Oral administration of cobalt acetate alters milk fatty acid composition, consistent with an inhibition of stearoyl-coenzyme A desaturase in lactating ewes

Consequences of herbal mixture supplementation on milk performance, ruminal fermentation, and bacterial diversity in water buffaloes

This study was aimed to evaluate the potential of a herbal mixture (HM) to improve production performance, rumen fermentation, and milk fatty acid profile in water buffaloes. Sixteen Murrah buffaloes (in four groups) were fed for 10 weeks with the same basal diet supplemented with 0 (control); 20 (HM20), 30 (HM30), and 40 (HM40) g/buffalo per day. The herbal mixture contained an equal quantity of black pepper (fruit), ginger (tubers), cinnamon (bark), peppermint (leaves), ajwain (seeds) and garlic (bulbs). After two weeks of adaptation, daily milk yield, and weekly milk composition were recorded. On the last day of the experiment, rumen contents were collected to determine rumen fermentation parameters and bacterial diversity through 16S rRNA sequencing. Results revealed no effect of treatment on dry matter intake (DMI), rumen fermentation parameters, and daily milk yield. However, milk fat (%) showed a tendency to increase (p = 0.07) in HM20 as compared with the control group. A significant increase in mono and polyunsaturated fatty acids (C14:1, C16:1, C18:2n6 and C18:3) whereas a decrease in saturated fatty acids (C18:0) in milk was observed in HM20 as compared with the control group. No significant change in bacterial diversity parameters (alpha and beta diversity) was observed in response to the treatment. Despite the substantial variation observed in the relative abundance of bacteria among treatment groups, no significant effect of treatment was observed when compared with the control group. Correlation analysis revealed several positive and negative correlations of rumen bacteria with rumen volatile fatty acids (VFA) and milk yield traits. Bacterial genera including Succinivibrionaceae, Butyrivibrio, Pseudobutyrivibrio, and Lachnospiraceae showed a positive correlation with VFA and milk yield traits. Overall, we observed 52 positive and 10 negative correlations of rumen bacteria with milk fatty acid contents. Our study revealed the potential of the herbal mixture at a lower supplemental level (20 g/day) to increase milk fat (%) and unsaturated fatty acid content in buffalo.

A Mixed Phytogenic Modulates the Rumen Bacteria Composition and Milk Fatty Acid Profile of Water Buffaloes

This study was aimed to evaluate the effect of a mixed phytogenic (MP) on rumen bacteria and their potential association with rumen fermentation and milk yield parameters in water buffaloes. Twenty Murrah buffaloes were fed a basal diet (consisting of maize silage, brewers' grains, and concentrate mixture) for 6 weeks supplemented with 0 (control), 15 (MP15), 25 (MP25), and 35 (MP35) g of mixed phytogenic/buffalo per d. The mixed phytogenic contained fennel (seeds), ajwain (seeds), ginger (tubers), Swertia chirata (leaves), Citrullus colocynthis (fruit), turmeric, fenugreek (seeds), Terminalia chebula (fruit), licorice (roots), and Phyllanthus emblica (fruit) in equal quantities. After 2 weeks of adaptation, daily milk yield, and weekly milk composition were recorded. On the last day of the experiment (d 42), rumen contents were collected to determine rumen fermentation parameters and bacterial diversity through 16S rRNA sequencing. Results revealed no change in dry matter intake, milk yield and rumen fermentation parameters except pH, which increased (P = 0.029) in response to MP supplementation. The mixed phytogenic increased (P < 0.01) milk fatty acids (C4 to C14:0) in MP15 only. The milk C16:1 content and its unsaturation index were higher (P < 0.05) in MP35 as compared to the control and other treatments. Furthermore, C18:3n3 was higher (P < 0.05) in the control, MP15, and MP25, as compared to MP35. Supplementation of MP tended to increase (P = 0.095) the Shannon index of bacterial alpha diversity and a difference (P < 0.05) among treatment groups was observed in beta diversity. Feeding MP increased the Firmicutes, Proteobacteria, and Spirochaetes but decreased Bacteroidetes numerically. In addition, the dominant genus Prevotella decreased in all treatment groups while Pseudobutyrivibrio, Butyrivibrio, and Succinivibrioanceae increased numerically in MP25 and MP35. The mixed phytogenic promoted groups of rumen bacteria positively associated with milk and fat yield. Overall, our study revealed 14 positive correlations of rumen bacteria with milk yield and eight with rumen fermentation parameters. Our findings reveal substantial changes in the rumen bacteriome composition and milk fatty acid content in response to MP but these results should be interpreted carefully, as the sample size of our study was relatively small.

