.3 kg DM cow
-1and the intake of the M treatment was intermediate (14.2 kg DM cow
-1). Treatment had a significant effect on pre-grazing HM (P < 0.05), the H treatment had a pre-grazing HM of 1,355 kg DM ha
-1(+ 388 kg DM ha
-1greater than the L treatment), the pre-grazing HM of the M treatment was intermediate (1200 kg DM ha
-1), similar to Roche et al. (1996) who found significantly lower HM on late closed swards compared to early closed swards the following spring. There was no effect of treatment on PostGSH (3.79 cm).
Table 1. The effect of opening farm cover high (H) (974 kg DM ha
-1), medium (M) (863 kg DM ha
-1) and low (L) (624 kg DM ha
-1) on daily milk and milk solids yield, and milk composition during the experimental period (6 February to 25 April).
Treatment
1H M L Standard error P-value
Milk yield (kg cow
-1) 23.5
a21.6
b22.3
ab0.48 0.027
Fat (g kg
-1) 46.9 48.8 47.5 0.11 0.435
Protein (g kg
-1) 34.2 35.2 33.4 0.05 0.099
Milk solids yield (kg cow
-1) 1.89 1.82 1.81 0.051 0.421
1 Treatments within a row with the same letter are not significantly different.
