DYNAMICS OF DM ACCUMULATION AND FEEDING VALUE OF THE FIRST CYCLE OF GROWTH OF SOME ASSOCIATIONS OF GRASSES WITH WHITE CLOVER - I. Razec, Maria Razec and G. Oprea

Grassland Research Institute, Cucului str. 5, 2200 Brasov, Romania

SUMMARY

Four associations of perennial grasses, Dactylis glomerata, Festuca pratensis, Lolium perenne, Phleum pratense with Trifolium repens (37 percent) were used to study the relationship between the stages of growth apex 8-10 cm; beginning of ear emergence end of ear emergence; flowering and the evolution of the feeding value.

The dynamics of DM accumulation for the first cycle was determined using sequence of cuts at intervals of seven days. Castred sheep were used in order to measure the voluntary intake and the digestibility.

The rate of growth increased according to the vegetation evolution. Higher growth rate was obtained after end of ear emergence. The harvest at apex 8-10 cm and beginning of ear emergence provided a high participation of white clover (40-50 percent), the harvest at end of ear emergence was maintained at nearly the initial balance, except the associations Dactylis glomerata - Trifolium repens.

The presence of white clover in mixtures had a positive effect on the feeding value, protein and energy content of mixtures presenting high values in the early stages of growth. The energy values ranged between 0.69 and 0.96 milk-FU on kg DM. The values of digestible proteins ranged between 140 g - 64 g PDIN on kg DM and 117 g - 60 g PDIE on kg DM.

Keywords: associations, digestibility, dry matter, feeding value, synthesis rhythm, white clover

INTRODUCTION

The studies of simple and complex associations of perennial grasses used for hay, showed that the majority of production is obtained at the first cycle of production, which corresponds to the most intense rhythm of dry matter accumulation. Also during this period the qualitative transformations are the most striking and are irreversible.

It is known that the species and varieties have different behaviours both in quantitative as well as in qualitative aspects.

Our research target is to evaluate which are the most important perennial grasses in association with white clover, concerning: the dynamics of dry matter accumulation and the qualitative transformation of the forage at the first cycle of growth.

Figure 1. Relationship between sward height and DM yield.

MATERIALS AND METHODS

Four perennial grasses of species: Dactylis glomerata (Poiana), Festuca pratensis (Paltar), Lolium perenne (Marta) and Phleum pratense (Tirom) were cultivated in association with Trifolium repens cv. Holandicum (37 percent). Each of these four simple associations was sown in three fields each of 600 m². Each field was divided into four plots of 150 m², which were harvested at different growth stages: i) apex 8-10 cm; ii) beginning of ear emergence; iii) and of ear emergence; iv) flowering. In each plot of 150 m² plots of 4 m² which were cut weekly for the determination of dynamic of dry matter accumulation were distributed.

Each mixture was fertilized in autumn with 50 P₂O₅ 50 K₂O kg.ha^-1 and in spring with 100 N kg.ha^-1.

At harvest samples were taken of 500 g for the determination of botanical composition and the DM content.

The feeding value of the associations was studied using castred sheep in digestibility cages for the determination of voluntary intake and the coefficient of digestibility.

RESULTS AND DISCUSSIONS

Figure 1 shows that the rhythm of DM synthesis in the first cycle of growth manifested a similar tract for all associations of the DM increase is associated with the highest vegetal cover. The rate of growth increased rapidly at the end of May, beginning June. This aspect was associated with the decrease in leaf/stem ratio, proportion of stems was higher.

Table 1. Composition and feeding value of herbage according to stages of vegetation (mean of three years).

