Leaf tissue flows and defoliation patterns of Alexandergrass grazed by heifers receiving energy supplement

The study was carried out to evaluate defoliation patterns and to quantify leaf tissue flows in Alexandergrass (Urochloa plantaginea (Link.) Hitch) grazed by beef heifers receiving whole rice bran in three levels of supplementation (0, 0.5 and 1 % of body weight). A rotational stocking grazing method and two area replications were utilized. The experimental design was completely randomized following a repeated measure arrangement. The supply of rice bran to heifers grazing Alexandergrass increased the stocking rate by 13%. Regardless of the feeding system, the heifers grazed the expanding leaf blades in the top stratum of the canopy more frequently compared to other types of leaf. Leaf tissue flows, leaf blade intake and grazing intensity have not been changed by supplement fed.

Keywords:
Defoliation intensity; defoliation frequency; Urochloa plantaginea stocking rate

Authorship

Paula de Oliveira Severo ^**Author for correspondence. E-mail: paulasevero.zoot@gmail.com

Universidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900, Santa Maria, Rio Grande do Sul, Brasil.Universidade Federal de Santa MariaBrazilSanta Maria, Rio Grande do Sul, BrazilUniversidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900, Santa Maria, Rio Grande do Sul, Brasil.

http://orcid.org/0000-0003-3471-133X

Luciana Pötter

Marta Gomes da Rocha

Mateus Negrini

Amanda Carneiro Martini

Vanessa Bayer da Rosa

*Author for correspondence. E-mail: paulasevero.zoot@gmail.com

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (1)
Tables (4)

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Figure 1
Leaf tissue flows and net balance (kg ha ^-1 day of DM) as a function of different feeding systems (A= heifers exclusively on Alexander grass; B = heifers feeding on Alexander grass + WRB; p > 0.10).

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Table 1
Rainfall and average temperature from February to April 2015 and historical averages, Santa Maria/RS.

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Table 2
Structural characteristics of Alexander grass in different feeding systems (Alexander grass (A) or Alexander grass + whole rice bran (A+WRB)).

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Table 3
Morphogenetic characteristics of Alexander grass in different feeding systems (Alexandergrass (A) or Alexandergrass + whole rice bran (A+WRB)).

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Table 4
Defoliation intensity of leaf blades and defoliation frequency total and by type of leaf blade in different feeding systems ( Alexander grass (A) or Alexander grass + whole rice bran (A+WRB)).

Figure 1 Leaf tissue flows and net balance (kg ha ^-1 day of DM) as a function of different feeding systems (A= heifers exclusively on Alexander grass; B = heifers feeding on Alexander grass + WRB; p > 0.10).

Table 1 Rainfall and average temperature from February to April 2015 and historical averages, Santa Maria/RS.

	February	March	April
Average temperature (°C)	25.2	24.3	20.6
Historical temperature(°C)¹	24	22.3	18.9
Rainfall (mm)	84.3	132.4	129.8
Rainfall historical (mm)¹	108.74	129.80	136.29

¹Historical average 1985-2015.

Table 2 Structural characteristics of Alexander grass in different feeding systems (Alexander grass (A) or Alexander grass + whole rice bran (A+WRB)).

	Grazing cycles*				Average	P **	P ***	SD
Feeding systems	1	2	3	4	Average	P **	P ***	SD
	Leaf :stem ratio
A	1.1	0.6	0.5	0.3	0.6	0.5040	0.7641	0.03
A+WRB	1.0	0.6	0.5	0.4	0.6
Average	1.0a	0.6b	0.5b	0.3c		<0.0001		0.03
	Tiller population density
A	1,196	1,368	2,316	1,184	1,516	0.6647	0.1671	93.5
A+WRB	1,088	1,222	1,866	1,639	1,453
Average	1,142b	1,295b	2,091a	1,411b		0.0019		133.6
	Height of pseudostem
A	22.0	28.8	19.8	12.8	20.8	0.2450	0.2448	1.3
A+WRB	27.9	27.1	18.6	19.8	23.3
Average	24.9a	27.9a	19.2b	16.3b		0.0032		1.8
	Leaf blade depth
A	9.9	5.3	13.7	12.5	10.3	0.1266	0.2177	1.0
A+WRB	7.0	7.5	10.8	5.0	7.6
Average	8.4b	6.4b	12.2a	8.8ab		0.0835		1.4
	Basal tiller weight
A	0.4	0.4	0.3	0.5	0.4	0.1043	0.1289	0.03
A+WRB	0.3	0.5	0.4	0.5	0.5
Average	0.3	0.5	0.4	0.5		0.1043		0.03
	Axillary tiller weight
A	0.1	0.2	0.1	0.2	0.2	0.3145	0.4757	0.03
A+WRB	0.1	0.2	0.2	0.2	0.2
Average	0.1c	0.2ab	0.1b	0.2a		0.0078		0.03

*Grazing cycles 1= 06/02 to 22/02, 2=22/02 to 10/03, 3=10/03 to 26/03, 4=26/03 to 19/04; **Probability of feeding systems or grazing cycles; ***Probability interaction between feeding systems and grazing cycles; Values followed by letters on the line indicate difference by the lsmeans test at the 10% level; SD = stander error.

Table 3 Morphogenetic characteristics of Alexander grass in different feeding systems (Alexandergrass (A) or Alexandergrass + whole rice bran (A+WRB)).

Variable	A	A+WRB	P*	PT*	EP¹
Leaf appearance rate²	0.012	0.011	0.7619	0.2032	0.001
Phyllochron³	84.43	96.11	0.1973	0.2904	5.9
Leaf lifespan³	307.6	361.2	0.2932	0.9606	31.0
Senescence rate⁴	0.067	0.067	0.5793	0.9337	0.003
Expansion rate⁴	0.04	0.04	0.9337	0.6880	0.003

*Probability between feeding systems, **Probability of interaction between feeding systems and grazing cycles, ¹standard error;²leaf degree^-1-day; ³degree-day; ⁴cm degree^-1-day.

Table 4 Defoliation intensity of leaf blades and defoliation frequency total and by type of leaf blade in different feeding systems ( Alexander grass (A) or Alexander grass + whole rice bran (A+WRB)).

Variables	A	A+WRB	P¹	P*T²	EP⁵
Defoliation intensity
Expanding leaf blades³	72.6	74.8	0.7025	0.7456	3.7
Expanded leaf blades³	56.0	57.9	0.7215	0.8128	3.4
Senescent leaf blades³	64.4	51.0	0.2008	0.1043	6.0
Total³	62.9	61,5	0.2450	0.2448	1.2
Defoliation frequency
Expanding leaf blades⁴	1.1	1.1	0.9021	0.1608	0.01
Expanded leaf blades⁴	1.8	1.8	0.9459	0.8460	0.1
Senescent leaf blades⁴	1.4	1.4	0.8185	0.0898	0.1
Total⁴	1.4	1.5	0.4305	0.4676	0.05

¹Probability between feeding systems, ²Probability of interaction between feeding systems and grazing cycles, ³%, ⁴ days of return, ⁵standard error of the mean.

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Leaf tissue flows and defoliation patterns of Alexandergrass grazed by heifers receiving energy supplement

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[1] *Author for correspondence. E-mail: paulasevero.zoot@gmail.com