Animal responses to white clover

J A Bax and R L M Schils*

Scottish Agricultural College, Crichton Royal Farm, Mid Park, Bankend Road, Dumfries DG1 4SZ, Scotland

* Research Station for Cattle, Sheep and Horse Husbandry (PR), Runderweg 6, 8219 PK Lelystad, The Netherlands

Abstract
Introduction
Potential nutritive value
Responses in dairy cattle
System studies
Responses in beef cattle and sheep
Conclusions
References

Abstract

There is increasing interest in more extensive systems of livestock management, in response to the continuing problems of excess production, combined with concerns over the environmental consequences of intensively managed livestock systems. Therefore there is renewed interest in the role that legumes can offer, of which white clover currently has the greatest potential. White clover has been shown to have improved digestion and higher intake characteristics than ryegrass, but considerable losses of nitrogen can occur during the digestion process in cattle. It has been suggested that specific supplements such as rumen-degradable carbohydrates be offered to reduce these losses. While small scale experiments have demonstrated the potential for white clover to improve dairy cow performance, this has not always occurred in larger scale system studies. Two such studies currently underway in Scotland and The Netherlands have not shown any consistent response to grass/white clover swards. Improvement in management, such as matching the nutritional requirements of the animals more closely to the growth pattern of mixed swards may help. A similar inconsistency in response has also been observed with beef cattle. Responses to clover with sheep systems can be obtained with relatively low clover contents, although to maximize animal performance, high clover contents appear to be beneficial.

Introduction

The superior nutritional characteristics of white clover compared to ryegrass have been well documented. Now, greater effort is being focused on exploiting the potential of white clover in animal production systems that can meet the financial and environmental requirements that are likely to prevail within Europe in the future. The continuing overproduction of animal products within the EC has stimulated interest in extensive management systems. As stocking rates are reduced the opportunity for incorporating white clover in the production cycle increase. There is also concern over the importation of nutrients and resources into intensive livestock systems and the subsequent problems associated with inefficient utilisation of nutrients, nitrogen especially, and the disposal of the waste products (Aarts et al., 1992).

Extensive livestock systems generally rely upon reduced variable costs, such as purchased fertiliser nitrogen, to offset any reductions in financial output that occur. However, if improved animal performance can also be achieved as a consequence of including white clover in the diet, the financial viability of the system will be further improved. Thomson (1984) suggested that the daily liveweight gain (DLWG) of sheep grazed on grass/white clover swards could be 25-30% higher than those on conventional grass swards, and 15 -20% for beef cattle, while a possible increase of 10% was suggested for milk production from grass/white clover swards. The following paper reviews some of the responses that have been observed when clover has been incorporated in diets.

Potential nutritive value

White clover has a higher nutritive value than grass, due largely to its lower structural fibre and higher protein content (Thomson, 1984). These characteristics give white clover improved digestion and higher intake capabilities. Beever et al. (1986b) showed that growing cattle maintained on ryegrass from May to September had mean intakes of 21.8 g/kg liveweight compared to 27.0 g/kg for clover. It has been observed that the rate of dry matter (DM) degradation during the first three hours after feeding can be 15% higher when fed clover compared to ryegrass (Moseley and Jones, 1984). They associated this with a greater reduction in particle size as twelve hours after feeding on clover the ratio of small: large particles in the rumen (< or > than 1 mm) was 3: 1, compared to 1: 1 when fed on ryegrass. Beever et al. (1986a) observed even greater differences in rates of DM degradation in cattle with 14%/h occurring on a clover diet compared to 7%/h for grass. They concluded that the extent of DM digestion observed on a white clover diet after 8 hours would not be achieved until 14 hours post feeding on a grass diet. Steg et al. (1993) compared in situ ruminal breakdown and intestinal protein digestion in dairy cows of N-fertilized perennial ryegrass (315 kg N/ha) and the white clover and ryegrass components of a mixed grass/white clover sward, fertilized with 90 kg N/ha in spring. They observed higher soluble fractions of organic matter (OM) and crude protein (CP) and lower rumen undegradable fraction of OM and CP in clover than in grass. The degradation rates of OM and CP were higher and similar respectively to those of grass.

