Effect of γ-aminobutyric acid producing bacteria on in vitro rumen fermentation, growth performance, and meat quality of Hanwoo steers

Objective: The present study aimed to evaluate the effects of γ-aminobutyric acid (GABA)- producing bacteria (GPB) on in vitro rumen fermentation and on the growth performance and meat quality of Hanwoo steers.Methods: The effects of GPB (Lactobacillus brevis YM 3-30)-produced and commercially available GABA were investigated using in vitro rumen fermentation. Using soybean meal as a substrate, either GPB-produced or commercially available GABA were added to the in vitro rumen fermentation bottles, as follows: control, no additive; T1, 2 g/L GPB; T2, 5 g/L GPB; T3, 2 g/L autoclaved GPB; T4, 5 g/L autoclaved GPB; T5, 2 g/L GABA; and T6, 5 g/L GABA. In addition, 27 Hanwoo steers (602.06±10.13 kg) were subjected to a 129-day feeding trial, during which they were fed daily with a commercially available total mixed ration that was supplemented with different amounts of GPB-produced GABA (control, no additive; T1, 2 g/L GPB; T2, 5 g/L GPB). The degree of marbling was assessed using the nine-point beef marbling standard while endotoxin was analyzed using a Chromo-Limulus amebocyte lysate test.Results: In regard to in vitro rumen fermentation, the addition of GPB-produced GABA failed to significantly affect pH or total gas production but did increase the ammonia nitrogen (NH3-N) concentration (p<0.05) and reduce total biogenic amines (p<0.05). Animals fed the GPB-produced GABA diet exhibited significantly lower levels of blood endotoxins than control animals and yielded comparable average daily gain, feed conversion ratio, and beef marbling scores.Conclusion: The addition of GPB improved in vitro fermentation by reducing biogenic amine production and by increasing both antioxidant activity and NH3-N production. Moreover, it also reduced the blood endotoxin levels of Hanwoo steers.

INFLUENCE OF BEEF MARBLING SCORE ON QUALITY INDICATORS DURING MEAT AGING

In the experiment, beef samples were used with the marbling scores «moderate» and «good» (n = 4). Half of the samples were packaged in a plastic film under vacuum, while the rest ones were left unpackaged. Aging was carried out for 4, 16, and 28 days in a storage chamber at a temperature of 2 ± 1 °C and a relative humidity of not more than 90 %. During beef aging, pH, sensory indicators of quality and freshness, microstructural indicators, and shear force were evaluated. Regardless of the marbling score, on day 28, sensory indicators of unpackaged beef had the signs of non-fresh meat, while the packaged samples had no deviations. Regardless of the marbling score, sensory evaluation indicated the high quality of boiled meat and broth during the entire aging period for packaged beef and during 16 days for unpackaged beef. Histological studies found that with the increase in beef aging period, the destructive changes in tissues increased as well. On days 16 and 28, samples of packaged beef, both with marbling score «good» and «moderate», corresponded to the second and third stage of meat aging. Changes in unpackaged beef at the corresponding days of aging were less pronounced. The results of a shear force study indicated that, during the entire observed aging period, a gradual decrease in shear force occurred.

Analysis of Growth Intensity and Carcass Characteristics of Wagyu‑Aberdeen Angus Crossbred Steers

The aim of this study was to evaluate growth ability (weight, daily weight gains) and selected carcass characteristics during fattening period of Wagyu × Aberdeen Angus crossbred steers (F1). A total of 72 animals were evaluated over a period of 4 years. The observed animals were monitored from rearing (8 months) to slaughter (30 months). Statistical evaluation was performed by SAS 9.3 (GLM procedure); variables were corrected for effects of the year, season of birth and sire effect. Sire effect proved to be the most significant in our evaluation. Offsprings sired by Bull 1 had significantly (P < 0.05) better growth ability than offsprings of other two tested bulls. Slaughter analysis of tested steers showed, that mean value of dressing percentage was 55.61 %. Significantly highest dressing percentage was found for Bull 1 offsprings (56.72 %, P < 0.05). The average carcass weight of tested steers was 443.46 kg and the highest carcass weight was again achieved by offsprings of Bull 1 (486.39 kg; P < 0.05). Average value of beef marbling score was 5.21. Slaughter analyses of carcass cuts (cut‑out, round, chuck, rump, tenderloin, shank, flank) and tallow showed that average weight of these lean cuts was 127.32 kg and tallow content was 39.31 kg at average. The highest values of these parameters were observed in offspring of bulls Bull 1 (P < 0.05).