The objective of the study was to test the hypothesis that birth weight (BtW) influences growth, carcass characteristics, meat quality, and postmortem (pm) proteolysis differently when pigs originate from small (S) or large (L) litters. Swiss Large White barrows (60) 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, 3 barrows were selected 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). The BW and total feed intake of the individually penned pigs were determined weekly. At slaughter, carcass characteristics were assessed. Meat quality traits were determined in the LM and dark portion of semitendinosus muscle. Titin, nebulin, desmin, and integrin proteolysis were evaluated by SDS-PAGE and Western blot technique, and mu - and m-calpain activities were monitored using casein zymography. Litter size affected BtW of L-BtW and M-BtW but not of H-BtW barrows (BtW x litter size interaction; P = 0.07). From weaning to slaughter, L-BtW barrows grew slower (P< 0.01), ingested less feed (P < 0.01), and were less efficient (P < 0.01) than H-BtW and M-BtW barrows. The carcass yields were greater (P < 0.01), and livers and kidneys were lighter (P

The effects of L-arginine on porcine foetal development and myogenesis were determined. Twenty Swiss Large White gilts were randomly allocated to either the control (C) or L-arginine treatment (A). In addition to the standard gestation diet, A-sows received 26 g L-arginine daily from days 14 to 28 of gestation. At day 75 of pregnancy, sows were sacrificed and the number and weight of foetuses were recorded. From each litter, the lightest, heaviest and the ones with an average foetal weight (FtW) were selected. Primary (P), secondary (S) and total myofiber number as well as S/P ratio were determined in the semitendinosus (ST) and rhomboideus (RH) muscles. In A-sows, the number of viable foetuses (13.0 v. 9.3) and total FtW (4925 v. 3729 g) was greater (P < 0.04) than in C-sows. Compared to C-sow foetuses, the ST of A-sow foetuses had 7% more (17 699 v. 16 477; P 5 0.04) P myofibers and the S/P ratio in both muscles was lower (ST 5 20.3 v. 21.5; RH 5 24.1 v. 27.1; P < 0.07). Regardless of the maternal diet, the S myofiber number and the S/P ratio in both muscles were greater (P < 0.01) in foetuses with a high FtW compared to low FtW. These data suggest that L-arginine supplemented to gilts during early gestation enhanced foetal survival and in the ST positively affected the primary phase of myofiber formation.

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High prolificacy of sows and increased fetal survival lead to greater incidence of intrauterine crowding (IUC), which may then affect pre- and postnatal development of the progeny. The aim of the study was to assess the impact of IUC, using unilaterally hysterectomized-ovariectomized gilts (UHO), on organ and muscle development of their progeny at birth. In the study, 7 UHO and 7 intact control (Con) Swiss Large White gilts were used. At farrowing, if available, 3 male and 3 female progeny with a low (>0.8 and <1.2 kg), medium (>1.2 and <1.4 kg), and high (>1.6 kg) birth weight (BtW) were killed. Internal organs and brain were weighed, and semitendinosus (STN), psoas major (PM), and rhomboideus (RH) muscles were collected. Histological analyses were performed in PM, RH, and STN (dark and light portion) using myofibrillar ATPase staining after preincubation at pH 10.3. Myosin heavy chain (MyHC) polymorphism was determined in the PM using SDS-PAGE gel electrophoresis. Despite that only one-half of the uterine space was available, litter size was smaller (P < 0.01) only by 35% in UHO compared with Con gilts. However, UHO progeny tended (P = 0.06) to be lighter than Con progeny. The average BtW of the selected piglets did not differ (P = 0.17) between the 2 sow groups, whereas PM and kidneys tended to be lighter (P < 0.07) in UHO than in Con progeny. Compared with Con progeny, the PM and the STN(dark) of UHO progeny had fewer (P ≤ 0.05) secondary and total myofibers as well as fewer (P = 0.10) primary myofibers in the PM. In the RH, the secondary-to-primary myofiber ratio was smaller (P < 0.01) in UHO than in Con progeny, whereas the total number of myofibers did not (P = 0.96) differ. The relative abundance of fetal MyHC was less (P = 0.02) and that of type I MyHC tended (P = 0.09) to be greater in UHO than in Con offspring. With increasing BtW, organ and brain weights increased (P < 0.01). Muscle cross-sectional area and total number of myofibers in the light portion of the STN were greater (P < 0.05) in high and medium than in low piglets. In conclusion, IUC reduced hyperplasia of secondary and total myofibers in the STN(dark) and PM. These effects were independent of the BtW and sex.