Increased intakes of silage DM have also been observed when clover was incorporated in the ration. Castle et al. (1983) mixed pure ryegrass and pure clover silage in differing proportions and observed that 50% inclusion rate of white clover silage raised the total silage dry matter intake (DMI) of early lactation dairy cows by 13% compared to offering only grass silage. Offering 100% clover silage raised the silage DMI by 17.5%.

The inclusion of clover in the diet can also promote changes in the nitrogen metabolism of ruminants with the potential for considerable losses of nutrients. Beever et al. (1986) fed either fresh ryegrass or clover to cattle at three stages through the growing season.

The increased crude protein content of the clover herbage compared to the ryegrass resulted in large increases in mean rumen ammonia concentrations (Table 1). However, despite a 90% increase in dietary crude protein intake the average duodenal non ammonia nitrogen (NAN) supply was only 15% higher when the cattle were offered clover. In order to compensate for the increased losses of N in the rumen Steg et al. (1993) suggested that clover based rations be supplemented with rumen-degradable carbohydrates.

Table 1 Nitrogen metabolism of cattle fed fresh ryegrass or white clover

Cut	early	Ryegrass mid	late	early	White clover mid	late
Dietary crude protein (g/kg OMI)	160	154	190	318	307	329
Mean rumen ammonia cone (mg/1)	50	68	242	283	372	393
Duodenal NAN (g/kg DOMI)	41.9	37.2	39.0	40.1	50.8	44.8

Responses in dairy cattle

The production responses observed in dairy cattle can be related to the clover content of the diet. In an experiment reported by Thomson et al. (1985) spring calved cows were grazed either on pure perennial ryegrass or pure white clover swards from weeks 4 to 18 of lactation. During this period the clover grazed cows produced 2.8 l/d more milk (Table 2).

Table 2 The productivity of cows grazing either perennial ryegrass or white clover (lactation weeks 4-18)

	Perennial ryegrass	White clover
Milk yield (l/d)	22.2	25.0
Milk fat (g/kg)	29.8	30.9
Milk protein (g/kg)	41.5	38.9
Total milk yield (1)	2396	2697

In addition to the improved milk yield and increased yields of fat and protein, they noted that the grass fed cows suffered a greater and longer period of body weight loss before repletion commenced at day 102 post calving compared to day 77 for the clover fed cows.

Further studies with cows grazed on mixed swards have demonstrated the potential benefits from white clover. Wilkins et al. (1991) grazed spring calving cows on swards that contained either 0.01 (1), 0.16 (m) or 0.23 (h) of the above ground herbage as white clover (Table 3).

Table 3 Milk production and composition for grazed swards with contrasting white clover contents (April-July)

	Yield			Composition (g/kg milk)
Clover content	concentrate (kg/d)	kg/d	FPCM(kg/d)	Fat	Protein	Lactose
Low	0	20.6	18.8	35.9	26.8	41.2
	2	23.2	21.4	36.4	27.6	42.1
	4	25.5	24.4	38.6	28.4	43.2
Medium	0	22.8	21.0	35.8	28.2	42.0
	2	27.1	25.7	38.1	28.4	42.8
	4	26.2	25.2	38.3	30.2	43.3
High	0	25.4	24.4	39.1	28.6	41.9
	2	25.9	25.0	39.0	29.5	43.6
	4	26.3	25.5	39.1	29.7	43.1

The experiment resulted in large differences between milk yield on the three sward types. When no concentrate supplementation was offered the fat and protein corrected milk yield (FPCM) was 5.6 kg/d higher from the high clover sward compared to the low clover sward. It was noted however that the nitrogen supply from the low clover sward may have been limiting as none of the swards received any nitrogen fertilizer. Of more interest was the increase in yield of 3.4 kg FPCM/d when cows were offered the high clover swards compared to the medium, which at 16% clover content would be typical of better grass/white clover swards that cows are turned out onto in the spring. Supplementation with concentrate produced similar responses in milk yield in the cows grazed on both the medium and high clover content swards.

