Milk Fat Depression and Trans-11 to Trans-10 C18:1 Shift in Milk of Two Cattle Farming Systems

Milk fat depression (MFD) syndrome, a consistent decrease in milk fat content, is related to important changes in fatty acid composition due to feed imbalances and the consequent ruminal metabolism alteration. Milk produced in two different farming systems was compared: Holstein Friesian fed with unified in intensive production and Podolica raised on a pasture in an extensive system. Milk chemical characteristics and fatty acid composition were determined comparing milk with a normal fat level (>3.8%) to milk with a low fat level (<3.2%) in each breeding system. Holstein Friesian milk showed the decrease in trans-11 and increase in trans-10 C18:1 (shift from trans-11 to trans-10 C18:1) in low fat with respect to normal fat milk with a consequent decrease in the trans-11/trans-10 C18:1 ratio. Even conjugated linoleic acid (CLA), C18:2 cis-9, trans-11, was lower while CLA trans-10, cis-12 was higher in low fat milk than in normal fat milk from Holstein Friesian. These changes, that are indicators of MFD syndrome, were not found in Podolica milk between fat levels. Holstein Friesian milk showed less short-chain fatty acids (9.48 % vs. 11.05%, p < 0.001), trans vaccenic acid (C18:1 trans-11, 0.51% vs. 3.39%, p < 0.001), rumenic acid (CLA C18:2 cis-9, trans-11, 0.32% vs. 1.45%, p < 0.001) and total CLA (0.53% vs. 1.91%, p < 0.001) contents than Podolica milk. Further losses of these human healthy nutrients in low fat Friesian milk reduced the nutritional quality of the milk, while the milk from animals raised on the pasture was of better quality even when the level of fat was low.

Stearic acid does not overcome trans-10, cis-12 CLA-induced milk fat depression in lactating ewes

The objective of this study was to test the hypothesis that stearic acid supplementation increases milk fat content and overcomes the antilipogenic effects of trans-10, cis-12 conjugated linoleic acid (CLA) in lactating ewes. Twenty-eight Lacaune ewes (36 ± 2 DIM; 70.5 ± 9.6 kg BW), producing 1.8 ± 0.4 kg of milk/day were used in a completely randomized design (7 ewes/treatment) for 21 days. The treatments were: 1) Control; 2) CLA (6.4 g/day of trans-10, cis-12 CLA); 3) SA (28 g/day of stearic acid) and; 4) CLASA (6.4 g/day of trans-10, cis-12 CLA plus 28 g/day of stearic acid). All data were analyzed using a mixed model that included the fixed effect of treatment and the random effect of ewe. SA did not alter milk fat content and yield relative to Control (91.9 vs. 91.2 ± 4.1 g/d). SA in association with trans-10, cis-12 CLA (CLASA) was not able to overcome the reduction in fat content and fat yield induced by CLA (75 vs. 82 ± 0.14 g/d). SA increased the relative abundance of CD36, FABP4 and PPAR-γ mRNA by 140%, 112% and 68% compared to CLASA. SA also reduced the relative abundance of ACACAα PII and SCD when compared to Control (45% and 39%). Compared to CLA, CLASA treatment had no effect on the mRNA abundance of FASN, LPL, CD36, SCD, FABP4, AGPAT6, SREBP1 and PPAR-γ. In conclusion, stearic acid supplementation did not increase milk fat synthesis and did not overcome the CLA-induced milk fat depression when associated with trans-10, cis-12 CLA.

