The fatty acid composition of muscle fat and subcutaneous adipose tissue of pasture-fed beef heifers: Influence of the duration of grazing

Abstract

Our objective was to determine the effect of the duration of grazing before slaughter on the fatty acid composition of muscle fat and s.c. adipose tissue (SAT) of beef heifers. Sixty crossbred Charolais heifers (n = 15 per treatment) were assigned randomly to one of four dietary treatments: 45 animals (Treatments 1, 2, and 3, respectively) were housed at the beginning of the experiment, and 15 (Treatment 4) were fed at pasture. Two groups of 15 heifers were moved to pasture 40 d (Treatment 2) and 99 d (Treatment 3) before slaughter, respectively, resulting in preslaughter grazing periods of 0, 40, 99, or 158 d for Treatments 1, 2, 3, and 4, respectively. Before grazing the predominantly perennial ryegrass pasture, animals were housed and offered grass silage ad libitum and 3 kg of concentrate diet (650 g of grass silage/kg of total DMI). After slaughter, the fatty acid profile of the neutral (NL) and polar lipid (PL) fractions of muscle fat from the LM and the total lipids from SAT were analyzed by gas chromatography. Duration of grazing showed a quadratic tendency on mean carcass weight (P = 0.08), but did not affect growth (P = 0.27) or the lipid content (P = 0.13) of the LM. Increasing the duration of grazing led to a linear increase (P < 0.001) in the concentration (on fresh-tissue basis) of CLA in muscle fat (from 11.80 to 17.75 mg/100 g of muscle in NL, and from 0.52 to 0.82 mg/100 of g muscle in PL) and in SAT (from 3.98 to 10.23 mg/g of SAT; P < 0.001), and increased the concentration of C18:1trans-11 in both muscle fat fractions (P < 0.001) and in SAT (P < 0.001). In the total muscle lipids, the polyunsaturated to saturated fatty acid ratio (P:S) increased from 0.12 to 0.15 with increased duration of grazing following a linear (P < 0.05) and cubic pattern (P < 0.05). Increasing the duration of grazing led to a linear decrease in the n-6:n-3 ratio of muscle fat from 2.00 to 1.32 (P < 0.001), and from 2.64 to 1.65 in the SAT lipids (P < 0.001), mainly as a consequence of the increased concentration of C18:3n-3. It is concluded that muscle fat and SAT fatty acid profile was improved from a human health perspective by pasture feeding, and that this improvement depended on the duration of grazing.

The effect of grazing on the fatty acid profile of longissimus thoracis muscle in Galician Blond calves

“…Even, a short concentrate period of 50 days cancelled the beneficial synthesis of the n-3 FA from pasture grazing. It seems that content of n-3 FA in muscle fat is highly influenced by the type of diet on which animals were fed during the finishing period, in accordance with other studies (Noci et al, 2005).…”

“…Calves fed exclusively on pasture grazing were able to synthesise higher amounts of n-3 PUFA than calves finished on concentrate, in accordance with the results of French et al (2000), Varela et al (2004) and Nuernberg et al (2005). It is widely documented that 18:3 n-3 can serve as a substrate for further desaturation and elongation of PUFA (Noci et al, 2005). Even, a short concentrate period of 50 days cancelled the beneficial synthesis of the n-3 FA from pasture grazing.…”

Value-addition of Beef Meat By-products: Lipid Characterization by Chromatographic Techniques

“…Schiavon and co-workers 25 showed a similar MUFA content in beef subcutaneous fat, whereas SFA and PUFA were present in higher and lower amount compared to our results. Noci et al 26 have observed low SFA concentration in heifers and MUFA and PUFA with higher values than our samples.…”

“…Palmitic acid C16:0 constituted the second major fatty acid detected [20][21][22][23][24][25][26][27][28] , followed by stearic acid C18:0, 10-19 , palmitoleic acid C16:1 cis, [2][3][4][5] , myristic acid C14:0, 2-4 and linoleic acid C18:2 n6, 2-10 . In the storage fat, the saturated fatty acids SFA were present in significantly p 0.05 greater amounts in calf and young bull 46.76 and 47.62…”

The inclusion of low quantities of lipids in the diet of ruminants fed low quality forages has little effect on rumen function

“…These changes in FAs are related to human-health benefits (Ha et al, 1987;Ochoa et al, 2004), changes in the microbial population (Boeckaert et al, 2006), influences on animal metabolism (Bauman et al, 2011) or to enhancement of the overall performance of offspring, when fed to dams during pregnancy and lactation (Pickard et al, 2008;Or-Rashid et al, 2010). There are known differences between the FA profile of meat of grass fed animals and animals fed silage or concentrate-based diets (Poulson et al, 2004;Noci et al, 2005), but there is little information regarding the FA profile of cattle fed tropical grasses. Lipid profile and concentration in the diet are two factors that can influence the profile of fat in muscle and milk.…”