Growth of weaned Friesian bull calves on a herb sward or with concentrate supplementation during late summer and early autumn

ABSTRACT

Growth rates of weaned bull calves in late summer/early autumn can be low in a ryegrass/white clover-based system. This experiment compared the liveweight gain of weaned bull calves (n = 18 per treatment per year, in 3 replicates of 6 bulls) grazed on a herb sward comprised of chicory, plantain, red clover and white clover with bulls grazed on either pasture supplemented with 1.8 kg DM/day of concentrate, or pasture without supplementation. The experiment was repeated over three years. Bulls grazed on the herb sward grew faster (P < .05) than bulls grazed on pasture with or without concentrate supplementation. Liveweight gain of bulls grazed on pasture was less than for bulls supplemented with concentrate in two of the three years (P < .05). A herb sward is a better quality alternative to late summer/early autumn pasture, and could be used to increase liveweight gain of bulls during this period.

KEYWORDS:

• Bulls
• weaned calves
• Friesian
• growth
• pasture
• herb sward
• concentrate
• New Zealand

Introduction

Friesian bull calves from the dairy industry are widely used for beef production in New Zealand (Morris & Hickson 2016). The bull-beef system typically involves artificially reared calves that are weaned off milk and concentrate by 100 kg live weight at approximately 12 weeks of age (Morris & Hickson 2016). Growth rate is a key driver of economic and biological efficiency in a bull-beef system; therefore, achieving high growth rates in young, weaned beef calves is important. Bulls that grow faster have increased efficiency of liveweight gain and reach target weights earlier than bulls that grow slower, thus increasing the productivity and profitability of a bull-beef system.

The majority of New Zealand’s beef cattle systems are based on a ryegrass or a ryegrass/white clover pasture (Waghorn & Clark 2004). Ryegrass can have high fibre content, especially during the summer period where dry environmental conditions and the reproductive state of ryegrass reduces its nutritive value (Burke et al. 2002; Litherland et al. 2002). Growth rate of bull calves has been reported to be 0.4–0.7 kg/day during the summer/autumn period on a hill country pasture (McRae 1988; Cosgrove et al. 2003), whereas they can grow at 1.2 kg/day during late autumn (Coutinho et al. 1998) when pasture is of better quality (Machado et al. 2005) and allowance are greater.

Methods of increasing the nutritive value of feed on offer to weaned calves during summer and autumn are of interest in a bull-beef system. Nutritive value of the diet can be increased by adding a high-quality concentrate supplement. Alternatively, previous research examining growth rates of weaned dairy heifers during their first summer and autumn has identified the potential for increased growth rates of heifers fed alternative herbages (either lucerne, or a plantain, chicory, red and white clover mixed sward) with improved nutritive value compared with traditional ryegrass/white clover pasture (de Clifford et al. 2014; Handcock et al. 2015). A plantain, chicory, red and white clover mixed sward has also been used to increase the growth rate of lambs during the summer and autumn, compared with lambs grazing a ryegrass/white clover sward (Somasiri et al. 2015a, 2015b).

The aim of this experiment was to quantify the growth rates that could be achieved in young, weaned Friesian bull calves offered a plantain, chicory, red and white clover mixed-sward or a concentrate supplement compared with a ryegrass and white clover pasture during their first summer and autumn.

Materials and methods

Animals and treatments

The experiment was conducted over a three-year period, using a new cohort of 54 weaned Friesian bull calves each year. Bulls were allocated to one of three treatments, and to one of three replicates within each treatment. Each replicate contained six bulls, and all replicates and treatments were balanced for initial live weight. The experimental period began on 17 January 2013 (year one), 26 November 2013 (year two), and 2 December 2014 (year three). Initial live weight (L.S.M. ± S.E.M.) of the bulls was 172 ± 4.0 kg, 110 ± 2.3 kg and 128 ± 2.3 kg in years one, two and three, respectively.

