Meat tenderness is regarded as the single most important characteristic of meat quality. Fifty Bonsmara feedlot steers were fed a commercial feedlot ration (10,5 MJ MElKg DM, 12% CP), supplemented with 0,15mg Zilmaxlkg live weight in the feed and with different levels of vitamin D3 (1 to 5 X 106 IU Vit D3 /day) for five days prior to slaughter. The steers were randomly allocated to the vitamin D3 treatments and a control group that received no vitamin D3 supplementation. The steers were fed from ca. 248 ± 3 kg live weight, while Zilmax was fed for the last 35 days to a target weight of ca 400kg. All steers were slaughtered at a commercial abattoir after a Zilmax withdrawal period of 7 days. Samples from m. longissimuss lumborum were collected 24h post-mortem for sheer force testing on an Instron apparatus equipped with a Wamer Bratzler shear blade. Cooking loss was determined by measuring the amount of fluid loss after cooking. Feedlot performance, carcass characteristics and drip loss of meat samples did not differ significantly between the different vitamin D3 treatments. The inclusion of 5 X 106 IU of vitamin. D3 resulted in significantly lower shear force (SF) values compared to the steers in the control group. The results suggest that dietary supplementation of 5 X 106 IU of vitamin. D3 may significantly improve the tenderness of meet from steers fed 0, IS mg Zilmax ®/kg live weight for the last 35 days in the feedlot. The aim of the second study was to explore the effectiveness of the use of electrical stimulation on tenderness of mutton. In this experiment 22 wethers of class AB weighing between 45 and 50kg were used. The carcasses were assigned to two treatment groups, of which group one was electrically stimulated (ES) and the other group was not electrically stimulated (NES). The results revealed that electrical stimulation did not significantly affect of the fatty acid content of meat and crude fat content. Treatment however, significantly (P< 0,038) influenced the moisture content of the samples. There was a variation in SF values between the two treatment groups; SF of samples from the ES group were lower compared to that of the NES group. This suggests that ES can be successfully applied to reduce the variation in tenderness within the class- AB mutton.
Dissertation (MSc(Agric) : Meat Science)--University of Pretoria, 2008.