Rune Haubo Bojesen Christensen

Effects of intraspecific variation in reproductive traits, pectoral fin use and burst swimming on metabolic rates and swimming performance in the Trinidadian guppy ( Poecilia reticulata )

SUMMARY There is considerable intraspecific variation in metabolic rates and locomotor performance in aquatic ectothermic vertebrates; however, the mechanistic basis remains poorly understood. Using pregnant Trinidadian guppies (Poecilia reticulata), a live-bearing teleost, we examined the effects of reproductive traits, pectoral fin use and burst-assisted swimming on swimming metabolic rate, standard metabolic rate (ṀO2std) and prolonged swimming performance (Ucrit). Reproductive traits included reproductive allocation and pregnancy stage, the former defined as the mass of the reproductive tissues divided by the total body mass. Results showed that the metabolic rate increased curvilinearly with swimming speed. The slope of the relationship was used as an index of swimming cost. There was no evidence that reproductive traits correlated with swimming cost, ṀO2std or Ucrit. In contrast, data revealed strong effects of pectoral fin use on swimming cost and Ucrit. Poecilia reticulata employed body-caudal fin (BCF) swimming at all tested swimming speeds; however, fish with a high simultaneous use of the pectoral fins exhibited increased swimming cost and decreased Ucrit. These data indicated that combining BCF swimming and pectoral fin movement over a wide speed range, presumably to support swimming stability and control, is an inefficient swimming behaviour. Finally, transition to burst-assisted swimming was associated with an increase in aerobic metabolic rate. Our study highlights factors other than swimming speed that affect swimming cost and suggests that intraspecific diversity in biomechanical performance, such as pectoral fin use, is an important source of variation in both locomotor cost and maximal performance.

The effect of skatole and androstenone on consumer response towards streaky bacon and pork belly roll

Consumer liking was assessed for streaky bacon and pork belly roll from entire male pigs with an androstenone (AND) content of up to 9.4 ppm and a skatole (SKA) content of up to 0.92 ppm in the back fat and castrates. No clear effect of either AND or SKA was seen in consumer liking, although an insignificant tendency was seen for SKA. A sensory profile analysis showed that AND increased the boar taint of bacon, while both AND and SKA increased the boar taint of the pork belly roll. Consumer sensitivity towards AND and SKA did not affect liking of the meat products. The lack of effect of AND and SKA on consumer liking could be due to a masking effect of the spices and smoke. Three consecutive weeks exposure to bacon did not change the liking score, irrespective of the AND and SKA content. This indicates that the consumers did not become more sensitive towards boar taint.

The effect of skatole and androstenone on consumer response towards fresh pork from m. longissimus thoracis et lumborum and m. semimembranosus

Consumer liking was assessed for boneless chops (m. longissimus thoracis et lumborum) and schnitzels (m. semimembranosus) from castrates and entire male pigs with an androstenone content of up to 9.4 ppm and a skatole content of up to 0.92 ppm in the back fat. Skatole affected both odour and flavour as assessed by trained sensory panellists (P<0.05-P<0.001), while androstenone particularly affected flavour (P<0.01-P<0.001). Furthermore, the skatole compound seemed to be more important in explaining the presence of boar taint in the chops, while androstenone seemed to be more important for the schnitzels. For the chops, tenderness was the most important attribute for consumer liking independently of both the androstenone and skatole contents (P<0.001). Furthermore, increasing contents of both androstenone (P=0.05) and skatole (P=0.04) resulted in a decreased liking of the chops. Skatole was the most important factor regarding consumer response towards the schnitzels (P=0.03). The very low liking scores for both chops and schnitzels were mainly attributable to the androstenone content.