Resumo

MARTINEZ-BORRAZ, Alfonso et al. Conjugated linoleic acid (CLA) content in milk from confined Holstein cows during summer months in northwestern Mexico. Rev. mex. de cienc. pecuarias [online]. 2010, vol.1, n.3, pp.221-235. ISSN 2448-6698.

Experimental animal studies suggest that conjugated linoleic acid (CLA) has beneficial health properties. Ruminant-derived products such as meat and milk are the principal natural sources of CLA. Milk CLA content is influenced by several factors, including diet and production system. An evaluation was done of CLA content in milk from confined Holstein cows at a farm in Hermosillo municipality, Sonora State, Mexico, during the summer months, when daytime temperatures surpass 40 °C. Milk samples were collected from 120 cows. Quality parameters such as fat, lactose, protein and total solids percentages were measured using AOAC methods. The fatty acid and CLA profile was generated by gas chromatography. Average milk production was 15.8 ± 0.5 kg/day, fat content was 1.91 ± 0.06%, lactose content was 4.30 ± 0.2%, protein content was 3.34 ± 0.03 and total solids content was 10.4 ± 0.09%. Unsaturated fatty acids content was higher (P<0.05) in August than during June and July. Average cis-9, trans-11 CLA concentration was 9.36 mg/g fat (10.78 ± 0.41 in June; 8.50 ± 0.37 in July; and 10.16 ± 0.39 in August), which is high compared to concentrations reported in countries with a temperate climate. The relatively high CLA content observed in the present study was probably caused by the 58.8% alfalfa content in the summer diet, since this legume is rich in CLA fatty acids precursors (linoleic and linolenic acid).

Palavras-chave : Conjugated linoleic acid; Cows milk; High ambient temperature.

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