Ruminal degradation of <i>Panicum</i> grasses in three post-regrowth ages

Garcez, Bruno Spindola; Alves, Arnaud Azevêdo; Macedo, Ernando de Oliveira; Santos, Claudiane Morais dos; Araújo, Daniel Louçana da Costa; Lacerda, Marlúcia da Silva Bezerra

doi:10.1590/1809-6891v21e-55699

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Zootecnia • Ciênc. anim. bras. 21 • 2020 • https://doi.org/10.1590/1809-6891v21e-55699 copy

Ruminal degradation of Panicum grasses in three post-regrowth ages

Degradabilidade ruminal de gramíneas do gênero Panicum em três idades de pós-rebrota

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The objective was to evaluate the chemical composition and in situ degradation of Maasai, Mombasa and Tanzania grasses belonging to the genus Panicum, at 22, 34 and 46 days after regrowth. The contents of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined. For the evaluation of ruminal degradation, 4 g sample were placed in nylon bags and incubated in the rumen of a fistulated animal, for 6, 24 and 72 h. The experiment had a completely randomized design for chemical composition analysis and a split-split plot completely randomized design for in situ degradation, with means compared by Tukey test at 5%. There was an increase in the contents of DM (+ 1.69%) and NDF (+ 5.06%) (P <0.05) of the grasses at the highest cutting ages with reduction in the CP fraction. The potential degradation (PD) of DM, NDF and CP decreased with advancing age of grasses, with an increase in colonization time (0.69 h) and NDF degradation rate (1.14%/h). The increase in the post-regrowth age of the Massai, Mombasa, and Tanzania grasses increases the acid detergent fiber content and reduces the crude protein content, with a negative effect on the degradation of DM, PB and NDF. The management of these cultivars is indicated at 22 and 34 days post-regrowth to obtain forage with better nutritional value.

Keywords:
Massai grass; chemical composition; in situ degradation

Grass	Constituents¹ 1 DM: Dry matter; MM: Mineral matter; CP: Crude protein; ADF: Acid detergent fiber; NDF: Neutral detergent fiber.	Cutting age (days)² 2 Mean values followed by different lowercase letters, in the same row, or different uppercase letters, in the same column, are significantly different by Tukey's test at 5%.
		22	34	46
	DM	91.73^bA	92.25^bA	93.56^aB
	MM	9.10^aC	8.57^aA	8.17^aB
Massai	CP	13.18^aB	9.02^bB	7.41^bB
	ADF	54.04^bB	55.09^bB	58.63^aB
	NDF	87.30^bA	87.51^bA	89.79^aA
	DM	91.99^bA	92.06^bA	93.33^aB
	MM	11.01^aA	9.13^bA	7.83^bB
Mombasa	CP	12.55^aB	11.57^abA	9.23^bAB
	ADF	53.36^bA	51,88^bC	58.54^bB
	NDF	81.75^bB	82.80^bA	85.24^aB
	DM	91.27^bB	92.60^bA	93.75^aA
	MM	9.87^aB	9.28^aA	11.17^aA
Tanzania	CP	12.70^aB	9.36^bB	8.19^bAB
	ADF	46.21^bB	46.26^bD	48.94^aB
	NDF	84.96^bA	85.16^bA	88.17^Ab

Grass	Cutting age (days)			Parameters¹ 1 Soluble fraction (a), potentially degradable (b), degradation rate of fraction b (c), potential degradation (PD) and effective degradation (ED) determined by the models PD = A - B.e-ct and ED = a + [(b×c)/(c + k)]10.			R²
		A	B	c (%/h¹)	PD	ED
						2%	5%	8%
	22	20.37	71.42	4.32	86.78	56.21	44.12	38.14	97.12
Massai	34	18.86	52.93	4.37	67.15	51.76	41.14	36.70	92.25
	46	20.15	43.29	5.17	56.81	48.21	40.43	36.19	96.55
	22	19.98	50.40	3.67	70.38	52.60	41.31	35.83	95.41
Mombasa	34	21.95	36.03	4.34	67.98	50.26	43.38	39.19	94.69
	46	19.64	31.15	4.33	50.79	45.29	39.92	36.41	82.95
	22	20.52	52.65	3.62	73.23	54.49	42.69	36.98	98.52
Tanzania	34	21.10	46.22	3.20	67.32	49.54	39.14	34.31	99.07
	46	19.76	39.33	4.67	59.09	47.30	38.75	34.26	97.74

Grass	Cutting age (days)	Parameters¹ 1 Soluble fraction (a), potentially degradable (b), degradation rate of fraction b (c), potential degradation (PD) and effective degradation (ED) determined by the models PD = A - B.e-ct and ED = a + [(b×c)/(c + k)]10.						R²
		A	B	c (%/h¹)	PD	ED
						2%	5%	8%
	22	38.25	48.72	2.56	86.97	59.6	49.84	46.2	99.88
Massai	34	35.21	36.18	2.34	75.12	51.34	47.75	41.98	96.21
	46	35.10	22.12	2.92	57.22	52.26	47.94	45.36	97.12
	22	30.25	59.76	2.31	90.01	62.28	49.13	43.64	96.92
Mombasa	34	32.47	44.06	2.23	76.53	55.70	46.06	42.07	94.89
	46	50.15	32.56	3.83	62.71	51.54	44.27	40.69	95.22
	22	29.85	65.76	2.00	95.61	62.73	48.64	43.0	95.72
Tanzania	34	26.68	59.98	1.53	89.83	53.71	41.02	36.31	98.24
	46	26.81	52.48	2.49	79.81	49.76	39.40	35.59	89.73

Grass	Cutting age (days)	Parameters¹ 1 Standardized potentially degradable fraction (Bp), standardized undegradable fraction (Ip), colonization time (lag), degradation rate (k) obtained by the models Rt = Be-cxt + I(11), Bp = B/(B+I) × 100(12) and Ip = I/(B+I) × 100(12).				R²
		Bp	IP	Lag	k (%/h)
	22	72.75	27.25	4.06	4.50	99.16
Massai	34	66.09	33.91	4.89	3.60	98.96
	46	64.66	35.34	4.27	1.90	99.24
	22	70.02	29.98	4.65	3.02	99.14
Mombasa	34	62.14	37.86	4.81	2.70	96.19
	46	51.07	48.93	4.85	2.49	95.16
	22	74.80	25.20	4.42	4.10	89.94
Tanzania	34	67.91	32.09	4.94	4.04	88.91
	46	66.83	33.17	4.76	2.24	94.96

Universidade Federal de Goiás Universidade Federal de Goiás, Escola de Veterinária e Zootecnia, Campus II, Caixa Postal 131, CEP: 74001-970, Tel.: (55 62) 3521-1568, Fax: (55 62) 3521-1566 - Goiânia - GO - Brazil
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[1] *Correspondent - brunosgarcez@veterinario.med.br