Endogenous synthesis of milk oleic acid in dairy ewes: In vivo measurement using 13C-labeled stearic acid

The use of stable isotopes is a reliable and risk-free alternative to radioactive tracers for directly examining in vivo fatty acid (FA) metabolism. However, very limited information is available in ruminants, and none is available in sheep. Therefore, we conducted an experiment in dairy ewes to determine, for the first time in this species, the uptake, Δ⁹-desaturation, and secretion of ¹³C-labeled stearic acid (SA) into milk with the aim of measuring in vivo endogenous synthesis of milk oleic acid (OA) and stearoyl-CoA desaturase activity. Six lactating Assaf ewes fed a total mixed ration (forage:concentrate ratio = 30:70) received an intravenous injection of 2 g of ¹³C-labeled SA. At -24, -15, 0, 4, 8, 12, 16, 20, 24, 36, 48, 60, and 72 h postinjection (p.i.), milk yield was recorded and milk samples were collected to examine fat concentration and FA composition, including compound-specific isotope analysis of SA and OA by gas chromatography-combustion isotope ratio mass spectrometry. Over the p.i. period, the SA proportion ranged from 7.6 to 8.3% of total FA, with a maximum ¹³C enrichment of 1.9%, whereas OA was more abundant (14.3-15.4% of total FA) and had lower ¹³C enrichments (up to 0.69%). On average, 15% of the isotopic tracer was transferred to milk within 72 h p.i., and 47 to 50% of the SA taken up by the mammary gland would have been desaturated to OA. The proportion of oleic acid being synthesized endogenously was estimated to represent between 48 and 57% of the amount secreted in milk. Further research under different dietary conditions is recommended.

Ruminal Infusions of Cobalt EDTA Modify Milk Fatty Acid Composition via Decreases in Fatty Acid Desaturation and Altered Gene Expression in the Mammary Gland of Lactating Cows

BACKGROUND

Intravenous or ruminal infusion of lithium salt of cobalt EDTA (Co-EDTA) or cobalt-acetate alters milk fat composition in cattle, but the mechanisms involved are not known.

OBJECTIVE

The present study evaluated the effect of ruminal Co-EDTA infusion on milk FA composition, mammary lipid metabolism, and mammary lipogenic gene expression.

METHODS

For the experiment, 4 cows in midlactation and fitted with rumen cannulae were used in a 4 × 4 Latin square with 28-d periods. Co-EDTA was administered in the rumen to supply 0, 1.5, 3.0, or 4.5 g Co/d over an 18-d interval with a 10-d washout between experimental periods. Milk production was recorded daily, and milk FA composition was determined on alternate days. Mammary tissue was biopsied on day 16, and arteriovenous differences of circulating lipid fractions and FA uptake across the mammary gland were measured on day 18.

RESULTS

Co-EDTA had no effect on intake, proportions of rumen volatile FA, or milk production but caused dose-dependent changes in milk FA composition. Alterations in milk fat composition were evident within 3 d of infusion and characterized by linear or quadratic decreases (P < 0.05) in FAs containing a cis-9 double bond, an increase in 4:0 and 16:0, and linear decreases in milk 8:0, 10:0, 12:0, and 14:0 concentrations. Co-EDTA progressively decreased (P < 0.05) the stearoyl-CoA desaturase (SCD)-catalyzed desaturation of FAs in the mammary gland by up to 72% but had no effect on mammary SCD1 mRNA or SCD protein abundance. Changes in milk FA composition were accompanied by altered expression of specific genes involved in de novo FA and triacylglycerol synthesis.

CONCLUSION

Ruminal infusion of Co-EDTA alters milk FA composition in cattle via a mechanism that involves decreases in the desaturation of FAs synthesized de novo or extracted from blood and alterations in mammary lipogenic gene expression, without affecting milk fat yield.

Milk fatty acid composition, rumen microbial population, and animal performances in response to diets rich in linoleic acid supplemented with chestnut or quebracho tannins in dairy ewes

The aim of the study was to evaluate milk fatty acid (FA) profile, animal performance, and rumen microbial population in response to diets containing soybean oil supplemented or not with chestnut and quebracho tannins in dairy ewes. Eighteen Comisana ewes at 122±6 d in milking were allotted into 3 experimental groups. Diets were characterized by chopped grass hay administered ad libitum and by 800 g/head and day of 3 experimental concentrates containing 84.5 g of soybean oil/kg of dry matter (DM) and 52.8 g/kg of DM of bentonite (control diet), chestnut tannin extract (CHT diet), or quebracho tannin extract (QUE diet). The trial lasted 4 wk. Milk yield was recorded daily, and milk composition and blood parameters were analyzed weekly. At the end of the experiment, samples of rumen fluid were collected to analyze pH, volatile fatty acid profile, and the relative proportions of Butyrivibrio fibrisolvens and Butyrivibrio proteoclasticus in the rumen microbial population. Hepatic functionality, milk yield, and gross composition were not affected by tannin extracts, whereas milk FA composition was characterized by significant changes in the concentration of linoleic acid (CHT +2.77% and QUE +9.23%), vaccenic acid (CHT +7.07% and QUE +13.88%), rumenic acid (CHT -1.88% and QUE +24.24%), stearic acid (CHT + 8.71% and QUE -11.45%), and saturated fatty acids (CHT -0.47% and QUE -3.38%). These differences were probably due to the ability of condensed versus hydrolyzable tannins to interfere with rumen microbial metabolism, as indirectly confirmed by changes in the relative proportions of B. fibrisolvens and B. proteoclasticus populations and by changes in the molar proportions of volatile fatty acids. The effect of the CHT diet on the milk FA profile and microbial species considered in this trial was intermediate between that of QUE and the control diet, suggesting a differential effect of condensed and hydrolyzable tannins on rumen microbes. Compared with control animals, the presence of B. fibrisolvens increased about 3 times in ewes fed CHT and about 5 times in animals fed QUE. In contrast, the abundance of B. proteoclasticus decreased about 5- and 15-fold in rumen liquor of ewes fed CHT and QUE diets, respectively. The use of soybean oil and a practical dose of QUE or CHT extract in the diet of dairy ewes can be an efficient strategy to improve the nutritional quality of milk.