The effect of feeding whole-crop barley or black oat silage in the fatty acid content of milk from cows in small-scale dairy systems in the highlands of Mexico.

Abstract

Diets have an important effect on the fatty acid (FA) content in milk from dairy cows so that feeding strategies may modify the FA profile. There is little information on the fatty acid contents of whole-crop barley (BLY) and black oat (BKO) silages and on milk from cows fed these silages that are an alternative forage for small-scale dairy systems (SSDS). Given the growing interest in foods with favourable health attributes, the objective was to identify the FA content of milk from dairy cows fed whole-crop BLY and BKO silages in small-scale systems. Three inclusion levels of BLY and BKO silage were assessed in nine lactating cows at pasture for 8h/day and supplemented with 4.6kg/DM/cow/day commercial concentrate. Treatments were BLY: 10kg DM/cow/day BLY silage; BKO: 10kg DM/cow/d BKO silage; and BLY/BKO: 5kg BLY and 5kg DM/cow/d BKO silages (50:50). A 3 × 3 Latin square design repeated three times with nine cows and 14-day periods was utilised. Variables evaluated were the content of fatty acids present in feeds and milk. Contents of linoleic (C18:2n-6) and linolenic (C18:3n-3) acids, as precursors of polyunsaturated fatty acids, were 46 in BLY and 50 BKO g/100g, lower than for multispecies pasture (61g/100g). There were statistical differences in the content of short-chain fatty acids in milk (P < 0.05), being lower for BLY (18.9g/100g) compared with BKO (20.4g/100g) and BLY/BKO (20.6g/100g), the saturated fatty acids and linoleic acid (C18:2n-6c) were higher in BLY/BKO in relation to BLY and BKO. Content of health-promoting polyunsaturated fatty acids in milk was higher in BLY/BKO (P < 0.05). There were no differences (P < 0.05) in the atherogenic index, with values within reports. Small-grain cereal forages may produce milk with a favourable fatty acid content for human health.