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Sixteen female pigs (Duroc x Landrace x Large White) were divided into 2 groups, which had either free access to the diet (control group) or were feed-restricted from d 28 to 80 and then had free access to the diet (compensatory growth group). The sensory analysis showed that the pigs exhibiting compensatory growth produced meat with increased tenderness compared with control pigs (P < 0.05). To gain further knowledge of the influence of compensatory growth on meat tenderness, the sarcoplasmic protein fraction of muscle tissue was studied at the time of slaughter and 48 h postmortem using proteome analysis. At slaughter, 7 different proteins were found to be affected by compensatory growth: HSC70, HSP27, enolase 3, glycerol-3-phosphate dehydrogenase, aldehyde dehydrogenase E2, aldehyde dehydrogenase E3, and biphosphoglycerate mutase. The HSC70 and HSP27 both belong to the heat shock family and are known to play a role during muscle development. Hence, they may be affected by compensatory growth and increased protein turnover. Forty-eight hours after slaughter, 8 different proteins were found to be affected by compensatory growth: myosin light chain (MLC) II, MLC III, sulfite oxidase, chloride intracellular channel 1, 14-3-3 protein % elongin B, and phosphohistidine phosphatase 14. The changes observed on MLC II and MLC III could be a consequence of enzymatic cleavage in the neck region of the globular myosin head domain that causes the release of MLC II and MLC III from the actomyosin complex. It has previously been hypothesized that compensatory growth results in an increased postmortem proteolysis; thus it was presumed that the intensity of some protein fragments would be affected by compensatory growth. However, the peptides that were found to be affected at 48 h postmortem were all full-length proteins. The 14-3-3 protein [gamma] has been proposed to play a role in the contraction of muscle during rigor and may thereby have an effect on meat tenderness. This study reveals some very interesting changes in the muscle proteome affected by compensatory growth, which may be useful in understanding the relationship among compensatory growth, protein turnover, and meat tenderness. Key words: compensatory growth, feeding strategy, meat quality, muscle growth, proteome analysis, sarcoplasmic protein

Compensatory growth is a phenomenon observed in pigs given free access to feed following a period of restricted feeding that results in increased growth rates. Compensatory growth is believed to increase protein turnover and thereby the proteolytic potential at the time of slaughter, leading to faster tenderization rates of meat. Nine litters of three gilts and three barrows were allocated within litter and gender to three dietary treatment groups. Pigs had ad libitum access to feed from d 28 to slaughter at d 140 (ALA) or were restricted to 69% ad libitum from d 28 to d 80 or 90, and then given ad libitum access to the diet until slaughter at d 140 (RA80 and RA90, respectively). Pigs in the RA80 and RA90 treatment groups had a 9.7% higher (P < 0.001) fractional growth rate in the second feeding period than those in the ALA group. Growth rate was correlated to the activity of m-calpain (r = 0.37; P < 0.01), [beta]-glucuronidase (r = 0.48; P < 0.001), and cathepsins B (r = 0.47; P < 0.001) and B+L (r = 0.31; P < 0.04). The LM of RA80-gilts received higher tenderness scores than the LM of ALA gilts, but tenderness scores were similar among barrows regardless of treatment (gender x treatment; P = 0.02). Conversely, tenderness scores were higher for the biceps femoris of ALA barrows than either ALA gilts or RA90 barrows (gender x treatment; P = 0.02). Desmin and troponin-T degradation, as well as myofibrillar fragmentation index, of the LM were not (P [greater than or equal to] 0.24) affected by treatment. No dietary treatment effects were observed on the activities of [mu]-calpain (P = 0.15), m-calpain (P = 0.74), or calpastatin (P = 0.91) at slaughter. The cathepsin inhibitors, cystatins, tended to be increased (P = 0.06) in RA80 and RA90 pigs. Sarcomere length was longer (P = 0.003) in the LM of gilts than barrows. Barrows in the RA80 group had lower i.m. fat concentrations than ALA; however, no differences were found in the LM of gilts (gender x treatment; P = 0.03). The underlying hypothesis that compensatory growth leads to an increased proteolytic potential at the time of slaughter could not be verified in this study. Key Words: Calpain, Cathepsin, Desmin, Intramuscular Fat, Muscle Growth, Proteolysis

