Produção e composição química do leite de vacas suplementadas com diferentes fontes proteicas

Milk production and chemical composition of dairy cows supplemented with different protein sources

ABSTRACT - The objective of this study was to evaluate the supplementation of dairy cows with different alternative protein sources on milk production and chemical composition. Eight crossbreed cows (Holstein × Gyr) were distributed into two simultaneous (4 × 4) Latin squares. The following treatments were tested: common-bean by-product, soybean meal, sunflower meal, and cottonseed meal. Variance-covariance structures were tested by corrected Akaike’s criterion to determine the best data adjustment. Regarding milk yield, there was a trend of superiority for soybean meal for common-bean by-product (for which soybean meal and sunflower showed the best results) and milk yield corrected to 4% fat, for which only soybean meal presented remarkable results. Soybean meal can be considered the most suitable with regard to milk yield and chemical composition.

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Introdução

Aiming at lower production costs for animal products, rational use of all food sources has been significantly emphasized in the present days. In this way, several by-products from agriculture and/or animal production, when employed in a rational manner, can contribute to reducing the costs of animal feeding (CARVALHO JÚNIOR et al. 2010).

By-products and wastes originating from the processing of grains are a promising alternative to reduce the feeding costs of dairy animals. Sensible use of these products depends on their nutritional properties and other factors (PEREIRA, 2000).

The substitution of soybean meal for alternative protein sources without reducing the animal performance can be an interesting alternative to reduce the costs of the feeding dairy animals. However, the auspicious possibility of employing these ingredients in diets for ruminants requires significant careful, strategic, technical, and financial evaluations and analysis upon the market opportunities (PINA et al. 2006).

The goal this study was to evaluate the effect of supplementing dairy cows with different protein sources (soybean meal, cottonseed meal, sunflower meal, and common-bean by-product) on nutrient intake and digestibility.

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Revisão Bibliográfica

Feeding represents the highest cost of livestock, especially when using a supplementary source such as soybeans, in spite of high nutritional quality, it is generally costly, making it necessary to use alternative food sources that are cheaper and do not compete directly with Human consumption (SANTOS, 2010).

The protein is considered an expensive nutritional ingredient, and, in most cases, the nutrient of highest quantitative requirement. For these reasons, the protein is an important object of studies aimed at increasing its use efficiency through strategic utilization, or substitution of the traditionally used feedstuffs for others with better cost-benefit ratio.

Generally, soybean meal is used as the main source of protein in animal feed. However, its use in human food and feed for non-ruminants leads to the need for importation, making its use restricted (SANTOS, 2010). In addition, the price of soybeans is regulated by the international market, depending on the demand by the consuming countries. Therefore, it is essential to search for alternative foods that do not compromise the performance of animals and that can make the productive system economically viable.

When using cottonseed meal associated with urea in replacement of soybean meal for cows with an average milk production of 11.55 kg / day Silva et al. (2009) observed that the consumption of dry matter was not influenced, this same behavior was also observed by Alves et al. (2010) and Pina et al. (2006), when they included dietary cotton meal for lactating cows.

Elfert et al., 2006 when evaluating the milk production and composition of cows fed soybean oil did not observe differences on milk production, the authors mention that the reduction in consumption allowed the diets with oil to present higher feed efficiency (9.8%).The literature has differed regarding the responses with alternative supplements for milk cows, which depend on the stage of lactation, the food and the level used.

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Materiais e Métodos

Eight crossbred cows (Holstein × Gyr) with an average weight of 554.59±30.43 kg, milk yield of 14.85±3.28 kg/day, and at 60 to 90 days in milk were used in this experiment. The animals were kept in paddocks with signal grass (Brachiaria brizantha cv. MG5) equipped with drinkers and troughs in a rotational grazing system.

Cows were distributed into two simultaneous 4 × 4 Latin squares. The experiment lasted 84 days, and each period had 21 days, with the first 14 days used for adaptation and the others seven days for data collection.

