Carcass and meat quality of young Angus steers with different growth potential finished exclusively grass-fed or corn supplemented

Beef cattle production has a large variety of systems with different performance and technology levels. This study compared young Angus steers carcass and meat quality traits of high growth potential early-finished animals fed exclusively on pasture with low growth potential late-finished animals. Besides the grazed forage, the low growth potential group received corn grain at 0.8% of their body weight right after the slaughtering of the first group. Following weaning, the 20 steers grazed pastures composed of oat, ryegrass, and clovers. At winter's onset, animals were moved to native pastures improved with fescue and clovers. The supplemented period of late steers began when the first group of ten early-finished animals reached the requirements for slaughter. Supplementation ended when the animals got the slaughter requirements. The high growth potential steers showed a ribeye area (P < 0.0001) and a Longissimus muscle width highly significantly (P < 0.0001) superior to the low growth group. However, corn-supplemented animals showed better dressing percentage (P < 0.0001), subcutaneous fat thickness (P < 0.0001), marbling (P < 0.0001), and muscle (P = 0.0033) scores, but lower shear force (P = 0.0001). The finishing system did impact fat lightness (L*; P = 0.0234) at the slaughter time. Grass-fed animals showed higher red-green color parameter (a*) values than corn supplemented on fat at 24 h (P = 0.0439) but lower hue angle (P = 0.0418). The consumer panel showed better results for tenderness and general acceptability for supplemented animals beef compared to grass-fed. The supplementation resulted in a higher carcass standardization. It also provided higher PUFA: MUFA and n-6: n-3 ratios, and a higher amount of n-3. Supplemental corn grain did not have adverse effects upon the beneficial effects to human health of the grass-fed beef.

Fatty Acid Characterization of Beef Longissimus from Steers Finished on Fodder Beet or Traditional Winter Forages in New Zealand Compared to US Grain-Fed Beef

Fatty acids were evaluated to characterize lipid profiles of beef from 3 feeding programs: New Zealand (NZ) fodder beet (FB), NZ grass/non-FB (NFB), and United States grain. Strip loins were selected within each program based on expected eating quality focusing on marbling, ossification, and pH. Selection resulted in 6 treatments: FB high quality, FB low quality, NFB high quality, NFB low quality, US Top Choice, and US Select. Samples were aged 21 d or 35 d postmortem. A subset of 152 samples (12–13 per treatment combination) were used for fatty acid characterization. Within the polar lipid fraction, US treatments had lower monounsaturated fatty acid (MUFA) and greater polyunsaturated fatty acid (PUFA) than NZ treatments (P &lt; 0.05). Within the neutral lipid fraction, concentrations of total neutral lipids and proportions of saturated fatty acid, MUFA, and PUFA were affected by treatment (P &lt; 0.05). Total neutral lipids were greatest in Top Choice (P &lt; 0.05) and greater in FB high quality than all other treatments (P &lt; 0.05). Proportions of satu- rated fatty acid in the neutral lipid fraction were greater in NFB treatments than US treatments (P &lt; 0.05); FB treatments were intermediate. Proportions of MUFA were greatest in Top Choice (P &lt; 0.05). Proportions of PUFA were greatest (P &lt; 0.05) in Select, greater in Top Choice than all NZ treatments (P &lt; 0.05), and greater in NFB treatments than FB treatments (P &lt; 0.05). No interactions occurred for any groups of fatty acids in either fraction ( P &gt; 0.05), and aging did not affect fatty acid composition. Lipid profiles were impacted by finishing diet; however, most differences were between US grain-fed beef and NZ treatments—with limited differences between FB and NFB samples—when product was selected based on quality descriptors. Therefore, FB could be substituted for grass forages to sustain the NZ beef industry through winter months and limit seasonality without detrimental effects on product quality.

Palatability of Beef Strip Loin Steaks Following Variable Length High-Concentrate Diet Exposure Prior to Pasture-Finishing

