O objetivo deste trabalho foi avaliar o perfil de ácidos graxos (AG) do leite de vacas Holandesas x Gir submetidos a dois tipos de manejo de pastejo (períodos de descanso fixo e variável) de pastagem de Urochloa brizantha 'Marandu'. Utilizou-se o delineamento de blocos ao acaso, com duas repetições de área de pastagem (blocos) por tratamento e quatro vacas por bloco. A produção e a composição do leite não foram influenciadas pelas estratégias de pastejo. Não houve efeito dos tratamentos sobre as proporções (g 100 g^-1 de AG totais) dos principais AG (palmítico, linoleico e α-linolênico) do pasto, mas suas ingestões (gramas por dia) foram influenciadas pelas diferenças de ingestão de matéria seca da forragem. As concentrações dos AG no plasma e na gordura do leite não foram influenciadas pelos tratamentos. As concentrações dos ácidos rumênico, vacênico, oleico e α-linolênico na gordura do leite variaram de 0,71 a 0,93, 1,40 a 1,50, 19,40 a 19,70 e 0,39 a 0,43 g 100 g^-1 de AG totais, respectivamente. As estratégias de pastejo de U.brizantha 'Marandu' não alteram o perfil de ácidos graxos do leite das vacas.

Termos para indexação:
Urochloa brizantha; ácido linoleico conjugado; ácido rumênico; gramínea tropical.

Autoria

Bárbara Cardoso da Mata e Silva

Universidade José do Rosário Vellano, Programa de Pós-Graduação em Reprodução, Sanidade e Bem-Estar Animal, Rodovia MG-179, Km 0, Trevo, CEP 37130-000 Alfenas, MG, Brazil. E-mail: barbaracmsilva@yahoo.com.brUniversidade José do Rosário VellanoBrazilAlfenas, MG, BrazilUniversidade José do Rosário Vellano, Programa de Pós-Graduação em Reprodução, Sanidade e Bem-Estar Animal, Rodovia MG-179, Km 0, Trevo, CEP 37130-000 Alfenas, MG, Brazil. E-mail: barbaracmsilva@yahoo.com.br

Norberto Mario Rodriguez

Universidade Federal de Minas Gerais, Departamento de Zootecnia, Avenida Antônio Carlos, no 6.627, CEP 31270-901 Belo Horizonte, MG, Brazil. E-mail: norberto.bhe@terra.com.brUniversidade Federal de Minas GeraisBrazilBelo Horizonte, MG, BrazilUniversidade Federal de Minas Gerais, Departamento de Zootecnia, Avenida Antônio Carlos, no 6.627, CEP 31270-901 Belo Horizonte, MG, Brazil. E-mail: norberto.bhe@terra.com.br

Mirton José Frota Morenz

Embrapa Gado de Leite, Rua Eugênio do Nascimento, no 610, Dom Bosco, CEP 36038-330 Juiz de Fora, MG, Brazil. E-mail: mirton.morenz@embrapa.br, marco.gama@embrapa.br, carlos.eugenio@embrapa.br, domingos.paciullo@embrapa.br, carlos.gomide@embrapa.br, fernando.lopes@embrapa.brEmbrapa Gado de LeiteBrazilJuiz de Fora, MG, BrazilEmbrapa Gado de Leite, Rua Eugênio do Nascimento, no 610, Dom Bosco, CEP 36038-330 Juiz de Fora, MG, Brazil. E-mail: mirton.morenz@embrapa.br, marco.gama@embrapa.br, carlos.eugenio@embrapa.br, domingos.paciullo@embrapa.br, carlos.gomide@embrapa.br, fernando.lopes@embrapa.br

Marco Antônio Sundfeld da Gama

Carlos Eugênio Martins

Domingos Sávio Campos Paciullo

Carlos Augusto de Miranda Gomide

Albert José dos Anjos

Universidade Federal dos Vales do Jequitinhonha e Mucuri, Programa de Pós-Graduação em Zootecnia, Rodovia MG-367, Km 583, no 5.000, CEP 39100-000 Diamantina, MG, Brazil. E-mail: albert@zootecnista.com.brUniversidade Federal dos Vales do Jequitinhonha e MucuriBrazilDiamantina, MG, BrazilUniversidade Federal dos Vales do Jequitinhonha e Mucuri, Programa de Pós-Graduação em Zootecnia, Rodovia MG-367, Km 583, no 5.000, CEP 39100-000 Diamantina, MG, Brazil. E-mail: albert@zootecnista.com.br