Treatments were formulated as follows: soybean meal, cottonseed meal, sunflower meal, and common-bean by-product. The diets were formulated according to the production requirements of the animals and in accordance with the recommendations of NRC (2001)

The milk was weighed and milk samples were collected on the 15th and 17th days of each experimental period. Right after collection, milk samples were sent to the laboratory, where the milk solids were analyzed.

The milk yield was corrected for 4% of fat (MY4, kg), using the formula described in NRC (1989): MY4 = 0.4 (kg milk) + 15 (kg milk fat).

The statistical model was adjusted using the PROC MIXED procedure of SAS (Statistical Analysis System, version 9) with restricted maximum likelihood (REML) as the estimation method. The REPEAT command was utilized with ck as subjects. 

The variance-covariance matrix was modeled as variance components, compound symmetry, first order auto-regressive correlations, and unrestricted variance–covariance structures (Littell et al. 2006). The likelihood of the different variance-covariance structures was assessed by computing Akaike’s information criterion (AKAIKE 1974). Treatment means were compared by Tukey’s test at 5% probability level.

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Resultados e Discussão

Milk yield and MY4 were influenced by the diets. In the first case, soybean meal and sunflower meal were superior, while for MY4, only the soybean meal showed higher values. For these two variables, the common-bean by-product was the worst supplement in productive terms (Table 1).

Regarding the chemical composition of milk, most of the components evaluated were not influenced by the diets, such that the average ± confidence interval estimates were presented as representative of these variables. The only exception was total solids, for which the soybean meal supplement demonstrated superiority in comparison with sunflower meal, while the other treatments resulted in intermediate values (Table 1).

Considering milk yield, the same trend of superiority for soybean meal was observed for MY (for which soybean meal and sunflower meal provided the best results), for which only soybean meal showed outstanding results.

The common-bean by-product showed the worst values for the milk yield variables. This shows that caution is necessary in the use of this supplement when the aim is milk production, notwithstanding the fact that the evaluation of this variable is not appropriate for the experimental design employed in this study, but a slight response trend can be obtained.

Controversial results are found in the literature as regards the productive yield of dairy cows supplemented with different protein sources. These studies reveal from absence of significant effect (PINA ET AL. 2006; MENA ET AL. 2004) to a linear decrease in milk production with the inclusion of common-bean by-product (MAGALHÃES et al. 2008).

The chemical composition of milk was not altered significantly by the supplement; the only exception is total solids, which followed the same trend as milk yield (and 4% fat-corrected milk yield), for which soybean meal was the best alternative.

 

     Table 1 - Yield and composition of milk according to experimental diet

Variable	Treatment				Mean ± CI
	Common-bean by-product	Soybean meal	Sunflower meal	Cottonseed meal
MY (kg day‒1)	12.1±1.6B	15.9±1.6A	15.3±1.6A	14.9±1.6AB	na
MY4 (kg day‒1)	10.5±1.7C	14.4±1.7A	12.1±1.7BC	12.7±1.7AB	na
Fat (g kg‒1)	27.5±4.5	28.9±4.5	22.8±4.5	25.0±4.5	26.1±4.4
P (g kg‒1)	31.5±3.1	32.2±3.2	31.6±3.2	31.4±3.2	31.7±3.1
L (g kg‒1)	45.1±2.5	45.3±2.5	45.4±2.5	45.6±2.5	45.3±2.5
TS (g kg‒1)	113.3±7.3AB	115.6±7.3A	108.9±7.3B	111.2±7.3AB	na
SN (g kg‒1)	85.7±3.9	86.7±3.9	86.1±3.9	86.3±3.9	86.2±3.9
SCC (× 1000 mL‒1)	88.1±15.9	127.1±127.2	124.4±37.1	188.5±138.9	132.0±154.8
UN (mg dL‒1)	16.8±1.7	18.5±1.7	17.6±1.7	15.9±1.7	17.2±1.7
C (g kg‒1)	23.9±2.8	24.3±2.8	24.1±2.8	24.1±2.8	24.1±2.8
PCas (g kg‒1 of protein)	759.5±18.3	753.9±18.3	761.5±18.3	767.8±18.3	760.7±18.3

Means in the row followed by different letters differ according to Tukey’s test (P<0.05).