The nutritional treatments were ‘herb sward’, ‘pasture’ and ‘concentrate’. Bulls in the herb sward treatment were offered a mixed sward of chicory (Cichorium intybus), plantain (Plantago lanceolata), red clover (Trifolium pratense) and white clover (Trifolium repens). Bulls in the pasture treatment were offered an Italian ryegrass (Lolium multiflorum) and white clover (Trifolium repens) pasture. Bulls in the concentrate treatment were offered pasture and 1.8 kg DM/bull/day of commercial calf concentrate (Denver Stock Feeds, Palmerston North, NZ). In year one, the pasture offered to bulls in the concentrate treatment was an established sward of mixed species (predominantly brown top, ryegrass and sweet vernal), whereas in years two and three these bulls were grazed on the same pasture offered to the bulls in the pasture treatment. The concentrate supplement was 90% DM and contained 12.5 MJ ME/kg DM and at least 16% crude protein (CP) on a DM basis. Bulls fed herb sward were transitioned to their treatments over a 10-day period during which they spent a progressively longer period of the day grazing the herb sward each day. Bulls fed concentrate were also gradually transitioned to the concentrate during this 10-day transition period, and were offered 1 kg concentrate/bull/day for 5 days, then 1.5 kg concentrate/bull/day for the next 5 days. The experiment began at the end of this transition period. Bulls consumed all concentrate offered every day of the experiment.

Bulls in all treatments were allocated to a new grazing area each week, or earlier if any one of the three replicates within the treatment reached the minimum post-grazing herbage mass of 1600 kg DM/ha. The duration of the feeding treatments was determined by the availability of sufficient herb sward to achieve ad libitum intakes (grazing height greater than 8 cm; Wright 1986). Dry conditions, historically atypical for the region, were recorded in each of the three years (climatic data was collected from a New Zealand Institute of Water and Atmospheric Research climate station, located approximately 2.75 km from the study site). In years one and two, rainfall was 60% and 69% of the 10-year average during the experimental period, respectively. In year three, rainfall was similar to the 10-year average over the whole period of the experiment, but only 64% of the 10-year average in the first 2 months of the experiment. In year one, at the time that there was insufficient herb sward to allow ad libitum intakes, the experiment was ended (Table 1). In year two, the bulls were removed from all treatments and grazed in a single herd under commercial conditions until sufficient herb sward existed to support ad libitum intakes, at which time bulls were returned to their original replicates and the experiment resumed. This period is referred to as the ‘off-treatment period’ (OT) (Table 1). In year three, during the OT, bulls were removed from the herb sward but the replicate groups remained separate. All replicates from all treatments grazed similar ryegrass-based pasture until such time as the herb sward had regrown to a minimum pre-grazing height of 15 cm. During year three, off-treatment period bulls in the concentrate treatment continued to receive their daily concentrate allowance in order to reflect the drought-tolerance of concentrate supplementation. Once experimental feeding resumed at the end of the off-treatment periods (Table 1), management and treatments were as they had been prior to the suspension of grazing the herb sward. In years two and three, the experiment continued until late May/early June when the herb sward was rested for winter.

Table 1. Date and length of the experimental periods in each of the three years of the experiment.

	Year 1	Year 2	Year 3
Period 1
Start	17 January 2013	26 November 2013	2 December 2014
End	6 March 2013	25 March 2014	13 February 2015
Days	48	119	73
Off period
Days		41	63
Period 2
Start		5 May 2014	17 April 2015
End		3 June 2014	21 May 2015
Days		29	34

All bulls were drenched to individual live weights (1 ml per 10 kg) every four weeks beginning at the start of the transition period with Matrix C oral drench (Merial New Zealand, Auckland, NZ). At the start of each year, blood samples were taken using coccygeal venepuncture to ascertain serum copper, selenium and vitamin B12 concentrations were within the normal reference ranges. The normal reference ranges were 8.0–20.0 µmol/l for copper, 150–3500 nmol/l for selenium and 80–1000 pmol/l for vitamin B12 (New Zealand Veterinary Pathology Ltd., Palmerston North, New Zealand). In year two, cobalt concentration was below the normal range, and all bulls were injected with Cobalex 2000 B12 cobalt injection (Jurox Pty Ltd, Rutherford, NSW, Australia). Blood samples were collected again for 10 bulls from each treatment at the end of the experiment each year, which confirmed all values were within the normal range.

Measurements

Unfasted live weight of the bulls was recorded at the start and end of each treatment period (Table 1). Average daily liveweight gain was calculated for each bull as the live weight at the end of a period less the live weight at the start of the period, divided by the number of days in the period.

