Effect of different dietary fat supplements on milk odd and branched chain fatty acids in dairy cows

Abstract Text:

The odd and branched chain fatty acid (OBCFA) profile of milk has emerged as an interesting, non-invasive option for evaluating rumen function. These fatty acids (FA) are synthesized by different ruminal microbe populations, absorbed in the intestine, and taken up by the mammary gland to be incorporated in milk fat. Lipid supplementation in lactating cows could affect different steps in these processes, as dietary FA have been reported to inhibit (step i) microbial growth, and (step ii) de novo microbial FA synthesis in the rumen, and to increase (step iii) the uptake preformed FA from dietary origin by mammary gland. Such phenomena could reduce synthesis and secretion of OBCFA, and thereby, when cows receive high fat diets, interfere with previously established relationships between these milk FA. To assess the influence of dietary lipids on milk OBCFA, 8 Holstein cows (101±11 DIM) were used in a double 4×4 Latin-square design with 14-d periods. Treatments were infusion of: CTL) fat-free emulsion in the rumen; SBR) 450 g emulsified unsaturated FA (soybean oil) in the rumen (putative effects on steps i, ii and iii); EBR) 450 g emulsified saturated FA (EnergyBooster) in the rumen (putative effects on steps ii and iii); and EBA) 450 g emulsified saturated FA in the abomasum (putative effects on step iii). Contrasts compared CTL to SBR, SBR to EBR, and EBR to EBA. The results indicate that dietary lipids do affect expression of various milk OBCFA; these effects would need to be considered in the development of models aiming to predict rumen parameters based on milk OBCFA.

Table 1. Milk fat concentrations (mg/g) of individual OBCFA

					CTL vs. SBR	SBR vs. EBR	EBR vs. EBA
Fatty acid	CTL	SBR	EBR	EBA	----------------	P-value	----------------
iso13:0	0.31	0.26	0.24	0.25	0.01	0.23	0.79
anteiso13:0	0.22	0.16	0.22	0.15	0.05	0.02	0.01
13:0	1.24	1.04	1.05	1.00	<0.01	0.79	0.35
iso14:0	1.36	1.47	1.40	1.74	0.20	0.40	<0.01
iso15:0	1.90	1.66	1.68	1.79	<0.01	0.58	0.02
anteiso15:0	8.17	7.50	7.48	7.92	0.05	0.95	0.19
15:0	12.2	10.2	10.7	10.6	<0.01	0.18	0.69
iso16:0	3.51	3.44	3.45	4.26	0.82	0.96	0.02
iso17:0	1.12	1.27	1.24	1.30	0.04	0.64	0.34
anteiso17:0	3.34	2.85	3.49	3.53	<0.01	<0.01	0.71
17:0	4.80	4.28	6.21	6.18	<0.01	<0.01	0.81
c9-17:1	1.46	1.32	1.71	1.74	0.01	<0.01	0.46
iso18:0	0.17	0.17	0.24	0.16	0.74	<0.01	<0.01

Keywords: Milk Fat Synthesis, Odd and Branched Chain Fatty Acids, Dietary Lipids