Economic Importance and Management Strategies for Alleviation of Milk Fat Depression in Dairy Animals: A Review

Dairying is an important service sector in India, contributing 4.11 per cent to national GDP and provides secondary occupation to 69.00 per cent of the farming community. From the decades there is a major concern and research mainly focused on increasing the milk yields while milk fat per cent is largely being ignored. As a result, FSSAI had to decrease cow milk standards by 0.30 per cent from average 3.50 per cent milk fat to 3.20 per cent. Milk fat per cent is the important determinant of milk price both in unorganized and organized sector. Per unit (0.10 per cent) of decrease in milk fat per cent can incur a direct loss of 1.66 per cent to dairy farmer’s income. Milk fat depression is largely a nutrition related metabolic disorder and trans-10, cis-12 CLA isomer has been found to be chief culprit. It is a less attended metabolic disorder in India; which is causing huge losses to the dairy farmers. Not a single factor is responsible for it and generally due to lack of adequate nutritional and management knowledge, farmers are unable to identify and cure this multi factorial disorder. Milk fat depression can be influenced and managed by different factors like particle size of feed / fodder, feed processing, ionophores, dietary fatty acid intake, conditions that cause decrease in rumen pH and overcrowding etc.

Milk Production and Energetic Metabolism of Heat-Stressed Dairy Goats Supplemented with Propylene Glycol

Heat-stressed dairy animals increase their reliance on glucose. This elevated glucose demand is partially met by increasing the conversion of glucogenic amino acids (AA) in the liver. Propylene glycol (PG) is a glucogenic precursor and was not tested in dairy goats under thermoneutral (TN) and heat stress (HS) conditions simultaneously. We hypothesize that if HS-goats are fed with PG, they would get more glucose and consequently spare more glucogenic AA for milk protein synthesis rather than gluconeogenesis. Eight multiparous dairy goats (40.8 ± 1.1 kg body weight; 84 ± 1 days in milk) were used in a replicated 4 × 4 Latin square design of 4 periods; 21 d each (14 d adaptation, 5 d for measurements, and 2 d of transition). Goats were allocated to one of 4 treatments in a 2 × 2 factorial arrangement. Factors were control (CO) without PG or 5% of PG, and thermoneutral (TN; 15 to 20 °C) or heat stress (HS; 12 h/d at 37 °C and 12 h/d at 30 °C) conditions. Feed intake, rectal temperature, respiratory rate, milk yield, milk composition, and blood metabolites were measured. Compared to TN, HS goats had lower (p < 0.01) feed intake (–34%), fat-corrected milk (–15%), and milk fat (–15%). Heat-stressed goats also tended (p < 0.10) to produce milk with lower protein (–11%) and lactose (–4%) contents. Propylene glycol increased blood glucose (+7%; p < 0.05), blood insulin (+37%; p < 0.10), and body weight gain (+68%; p < 0.05), but decreased feed intake (–9%; p < 0.10) and milk fat content (–23%; p < 0.01). Furthermore, blood non-esterified fatty acids (–49%) and β-hydroxybutyrate (–32%) decreased (p < 0.05) by PG. In conclusion, supplementation of heat-stressed dairy goats with propylene glycol caused milk fat depression syndrome, but reduced body weight loss that is typically observed under HS conditions. Supplementation with lower doses of PG would avoid the reduced feed intake and milk fat depression, but this should be tested.

Liver X receptor α participates in LPS-induced reduction of triglyceride synthesis in bovine mammary epithelial cells

Lipopolysaccharides (LPS) could induce milk fat depression via regulating the body and blood fat metabolism. However, it is not completely clear how LPS might regulate triglyceride synthesis in dairy cow mammary epithelial cells (DCMECs). DCMECs were isolated and purified from dairy cow mammary tissue and treated with LPS. The level of triglyceride synthesis, the expression and activity of the liver X receptor α (LXRα), enzymes related to de novo fatty acid synthesis, and the expression of the fatty acid transporters were investigated. We found that LPS decreased the level of triglyceride synthesis via a down-regulation of the transcription, translation, and nuclear translocation level of the LXRα. The results also indicated that the transcription level of the LXRα target genes, sterol regulatory element binding protein 1 (SREBP1), fatty acid synthetase (FAS), acetyl-CoA carboxylase-1 (ACC1), were significantly down-regulated in DCMECs after LPS treatment. Our data may provide new insight into the mechanisms of milk fat depression caused by LPS.