Herbage samples representative of herbage intake of the grazing calves were hand-plucked for herbage quality analysis. These samples were taken pre-grazing at weekly intervals in year one and at 4-weekly intervals in years two and three, and were pooled across replicates within treatments. Samples were freeze dried then analysed using an in vitro digestibility analysis (Roughan & Holland 1977) to measure: in vivo organic matter digestibility (OMD%), dry matter digestibility (DMD%), and digestible organic matter in the dry matter (DOMD%). CP was analysed by wet chemistry (Dumas 1831). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) content were determined by the method of Van Soest et al. (1991). Metabolisable energy (ME) was calculated as ME = DOMD% × 0.16 (Geenty & Rattray 1987).

Pre- and post-grazing herbage mass was measured by cutting all herbage from within four randomly selected 0.18 m² quadrats to ground level (Frame 1993) within each replicate. Samples were washed and then dried in a draught oven at 75°C for 24–48 h until a constant weight was reached (Grasslands Research Institute 1961) before being weighed again. The mean of the 4 samples was calculated for each replicate. These measurements were collected every week from each replicate in years one and two. In year three, these measurements were collected every four weeks.

Botanical composition of the herbage in each treatment was measured by cutting a single quadrat to ground level in each of the three replicates within each treatment on each occasion. Samples were sorted into chicory, plantain, red clover, white clover, grasses (including ryegrass and other grasses), weed species and dead matter of any species. Within chicory, plantain and grasses, leaves were separated from stems. Seed heads were grouped with stems. Once separated, samples were dried in individual bags for 48 hours at 75°C and then weighed to determine the percentage of total DM for each component. Botanical composition was determined once in late February in year one, and monthly from late November to late February in year two and monthly from mid-November to mid-February in year three.

Statistical analysis

Data were analysed using SAS (SAS Institute, version 9.4, Carey NC). Within year, live weight at the start and end of the experimental periods, and live weight gain during a particular period were analysed using general linear models that included the fixed effects of treatment and replicate nested within treatment. Pre- and post-grazing herbage masses and herbage quality parameters were analysed using general linear models that included the fixed effects of treatment and year.

Results

During the initial treatment period (Tables 2–4), bulls that were fed the herb sward grew faster than bulls in the other two treatments in all three years, by 0.07 kg/d to 0.71 kg/d (P < .01). Bulls on the concentrate and pasture treatments had similar liveweight gain in year one (Table 2). Liveweight gain was greater (P < .001) for bulls fed concentrate than for bulls fed pasture during the second (Table 3) and third (Table 4) years of the experiment. In year one, final live weight was similar for all treatments.

Table 2. The mean daily liveweight gain (kg/day) and initial and final live weight (kg) of weaned Friesian bull calves fed either a herb sward (chicory, plantain, and red and White clover), concentrate (pasture supplemented with 1.8 kg DM/bull/day concentrate) or pasture over summer and autumn in year one (2012–2013).

	Herb sward	Concentrate	Pasture	S.E.M.	Significance^1
Initial live weight (kg)	175	169	171	.0	NS
Liveweight gain (kg/day)	1.21^b	1.08^a	1.06^a	0.04	*
Final live weight (kg)	237	229	229	4.3	NS

Note: Values are L.S.M.

¹NS, not significant (P > .05), * P < .05.

^a,bValues within column within year without letters in common differ at the P < .05 level.

Table 3. The mean daily liveweight gain (kg/day) and final liveweight (kg) of weaned Friesian bull calves fed either a herb sward (chicory, plantain, and red and White clover), concentrate (pasture supplemented with 1.8 kg DM/bull/day concentrate) or pasture over summer and autumn in year two (2013–2014).

	Herb sward	Concentrate	Pasture	S.E.M.	Significance^1
Initial live weight (kg)	110	110	110	2.3	NS
Liveweight gain (kg/day)
Experimental period 1 (P1)	1.33^c	1.00^b	0.62^a	0.02	***
Off-treatment period (OT)	−0.01^a	0.36^b	0.39^b	0.05	***
Experimental period 2 (P2)	1.27	1.26	1.43	0.06	NS
OT + P2	0.52^a	0.73^b	0.82^b	0.04	***
P1 + P2	1.31^c	1.05^b	0.78^a	0.02	***
P1 + OT + P2	1.03^c	0.90^b	0.70^a	0.02	***
Final live weight (kg)	310^c	290^b	248^a	5.6	***

Note: Liveweight gains are presented for period 1 (119 days), the off-treatment period (41 days), and period 2 (29 days). Values are L.S.M.

