The effect of feed withdrawal on the meat quality of sheep

Forty female Perendale lambs (live weight 27.24 Kg ±1.68, approx. 8 months old) were transported for 4h to the Lincoln University farm two days prior to the start of feed withdrawal. On arrival they were weighed, tagged and released to the university paddocks. All the animals were nominally (according to tag number) allocated to four groups of ten animals each to minimise the live weight differences between the groups. The feed withdrawal periods were 0 days, 1 day, 3 day and 7 days for the T1, T2, T3 and T4 groups respectively. All the animals were slaughtered using captive bolt stunning and transverse incision in the neck region. The carcasses were hung from the Achilles tendon for 5.5 h at room temperature (18 °C), 8 h at 10 °C and 58.5 h at 2 °C until the experiment finished. Muscle biopsies were collected within 15 minutes of slaughter from the following muscles: Supraspinatus (SS), Longissimus dorsi (LD), Psoas major (PM), Semitendinosus (ST), Semimembranosus (SM) and Biceps femoris (BF). The pH and temperature were measured in all the muscles at 3h, 6h, 12h and 24h post-mortem. All the muscles were sampled to measure the colour, cooking loss and tenderness at 6h and 3 days post-mortem and the samples were stored at -20°C until further analysis. The biopsies were analysed by the combination of amyloglucosidase hydrolysis and spectrophotometry to determine the glycogen and glucose levels. Frozen muscle samples were thawed at 4 °C overnight and the colour determined by Minolta Chroma Meter (CIE L*a* b*). Samples were weighed before and after cooking to determine cooking loss. The tenderness was determined using the MIRINZ tenderometer. At slaughter, glycogen contents (µ mol glycosyl units/g) of control samples (no feed withdrawal) were lower (fast-red: LD= 33 SM= 26; fast-white: ST= 30, PM= 20; Slow-red: SS= 33; intermediate: BF= 33) than the values cited in the literature. Mean ultimate pH value of muscles were 5.92, 6.0, 5.94, 5.87, 6.04, and 6.04 for the BF, PM, LD, SM, SS and ST respectively. Those values were not significantly different at 0.05 probability. The cooking loss percentages were 27, 24, 18, 15, 16 and 21 in the SS, BF, PM, ST, LD and SM respectively. The highest tenderisation rates were observed in the LD and BF. All the muscles were tender after 72 h of aging. The MIRINZ shear force values were 5.29, 6.29, 4.88, 5.45 and 5.10 in SS, BF, PM, LD and SM respectively. The BF, PM and ST had low lightness and redness values compared to SS, SM and ST which demarcated the muscles into two prominent groups. The SS, SM and PM were selected to observe the effect of fasting on meat quality. Fasting reduced the muscle weight of the SS. Other muscles did not show any significant changes (P