Afrânio Silva Madeiro

Escola Agrotécnica da Universidade Federal de Roraima, Campus Murupu, Rodovia 174, Km 37, s/no, CEP 69300-000 Boa Vista, RR, Brazil. E-mail: afraniomadeiro@hotmail.comUniversidade Federal de RoraimaBrazilBoa Vista, RR, BrazilEscola Agrotécnica da Universidade Federal de Roraima, Campus Murupu, Rodovia 174, Km 37, s/no, CEP 69300-000 Boa Vista, RR, Brazil. E-mail: afraniomadeiro@hotmail.com

Fernando César Ferraz Lopes

SCIMAGO INSTITUTIONS RANKINGS

Tabelas

Tabelas (7)

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Table 1.
Effect of rest period and grazing cycle on the concentrations of plasma metabolites in Holstein x Gyr cows grazing Urochloa brizantha 'Marandu'⁽¹⁾.

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Table 2.
Effect of rest period and grazing cycle on the chemical composition (% DM) and fatty acid profile (g 100 g^-1 of total fatty acids) of Urochloa brizantha 'Marandu'⁽¹⁾.

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Table 3.
Effect of rest period and grazing cycle on the estimated consumption of nutrients and fatty acids by Holstein x Gyr cows, in Urochloa brizantha 'Marandu' pasture⁽¹⁾.

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Table 4.
Effect of the rest period and grazing cycle on the production and composition of milk from Holstein x Gyr cows in an Urochloa brizanth a 'Marandu' pasture⁽¹⁾.

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Table 5.
Effect of rest period and grazing cycle on plasma fatty acid composition of Holstein x Gyr cows consuming Urochloa brizantha 'Marandu' pasture⁽¹⁾.

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Table 6.
Effect of the rest period and grazing cycle on milk fatty acid composition from Holstein x Gyr cows consuming Urochloa brizantha 'Marandu' pasture⁽¹⁾.

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Table 7.
Effect of the rest period on the milk fatty acid (FA) composition of Holstein x Gyr cows consuming Urochloa brizantha 'Marandu' pasture⁽¹⁾.

Table 1. Effect of rest period and grazing cycle on the concentrations of plasma metabolites in Holstein x Gyr cows grazing Urochloa brizantha 'Marandu'⁽¹⁾.

Plasma metabolite⁽²⁾	Rest period	Grazing cycle			SEM
Plasma metabolite⁽²⁾	Rest period	1	2	3	SEM
Nonesterified fatty acids (mmol L^-1)	Fixed	0.248Aa	0.136Ab	0.073Ab	0.0348
Nonesterified fatty acids (mmol L^-1)	Variable	0.131Aa	0.106Aa	0.112Aa	0.0348
Glucose (mg dL^-1)	Fixed	62.3Aa	61.3Aa	62.6Aa	1.4999
Glucose (mg dL^-1)	Variable	63.6Aab	65.0Aa	60.7Ab	1.4999
Nitrogen urea (mg dL^-1)	Fixed	16.2Ab	17.5Aab	19.0Aa	1.0142
Nitrogen urea (mg dL^-1)	Variable	15.8Ab	17.3Ab	21.7Aa	1.0142

⁽¹⁾
Means followed by equal letters, uppercase in the columns and lowercase in the rows, do not differ at 5% probability by the LSMeans test of SAS software (SAS Institute, Inc., Cary, NC, USA).⁽²⁾Treatment x grazing cycle interaction was significant at 5% probability. SEM, standard error of the mean.

Table 2. Effect of rest period and grazing cycle on the chemical composition (% DM) and fatty acid profile (g 100 g^-1 of total fatty acids) of Urochloa brizantha 'Marandu'⁽¹⁾.

