Kurzbeschreibung
(Englisch)
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Body weight at birth is determinant for postnatal growth performance, carcass characteristics, and meat quality traits. Poorer meat quality can be expected from pigs born with a low compared to a high birth weight. It has been suggested that one of the main reason for these differences is related to the larger myofiber size found in low compared with high birth weight pigs. Based on observations from the ALP -sow herd, intra-litter variations in birth weight seems to be larger in large (n = 14 piglets/litter) compared to small (n = 10 piglets/litter) litters probably due to differences in the maternal nutri-ent supply during embryonic development. Thus, we hypothesize that prenatal development differs between low and high birth weight piglets born from small and large litters. The goal of the first experiment of this project is to determine the dif-ferences in the overall growth performance from birth to slaughter, the carcass characteristics, the meat quality traits, and the size and distribution of myofibers of various porcine muscles between progeny with a high, medium, or low birth weight born from small and large litters. Because drip loss and tenderness is impaired in low birth weight pigs a special emphasis will be placed on postmortem proteolysis aiming at determining whether protein degradation and early postmortem prote-olytic capacity differs between birth weight and litter size classes. Meat quality traits like drip loss and tenderness depend on the proteolytic capacity at the time of slaughter as well as on the protein degradation early postmortem. The objective of the second trial is to test whether by using the compensatory growth phenomenon in order to boost protein turn-over before slaughter will be effective to improve the pork quality especially in low birth weight pigs from large litters.
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Partner und Internationale Organisationen
(Englisch)
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BE, CH, DE, DK, ES, FI, FR, GR, HU, IE, IT, NL, NO, PL, PT, SE, SI, TR, UK
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Abstract
(Englisch)
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There is a certain evidence that, within litter, low-birth weight (BtW) pigs not only grow slower and have fatter carcasses but also meat quality traits like drip loss or shear force are impaired compared to their high BtW siblings. Because the variability of the body weight (BW) at birth is greater in large compared to small litters, the aim of the present study was to test the hypothesis that effects of BtW on growth performance, carcass characteristics and meat quality differ when pigs originate from small or large litters. In the present study, we also investigated whether BtW of the pig or litter size are related to post mortem proteolysis of various muscle proteins such as titin, nebulin, and integrin, and how the degree of degradation is related to pork quality traits. The 60 Swiss Large White barrows used in this study originated from 20 litters with either less than 10 (S) or more than 14 (L) piglets born per litter. Within each of the S- and L-litters, three barrows were selected per litter at birth: the lightest (L-BtW), the heaviest (H-BtW), and the one with a BtW nearest to the average BtW of the litter (M-BtW). At weaning the barrows were individually penned and they had free access to standard diets until slaughter. At slaughter, the weights of the hot carcass, heart, liver, and kidney were assessed. The pH 24 h post mortem, the drip loss after 48 h, the thawing loss, and the shear force were measured in the longissimus dorsi muscle (LD) and in the dark portion of semitendinosus (STD). In both muscles collected at 30 min, 24 and 72 h post mortem, proteolysis of intact titin and nebulin as well as of integrin was determined by SDS-PAGE and Western-Blot technique, respectively. The L-BtW (1.2 vs. 1.6 kg) and M-BtW barrows (1.6 vs. 1.9 kg) from L-litters were lighter than from S-litters whereas no differences in BtW were observed in H-BtW barrows (1.9 vs. 2.0 kg) (litter size ? BtW interaction; P < 0.01). Compared to H-BtW and M-BtW barrows, the L-BtW barrows grew slower (0.90 vs. 0.81 kg; P < 0.01), ingested less feed (2.42 vs. 2.30 kg; P = 0.03), and were still less efficient (2.71 vs. 2.84 kg feed/kg gain; P < 0.01). The carcass yields were higher (82 vs. 81%; P < 0.01) and livers (1.58 vs. 1.74 kg), and kidneys (0.31 vs. 0.34 kg) were lighter (P < 0.01) in L-BtW compared to H-BtW barrows. Regardless of the BtW, barrows from S-litters had higher percentages of shoulder (12.4 vs. 12.1%; P = 0.02) and lower percentages of omental fat (1.8 vs. 2.1%; P = 0.06) than barrows from L-litters. Litter size and BtW had only a small impact on meat quality traits in the LD but the STD was more tender and had a higher 24 h post mortem pH in M-BtW than in H-BtW and L-BtW barrows. Regardless of the litter size, the extent (expressed as the relative abundance of the intact protein band) of titin proteolysis at 24 h post mortem (1.40 vs. 2.57; P = 0.06) and nebulin proteolysis at 72 h post mortem (0.15 vs. 0.25; P = 0.07) tended to be greater in the LD of H-BtW than the LD of L-BtW barrows. Even though shear force was not affected by the BtW, the relative abundance of titin at 24 and 72 h and nebulin at 24 h post mortem was positively correlated (P ? 