Preliminary results from ongoing experiments in The Netherlands are presented in Table 4. Bruins (1993) compared the intake of dairy cows fed fresh cut grass (300 kg N/ha/year) or grass/white clover (50 kg N/ha/year in spring) with 60-65 % of white clover in the DM. The herbage fed in May was from a second cut with a growing period of two to three weeks and the herbage fed in autumn was from the fifth and sixth cut with a growing period of four to five weeks.

Table 4 The intake and productivity of cows fed grass (G) or grass/clover (GC) (lactation weeks 18-21)

	May		August/September
	G	GC	G	GC
Intake Herbage (kg DM)	16.5	17.5	18.5	17.6
Concentrate (kg DM)	2.3	2.3	3.8	3.8
Milk (kg/cow/d)	26.0	26.3	24.1	25.4
Fat (g/kg)	43.5	42.7	43.2	40.9
Protein (g/kg)	32.1	32.5	33.1	33.1

System studies

When the potential of grass/white clover swards has been investigated in system studies, contrasting results have been obtained. Ryan (1989) reported on a 5-year experiment in which spring calving cows were rotationally grazed on either conventionally fertilized grass swards or on grass/white clover swards (Table 5).

Table 5 Stocking rate and summer milk yield for four grazing systems

	Stocking rate	Milk yield
	(cows/ha)	(l/cow)	(l/ha)
Grass/white clover	2.08 (L)	2810	5856
Grass/white clover	2.52 (M)	2738	6908
Grass plus nitrogen	2.46 (M)	2740	6764
Grass plus nitrogen	3.20 (H)	2578	8266

Although the greatest output of milk per hectare was achieved from the grass plus nitrogen (H) treatment, the highest yield per cow was produced from the grass/white clover swards stocked at 2.08 cows/ha. The clover cows which were stocked moderately, produced a similar milk yield per cow and 144 l/ha more milk than the moderately stocked grass plus nitrogen group. Detailed data on the swards were not published, but it was noted that the peak clover contents of the swards declined over a 6 - year period from 50% to 25%.

Detailed whole farm system studies investigating the potential of clover - rich swards for dairy production are being undertaken at two sites in Europe, one near Dumfries in south-west Scotland (SAC) and another at Lelystad in The Netherlands (PR). In Scotland two herds of 70 autumn - calving Friesian Holstein dairy cows plus their youngstock were maintained on either grass/nitrogen swards, receiving up to 350 kg N/ha/annum or on grass/white clover swards. For the first two years of the study both herds were each allocated 36 ha of grassland, and 400, 000 1 milk quota (Bax 1992). The cows were set-stocked during the summer, and offered a grass or grass/white clover silage based complete mix during the winter. It was found that between 25% and 33% more concentrate per litre of milk sold was necessary to reach the quota target on the clover based system when the overall stocking rate was maintained at 2.4 lu/ha.

Table 6 Comparison of a grass/nitrogen system with a grass/clover system on animal performance when managed at similar stocking rates

	Grass/Clover		Grass/Nitrogen
	1988/89	1989/90	1988/89	1989/90
No cows	71	70	70	72
Milk sales (l/cow)	5658	5605	5764	5532
Cones (kg/cow)	1709	1554	1412	1185
Milk fat (g/kg)	40.0	39.9	39.5	40.7
Milk protein (g/kg)	31.9	31.9	31.8	31.3

Subsequently, the intensity of production was reduced when the land area of the grass/clover herd was increased by 25% which reduced the overall stocking rate to 1.9 lu/ha. The reduction in stocking rate for the grass/clover herd ensured that there was no shortage of forage and when both herds were allocated the same milk quota, the concentrate use, milk composition and milk yield per cow were very similar (Table 7).