The objective of this study was to examine the intralitter variation in postnatal growth performance, meat quality, and muscle fiber characteristics when littermates were categorized by carcass weight. Thirty-nine litters were weaned at 4 wk of age and had free access to feed from 2 wk of age until slaughter. They were slaughtered by litter at an average BW of 104 [+ or -] 14 kg, and six pigs per litter were selected for analysis: the heaviest- (HW), middle- (MW), and lightest-weight (LW) pig of each sex. Categorizing littermates in LW, MW, and HW pigs at the same age reflected the differences in postnatal growth rate within a litter; thus ADG, muscle mass, and muscle deposition rate differed across pig weight groups (P < 0.001). Also, the total DNA content was different among pig weight groups (P < 0.001) and reflected differences in muscle growth rate. The difference in muscle growth rate between LW and MW pigs could be explained by a larger (P < 0.05) mean fiber area (MFA) in MW pigs, whereas the number of muscle fibers was similar. Growth rate differences between MW and HW pigs could in part be explained by a higher number (P < 0.01) of equal-sized muscle fibers in HW pigs. The difference in MFA was due to a higher estimated DNA and RNA content per muscle fiber in MW and HW compared with LW pigs (P < 0.05). Pigment content was higher in MW and HW compared with LW pigs (P < 0.01), but no other measured meat quality traits were significantly different across pig weight groups. These results indicate that both the number and the growth rate of muscle fibers contribute to intralitter variation in postnatal growth performance. Key Words: Meat Quality, Muscle Fiber Characteristics, Performance, Pigs, Within-Litter Variation

The objective of this study was to examine how increased feed intake of the sow during early to mid-gestation affects sow performance and the muscle fiber number, performance, and technological meat quality of the offspring. Thirty-nine pregnant sows (Landrace x Large White sows mated to Landrace or Large White boars) in their fourth parity were assigned to one of three treatments: 1) the sows were either fed restrictively (control = 15 MJ of NE/d from d 1 to 90, then 24 MJ of NE/d from d 91 to 112, and again 15 MJ of NE/d from d 113 to 115 of gestation); 2) fed ad libitum from d 25 to 50 ([A.sub.25-50]); or 3) ad libitum from d 25 to 70 ([A.sub.25-70]) and as control in the remaining periods. The offspring were weaned at 4 wk of age and had free access to feed from 2 wk of age until slaughter. They were slaughtered litterwise at an average body weight of 104 [+ or -] 14 kg. Estimates for total, primary (P-), and secondary (S-) muscle fiber number; muscle fiber area; and DNA and RNA content were analyzed in semitendinosus muscle (ST) samples from the heaviest, middle, and lightest weight (LW) pigs of each sex within litter selected at slaughter. Technological meat quality traits (pH at 24 h postmortem, drip loss, Minolta color, and pigment) were analyzed in longissimus dorsi muscle. Fiber number, fiber area, and concentrations and content of DNA and RNA of the offspring were not significantly affected by increased maternal nutrition. The ST muscle weight was lower in offspring from [A.sub.25-50] than control sows (P = 0.019). Average daily gain, carcass weight, and the muscle deposition rate also were numerically lower for [A.sub.25-50] than control and [A.sub.25-70] pigs. An interaction between treatment and pig weight was found for muscle deposition rate (P = 0.006), in that LW pigs from treatment [A.sub.25-50] had a lower deposition rate than LW pigs from control. We found no effect of treatment on the meat quality traits in the offspring. Also, barrows had a higher (P < 0.05) number of P-fibers, higher daily gain, and carcass weight than female pigs. No differences were found on any meat quality traits between sexes. Thus, ad libitum feeding of pregnant sows from d 25 to 50 or d 25 to 70 of gestation did not have any beneficial effect on muscle fiber number and area in the offspring. It seems that maternal ad libitum feeding from d 25 to 50 in gestation had a negative effect on postnatal muscle growth, with especially the LW pigs being affected. Key Words: Growth, Maternal Nutrition, Meat Quality, Muscle Fiber, Pig

