The present study was conducted to elucidate the effect of dietary lysine levels on the intramuscular fat (IMF) content in the Longissimus dorsi (L. dorsi) muscles of finishing gilts. Eleven gilts in total from two litters of pigs aged 110 days were used. The average initial bodyweight of the pigs was 61.7 kg. Six pigs were assigned to the low lysine (LL) diet group (lysine content: 0.43 or 0.40%) and five pigs were assigned to the control group (lysine content: 0.65 or 0.68%). The diets were iso-energetic and iso-protein, and contained all essential amino acids (apart from lysine) in the recommended amounts. The pigs were fed these diets until their live weights reached 110 kg. Live weight gain and feed efficiency tended to be lower in the LL group ( P = 0.118 and P = 0.052, respectively). Pigs from the LL group took 5 days longer to reach 110 kg ( P < 0.01). The IMF content in the L. dorsi of the LL group was twice as high as that of the control group (6.7 vs 3.5%; P < 0.01). The percentage of oleic acid in the L. dorsi of the LL group tended to be higher than that of the control group ( P = 0.052), whereas the percentage of linoleic acid and the total percentage of polyunsaturated fatty acids in the L. dorsi were lower ( P < 0.05) in the LL group. Free L-carnitine content in the L. dorsi was lower ( P < 0.05) in the LL group. The average abundance of peroxisome proliferator-activated receptor gamma mRNA in the L. dorsi of the LL group was threefold higher than that of the control group. The leptin mRNA abundance in the L. dorsi of the LL group was 3.3-fold higher than that of the control group ( P < 0.01). These results suggest that a higher activity of adipogenesis may have been involved in the promoted accumulation of IMF in the L. dorsi muscles of pigs, induced by a dietary LL level.

Analytical conditions for the quantitative determination of adenosine 5'-triphosphate(ATP), adenosine 5'-diphosphate(ADP), inosine 5'-monophosphate(IMP), adenosine 5'-monophosphate(AMP), hypoxanthine(Hyp), xanthine(Xan), inosine(Ino) and adenosine(Ado) in meat extracts by reversed-phase high-performance liquid chromatography (HPLC) were examined. A commercial ODS column with a 5-urn particle diameter was used, and expeimental parameters affecting the separation were discussed. Peaks in chromatograms of meat extracts were identified by retention time, co-injection with standards, absorbance ratios and the enzymatic peak shift method. The procedure proposed was adaptable as an indication of freshness of meat.

The objective was to evaluate effects of feeding level of milk replacer on body growth, plasma metabolite and insulin concentrations, and allometric growth of visceral organs in suckling calves. Holstein bull calves (n = 8; 3-4 days of age) were fed either a low amount (average 0.63 kgDM/day, LM) or high amount (average 1.15 kgDM/day, HM) of high protein milk replacer until they were slaughtered at 6 weeks of age. Body weight (BW) at 4, 5, and 6 weeks of age, feed intake, average daily gain, and feed efficiency were higher in the HM than LM calves. The HM group had higher plasma glucose at 3 and 4 weeks of age and insulin levels after the age of 4 weeks compared with LM calves whereas no effect was detected on plasma nonesterified fatty acid or urea nitrogen concentrations. The HM calves had greater empty body weight (EBW), viscera-free BW and most of the organs dissected than LM calves. Relative weights (% of EBW) of liver, spleen, kidneys, and internal fat were higher, whereas head and large intestine was lower in HM than LM calves. The results suggest that increased milk feeding levels would accelerate the growth of the body and specific organs.

Japanese Black cattle (Wagyu), deposit much higher amounts of intramuscular fat, known as marbling, than other breeds of cattle. To determine whether this unique fat deposition is attributable to the somatotropic axis, we compared pulsatile growth hormone (GH) secretion, plasma levels of insulin-like growth factor-1 (IGF-1) and cellular density of somatotrophs (GH-expressing cells) in the anterior pituitary glands of Japanese Black and Holstein steers. Blood samples were withdrawn every 15 min for 6 h from 14 Japanese Black and 12 Holstein steers at about 17 months of age, and GH and IGF-1 concentrations were determined. The distribution and proportion of GH-expressing cells were analysed by immunohistochemistry combined with point-count morphometry in pituitaries from six steers from each breed aged about 18 to 21 months. Overall mean and baseline plasma GH concentrations were lower (P < 0·001) in Japanese Black than Holstein steers. In addition, Japanese Black had smaller (P < 0·05) amplitudes of GH secretory pulses than Holstein steers, whereas the GH pulse frequency did not differ between the breeds. Japanese Black steers also had lower (P < 0·001) plasma levels of IGF-1 than Holstein steers. The marbling score of Japanese Black steers was higher (P < 0·001) than that of Holsteins at the same carcass weight. The proportion of GH-expressing cells was smaller (P < 0·05) in Japanese Black than Holstein steers at the hind dorsal and hind ventral regions of the adenohypophysis. Thus, in Japanese Black and Holstein steers, the breed difference in the relative density of GH-expressing cells corresponded to that in profiles of pulsatile GH secretion. These results suggest that the features of the somatotropic axis intrinsically differ between Japanese Black and Holstein cattle and that these features may be partly responsible for the genetic ability of the former to deposit greater amounts of marbling fat and for the smaller frame of Wagyu cattle.

The relationship between shear-force value and collagen architecture of connective tissue of the longissimus thoracis (LT) muscle of Japanese Black (n = 10) and Brown (Kumamoto) (n = 5) steers (body weight: 688.4 +/- 8.6 kg as average and standard error) was investigated. There were negative correlations between the shear-force value and lipid content (n = 15, R(2)= 0.3709, P < 0.01) and protein content and lipid content (n = 15, R(2)= 0.6748, P < 0.01). Shear-force value and collagen content (n = 15, R(2)= 0.4344, P < 0.01) were positively correlated. In scanning electron microscopic photographs of the macerated preparation, the perimysium of the high-lipid LT muscle was broken down compared with the low-lipid LT muscle. The endomysium in all LT muscle fibers showed similar architecture. The fine surface cover of reticular collagen fibers around an adipocyte was observed in the high-lipid LT muscle perimysium. These results suggested that the shear-force value of the LT muscle was related to change in collagen architecture and of the perimysium in particular.