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Arkansas Animal Science Department Report 2001 Table 4. Estimated genetic parameters for ADG, average daily feed intake (ADFI), loin eye area (LEA), and backfat using appropriate two-trait models a that included weight at 100 d of age (WT100) for each breed. Breed Item b Landrace Yorkshire Duroc Hampshire ADG h 2 a 0.28 0.26 0.14 0.17 h 2 m 0.02 0.02 0.03 0 r am -0.62 -0.33 0 0 c 2 0.14 0.17 0.15 0.18 ADFI h 2 a 0.34 0.31 0.20 0.23 h 2 m 0.05 0 0 0 r am -0.73 0 0 0 c 2 0.22 0.20 0.24 0.24 LEA h 2 a 0.48 0.39 0.26 0.25 h 2 m 0.06 0.04 0 0 r am -0.67 -0.67 0 0 c 2 0.09 0.14 0.12 0.18 Backfat h 2 a 0.63 0.65 0.35 0.31 h 2 m 0.07 0.06 0 0 r am -0.66 -0.69 0 0 c 2 0.08 0.10 0.12 0.10 a Models for each trait included effects that were found to be important (Table 2). When maternal genetic effects or the correlation between additive direct and maternal genetic effects were found to be unimportant, these effects are reported as 0. b Notation: heritability for additive direct effects (h 2 a); heritability for maternal genetic effects; (h 2 m); correlation between direct and maternal effects (r am ); proportion of common litter environmental effects (c 2 ). 44
Effect of Treatment to Temporarily Block Germinal Vesicle Breakdown on Porcine Oocyte Maturation and Subsequent Parthenogenetic Development T. R. Bilby and R. W. Rorie 1 Story in Brief Porcine oocytes matured in vitro undergo nuclear maturation more rapidly than cytoplasmic maturation. Treatment or procedures to synchronize the completion of nuclear and cytoplasmic maturation might enhance oocyte developmental competence. These studies assessed the effectiveness of various treatments to prevent or slow nuclear progression for a period of 20 h without detrimental effects to subsequent maturation and cleavage. Cumulus-oocyte complexes (COC’s) were aspirated from sow ovarian follicles and assignment across treatments. Experiment 1 compared the effect of timing of follicle stimulating hormone (FSH) and luteinizing hormone (LH) on nuclear maturation. Experiment 2 compared the effectiveness of various treatments [dexamethasone (DEX), dimethylaminopurine (DMAP) and dibutyryl cyclic adenosine monophosphate plus testosterone (dbcAMP + T)] to temporarily block nuclear maturation without detrimental effects on subsequent development. In both experiments, oocyte nuclear maturation was assessed at 20 and 46 h of culture. Also, oocytes were chemically activated and then cultured to assess parthenogenetic cleavage and development to the blastocyst stage. Results of Experiment 1 indicate that delaying FSH and LH supplementation until after 20 h of maturation reduced maturation of oocytes to metaphase II (MII) and cleavage. Experiment 2 showed that DMAP irreversibly blocked nuclear maturation, resulting in few oocytes maturing or cleaving after activation. Both DEX and dbcAMP + T treatments appeared to be reversible and resulted in similar rates of maturation to MII and cleavage. When compared to the control group, all treatments reduced cleavage. Introduction In order to achieve developmental competence, porcine oocytes must undergo both nuclear and cytoplasmic maturation. Nuclear maturation results from breakdown of the germinal vesicle (GV) and progression of meiosis to metaphase II (MII). Cytoplasmic maturation is the accumulation, within the oocyte’s cytoplasm, of products necessary for fertilization, cleavage and development, prior to activation of the embryonic genome. In vitro studies show that porcine oocytes require a maturation period of about 44 h in vitro to achieve adequate cytoplasmic maturation for developmental competence. However, nuclear maturation to metaphase II occurs within the first 24 h of culture (Day & Funahashi, 1996). This suggests that nuclear maturation events undergo aging while awaiting adequate cytoplasmic maturation, which in turn may decrease developmental competence. Better synchrony between nuclear and cytoplasmic maturation might be achieved by temporarily blocking the spontaneous nuclear maturation that occurs when oocytes are removed from follicles and placed into culture. This might be achieved through the use of chemical blocking agents or altering the timing of addition of hormones to maturation medium. The present studies were conducted to determine if the presence or absence of gonadotropins (FSH and LH) during the first or second half of in vitro maturation affected porcine oocyte maturation to M II and subsequent cleavage. Also, the studies assessed the effectiveness of various chemical treatments to prevent porcine oocyte germinal vesicle breakdown (GVBD) for a period of 20 h without detrimental effects to subsequent maturation and cleavage. Experimental Procedures Sow ovaries were collected from an abattoir and 3 to 7 mm follicles were aspirated to recover cumulus-oocyte complexes (COC's). Recovered COC's were rinsed three times and held in M-199 medium supplemented with 10 mM HEPES and 50 µg/ml gentamicin until assignment to maturation treatments. In Experiment 1, the base in vitro maturation (IVM) medium was M-199 supplemented with 0.1 mM glutathione, 10% fetal calf serum and 50 µg/ml gentamicin. The COC's were matured for a total of 46 h. In Treatment 1, the base medium was supplemented with FSH and LH for the first 20 h and no hormones the last 26 h of maturation. In Treatment 2, FSH was used the first 20 h and LH the last 26 h of maturation, while in Treatment 3, no hormones were used the first 20 h, but FSH and LH were added the last 26 h of maturation. The FSH and LH used were each supplemented at 0.05 NIH units/ml. In Experiment 2, the base IVM medium for 0 to 20 h was M-199 medium, supplemented with 0.1 mM glutathione, 10% FCS, 50 µg/ml gentamicin, and 0.05 NIH units/ml of FSH. This medium was used alone (Control), or was supplemented with either 10 mg/ml dexamethasone (DEX), 2 mM dimethylaminopurine DMAP, or 1 mM dibutyryl cyclic adenosine monophosphate plus 1 µM testosterone (dbcAMP 1 Department of Animal Science, Fayetteville 45
Page 1 and 2: Arkansas Animal Science Department
Page 3: spine copy ARKANSAS ANIMAL SCIENCE
Page 6 and 7: INTRODUCTION The faculty and staff
Page 8 and 9: COMMON ABBREVIATIONS Abbreviation T
Page 10 and 11: The Effects of Nitrogen Fertilizati
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Page 22 and 23: Efficacy of Mannan Oligosaccharide
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Arkansas Animal Science Department
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Economics of Production Systems Inv
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Influence of Moisture Concentration
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The Use of Hurdle Technology to Red
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Consumer Acceptability of Forage Fe
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