<strong>Arkansas</strong> Animal Science Department Report 2001 Table 3. Effect <strong>of</strong> chemical treatments to block germinal vesicle breakdown and subsequent nuclear maturation to metaphase II (MII). Maturation treatment No(%) oocytes, GV stage @ 20h No(%) oocytes, M II stage @ 46h Control 63/128 (49.2) c 74/106 (69.8) a DEX 96/142 (67.6) b 93/123 (75.6) a dbcAMP + T 86/103 (83.5) ab 101/136 (74.3) a DMAP 119/128 (93.0) a 16/119 (13.4) b a,b,c Within the same column, values with different superscripts differ (P < 0.05). Maturation treatment Table 4. Effect <strong>of</strong> chemical treatments on subsequent parthenogenetic cleavage and embryo development to the blastocyst stage. No(%) oocytes with cleavage No(%) cleaved to blastocyst Mean cell number per blastocyst Control 69/153 (45.1)a 8/69 (11.59) a 31 a DEX 51/163 (31.3)b 2/51 (3.92) ab 22 a dbcAMP + T 51/158 (32.3)b 3/51 (5.88) a 36 a DMAP 26/181 (14.4)c 0/26 (0.0) b --- a,b Within the same column, values with different superscripts differ (P < 0.05). 48
Genetic Parameter Estimates <strong>of</strong> Yearling Live Animal Ultrasonic Measurements in Brangus Cattle A. M. Stelzleni, 1 T. L. Perkins, 2 A. H. Brown, Jr., 1 F. W. Pohlman, 1 Z. B. Johnson, 1 and B. A. Sandelin 1 Story in Brief The objective <strong>of</strong> this study was to estimate genetic parameters for real-time ultrasound measurements <strong>of</strong> longissimus muscle area (LMAU), 12th-rib back fat thickness (FTU), percent intra-muscular fat (PFAT), and yearling weight (YW) for 1,299 yearling Brangus bulls and heifers. A single ultrasound technician took all measurements. Number <strong>of</strong> observations was 1,298, 1,298, 1,215, and 1,170 for LMAU, FTU, PFAT, and YW, respectively. Genetic parameters were estimated for each trait using single- and multiple-trait DFREML procedures (MTDFREML). Each trait was analyzed as a single-trait, then in combination with each other trait in a series <strong>of</strong> two-trait models. Means for LMAU, FTU, PFAT, and YW were 11.13 ± 2.25 in 2 , 0.22 ± 0.10 in, 3.27 ± 0.92 %, and 1030.51 ± 188.23 lb, respectively. Heritabilities obtained from single-trait analysis <strong>of</strong> LMAU, FTU, PFAT and YW were 0.31, 0.26, 0.16, and 0.53, respectively. Average heritabilities from the two-trait analyses for LMAU, FTU, PFAT, and YW were 0.31, 0.27, 0.15, and 0.53, respectively. Genetic correlations for LMAU and FTU, LMAU and PFAT, LMAU and YW, FTU and PFAT, FTU and YW, and PFAT and YW were -0.09, -0.25, 0.44, 0.36, 0.42, and 0.31, respectively. These data suggest a substantial additive genetic effect for YW, FTU, and LMAU implying a strong relationship between phenotypic value and breeding value for these traits. Introduction Collection <strong>of</strong> ultrasound measurements is faster, easier, and more economical than traditional methods <strong>of</strong> collecting carcass data that include harvesting <strong>of</strong> animals. Green (1996) stated the amount <strong>of</strong> useful carcass data that can be easily and economically collected is unlimited. Some beef cattle breed associations collect yearling live-animal ultrasound measurements <strong>of</strong> carcass traits for purebred bulls and heifers. These measurements are to be used in collaboration with genetic performance records already used by seedstock and commercial cattle breeders. Research and literature reporting on analysis <strong>of</strong> genetic parameters for carcass trait measurements taken by live-animal ultrasound techniques is plentiful. Before these data can be effectively utilized, each association must state proven heritabilities and correlations for their respective breeds for ultrasound measurements <strong>of</strong> these carcass traits. The objective <strong>of</strong> this research was to obtain accurate estimates <strong>of</strong> heritabilities and genetic correlations for carcass traits <strong>of</strong> yearling bulls and heifers in the Brangus breed. Experimental Procedures Animals and Data Collection. Purebred Brangus cattle (n = 1,299) had real-time ultrasound (RTU) measurements taken for inclusion in this study. Of these animals 226 were heifers and 1,073 were yearling bulls. All animals were scanned by a single ultrasound technician, and were taken in accordance to the Beef Improvement Federation guidelines (BIF, 1996). At the time <strong>of</strong> ultrasounding, measurements were taken <strong>of</strong> the 12th-rib longissimus muscle area (LMAU), 12th-rib fat thickness (FTU), percent intra-muscular fat (PFAT), and yearling weight (YW). Other data collected included location <strong>of</strong> ranch, sex <strong>of</strong> animal, age <strong>of</strong> animal, and animal registration number in accordance with the International Brangus Breeders Association (IBBA; San Antonio, TX). All animals included in the study had pedigrees traced back to paternal and maternal grandparents. The equipment used in the collection <strong>of</strong> data was the Aloka 500V system (distributed by Aloka USA, Inc., Wallingford, CT) along with a superflab to ensure proper fit <strong>of</strong> the transducer to the curvature <strong>of</strong> the animal's natural body shape. The s<strong>of</strong>tware used was the Critical Vision (CVIS) s<strong>of</strong>tware (Critical Vision, Inc., Atlanta, GA). Placement <strong>of</strong> the transducer was determined by palpating the left side <strong>of</strong> the animal between the 12th and 13th ribs. Once the scanning area was determined, the location was oiled, curried free <strong>of</strong> dirt and debris, and oiled again before transducer placement. The transducer was placed toward the midline and parallel to the 12th and 13th rib bones and moved laterally until the longissimus muscle came into full view on the screen. Fat thickness was estimated at the 3/4 position from the chine bone end <strong>of</strong> the longissimus muscle (U.S.D.A. beef carcass grade standards) using the cross sectional ribeye image. A 1 Department <strong>of</strong> Animal Science, Fayetteville 2 Southwest Missouri State <strong>University</strong>, Springfield 49
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