0.09) with shear force, suggesting that tenderness scores could be impaired by low BtW. At 72 h post mortem, intact integrin of the LD tended to be less degraded (0.17 vs. 0.08; P = 0.08) in barrows originating from S- than from L-litters. Furthermore, the present results indicated that the relative abundance of the intact integrin band at 24 h post mortem was negatively (P < 0.05) correlated with the percentage drip and thaw loss. The present results confirm the effect of BtW on growth performance and carcass characteristics. However, the hypothesized impact on meat quality traits could only be partially demonstrated. Although litter size affected average BtW of the L-BtW and M-BtW barrows, its impact on growth performance, carcass characteristics and meat quality was minor. The study confirms the relationships between protein degradation post mortem, and meat quality traits. The reason that could explain the lower impact of the litter size on growth performance, carcass characteristics and meat quality is that litter size per se only partly explains the intrauterine crowding effect. Moreover, results of recent studies revealed that carcass characteristics and meat quality traits are more affected by BtW variations in gilts than in barrows. Thus in the second experiment the aim was to verify if growth performance, carcass characteristics, and meat quality traits differ between gender and / or BtW classes of pigs originating from large litters. Sixty pigs were selected at the birth from 10 large litters (litter size: > 16 piglets born). Within each litter 6 piglets (3 barrows and 3 female pigs) were chosen: the lightest (L-BtW), the heaviest (H-BtW), and the one with a BtW nearest to the average BtW of the litter (M-BtW). At weaning the pigs were individually penned and they had free access to standard diets until slaughter. Growth performance as well as data on the carcass characteristic were assessed. The pH 24 h post mortem, the drip loss after 48 h, the thawing loss, and the shear force were measured in the longissimus dorsi muscle (LD) and in the dark portion of semitendinosus (STD) [The quality data are not available yet]. The current results revealed that within the BtW group (H-BTW: barrows = 1.72 kg, gilts: 1.74 kg; M-BtW: barrows = 1.49 kg, gilts: 1.42 kg) BtW of barrows were similar (P > 0.05) compared to gilts. By contrast, L-BtW barrows (1.24 kg) were markedly (P < 0.05) heavier than L-BtW gilts (1.01 kg). That gender differences in BtW were observed only in the light BtW group could imply that a relationship between gender and prenatal development exists. As expected, due to faster growth, barrows reached the slaughter weight of 115 kg BW earlier than gilts (age at slaughter: barrow = 161 d and gilt = 169 d). Furthermore, growth rate differed between BtW groups as M-BtW barrows (722 g/d) grew (P < 0.05) faster than H-BtW (704 g/d) and L-BtW barrows (674 g/d) and H-BtW gilts (691 g/d) grew faster than M-BtW (649 g/d) and L-BtW gilts (649 g/d). In barrows lean meat percentage of the carcass was not (54.8%; P < 0.05) affected by the BtW whereas the carcasses of H-BtW (57.0%) and M-BtW gilts (57.3%) were markedly leaner (P < 0.05) than those of the L-BtW gilts (55.2%). These findings showed that depending on the gender intrauterine growth retardation affects prenatal and postnatal growth as well as carcass characteristics. In accordance to the findings in our previous experiment there is evidence that the unfavorable conditions during gestation have a greater impact on female than male pigs. The ongoing investigations will show whether this has also an impact on pork quality. Arginine level is known to be elevated in porcine amniotic and allantoic fluid during early pregnancy suggesting that it plays an important role in embryonic, placental and fetal development. Thus, the aim of the third study was to determine the effect of dietary arginine supplementation to primiparous gilts on litter size, fetal weight (FW) and myogenesis at d 75 of gestation. At the day of mating 20 Swiss Large White gilts were randomly allocated to either control (C) or the arginine treatment (A). All gilts were offered daily 3 kg of a standard diet from mating to d 75 of gestation. Additionally, A-sows received from d 14 to 28 daily 25 g L-arginine. Because of non-pregnancy 3 C-gilts were ex-cluded from the trail. At d 75 of gestation all sows were sacrificed and all fetuses counted and weighed. From each litter the lightest, heaviest, and the ones with an average FW from both genders were selected and the semitendinosus (ST) muscles were excised. The cross-sectional area of the ST and the number of primary (P) and secondary fibers (S) and the S/P ratio were determined. In A-sows litter size was greater (13.0 vs. 9.3; P = 0.04) than in C-sows whereas FW did not (P = 0.95) differ. The ST of A-sows fetuses had more P (17699 vs. 16477; P < 0.04) and the S/P ratio was lower (20.3 vs. 21.5; P < 0.07) than in fetuses from C-sows. Regardless of treatment, the cross-sectional area of the ST was larger (28.4 vs. 23.7 mm2; P < 0.01) and the total number of S (384389 vs. 340471), the S/P fiber ratio (21.6 vs. 19.5) and the total fiber number were greater (401975 vs. 357193; P < 0.05) in fetuses with a high compared to a medium or low FW. Neither ovulation rate (yellow body count) nor the number of mummies differed among treatments, which implies that dietary arginine supplementation during early gestation improved embryo implantation rate without negatively affecting FW. The greater number of P in the ST of fetuses from A-sows suggest that total fiber number at birth might be positively affected by L-arginine since hyperplasia of P is terminated at d 55 of gestation and P serve as scaffold for subsequent S formation.
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