Table 7 Comparison of a grass/nitrogen system with an extensive grass/white clover system

 

	Extensive grass/white clover		Grass/Nitrogen
	1990/91	1991/92	1990/91	1991/92
Milk quota	420,000	350,000	400,000	400,000
No of cows	70	70	69	69
Milk sales (l/cow)	5719	5294	5724	5941
Cone use (kg/cow)	1096	501	1101	1077
Milk fat (g/kg)	40.5	41.3	40.4	40.8
Milk protein (g/kg)	32.4	31.8	31.8	32.0

However, there was no production response to the white clover, with the more extensively managed herd yielding only 22 kg FPCM more per cow than the herd maintained on conventional grass swards. In the following year the target milk yield for the extensive herd was reduced to 5000 l/cow, and as a consequence the concentrate use dropped to 501 kg/cow. The increase in milk fat and reduction in milk protein could be attributed to the increased forage: concentrate ratio rather than any clover effect.

The lack of animal response over the four - year period may have been partly a function of the herbage quality and of the calving pattern. The crude protein content of the grass/white clover herbage was consistently lower in early season than that of the grass/nitrogen swards, which also resulted in low crude protein first cut silage which provided the bulk of the winter feeding. (Bax, 1992, Frame et al., 1992). The crude protein ranged from 126 to 107 g/kg DM with corresponding clover contents of 12.5 to 17.1% in total dry matter. However, in year three, the crude protein content of the grass/white clover silage was 171 g/kg DM. This may have been due to cutting earlier and an increased clover content of 28.1 % (Bax, 1992). The clover contents of the mixed swards followed the normal pattern, with mean values of 39.3% and 38.8% at second and third silage cuts respectively over a four - year period. Both herds calved between October and December each year, and at turnout the following spring were in mid-lactation (lactation weeks 16-29). The lack of animal response could have been due to a winter feeding regime based on silage with relatively low clover and crude protein contents, followed by turnout onto pastures in which nitrogen could have been limiting animal responses in early season.

The systems study in The Netherlands consisted of two herds of 60 winter (October-April) calving cows plus 40 youngstock. The grass/nitrogen swards received approximately 275 kg N/ha and the grass/clover swards were given 70 kg N/ha in spring. With an anticipated yield difference of 20% the area of the grass/clover and nitrogen farm was 41 and 34 ha respectively. Dairy cows and youngstock grazed rotationally on paddocks of 1.25 ha in a leader/follower system. Silage was cut at an average DM yield of 2500-3000 kg/ha. There were only minor differences in energy values in silage of both systems. The average (1990/91 and 1991/92) crude protein content of grass/clover and grass/nitrogen silages were 175 and 166 g/kg DM respectively. The results in 1990/91 showed a minor advantage in milk production for the grass/clover system but in 1991/92 there was no difference at all. The concentrate use in 1991/92 was higher because of extremely dry weather in August and September of that year.

Table 8 Comparison of a grass/nitrogen system with a grass/while clover system

	Grass/Clover		Grass/Nitrogen
	1990/91	1991/92	1990/91	1991/92
Milk quota (1)	420,000	420,000	420,000	420,000
No of cows	57	58	58	58
Milk sales (1)	7402	7174	7180	7177
Cone use (kg/cow)	1599	1675	1582	1648
Milk fat (g/kg)	45.1	45.6	44.6	45.1
Milk protein (g/kg)	34.2	34.8	34.5	34.8

The average white clover content (October) was satisfactory with 34 and 18% respectively, but there was a large variation between the paddocks with a minimum of 1 % and a maximum of 68%. This variation was partly a result of variation in the initial phase after seeding but also a result of other factors such as management and grass and clover variety. The consequences of this high variability were paddocks of poorer quality with low clover contents and an increased incidence of bloat where there were higher clover contents.

