Effect of dietary proportion of grass silage on milk fat with emphasis on odd- and branched-chain fatty acids in dairy cows

Abstract

High proportions of forage in diets fed to dairy cows are interesting options in conventional production, and mandatory in organic dairy farming (e.g., within the European Union). The objectives of the present study were to study the milk fatty acid (FA) profiles, with particular focus on the odd- and branched-chain FA (OBCFA) and their association with diet composition, using 3 different proportions of grass silage in the diet. The OBCFA profiles in milk have been suggested to be potential markers to assess nutrient supply to the cows. The study included data from 24 cows in 2008 and 26 cows in 2009, using pooled milk samples from morning and evening milking within 24 h. The 3 diets were composed of the same feeds: grass silage and grain-based concentrate, but the silage component was fed in different proportions, namely 50, 70, and 85% of total dry matter intake. The cows were in late lactation, with a mean of 220 (SD=15) days in milk in 2008, and 216 (SD=35) days in milk in 2009, at the onset of the trial. Increased proportions of grass silage in the diet increased the intake of C18:3n-3, and decreased the intake of C18:2n-6 and intake of total FA. The daily intake of C18:3n-3 and C18:2n-6 was reflected in a similar increase in milk C18:3n-3, whereas the concentration of milk C18:2n-6 decreased with increasing proportion of grass silage in the diet. Increased proportions of grass silage in the diet increased the concentration of conjugated linoleic acid and the linear odd-chain FA C15:0 and C17:0, the branched-chain iso C15:0 and total OBCFA in milk. The concentration of total OBCFA in milk was shown to be positively correlated with dietary content of neutral detergent fiber. This suggests that the concentration of milk OBCFA may be useful in the future to indicate low forage intake in cows under conditions when it is not possible to measure individual forage intake.

Fatty acid profile in vertical strata of elephant grass subjected to intermittent stocking

“…The milk and meat from animals with a pasturebased diet reportedly have a better nutritional quality due to increased PUFAs in these products, mainly omega-3 and CLA cis-9 trans-11 (Patel et al 2013). This fact is directly associated with the high content of PUFA, mainly linolenic acid, in green forage (Dewhurst et al 2006); studies with temperate forages have shown that some pasture management strategies can increase its concentrations in plants (Glasser et al 2013, Witkowska et al 2008).…”

The Effects of Subacute Ruminal Acidosis on Milk Fatty Acid Profile in Dairy Cattle

“…Vlaeminck et al (2006) found similar results where iso C15:0 increased in proportion to grass silage. Another study by Patel et al (2013) also discovered that augmented proportions of grass silage in the diet increased the branched-chain FAs iso C15:0 and iso C17:0. …”

“…Higher concentrations of branched chain FA in milk are typically a result of high forage diets, due to a larger population of cellulolytic bacteria that can produce acetate (Patel et al, 2013). Acetate can be elongated into branched-chain FAs, which will eventually be deposited into the milk (Patel et al, 2013). In SARA, there are more amylolytic bacteria in the rumen, which produce propionate, leading to less branched-chain FAs being produced (Fievez et al, 2012).…”

“…The reduced branched chain FAs is likely due to a decline in the forage: Concentrate ratio. Higher concentrations of branched chain FA in milk are typically a result of high forage diets, due to a larger population of cellulolytic bacteria that can produce acetate (Patel et al, 2013). Acetate can be elongated into branched-chain FAs, which will eventually be deposited into the milk (Patel et al, 2013).…”

“…Milk fat contains about 2 to 3% Odd-and Branched-Chain Fatty Acids (OBCFA) rising from microbial FA (Patel et al, 2013). OBCFA profiles in milk can be potential markers for duodenal flow of microbes The FA composition in cow milk can be altered through feeding (Patel et al, 2013), for example changing the forage proportion are known to alter FA profiles in milk (Chilliard et al, 2007); therefore OBCFAs could be used as a noninvasive tool to predict ruminal acidosis.…”