Proximate composition, Warner-Bratzler shear force (WBSF), consumer sensory traits, fatty acid composition, and volatile flavor compounds were assessed on steaks from USDA Select strip loins (n = 40; 8/treatment) representing grass-fed beef sourced from New Zealand (NZ) with marbling consistent with USDA Select along with strip loins from four feeding treatments designed to evaluate the effects of early exposure to grain-based diets for 0 d (0D), 40 d (40D), 80 d (80D), or 120 d (120D) prior to pasture-finishing on meat quality and composition. Percent fat, moisture, and protein and WBSF did not differ (P > 0.05), but percent ash was decreased in 120D samples compared to those from NZ, 0D, and 40D (P < 0.05). Consumer scores for all traits differed among samples from the treatments (P < 0.05), with steaks from NZ receiving greater scores for flavor liking than those from 0D, 40D, and 80D (P < 0.05). Consumers also rated NZ and 120D samples greatest for overall liking (P < 0.05). Saturated fatty acids were decreased, and monounsaturated fatty acids were increased in NZ samples compared to samples from all other treatments (P < 0.05), and conjugated linoleic acid was least in samples from NZ (P < 0.05). The ratio of omega-6 to omega-3 fatty acids was greater in 80D and 120D samples than those from all other treatments (P < 0.05). Non-enzymatic browning-derived ketones and 2-pentylfuran were increased in samples from NZ compared to those from all other treatments (P < 0.05), and differences among treatments in lipid-derived compounds were primarily of alcohols and aldehydes. Early exposure to grain-based diets for 120 d prior to pasture-finishing produces beef that is comparable to grass-fed beef from New Zealand in palatability but differs in chemical composition.

Timing of Exposure to High-Concentrates versus High-Quality Forages on Growth and Marbling Deposition in Steers

Forty Angus-cross steers (280 ± 21.4 kg BW, 8 mo.) were used to examine the effects of exposure to 2 diets [high concentrate diets (CONC) versus high quality forages (FOR)] during 2 time periods [early (EARLY; at 30-d post weaning) or late (LATE; just prior to slaughter)] on animal growth, marbling deposition and tenderness. Steers were blocked by weight and randomly assigned to four dietary treatments: 1) CONC-FOR, 2) CONC-CONC, 3) FOR-CONC, or 4) FOR-FOR. Exposure to CONC during the EARLY or LATE period increased (P < 0.05) growth and fat deposition compared to FOR-FOR. Hot carcass weight was greater (P < 0.05) for CONC-CONC and FOR-CONC steers than FOR-FOR and CONC-FOR due to changes in dressing percent. Marbling score was greater (P < 0.05) for CONC-CONC and CONC-FOR compared to FOR-FOR. Exposure to CONC during the EARLY period (CONC-FOR and CONC-CONC) increased (P < 0.05) n-6 polyunsaturated fatty acids (PUFA) deposition in longissimus muscle (LM) and subcutaneous adipose tissue (SQ); whereas, exposure to CONC during the LATE period (CONC-CONC and FOR-CONC) reduced (P < 0.05) n-3 PUFA, trans-11 octadecenoic acid and cis-9 trans-11 isomer of conjugated linoleic acid (CLA). Warner-Bratzler shear force at d 2 and 7 of postmortem aging in ribeye steaks from CONC-CONC and FOR-CONC was greater (P < 0.05) than FOR-FOR and CONC-FOR. Lipogenic gene expression was up-regulated (P < 0.05) and lipolytic gene expression was downregulated (P < 0.06) in SQ from CONC-CONC and FOR-CONC compared to FOR-FOR. Overall, exposure to CONC in both periods increased growth rate and marbling deposition but LATE exposure had the greatest impact on adipose lipogenesis and lipolysis, fatty acid composition, and tenderness.

Nutritional milieu of isolated stromal vascular cells determines their proliferative, adipogenic, and lipogenic capacity in vitro

The objective was to determine the effect of nutritional milieu of isolated stromal vascular (SV) cells on proliferative capacity of preadipocytes, and adipogenic and lipogenic capacity in adipocytes in vitro. Proliferation of the preadipocytes increased over time with 48 and 72 h being greater than 24 h; however, preadipocytes from steers supplemented with corn (LC) had lower proliferation rates compared with those without corn grain supplementation (L) at 72 h. Adipocyte cultures isolated from LC group had higher mean diameter on d 4 and 6, and higher mean volume on d 0, 4, 6, and 12 of culture. Adipocytes from steers supplemented with corn grain (LC) had lower expression of key adipogenic genes during extended days in culture. The results show that prior nutritional treatment of the donor animal used to isolate SV cultures alters their proliferative, adipogenic, and lipogenic capacity in culture. These differences may be related to lower induction/expression of AP2 gene in the adipose cultures from corn supplemented group. Corn grain supplementation to steers grazing legumes could have stimulated more active adipogenic progenitor cells to differentiate, which would leave fewer behind in the SV pool for subsequent isolation.