Lactation records of cows born since 1964 were used to compute Cow Indexes (CI) for 581,519 Holsteins and 352,758 Jerseys. CI were used to predict Modified Contemporary Deviations (MCD) of daughters at three levels each of herd mean (µ) and standard deviation (σ), and regressions were compared to expected values. For Holsteins, regressions were greater than expected in herds with average µ or high σ, suggesting that heritability (h²) should be higher for cows in those herds. Heritability estimates agreed with observed regressions for herd σ (h2 of .178, .193, and . 206 as herd σ increased) but not for herd µ (h² of . 222, .163, and .206). For Jerseys, regression results indicated that h² should increase with herd µ, but there was no trend for herd σ. Heritability estimates agreed with the observed regressions for µ (h² of .246, .291, and .331) but not for σ, as h² increased substantially ( .254, .293, and .371) as herd σ increased. Eight adjustments were made for CI: two varied h² to adjust for genetic effects, two adjusted MCD for environmental effects, and four were combinations of these. For Holsteins, regressions of daughter MCD on darn CI were greater than expected for all CI, but regressions of son MCD on darn CI were less than expected. Rankings of CI, based on R² , differed considerably for the three groups examined (all daughters, daughters of elite cows, and sons). For Jerseys, CI of elite darns predicted offspring MCD as expected, but for several CI, regressions for all daughters were less than expected. There were smaller differences in rankings of CI than for Holsteins. Under the assumption that large true breed differences are unlikely, the best CI for both breeds had MCD standardized to a common variance, with h² of .20. This was nearly optimal for Jersey groups, although less than optimal for Holsteins. This CI adjusted for environmental effects of herd a, ignoring differences in genetic variation. It decreased differences among CI for cows in high variance herds, and increased differences in low variance herds. / Ph. D.

Three experiments were conducted to determine an efficient method of obtaining oocytes from cows via ultrasound-guided transvaginal follicular aspiration. Transvaginal oocyte recovery combined with in vitro maturation, fertilization, and culture (IVMlIVFIIVC) can produce pre-implantation stage bovine embryos and also supply a source of ova for gene microinjection. In Experiment 1, once- (IX) vs. twice-weekly (2X) oocyte recovery frequencies were compared. No differences in recovery per session were observed (IX = 6.8 vs. 2X = 6.3 oocytes/session; p>O.1 0). However, the 2X group generated more oocytes on a weekly basis (IX = 6.8 vs. 2X = 12.6 oocytes/week; p<O.OS). In Experiment 2, in vitro embryo production was compared among the groups aspirated once-weekly (1 X), twice-weekly (2X), and twice-weekly after receiving I5 mg FSH (2XF). No differences existed among the aspiration groups in the proportion of blastocysts produced following IVMIIVFIIVC (IX = 23.10/0, 2X = 26.1%, 2XF = 18.0%, % viable). However, the 2X group generated more oocytes and embryos throughout the experiment (2X = 83/318, 2XF = 38/211, IX = 58/2SI viable blastocyst/total oocytes; p<O.O5) than the other groups. A higher proportion of 2X or 2XF generated embryos were of excellent quality (2X = 60.2%, 2XF = 60.5%) compared to the IX group (37.9%) In Experiment 3, in vitro embryo development rates were compared among oocytes from follicular aspiration (TVFA) and oocytes derived from slaughterhouse ovaries (SHD). Oocytes (65%) from both sources were subjected to pronuclear-microinjection of foreign DNA while the remainder served as non-injected controls. Only control oocytes differed, with TVF A-derived oocytes developing to blastocyst more successfully than SHD oocytes (40.8% vs. 30.0olo~ p<0.05). Microinjected embryo development was similar between the groups (TVFA 15.9%, vs. SHD = 12.8% viable blastocyst/total;) with the TVFA oocytes holding a slight but non-significant numerical advantage (p>O.IO) In these experiments, twice-weekly follicular aspiration without exogenous FSH, was the best scheme of oocyte recovery. This program provided a source of consistent, high quality oocytes that responded favorable to the IVMIIVFIIVC system and microinjection. / Master of Science

Data for this study were 79,997 evaluations for 12 individual body and udder traits of Holstein cows. Type scores were subjectively assigned by trained personnel of Select Sires, Inc., Plain City, OH, through their corrective mating and young sire evaluation programs. After editing data to remove incomplete, erroneous and duplicate records, 56,642 records were used to calculate overall and regional age adjustment factors. Genetic parameters were estimated. Heritabilities ranged from .40 for stature to .14 for fore udder. Standard errors ranged from .039 for stature to .018 for fore udder. Genetic correlations ranged from +.75 between teats and udder support to -.61 between feet and legs. Phenotypic correlations were generally smaller than genetic correlations, ranging from .56 between udder support and teats to -.23 for dairyness and strength. These findings were in general agreement with previous research. Genetic evaluations for the 12 individual linear traits were made using Herdmate Comparison (HC) and Best Linear Unbiased Prediction (BLUP) methods. Mean evaluations by HC were near zero, and ranged from .026 for stature to -.027 for teats. Mean repeatability also showed very little variation, ranging from .404 for stature to .241 for teats. BLUP evaluations were similar to HC evaluations, with mean evaluation ranging from .121 for feet to -.183 for dairyness. Direct correlations between BLUP and HC evaluations ranged from .90 for stature to .74 for dairyness. Forty-eight different combinations of minimum daughter numbers and model variables were tested to predict sires' overall evaluations for type from linear trait evaluations using regression analysis. Results indicate that with 5 or more daughters per sire, all predictions tested were similar in accuracy for Predicted Difference for Type. / M.S.