In pigs, myogenesis is a biphasic phenomenon with the formation of primary and secondary fibres. Hyperplasia was reported to be accomplished around 90 days of gestation. However, some studies suggest a substantial increase in the total fibre number (TFN) from birth to weaning by counting fibre number in the muscle cross sections. The aim of this study was to establish in which way TFN increases after birth and whether this increase is imputable to new (tertiary) myofibres and/or fibre elongation. The semitendinosus muscle of 128 piglets was examined at days 1 (n = 63), 7 (n = 12), 21 (n = 12), and 28 (n = 41) of age. TFN was increased at days 7, 21 and 28 of age when compared with day 1 (P < 0.01). From day 1 to 28, TFN increased from 463 × 10(3) to 825 × 10(3). Microscopy of longitudinal and transversal serial sections revealed that at day 7 of age very small fibres expressing the embryonic myosin heavy chain (MyHC) isoform were apparent all over the muscle. In addition, intrafascicular terminations of normal-sized fibres expressed the embryonic MyHC isoform. These data suggest that the TFN in the pig muscle is not fixed at birth and its postnatal increase may be related to both elongation of existing muscle fibres and genesis of tertiary myofibres, mainly between birth and 3 weeks of age.

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1. Forage selection by herbivores is a major driver of plant diversity in pasture vegetation. Yet, we know relatively little about how plant traits influence decisions of different herbivore species and breeds to select or avoid a certain plant species on semi-natural pastures.2. We quantified the influence of the traits leaf N and P content, leaf dry matter content (LDMC), specific leaf area (SLA) and physical defence mechanisms on plant species selection for three cattle breeds: high-yielding Angus × Holstein crossbreed, dual-purpose Original Braunvieh and undemanding Highland Cattle. The cattle grazed a series of adjacent paddocks in different alpine pastures. Plant species selection was quantified by assessing the difference in biomass proportions of all plant species in 66 vegetation subplots per breed before and after grazing. Plant traits and indicator values were extracted from the TRY database. Data on 152 plant species were analysed using a local mixed-effects model and a global multivariate hierarchical regression model. 3. Plant traits had a clear impact on forage behaviour. Plants with high SLA, leaf N and P contents were significantly selected, whereas plants with high LDMC (e.g. woody plants) and defence mechanisms (e.g. thistles) were generally avoided. Species with high forage quality indicator values as defined by Briemle et al. (2002) were significantly preferred. More importantly, significant differences between forage behaviour of cattle breeds were detected. Selection by less-productive Highland Cattle was much less influenced by plant traits than the selection by the two higher-yielding breeds. 4. Results indicate a clear impact of plant traits on forage selection and demonstrate breed-specific influences. Highland Cattle (and possibly other robust breeds) graze less selectively and impose less selective exclusion on plants. Thereby, they likely influence plant species composition of pastures in a different way than highyielding breeds, thereby creating a distinct habitat. K E Y W O R D S alpine pastures, Bayesian statistics, cattle breeds, forage selection, plant traits, species diversity | 981 Functional Ecology PAULER Et AL.

Pauler et al. Grazing Allometry of Cattle Breeds composition influenced cattle behavior: On pastures of low forage quality, animals walked more, foraged more selectively, and used space less evenly. In conclusion, the observed breed-specific differences can be used to improve pasture management and grassland conservation.