¹ NS, not significant (P > .05), *** P < .001.

^a,b,cValues within column within year without letters in common differ at the P < .05 level.

Table 4. The mean daily live weight gains (kg/day) and final live weights (kg) of weaned Friesian bull calves fed either a herb sward (chicory, plantain, and red and White clover), concentrate (pasture supplemented with 1.8 kg DM/bull/day concentrate) or pasture over summer and autumn in year three (2014–2015).

	Herb sward	Concentrate	Pasture	S.E.M.	Significance^1
Initial live weight (kg)	128	129	128	2.3	NS
Liveweight gain (kg/day)
Experimental period 1 (P1)	1.16^c	1.09^b	0.90^a	0.02	***
Off-treatment period (OT)	0.20^a	0.41^c	0.27^b	0.02	***
Experimental period 2 (P2)	1.43^b	0.92^a	0.95^a	0.09	***
OT + P2	0.63	0.59	0.51	0.03	NS
P1 + P2	1.25^c	1.04^b	0.91^a	0.04	***
P1 + OT + P2	0.85^c	0.76^b	0.65^a	0.02	***
Final live weight (kg)	284^b	275^b	250^a	4.9	***

Note: Liveweight gains are presented for period 1 (81 days), the off-treatment period (63 days), and period 2 (34 days). Values are L.S.M.

¹NS, not significant (P > .05), *** P < .001.

^a,b,cValues within column within year without letters in common differ at the P < .05 level.

Herb-sward-fed bulls gained the least live weight during the off-treatment period in both years two and three (Tables 3 and 4). In year two, bulls in the pasture and concentrate treatments grew similarly to each other, whereas in year three, when concentrate supplementation continued during the off-treatment period, concentrate-fed bulls had the greatest liveweight gain during this time (P < .001). Liveweight gain during the second experimental period, which only occurred in years two and three, showed a variable response between years (Tables 3 and 4). In year two, there were no differences (P > .05) in the liveweight gains of bulls from all three treatments, whereas in year three, the bulls in the herb sward treatment grew faster (P < .001) than both concentrate-fed and pasture-fed bulls. In both years two and three, over the whole period (period one plus the off-treatment period plus period two), liveweight gain was greatest for herb-sward-fed bulls and least for pasture-fed bulls (Tables 3 and 4; P < .001).

Pre-grazing herbage mass did not differ among treatments (P > .05) except in year three (Table 5), when it was greater (P < .05) for the concentrate and pasture treatments than the herb sward treatment. Post-grazing herbage mass did not differ among treatments in any year (P > .05). Least squares means for post-grazing herbage mass were above the minimum threshold of 1500 kg DM/ha and all individual grazing areas exceeded 1500 kg DM/ha (data not shown). In year one, the pasture offered to bulls in the pasture treatment had more protein and ME, less ADF and greater OMD and DOMD than pasture offered to bulls in the concentrate treatment (P < .05), whereas in the second and third years, the quality of pasture offered to these bulls did not differ between treatments (P > .05; Table 5). The quality of the herb sward relative to the pasture and concentrate treatments varied among years, but the herb sward consistently had less ADF and NDF (P < .05) and generally had greater OMD than pasture offered to either the concentrate or pasture treatments. Metabolisable energy content of the herb sward was 1.3–2.1 MJ/kg DM greater than that of the pasture offered to bulls fed concentrate or pasture in the first year (P < .05), 0.5–0.8 MJ/kg DM greater in the second year, and not different in third year (P > .05).

Table 5. Pre- and post-grazing herbage mass (kg DM/ha), and CP, neutral detergent fibre (NDF), acid detergent fibre (ADF), dry matter digestibility (DMD), ash content and metabolisable energy content (ME) assessed on hand-plucked samples for each treatment in each of the three years of the experiment.