Stages of veg.	Chemical composition %			Voluntary intake g·kg LW⁰⁷⁵		Digestibility		Feeding value (on 1 kg DM)
	OM	Nt	ADF	DM	OM	DM	OM	PDIN	PDIE	FUM	FUB
Dactylis glomerata (Poiana) - Trifolium repens (Magurele 1)
i	90.01	2.79	27.33	-	-	73.9^*	75.4^*	132.03	96.3	0.91	0.85
ii	90.05	1.93	31.77	72.15	65.65	65.0	66.8	109.2	82.8	0.83	0.77
iii	91.80	1.77	32.09	57.98	53.32	59.2	61.3	77.5	81.2	0.73	0.65
iv	91.36	1.26	37.99	48.46	44.79	56.4	58.3	60.0	71.0	0.66	0.57
Phleum pratense (Tirom) - Trifolium repens (Magurele 1)
i	88.64	3.55	25.41	-	-	77.2^*	79.6^*	119.4	100.6	0.94	0.89
ii	90.51	2.75	27.16	80.06	72.44	69.6	71.3	87.9	83.9	0.94	0.89
iii	92.19	1.78	32.44	66.95	61.80	61.3	63.3	64.8	60.7	0.69	0.60
iv	92.92	1.40	39.21	63.23	59.68	59.4	61.6	53.3	54.8	0.62	0.53
Festuca pratensis (Paltar) - Trifolium repens (Magurele 1)
i	90.77	3.17	29.32	-	-	69.3^*	71.5^*	134.4	109.1	0.93	0.88
ii	91.16	2.74	30.96	76.47	69.70	66.6	68.0	110.6	94.4	0.90	0.84
iii	93.49	2.03	32.36	64.88	60.65	58.3	60.6	88.0	84.1	0.79	0.72
iv	93.03	1.64	37.63	58.10	54.04	51.0	53.6	65.3	67.6	0.71	0.64
Lolium perenne (Marta) - Trifolium repens (Magurele 1)
i	88.87	1.13	23.55	-	-	79.3^*	82.0^*	140.7	117.6	1.00	0.92
ii	91.30	0.85	27.81	80.96	73.72	72.0	74.8	118.5	100.0	0.94	0.90
iii	92.95	0.64	31.11	66.23	61.60	66.8	68.2	92.6	84.9	0.84	0.77
iv	93.55	0.54	34.71	63.48	60.23	60.3	62.0	73.3	72.2	0.72	0.64

Figure 2. Annual DM production at first cycle and white clover over three years for all stages of harvest.

The annual DM yield for the first cycle associated with white clover proportion showed in Figure 2. The harvest at apex 8-10 cm and beginning of ear emergence provides high participation of white clover every year, reaching more than 50 percent during the third year, that harvested at the end of ear emergence maintains nearly 30 percent and the harvest at flowering reduces the participation of white clover to less than 20 percent. The species Dactylis glomerata (Poiana) shows a high aggression for white clover which is less than 10 percent for all stages of harvest. In the third year of exploitation the species Lolium perenne and Festuca pratensis demonstrated a tendency of disappearance from the associations, because of the harvesting made by cutting.

The fodder quality expressed by chemical composition, voluntary intake and digestibility was different depending on the stage maturity at harvest (Table 1). The N concentration was always higher at apex 8-10 cm than in other stages between 2.79-3.99 percent Nt and lower at flowering 1.26-2.38 percent Nt.

The proportions of ADF increased during the first cycle of growth between 23.5-39.2 percent. The voluntary intake provides a high value at the beginning stage of ear emergence between 72.1-80.9 g kg LW⁰⁷⁵ for DM and 65.6-73.7 g kg LW⁰⁷⁵ for OM.

This parameter gives a different digestibility for DM and OM. Good values were obtained in states i, ii and iii, over 59 percent for DM and 61 percent for OM. The presence of white clover in associations has a positive effect on DM productions and on the feeding value. At apex 8-10 cm stages FUM content is 0.91-1 on kg DM, this content decreasing by approximately 0.07-0.13 FUM for each stage of growth.

CONCLUSION

For a good yield allocation it is necessary to harvest at the beginning of ear emergence to end of ear emergence. This management was good to maintain a good clover content and a high feeding value of forages.

REFERENCES

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Emille, J.C. & Troineau, R. 1991. Valeur alimentaire comparée de cultures pures et d'association graminée grande légumineuse. Fourages nr. 126, p. 239/253.

Osbourn, D.F. 1980. The feeding value of grass and grass product. Grass its production and utilization. Edited by W. Holmes, cap. 3, p.70-124.

Razec, I. 1995. Productivitatea unor asociatii de graminee si leguminoase perene in diferite stadii de vegetatie, Lucrari stiintifice ale ICPCP Brasov, vol. XVII p. 125-139.