Abstract
Compared to pasture based sistems, milk produced in confined dairy systems is characterized by a high saturated fat (SF) content with a lower concentration of healthy fatty acids (FA) such as vaccenic (VA, trans-11C18:1), conjugated linoleic cid (cis-9, trans-11 C18:2, CLA), α-linolenic (cis-9, cis-12, cis-15C18: 3), eicosapentaenoic (EPA, C20:5) and docosahexaenoic (DHA, C22:6) whose presence in milk and dairy products can be increased by feeding polyunsaturated FA (PUFA). The aim of the study was to determine the differences in milk composition and FA profile between a regular (Reg) milk (Reg-Milk), a Reg-Dambo type cheese (Reg-DCh) and a Reg yogurt (Reg-Yog) with that obtained after including a blend (7:1) of soybean (SO) and fish (FO) oils in the total mixed ration (TMR) of lactating dairy cows. The experiment was carried out at the Talar Farm located at Laguna del Sauce, Maldonado Department, Punta del Este, Uruguay Republic during a period of 30 experimental days using a single production batch of 29 Holstein cows. Within this batch, one group of 8 cows (1.88 ± 0.99 calves) in early lactation (135 ± 19 days postpartum) was selected to individually measure milk yield and composition. During the first 7 days of the experiment, cows were fed a TMR without oil-blend inclusion to obtain the Reg-Milk, Reg-DCh and Reg-Yog. From the 8th day onwards, the oil blend was added to the TMR at 4% DM (1.0 kg oil blend cow-1 day-1) and after 23 days of feeding, the modified milk (Mod-Milk) was analyzed and collected to elaborate the modified Dambo-type cheese (Mod-DCh) and Mod-yogurt (Mod-Yog). Milk yield was recorded daily in the selected 8 cows and milk composition was determined over two consecutive days prior to the start of blend-oil supply (Reg-Milk) and at the end of oil supplementation (Mod-Milk) on days 29th and 30th. Milk-tank samples of Reg-Mi and Mod-Mi were also collected and analyzed for chemical composition and milk FA profile. Cheese and yogurt were assayed for its FA profile. Differences in milk yield and composition and in the FA profile before and after oil-feeding were stated using the Student T-test for paired observations. Milk production (kg·cow-1·day-1) slightly (-6.7%) decreased (P -1 g leading to a lower (P -1·day-1) of fat corrected milk (4%FCM) from 32.83 (before) to 29.63 after oil. Milk protein content (g 100 g-1) increased (P -1·day-1) (P -1 in Mod-Mi as it was observed (P -1). Yield of NFS tended (P -1·day-1after oil supply. Content of atherogenic FA (C12:0 to C16:0) was significantly (P -1 (Mod-Mi) with a concomitant decrease (P -1 FA) of elaidic (trans-9 C18:1) and trans-10 C18:1 FA was low in Reg-Mi (0.22 and 0.34 respectively) but tended (P -1 FA) of VA resulted higher (+110%, P -1 FA) increased (P -1) of α-linolenic were higher (P cis-9 C18:1) content (g 100 g-1) remained unchanged (P < 0.504) averaging 21.99 in Reg-Mi and 22.86 in Mod-Mi. Composition of FA of the Mod-DCh was highly correlated (R2 = 0.999) with FA profile from its original Mod-Mi. A serving of the M-DCh (30 g) theoretically involved a 12.1% reduction in total fat consumption with 16.9% less in SF intake compared to the Reg-Ch. A serving of the M-DCh could putatively increase total CLA consumption by 72.7% compared to the Reg-DCh. Compared to Reg-Yo, a portion (178 g) of the Mod-Yo could increase (69.4%) total CLA intake. The nutritional value of milk fat was improved by feeding a blend of PUFA oils to confined dairy cows and the consumption of the mofified dairy products obtained could promote a lower intake of the potentially atherogenic saturated FA and some increase in healthy FA ingestion.
Highlights
The growing incidence in the modern society of noncommunicable cardiovascular and chronic diseases plus the increase of cases of childhood obesity implies a significant economic and social burden for the states and creates the need to produce food capable of mitigating these risks
The aim of the study was to determine the differences in milk composition and fatty acids (FA) profile between a regular (Reg) milk (Reg-Milk), a Reg-Dambo type cheese (Reg-DCh) and a Reg yogurt (Reg-Yog) with that obtained after including a blend (7:1) of soybean (SO) and fish (FO) oils in the total mixed ration (TMR) of lactating dairy cows
The TMR averaged 43.26% DM with 17.62% crude protein, 35.91% neutral detergent fiber (NDF), 2.74 Mcal∙kg−1 DM of estimated metabolizable energy content and a forage:concentrate ratio of 47:53. It was offered at 4.55% of the average live weight of the production-batch (29 cows) and thoroughly consumed by cows which implied a daily allowance of 25 kg DM cow−1∙day−1 equivalent to 57.8 kg TMR as fed
Summary
The growing incidence in the modern society of noncommunicable cardiovascular and chronic diseases plus the increase of cases of childhood obesity implies a significant economic and social burden for the states and creates the need to produce food capable of mitigating these risks. Milk and its derivatives represent the largest contribution in the consumption of saturated fatty acids (SFA), which represents a potential risk of chronic cardiovascular diseases, obesity and metabolic syndrome [1] [2] [3]. The potentially unhealthy milk SFA are lauric (C12:0), myristic (C14:0) and palmitic (C16:0) for their putative atherogenic role when consumed in excess [4]. Those SFA have been associated with the risk of cardiovascular disease [5] [6]. Milk and dairy are the main natural foods containing the conjugated linoleic acids (CLA) with promising cardioprotective [3] and antitumor [7] [8] [9] properties. Experimental evidence of the CLA’s contribution to cancer patients is still insufficient but both, cis-9, trans-11C18:2 CLA (rumenic acid) and trans-10, cis-12C18:2 CLA, have shown promising effects in animal studies or in in vitro cell cultures with different tumor lines [7] [8] [9]
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