	Pre-grazing herbage mass (kg DM/ha)	Post-grazing herbage mass (kg DM/ha)	Crude protein (% of DM)	NDF (% of DM)	ADF (% of DM)	DMD (% of DM)	DOMD (% of DM)	OMD (% of DM)	Ash (% of DM)	ME (MJ/kg DM)
Year 1
Herb sward	4336 ± 227	2832 ± 361	16.4 ± 1.0^b	23.9 ± 2.0^a	17.1 ± 1.2^a	79.6 ± 1.4^c	73.5 ± 1.0^c	83.5 ± 1.1^c	12.8 ± 0.9	11.8 ± 0.2^c
Concentrate^1	4171 ± 227	3313 ± 361	12.6 ± 1.0^a	53.0 ± 2.0^c	29.7 ± 1.2^c	65.8 ± 1.4^a	60.5 ± 1.0^a	67.6 ± 1.1^a	10.9 ± 0.9	9.7 ± 0.2^a
Pasture	3818 ± 227	2962 ± 361	23.5 ± 1.0^c	46.4 ± 2.0^b	24.5 ± 1.2^b	71.5 ± 1.5^b	65.4 ± 1.0^b	73.9 ± 1.2^b	12.6 ± 0.9	10.5 ± 0.2^b
Year 2
Herb sward	4739 ± 300	3770 ± 477	19.2 ± 1.2^b	29.8 ± 2.4^a	20.3 ± 1.4^a	70.1 ± 1.6	63.4 ± 1.1^b	71.0 ± 1.3^b	12.2 ± 1.1	10.2 ± 0.2^b
Concentrate^1	5631 ± 347	4562 ± 551	12.1 ± 1.2^a	52.7 ± 2.4^b	29.2 ± 1.4^b	67.9 ± 1.6	58.7 ± 1.1^a	65.2 ± 1.3^a	9.1 ± 1.1	9.4 ± 0.2^a
Pasture	5486 ± 300	4187 ± 551	13.9 ± 1.2^a	51.8 ± 2.4^b	29.1 ± 1.4^b	70.5 ± 1.6	60.3 ± 1.1^a,b	67.3 ± 1.3^a	10.5 ± 1.1	9.7 ± 0.2^a,b
Year 3
Herb sward	3674 ± 347^a	3984 ± 551	22.2 ± 1.5^b	30.1 ± 3.1^a	18.7 ± 1.8^a	76.5 ± 2.1	65.1 ± 1.5	73.1 ± 1.6^b	11.5 ± 1.4	10.4 ± 0.2
Concentrate^1	5523 ± 347^b	4556 ± 551	15.7 ± 1.5^a	47.2 ± 3.1^b	27.9 ± 1.8^b	74.4 ± 2.1	61.2 ± 1.5	68.1 ± 1.6^a	9.2 ± 1.4	9.8 ± 0.2
Pasture	5410 ± 347^b	4630 ± 551	17.9 ± 1.5^a,b	42.3 ± 3.1^b	24.7 ± 1.8^b	72.4 ± 2.1	63.0 ± 1.5	70.4 ± 1.6^a,b	9.5 ± 1.4	10.1 ± 0.2
P values
Treatment	.009	.341	<.001	<.001	<.001	.001	<.001	<.001	.054	<.001
Year	<.001	<.001	.006	.066	.066	.009	<.001	<.001	.076	<.001
Treatment × year	.009	.868	<.001	.131	.359	.002	.002	.001	.915	.002

Note: Values are L.S.M. ± S.E.M.

¹Values for the concentrate treatments are values for the pasture grazed by the calves supplemented with concentrate.

^a,b,cValues within column within year without letters in common differ at the P < .05 level.

Botanical composition of the samples showed some establishment of grasses in the herb sward in year three (Table 6), and a decline in the percentage of plantain leaf over the three years. The pasture offered to bulls in the pasture treatment was of similar composition to that offered to bulls in the concentrate treatment in years two and three, but differed in year one.

Table 6. Botanical composition (percentage of total DM) of herbage within quadrat cuts from each treatment in the three years of the experiment.

	Year 1	Year 2	Year 3
Herb sward
Chicory	37	14	20
Plantain	30	12	6
Red clover	9	30	16
White clover	2	1	2
Grass leaf^a	0	0	12
Stem^b	–	16	11
Weeds	0	1	4
Dead matter	22	26	30
Concentrate
White clover	1	6	6
Grass leaf^a	73	37	26
Stem	0	8	33
Weeds	12	6	1
Dead matter	14	42	34
Pasture
White clover	10	5	13
Grass leaf^a	30	37	27
Stem	29	9	22
Weeds	15	1	2
Dead matter	16	48	36

Note: Values are a single late February sample in year one, the average of monthly samples from late November to late February in year two, and the average of monthly samples from mid-December to mid-February in year three.