Chemical composition⁽²⁾	Rest period	Grazing cycle			SEM
Chemical composition⁽²⁾	Rest period	1	2	3	SEM
Crude protein	Fixed	13.8Ab	15.2Aa	14.6Bab	0.2979
Crude protein	Variable	14.9Ab	14.1Ab	16.9Aa	0.2979
Ether extract	Fixed	3.2Aa	3.6Aa	3.5Aa	0.3131
Ether extract	Variable	3.8Aa	3.7Aa	4.0Aa	0.3131
Neutral detergent fiber	Fixed	61.8Aa	61.7Aa	61.8Aa	0.9115
Neutral detergent fiber	Variable	64.2Aa	62.8Aa	60.7Aa	0.9115
Lignin	Fixed	3.3Aa	3.9Aa	3.4Aa	0.3097
Lignin	Variable	3.5Aa	3.4Aa	3.8Aa	0.3097
In vitro dry matter digestibility(%)	Fixed	61.0Ba	63.0Aa	62.3Bab	0.5127
In vitro dry matter digestibility(%)	Variable	63.1Ab	61.6Ab	68.4Aa	0.5127
C16:0	Fixed	30.6Aa	29.6Aa	29.7Aa	0.5951
C16:0	Variable	29.7Ab	32.5Aa	27.5Ac	0.5951
C18:0	Fixed	1.8Aa	1.7Aa	1.6Aa	0.0475
C18:0	Variable	1.7Ab	2.0Aa	1.5Ab	0.0475
cis-9 C18:1	Fixed	3.5Aa	3.2Aa	3.6Aa	0.2509
cis-9 C18:1	Variable	3.0Aa	4.2Aa	3.0Aa	0.2509
cis-9, cis-12 C18:2	Fixed	21.1Aa	20.5Aa	21.5Aa	0.3967
cis-9, cis-12 C18:2	Variable	20.8Aa	22.6Aa	19.5Aa	0.3967
cis-9, cis-12, cis-15 C18:3	Fixed	35.8Ab	37.3Aab	37.9Aa	0.5169
cis-9, cis-12, cis-15 C18:3	Variable	39.4Aa	33.6Ab	37.8Aa	0.5169

⁽¹⁾
Means followed by equal letters, uppercase in the columns and lowercase in the rows, do not differ at 5% probability by the LSMeans test. ⁽²⁾Treatment x grazing cycle interaction was significant at 5% probability for crude protein and in vitro dry matter digestibility. SEM, standard error of the mean.

Table 3. Effect of rest period and grazing cycle on the estimated consumption of nutrients and fatty acids by Holstein x Gyr cows, in Urochloa brizantha 'Marandu' pasture⁽¹⁾.

Nutrient/Fatty Acid⁽²⁾	Rest period	Grazing cycle			SEM
Nutrient/Fatty Acid⁽²⁾	Rest period	1	2	3	SEM
Dry matter (kg per cow per day)	Fixed	11.6Aa	10.6Aa	11.4Ba	0.1918
Dry matter (kg per cow per day)	Variable	12.0Ab	10.6Ac	15.5Aa	0.1918
Dry matter (% live weight)	Fixed	2.35Aa	2.12Ab	2.23Bab	0.0585
Dry matter (% live weight)	Variable	2.34Ab	2.07Ac	3.04Aa	0.0585
Crude protein (kg per cow per day)	Fixed	1.60Ba	1.60Aa	1.66Ba	0.0421
Crude protein (kg per cow per day)	Variable	1.77Ab	1.50Ac	2.64Aa	0.0421
Ether extract (g per cow per day)	Fixed	364.5Bb	376.1Aab	401.9Ba	0.1521
Ether extract (g per cow per day)	Variable	453.6Ab	390.4Ac	624.3Aa	0.1521
Neutral detergent fiber (kg per cow per day)	Fixed	7.17Ba	6.52Ab	7.07Ba	0.1166
Neutral detergent fiber (kg per cow per day)	Variable	7.67Ab	6.65Ac	9.43Aa	0.1166
cis-9 C18:1 (g per cow per day)	Fixed	7.8Aa	6.2Bb	8.1Ba	0.5575
cis-9 C18:1 (g per cow per day)	Variable	7.7Ab	7.9Ab	10.6Aa	0.5575
cis-9, cis-12 C18:2 (g per cow per day)	Fixed	47.3Aa	39.5Ab	48.1Ba	2.1842
cis-9, cis-12 C18:2 (g per cow per day)	Variable	52.5Ab	42.7Ac	68.4Aa	2.1842
cis-9, cis-12, cis-15 C18:3 (g per cow per day)	Fixed	80.4Ba	72.0Ab	84.7Ba	2.9320
cis-9, cis-12, cis-15 C18:3 (g per cow per day)	Variable	99.2Ab	63.8Bc	132.9Aa	2.9320

⁽¹⁾
Means followed by equal letters, uppercase in the columns and lowercase in the rows, do not differ at 5% probability by the LSMeans test. ⁽²⁾Treatment x grazing cycle interaction was significant at 5% probability. SEM, standard error of the mean.

Table 4. Effect of the rest period and grazing cycle on the production and composition of milk from Holstein x Gyr cows in an Urochloa brizanth a 'Marandu' pasture⁽¹⁾.

