Postruminal synthesis modifies the odd- and branched-chain fatty acid profile from the duodenum to milk

Abstract

Milk odd- and branched-chain fatty acids (OBCFA) have been suggested as potential biomarkers for rumen function. The potential of milk OBCFA as a biomarker depends on whether their profile reflects the profile observed in the duodenum. The objective of this study was to evaluate whether the OBCFA profile in duodenum samples is reflected in plasma and milk. For this, 2 dairy cattle experiments were used. In experiment 1, 4 Holstein cows fitted with rumen and proximal duodenum cannulas were used in a 4×4 Latin square design. The treatments consisted of 2 nitrogen levels (143 vs. 110g of crude protein/kg of dry matter for high and low N, respectively) combined with either 1 of the 2 energy sources (i.e., starch from barley, corn, and wheat or fiber from soybean hulls and dehydrated beet pulp). In experiment 2, 4 Holstein cows fitted with rumen and proximal duodenum cannulas were used in a 3×3 Latin square design, with the treatments consisting of 3 diets: (1) RNB-, a diet with a crude protein content of 122g/kg of dry matter, predicted to provide protein digested in the small intestine according to the requirement of the animals, but with a shortage of rumen degradable protein; (2) RNB- to which 6g/d of niacin was added through inclusion in the mineral and vitamin premix, and (3) RNB- to which urea was added to balance rumen degradable N supply resulting in a CP content of 156g/kg of dry matter. In both experiments, samples of duodenal digesta, plasma, and milk were collected and analyzed for fatty acids. Additionally, lipids in plasma samples were separated in lipid classes and analyzed for fatty acids. The OBCFA profile in milk was enriched in 15:0, iso-17:0, anteiso-17:0, and cis-9-17:1 as compared with duodenal samples, and milk secretions even exceeded duodenal flows, which suggests occurrence of postruminal synthesis, such as de novo synthesis, desaturation, and elongation. The postruminal modification of the OBCFA profile might hamper the application of OBCFA as diagnostic tools of rumen function.

Milk saturated fatty acids, odd- and branched-chain fatty acids, and isomers of C18:1, C18:2, and C18:3n-3 according to their duodenal flows in dairy cows: A meta-analysis approach

“…For iso-C17:0, apparent transfer between duodenum and milk (on a g/d basis) was high (slope = 0.85), associated with a high intercept (1.80 g/d), whereas for anteiso-C17:0, the slope was greater than 1. This reflects that milk yield of these FA exceeds their duodenal flow, as previously reported by Vlaeminck et al (2006Vlaeminck et al ( , 2015, which may be attributed to either mobilization from adipose tissue or to synthesis of the 2 FA in the mammary gland. Mobilization of iso-C17:0 and anteiso-C17:0 from adipose tissue is probably of minor importance, because most of the trials included in that meta-analysis were designed with cows in mid-lactation when lipomobilization is negligible.…”

“…However, the slopes of the models that represent apparent transfer efficiency from duodenal into milk were around 0.5 (when expressed on a yield basis for C15:0 and C17:0). This value is slightly lower than those reported by Vlaeminck et al (2015) that estimated the contribution of duodenal odd-chain FA to milk yield to be between 0.63 and 0.67. This indicates that part of the yield of these FA in milk arises from de novo mammary synthesis in line as reflected by the significant intercept of the model of milk C17:0 concentration (% of total FA) and the significant contribution of ruminal propionate to the secretion of C15:0 (Table 4).…”

Milk fatty acids as possible biomarkers to diagnose hyperketonemia in early lactation

“…Studies with cultured human intestinal cells revealed the potential of branched-chain FA to be elongated by the action of this enzyme (Ran-Ressler et al, 2010). Based on daily milk secretion of anteiso C17:0, which exceeded its daily duodenum flow, we suggested the possibility of elongation of this branched-chain FA from anteiso C15:0 in animal tissues (Vlaeminck et al, 2015). Similarly, iso C15:0 elongation to iso C17:0 was suggested.…”

Replacement of alfalfa hay ( Medicago sativa ) with maralfalfa hay ( Pennisetum sp.) in diets of lactating dairy goats

“…Odd and branched chain fatty acids in milk are predominantly of microbial origin. Milk C15:0 and C17:0 are potential biomarkers of rumen function, as they are found in rumen bacterial lipids and may be partially synthesized endogenously from rumen substrates in the mammary gland (Fievez et al, 2012 andVlaeminck et al, 2015). The differences found between treatments (higher contents of these fatty acids in the milk of M goats) suggest an amylolytic rumen bacterial metabolism (Table 8).…”