^aIncludes all varieties of grasses.

^b Stems were not separated from leaves for chicory and plantain in year one.

Discussion

The aim of this experiment was to investigate the effect on liveweight gain of grazing weaned Friesian bull calves on a herb sward containing chicory, plantain, red clover and white clover, compared with bulls grazed on ryegrass/white clover pasture with or without concentrate over summer and autumn. Concentrate supplementation increased liveweight gain compared with grazing on pasture alone, except in the first year when the bulls supplemented with concentrate grazed a poorer quality pasture. This is consistent with a previous study by Muir et al. (2000) in which concentrate supplementation increased the growth rate of un-weaned bull calves. Theoretical calculations indicate that young 100 kg bulls growing at 1 kg/day require 42 MJ ME/day for maintenance and growth (Nicol & Brookes 2007). The bulls supplemented with concentrate received 22.5 MJ ME/day from concentrate, leaving 19.5 MJ ME to be consumed from pasture. This is approximately 2 kg DM/day of pasture consumed, indicating that the concentrate made up a significant proportion of the diet at the start of the experiment. At 200 kg live weight, their energy requirement and, therefore, their pasture consumption would have increased concurrently, to reach around 64 MJ ME/day, or around 4 kg DM/day from pasture by the end of the experiment. Therefore, the relative contribution of the concentrate to their diet decreased as the bulls grew. In comparison, a bull in the pasture treatment growing at 0.62 kg/day would require 35 MJ ME/day, or approximately 3.5 kg DM pasture at 100 kg, increasing to 54 MJ ME/day or 5.4 kg DM pasture. Although it appears there was a relatively high rate of substitution, replacing low quality pasture with high-quality concentrate allowed growth rate of the bulls to increase.

Bulls grazing the herb sward achieved greater growth rates than either of the other two treatments. de Clifford et al. (2014) and Handcock et al. (2015) reported superior growth rates of weaned dairy heifer calves that were fed alternative herbages (lucerne, or a herb sward) compared with heifers grazing pasture. This was attributed to the lower fibre content and greater ME content and digestibility of the alternative forages compared with pasture in those experiments (de Clifford et al. 2014; Handcock et al. 2015). Herbage quality in the present experiment was assessed on the basis of a hand-plucked sample that was representative of the parts of the plants grazed by the bulls, and of the relative proportions of the different plant species in the sward. An experiment by Back et al. (2016) examined species selection by 4.5-month-old weaned dairy heifers within a herb sward that contained chicory, plantain, red clover and white clover, and reported that calves preferentially grazed red clover and chicory compared with plantain and white clover. If the bulls exhibited similar preferences, they would have consumed a diet of different composition to that reported in Table 5.

Of note in this experiment was the variability among years in the growth rate of bulls grazing pasture compared with herb sward or supplemented with concentrate. In all years, this was a first- or second-year pasture, and calves were offered ad libitum intakes. Live weight gain was 1.06 kg/day in year one, but only 0.62 kg/day in year two. Table 5 shows that the pasture offered in year two was lower in protein and energy but higher in fibre than that offered in year one, likely explaining this variation. Table 3 highlights that in year 2, when pasture quality was poor and consequently, liveweight gain of bulls grazing pasture was low, there was a greater advantage gained from either supplementing with concentrate or grazing a herb sward. This is unsurprising, given previous authors have reported that high-quality pasture is an excellent feedstuff for ruminants, but low quality pasture is likely to limit performance (Burke et al. 2002; Waghorn & Clark 2004).

Conclusion

Bulls grazing a herb sward of chicory, plantain, red clover and white clover consistently grew faster than bulls grazing pasture and bulls grazing pasture supplemented with concentrate. A concentrate supplement of 1.8 kg DM/bull/day increased liveweight gain of bulls above that of bulls fed pasture in two out of three years. Grazing a herb sward appears to be an effective means of increasing liveweight gain of young weaned bull calves during the late summer/early autumn periods when growth rates for bulls grazing pasture can be low. Further research is needed to quantify the persistence of the liveweight advantage beyond the period of grazing on the herb sward.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by the Blake Family Foundation, administered by Massey University.