MY – milk yield; MY4 - 4% fat-corrected milk yield; P – protein; L – lactose; TS – total solids; SN – solids nonfat; SCC - somatic cell count; UN – urea nitrogen; C – casein; PCas - protein from casein; na - not applicable

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Conclusões

Considering the supplements employed in this study, soybean meal can be considered the most suitable with regard to milk yield and chemical composition. The common-bean by-product may be an interesting alternative to soybean meal in regions where it is available in large quantities. However, caution is necessary in the use of this waste, due mainly to the possible decrease in milk production.

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Gráficos e Tabelas

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Referências

AKAIKE H. A new look at the statistical model identification. IEEE Trans. Automat. Contr. V.19, p.716-723, 1974.

 

ALVES, F.A.; ZERVOUDAKIS, L.K.H.; CABRAL, L.S., et. al. Substituição do farelo de soja por farelo de algodão de alta energia em dietas para vacas leiteiras em produção: consumo, digestibilidade dos nutrientes, balanço de nitrogênio e produção leiteira. Revista Brasileira de Zootecnia, v.39, n.3, p.532-540, 2010.

 

CARVALHO, J.R.; PIRES, A.J.V.; VELOSO, C.M.; SILVA, F.F.; REIS, R.A.; CARVALHO, G.G.P. Digestibilidade aparente da dieta com capim-elefante ensilado com diferentes aditivos. Arquivo Brasileiro de Medicina Veterinária e Zootecnia. V.62, p.889-897, 2010.

 

EIFERT, E.D.C.; LANA, R.D.P.; LANNA, D.P.D.; LEOPOLDINO, W. M.; OLIVEIRA, M. V. M. D.; ARCURI, P. B.; VALADARES FILHO, S. D. C. Consumo, produção e composição do leite de vacas alimentadas com óleo de soja e diferentes fontes de carboidratos na dieta. Revista Brasileira de Zootecnia. V. 35, p. 211-218, 2006.

 

LITTELL, R.C.; MILLIKEN, G.A.; STROUP, W.W.; WOLFINGER, R.D.; SCHABENBERGER O. SAS^® for Mixed Models. SAS Institute Inc, Cary, USA. 2006.

 

MAGALHÃES, A.L.R.; ZORZI, K.; QUEIROZ, A.C.; MELLO, R.; DETMANN, E.; PEREIRA, J.C. Consumo e digestibilidade aparente total dos nutrientes, produção e composição do leite de vacas alimentadas com dietas contendo diferentes fontes de proteína. Revista Brasileira de Zootecnia, V.37, p.529-537, 2006.

 

MENA, H.; SANTOS, J.E.P.; HUBER, J.T.; TARAZON, M.; CALHOUN, M.C. The effects of varying gossypol intake from whole cottonseed and cottonseed meal on lactation and blood parameters in lactating dairy cows. J. Dairy Sci. v. 87, p.2506-2518, 2004.

 

NRC - National Research Council.. Nutrient requirements of dairy cattle. 7th ed. National Academic Press, Washington, D.C. 381p. 2001.

 

PEREIRA, J.C. Vacas leiteiras – aspectos práticos da alimentação. Viçosa, MG: Editora Aprenda Fácil, 198p. 2000.

 

PINA, D.S.; VALADARES FILHO, S.C.; VALADARES, R.F.D.; CAMPOS, J.M.S.; DETMANN, E.; MARCONDES, M.I.; OLIVEIRA, A.S.; TEIXEIRA, R.M.A. Consumo e digestibilidade aparente total dos nutrientes, produção e composição do leite de vacas alimentadas com dietas contendo diferentes fontes de proteína. Revista Brasileira de Zootecnia. V.35, p.1543-1551, 2006.

 

SILVA, M.S.; FERREIRA, M.A.; GUIM, A. et al. Replacement of soybean meal by cottonseed meal in diets based on spineless cactus for lactation cows. Revista Brasileira de Zootecnia, v.38, n.10, p.1995-2000, 2009.

SANTOS, V.F.L. Fontes alternativas de proteína para vacas em lactação. 42. Dissertação – Universidade Federal Rural do Pernanbuco. 2010.