Variable	Rest period	Grazing cycle			SEM
Variable	Rest period	1	2	3	SEM
		Milk composition
Fat (%)	Fixed	3.80Aa	3.79Aa	3.86Aa	0.2150
Fat (%)	Variable	3.57Ab	4.01Ab	4.30Aa	0.2150
Protein (%)	Fixed	2.91Ac	3.22Ab	3.41Aa	0.1175
Protein (%)	Variable	3.12Ac	3.40Ab	3.58Aa	0.1175
Lactose (%)	Fixed	4.48Aab	4.55Aa	4.42Ab	0.0541
Lactose (%)	Variable	4.40Aab	4.45Aa	4.30Ab	0.0541
Total solids (%)	Fixed	12.02Ab	12.37Aab	12.60Aa	0.2640
Total solids (%)	Variable	11.91Ac	12.62Ab	13.13Aa	0.2640
Nitrogen urea⁽²⁾ (mg dL^-1)	Fixed	14.29Bc	16.55Ab	18.70Ba	0.6965
Nitrogen urea⁽²⁾ (mg dL^-1)	Variable	16.38Ab	17.26Ab	22.01Aa	0.6965
		Milk production and components (kg per cow per day)
Milk⁽²⁾	Fixed	15.39Aa	13.75Ab	14.19Ab	0.5203
Milk⁽²⁾	Variable	16.38Aa	14.25Ab	12.81Ac	0.5203
Fat	Fixed	0.585Aa	0.513Aa	0.542Aa	0.0254
Fat	Variable	0.576Aa	0.567Aa	0.545Aa	0.0254
Protein	Fixed	0.448Aa	0.441Aa	0.482Aa	0.0149
Protein	Variable	0.504Aa	0.477Aa	0.453Aa	0.0149
Lactose⁽²⁾	Fixed	0.691Aa	0.626Ab	0.627Ab	0.0246
Lactose⁽²⁾	Variable	0.720Aa	0.635Ab	0.552Bc	0.0246
Total solids⁽²⁾	Fixed	1.851Aa	1.692Ab	1.780Aab	0.0523
Total solids⁽²⁾	Variable	1.935Aa	1.709Aab	1.668Ab	0.0523

⁽¹⁾
Means followed by equal letters, uppercase in the columns and lowercase in the rows, do not differ at 5% probability by the LSMeans test. ⁽²⁾Treatment x grazing cycle interaction was significant at 5% probability. SEM, standard error of the mean.

Table 5. Effect of rest period and grazing cycle on plasma fatty acid composition of Holstein x Gyr cows consuming Urochloa brizantha 'Marandu' pasture⁽¹⁾.

Fatty acid (g 100g^-1)	Rest period	Grazing cycle			SEM
Fatty acid (g 100g^-1)	Rest period	1	2	3	SEM
C16:0⁽²⁾	Fixed	9.654Aa	9.221Ab	9.033Ab	0.1398
C16:0⁽²⁾	Variable	9.008Ab	9.546Aa	9.385Aa	0.1398
C18:0⁽²⁾	Fixed	15.312Aab	15.028Ab	15.608Aa	0.3954
C18:0⁽²⁾	Variable	14.319Ac	15.263Ab	15.741Aa	0.3954
trans-11 C18:1	Fixed	0.677Ab	0.650Ab	0.771Aa	0.0428
trans-11 C18:1	Variable	0.606Ab	0.609Ab	0.728Aa	0.0428
cis-9 C18:1	Fixed	11.036Aa	10.764Aa	10.449Aa	0.3692
cis-9 C18:1	Variable	10.630Aa	11.333Aa	10.802Aa	0.3692
cis-9, cis-12 C18:2	Fixed	22.041Aa	21.682Aa	20.396Ab	0.6333
cis-9, cis-12 C18:2	Variable	22.082Aa	21.730Aa	20.592Ab	0.6333
cis-9, cis-12, cis-15 C18:3⁽²⁾	Fixed	5.326Ab	5.181Ab	5.842Aa	0.2969
cis-9, cis-12, cis-15 C18:3⁽²⁾	Variable	5.808Aa	5.033Ab	5.652Aa	0.2969
cis-9, trans-11 CLA	Fixed	0.119Aa	0.112Ab	0.119Aa	0.0083
cis-9, trans-11 CLA	Variable	0.127Aa	0.104Ab	0.121Aa	0.0083
C20:5 ω-3 Eicosapentaenoic acid (EPA)	Fixed	0.916Ab	0.982Ab	1.049Aa	0.0432
C20:5 ω-3 Eicosapentaenoic acid (EPA)	Variable	0.984Ab	1.047Ab	1.125Aa	0.0432

⁽¹⁾
Means followed by equal letters, uppercase in the columns and lowercase in the rows, do not differ at 5% probability by the LSMeans test. ⁽²⁾Treatment x grazing cycle interaction was significant at 5% probability. SEM, standard error of the mean.

Table 6. Effect of the rest period and grazing cycle on milk fatty acid composition from Holstein x Gyr cows consuming Urochloa brizantha 'Marandu' pasture⁽¹⁾.