The effects of various growth rates in pigs induced by four different feeding strategies on the activity of the calpain system and on postmortem (PM) muscle proteolysis and tenderness development were studied. An increased growth rate may be caused by an increased protein turnover, which results in up-regulated levels of proteolytic enzymes in vivo that, in turn, possibly will affect PM tenderness development. It can be hypothesized that increased proteolytic activity pre-slaughter will increase the PM tenderization rate. From postnatal d 28 to d 90 (phase 1) the pigs were divided into two groups, given either ad libitum (A) or restricted (R, 60% of ad libitum) access to feed. The two groups were then divided into two subgroups, given either restricted or ad libitum access to feed from d 91 to slaughter at d 165 (phase 2). Measurements of the activity of [micro]-calpain, m-calpain, and calpastatin; concentrations of total collagen and the percent of soluble collagen; and RNA, DNA, and elongation factor-2 where made at slaugther. Myofibrillar fragmentation index (MFI) was determined at slaughter and 24 h PM. Warner-Braztler shear force was determined 1 d and 4 d PM. Pigs fed restricted diets in phase 1 and fed ad libitum in phase 2 (RA pigs) had increased growth rates in the last phase compared to pigs fed ad libitum during both phase 1 and phase 2 (AA pigs). The increased growth rate (compensatory growth) was followed by an increased proteolytic potential ([micro]-calpain:calpastatin ratio), increased MFI values, and higher tenderization rates. There was a positive correlation between the activities of m-calpain and growth rates (r = 0.35, P = 0.03), and between RNA levels and growth rates (r -0.43, P = 0.006). The proposed hypothesis is largely supported by the results. The activities of both [micro]- and m-calpain at slaughter were highest in fast-growing pigs. The calpain activity was highest in RA pigs, which in turn also had the fastest growth rates prior to slaughter among the four groups. This implies that the synthesis of these enzymes was up-regulated during the second feeding period to a larger extent in RA pigs. The proteolytic potential and the MFI values indicate that the up-regulated in vivo calpain activity had an effect on PM protein degradation, which also is supported by the higher tenderization rate in RA pigs. Key Words: Calpain, Growth, Pork, Proteolysis, RNA, Tenderness

In the present study, we examined the effect of temperature during early incubation on muscle growth and bone characteristics in 34/35 d old broilers using a support muscle (M. gastrocnemius) and a muscle with a high economic value (M. pectoralis). Fertilised Ross 308 eggs were incubated at four temperatures (36.5°C, 37.5°C (Control), 38.5°C, or 39.0°C) from embryonic day (ED) 4 to ED7. Otherwise, the temperature was held at 37.5°C. The live weight at d 32 was not dependent on temperature whereas the ratio between weight of M. pectoralis and M. gastrocnemius at day 34 tended to decrease at 36.5°C and 38.5°C compared to 37.5°C. A tendency was found for a temperature effect on the slope of the breaking strength curve (N/mm) of tibia bone. The slope was numerically largest at an incubation temperature of 37.5°C and lowest at 38.5°C (P< 0.100). The distance to fracture (P=0.013), the area under the curve (energy) (P=0.059), and the diameter of tibia (P=0.047) were largest for male broilers incubated at 38.5 to 39.0°C while females did not respond. In conclusion, early incubation temperature did not seem to change muscles quantitatively. In contrast, increasing incubation temperature to 38.5-39.0°C from ED4-ED7 is beneficial for male broilers, where the bone strength of tibia was increased suggesting an increased ability to walk, although gait score was not affected. [ABSTRACT FROM AUTHOR]