Effect of corn supplementation of grass finishing of Holstein bulls on fatty acid composition of meat lipids.

Finishing Holstein young bulls exclusively on pasture generally results in very lean carcass and meat, but corn supplementation is expected to simultaneously improve carcass traits and intramuscular lipids (IML). The expected increase in IML would allow for a larger 18:2c9,t11 (CLA) deposition in meat without affecting the n-3 PUFA present in LM phospholipids (PL). Holstein bulls (n = 33) with initial BW of 423 ± 52.4 kg reared exclusively on pasture were assigned to 1 of 3 finishing period (85 d) diets: finished exclusively on pasture (P0) or finished on pasture and individually supplemented with 4 (P4) or 8 kg/d (P8) of ground corn. Final BW (546 ± 56.3 kg) was not affected (P > 0.05) by corn supplementation, but ADG increased (P < 0.01) with the increasing corn supplementation level from 1.23 kg/d for P0 to 1.44 kg/d for P4 and to 1.67 kg/d for P8. Subcutaneous fat depth in P0 bulls was 0.8 mm and increased (P < 0.001) in both P4 (2.9 mm) and P8 (2.7 mm) bulls, but no difference (P = 0.73) was observed between P4 and P8 bulls. Similarly, the IML increased with corn supplementation, from 1.84 g/100 g muscle in P0 to 2.96 in P4 and to 3.24 in P8, but no difference (P = 0.55) was found between P4 and P8 bulls. Corn supplementation decreased (P < 0.01) 18:1t11 in neutral lipids (NL) but not 18:2c9,t11 (P > 0.34). The 18:1t10 (mg/g total NL fatty acid [FA] ± SEM) were 2.5 ± 0.13 in P0, 5.5 ± 1.68 in P4, and 14.8 ± 3.18 in P8 bulls, being greater in P8 compared with P4 (P = 0.02). Total FA in muscle PL and SFA were unaffected, but increasing corn supplementation resulted (P < 0.001) in an increase of 18:2n-6 in PL by replacement of mostly the 18:1c9 and 18:3n-3. Notably, the total number of cis double bonds present in FA of PL remained constant (P = 0.74) with corn supplementation. Compared with P0, corn supplementation maintained (P > 0.05) the high n-3 PUFA content in meat (mg/100 g meat) and increased the 18:2c9,t11 (P = 0.028) and 18:1c9 (P < 0.001). However, increasing corn supplementation from 4 to 8 kg/d increased the 18:1t10 (P = 0.031) and had no effect on 18:2c9,t11. Therefore, supplementing grass-finished Holstein bulls with moderate amounts of ground corn (4 kg/d) increased carcass fat cover and IML, maintained n-3 PUFA, and increased 18:2c9,t11 content in meat, whereas greater corn supplementation (8 kg/d; P8) resulted in no further improvements.

Fatty acid composition, conjugated linoleic acid isomers and cholesterol in beef from crossbred bullocks intensively produced and from Alentejana purebred bullocks reared according to Carnalentejana-PDO specifications.

The purpose of this study was to characterise and compare the nutritional value of Portuguese Carnalentejana-PDO beef, obtained from Alentejana purebred bullocks reared in a semi-extensive system, with the meat from Alentejana×Charolais crossbred bullocks produced in a conventional intensive concentrate-based system. In addition, seasonal changes in Carnalentejana-PDO beef quality were assessed, by analysing meat samples from animals slaughtered in early autumn and late spring. The results showed that beef-PDO has different intramuscular fat characteristics in comparison with meat from crossbred bullocks fed intensively with concentrate. However, the finishing period of Alentejana purebred bullocks with concentrate seems to attenuate most of the typical grass-fed characteristics of meat fat. Nevertheless, from a human nutrition perspective, Carnalentejana-PDO beef seems to be healthier than that from intensively reared animals since it has a lower n-6/n-3 ratio, although always above the recommended guidelines for human diet, and higher proportions of c9,t11 conjugated linoleic acid (CLA) isomer and total CLA relative to saturated fatty acids plus total cholesterol (CLA/SFA+CHR). Furthermore, no seasonal variation in the nutritional quality of beef-PDO was apparent. Taken together, the data indicate that Carnalentejana-PDO beef is of greater nutritional value than intensively produced beef from crossbred bullocks throughout the year.