Fatty acid (g 100g^-1)⁽²⁾	Rest period	Grazing cycle			SEM
Fatty acid (g 100g^-1)⁽²⁾	Rest period	1	2	3	SEM
Σ short-chain FA (C4:0 + C6:0 + C8:0 + C10:0)	Fixed	9.596Aa	9.638Aa	9.672Aa	0.2875
Σ short-chain FA (C4:0 + C6:0 + C8:0 + C10:0)	Variable	10.115Aa	9.700Ab	9.508Ab	0.2875
C12:0	Fixed	3.025Aa	3.082Aa	2.986Aa	0.1195
C12:0	Variable	3.269Aa	3.205Aa	2.932Ab	0.1195
C14:0	Fixed	10.759Aa	11.132Aa	10.599Ab	0.2295
C14:0	Variable	11.104Aa	11.199Aa	10.383Ab	0.2295
C18:0	Fixed	10.793Aa	9.405Ac	9.937Ab	0.3483
C18:0	Variable	10.567Aa	9.772Ab	11.078Aa	0.3483
trans-10 C18:1	Fixed	0.194Ab	0.152Ac	0.218Aa	0.0090
trans-10 C18:1	Variable	0.175Ab	0.142Ac	0.242Aa	0.0090
cis-9, cis-12, cis-15 C18:3 (ω-3)	Fixed	0.400Ab	0.407Ab	0.431Aa	0.0140
cis-9, cis-12, cis-15 C18:3 (ω-3)	Variable	0.400Aab	0.385Ab	0.421Aa	0.0140
cis-9, trans-11 CLA	Fixed	0.756Ab	0.791Ab	0.927Aa	0.0449
cis-9, trans-11 CLA	Variable	0.763Ab	0.711Ac	0.877Aa	0.0449

⁽¹⁾
Means followed by equal letters, uppercase in the columns and lowercase in the rows, do not differ at 5% probability by the LSMeans test. ⁽²⁾Treatment x grazing cycle interaction was significant at 5% probability. SEM, standard error of the mean.

Table 7. Effect of the rest period on the milk fatty acid (FA) composition of Holstein x Gyr cows consuming Urochloa brizantha 'Marandu' pasture⁽¹⁾.

FA (g 100 g^-1)	Rest period		Standard error of the mean	p-value
FA (g 100 g^-1)	Fixed	Variable	Standard error of the mean	p-value
C16:0	29.564a	28.896a	0.7296	0.5283
trans-9 C16:1	0.080a	0.073a	0.0330	0.1479
trans-9 C18:1	0.183a	0.176a	0.0028	0.0748
trans-11 C18:1	1.497a	1.444a	0.0540	0.5035
∑ trans C18:1 FA⁽²⁾	2.824a	2.780a	0.0659	0.6428
cis-9 C18:1	19.437a	19.724a	0.4843	0.6818
cis-9, cis-12 C18:2	0.766a	0.771a	0.0301	0.9128
trans-10, cis-12 CLA	0.009a	0.009a	0.0004	0.2297
trans-9, cis-11 CLA	0.022a	0.021a	0.0010	0.8117
C20:5 ω-3 (EPA)	0.038a	0.039a	0.0013	0.7561
C22:5 ω-3 (DPA)	0.068a	0.077b	0.0024	0.0289
∑ OBCFA⁽³⁾	4.277a	4.265a	0.0790	0.9132
Σ cis ω-3 FA	0.519a	0.518a	0.0142	0.9392
Σ cis ω-6 FA	0.998a	1.021a	0.0355	0.6524

⁽¹⁾
Means followed by equal letters do not differ at 5% probability by the LSMeans test. ⁽²⁾Σ trans C18:1 FA = trans-4 C18:1 + trans-5 C18:1 + trans 6-8 C18:1 + trans-9 C18:1 + trans-10 C18:1 + trans-11 C18:1 + trans-12 C18:1 + trans-13 and trans-14 C18:1 + trans-16 C18:1. ⁽³⁾Σ OBCFA (odd and branched-chain fatty acids) = Σ anteiso FA + iso FA + (C5:0 + C7:0 + C9:0 + C11:0 + C15:0 + C17:0 + cis-9 C17:1 + C21:0 + C23:0).

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[TFN1] ⁽¹⁾
Means followed by equal letters, uppercase in the columns and lowercase in the rows, do not differ at 5% probability by the LSMeans test of SAS software (SAS Institute, Inc., Cary, NC, USA).⁽²⁾Treatment x grazing cycle interaction was significant at 5% probability. SEM, standard error of the mean.