The efficacy of a vitamin D3 metabolite for improving the myofibrillar tenderness of meat from Bos indicus cattle

The influence of a once only administration of a metabolite of vitamin D3 (HY · D®-25-hydroxy vitamin D3) on myofibrillar meat tenderness in Australian Brahman cattle was studied. Ninety-six Brahman steers of three phenotypes (Indo-Brazil, US and US/European) and with two previous hormonal growth promotant (HGP) histories (implanted or not implanted with Compudose®) were fed a standard feedlot ration for 70 d. Treatment groups of 24 steers were offered daily 10 g/head HY · D® (125 mg 25-hydroxyvitamin D3) for 6, 4, or 2 d before slaughter. One other group of 24 steers was given the basal diet without HY · D®. Feed lot performance, blood and muscle samples and carcass quality data were collected at slaughter. Calcium, magnesium, potassium, sodium, iron and Vitamin D3 metabolites were measured in plasma and longissimus dorsi muscle. Warner–Bratzler (WB) shear force (peak force, initial yield) and other objective meat quality measurements were made on the longissimus dorsi muscle of each steer after ageing for 1, 7 and 14 d post-mortem at 0–2 °C. were no significant effects of HY · D® supplements on average daily gain (ADG, 1.28–1.45 kg/d) over the experimental period. HY · D® supplements given 6 d prior to slaughter resulted in significantly higher (P < 0.05) initial yield values compared to supplements given 2 d prior to slaughter. Supplementation had no significant effect on meat colour, ultimate pH, sarcomere length, cooking loss, instron compression or peak force. There was a significant treatment (HY · D®) by phenotype/HGP interaction for peak force (P = 0.028), in which Indo-Brazil steers without previous HGP treatment responded positively (increased tenderness) to HY · D® supplements at 2 d when compared with Indo-Brazil steers previously given HGP. There were no significant effects of treatment on other phenotypes. HY · D® supplements did not affect muscle or plasma concentrations of calcium, potassium or sodium, but did significantly decrease plasma magnesium and iron concentrations when given 2 d before slaughter. There were no detectable amounts of 25-hydroxyvitamin D3 in the blood or muscle of any cattle at slaughter.