Productive performance and composition of milk protein fraction in dairy cows supplemented with fat sources

Abstract

-The objective of this study was to evaluate the use of fat sources in rations for lactating cows on the productive performance and composition of milk protein fraction. Twelve Holstein cows were used, grouped in three balanced 4 × 4 Latin squares, fed with the following rations: control; refined soybean oil; whole raw soybean; and calcium salts of unsaturated fatty acid (Megalac-E). Dry matter and nutrient intake, and daily milk production were evaluated. The samples used to analyze milk composition were collected in two alternate days and were obtained from two daily milking. Milk composition and total nitrogen, non-protein nitrogen and non-casein nitrogen ratios were analyzed. The casein, serum protein and true protein ratios were obtained by difference. Dry matter and nutrient intakes were lower when cows received the diet containing calcium salts of fatty acids, in relation to the control diet. Among the diets with fat sources, the one with whole raw soybean and calcium salts decreased milk production. There was no effect of fat sources added to the diet on crude protein, non-protein nitrogen, non-casein nitrogen, true protein, casein, casein/milk true protein ratio and serum protein. Similarly, the experimental diets did not influence the protein fractions when expressed in percentage of milk crude protein. The utilization of fat sources in diets changes milk production and composition of lactating cows, but does not influence the composition of milk protein fractions.Key Words: fat supplementation, intake, milk production and composition, non-protein nitrogen, true proteinDesempenho produtivo e composição da fração proteica do leite de vacas leiteiras sob suplementação com fontes de gordura RESUMO -Objetivou-se com este estudo avaliar a utilização de fontes de gordura em rações para vacas em lactação sobre o desempenho produtivo e a composição da fração proteica do leite. Foram utilizadas 12 vacas da raça Holandesa, agrupadas em três quadrados latinos balanceados 4 × 4, alimentadas com as seguintes rações: controle; óleo de soja refinado; grão de soja in natura; e sais de cálcio de ácidos graxos insaturados (Megalac-E). Avaliaram-se o consumo de matéria seca e de nutrientes, e a produção diária de leite. As amostras utilizadas para análise da composição do leite foram coletadas em dois dias alternados e foram provenientes das duas ordenhas diárias. Foram analisados a composição do leite e os teores de nitrogênio total, nitrogênio não-proteico e nitrogênio não-caseinoso. Por diferença, foram obtidos os teores de caseína, proteína do soro e proteína verdadeira. O consumo de matéria seca e de nutrientes foi menor quando as vacas receberam a ração contendo sais de cálcio de ácidos graxos em relação à ração controle. Entre as rações com fontes de gordura, aquela com grão de soja e sais de cálcio diminuiu a produção de leite. Não houve efeito das fontes de gordura adicionadas nas rações sobre os teores de proteína bruta, nitrogênio não-proteico, nitrogênio não-caseinoso, proteína verdadeira, caseína, r...

Productive performance and milk protein fraction composition of dairy cows supplemented with sodium monensin

“…The results for casein content found in this study are similar to the levels reported by Bateman et al (1999). Concentrations of milk true protein, and casein, as expressed in %CP, are in accordance to the values reported by Coulon et al (1998) andFreitas Jr. et al (2010).…”

Intake, apparent digestibility, production, and composition of milk from cows fed diets with different sources of lipids

“…Furthermore, we believe that the quality of the pasture provided a satisfactory intake of nutrients, which met the requirements of the animals when associated with the forage, thus fulfilling the requirements for their milk production levels. Freitas Júnior et al (2010) did not find any effects on the corrected milk production when using different sources of lipids in the diet of lactating cows with 55.0 g/kg of EE in the dietary dry matter. According to the results of Borba et al (2006), Freitas Júnior et al (2010, and the present work, levels of up to 80 g/kg of EE in the diet do not interfere with the production, and the producer may opt for the diet that is most economic.…”

“…Freitas Júnior et al (2010) did not find any effects on the corrected milk production when using different sources of lipids in the diet of lactating cows with 55.0 g/kg of EE in the dietary dry matter. According to the results of Borba et al (2006), Freitas Júnior et al (2010, and the present work, levels of up to 80 g/kg of EE in the diet do not interfere with the production, and the producer may opt for the diet that is most economic. Costa et al (2007) reported increased corrected milk production when using diets with 50.0 g/kg of EE containing protected oil, whole rice meal plus rice oil, and whole rice meal plus bovine tallow as sources of lipids.…”

“…Vargas et al (2002) observed a reduction in dry matter intake when soybeans and soy oil were used in the diets of dairy cows, with a higher decrease in DMI occurring in the diet containing soy oil. Moallem et al (2007) and Freitas Júnior et al (2010) also reported a reduction in DMI with the use of protected (calcium salts) and unprotected (soy oil) lipid sources.…”

“…They each have specific characteristics that impart different effects on ruminal fermentation, nutrient digestibility, dry matter intake, and milk production and composition (Freitas Júnior et al, 2010). Generally, alternative sources of lipids such as frying oil and cottonseed are low-cost, which increases interest in maximizing their use in the dairy cow diets.…”