Responses in beef cattle and sheep

In beef systems enhanced rates of liveweight gain have been reported on grass/clover swards and silage, but as with dairy cattle a response does not always occur. Younie et al. (1987) compared Hereford and Friesian steers in an 18 - month beef system over a period of three years, using clover - rich swards or grass swards given 260 kg N/ha/annum. Despite a mean clover content of between 36% and 39% (in the DM) compared to less than 6% in the fertilized swards, there was no difference in daily liveweight gain (DLWG) between the two systems during the grazing season. However, during the fattening phase, the cattle fed on silage made from the grass/white clover swards had a 16% higher DLWG than those fed on grass N silage. Clarke (1988) reviewed a series of beef cattle experiments and concluded that while stocking rates on grass/white clover swards were about 80% of those achieved when between 180 and 400 kg N/ha were applied, differences in individual animal grazing DLWG were relatively small, resulting in lower lwg/ha on clover-rich swards. More recently Young (1992) also reported that beef cattle grazing clover-rich swards, 36% - 40% clover in the herbage dry matter, had a similar DLWG to cattle grazed on grass swards given 200 kg N/ha (See Table 9).

Table 9 Daily liveweight gain (g/head) and liveweight gain/ha (kg) of beef cattle on grass/white clover and grass/N swards

	Grass/white clover		Grass/N
	DLWG	lwg/ha	DLWG	lwg/ha
Steen and Laidlaw (1985)	1100	1113	1050	1459
Younie et al. (1987)	1095	831	1075	1056
Young (1992)	900	794	920	950

The effect of sward height of grass/white clover swards on grazing beef cattle performance was investigated by Moore et al. (1992). They found that steers grazed on clover-rich swards maintained at a sward height of 5 cm in early season had a significantly lower DLWG than steers grazing swards maintained at 7 cm or 9 cm. Daily liveweight gains were 0.60, 1.04 and 1.06 kg respectively. Similarly in the later part of the season, early August to late September, significantly higher liveweight gains were obtained from swards maintained at 9 cm rather than 7 cm, 1.11 kg/d compared to 0.85 kg/d. It was interesting to note that the more relaxed grazing treatments produced a mean output of 1265 kg liveweight gain per hectare over a three year period.

By contrast more consistent animal responses have been reported with sheep grazing grass-white clover swards (Newton et al., 1985, Vipond and Swift, 1992). One of the difficulties reported with clover/sheep systems was maintaining adequate clover contents under continuous sheep grazing. Orr et al. (1990) observed a progressive decline in clover content in clover-rich swards continuously grazed by sheep, over a three year period, when maintained at 3, 6 or 9 cm. In the first year the lamb liveweight gains from the grass/clover swards were 223, 268 and 295 g/d respectively compared to 260 g/d for lambs maintained on a grass sward given 420 kg N/ha and maintained at 6 cm.

Although the clover content of the 6 cm grass/clover sward declined to approximately 5 % in year 3, it maintained the same animal output per hectare relative to the sward given 420 kg N, 82%, as it had in year 1. The swards used in this experiment were based upon perennial ryegrass cv, Aberystwyth S 23 and grasslands Huia. Vipond and Swift (1992) evaluated a sheep system based upon perennial ryegrass cv. Condesa and Aberystwyth S S S 184 clover. They observed that over a three year period the mean lamb liveweight gain was 1037 kg/ha compared to 975 kg/ha from a Condesa + 160 kg N/ha sward. They also observed that the mixture of tetraploid late-heading perennial ryegrass and small leaved clover enabled a clover content of 29 % to be maintained from mid to late season in year 3 despite being continually grazed throughout the growing season.

Wright et al. (1992) investigated the potential for combining cattle and sheep grazing to improve animal output from grass/white clover swards. They found that grazing by cattle in early season resulted in significantly higher clover contents than when grazed with sheep, 12.1% compared to 6.5% of the live herbage mass in July. When weaned lambs were then grazed on the swards the mean liveweight gains were higher on those previously grazed by cattle, than by sheep, 124 g/d compared to 101 g/d.

Conclusions

When more extensive systems of livestock management are required, grass/white clover swards can be successfully integrated into beef, sheep and dairy enterprises. With the correct sward management and choice of varieties, satisfactory clover contents can be maintained. However, more data are required to further exploit the potential animal responses for beef and dairy cattle maintained on mixed swards, as the individual animal responses observed in small scale experiments, have not in general been observed on larger scale system studies.

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