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

No description available.

No description available.

No description available.

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.

Two studies were conducted to evaluate the effects of varying dietary sources of rumen available carbohydrate (RAC) and rumen available protein (RAP) on milk yield and milk composition, nutrient flow to the duodenum, ruminal and total tract nutrient digestibilities, and ruminal pH, ammonia-N, and VFA concentrations in lactating cows. The first study was a response surface design utilizing nine dietary combinations of RAC and RAP. The response surfaces of all milk variables were saddle-shaped. Because of the saddle-shaped surfaces, an optimum combination of RAP and RAC for milk production variables was not obvious from the limited range of RAC and RAP used in this study. Ridge analysis of the saddle surfaces predicted maximum milk yield when dietary RAC was below 69 % of the DM and RAP below 60% of CP in alfalfa-corn silage based diets. In the second study, four cannulated (ruminal and duodenal) cows were utilized in a 4x4 Latin square design. Four of the nine original diets were selected to provide the largest range of RAC and RAP. Nutrient flow, digestiblities and ruminal parameters were evaluated. Although the in situ incubations indicated that rates of DM, CP, and NDF degradabilities differed among diets, no effects on overall ruminal pH and total VFA concentrations were detected. Additionally, DM, OM, NDF, ADF, and N flows to the duodenum were not affected by dietary treatment. Nonmicrobial N flow was greater for the barley-based diet, yet microbial flow was not different. The differences in rates of availability determined by in situ methods were not large enough to illicit a measurable difference in nutrient digestion and utilization. Additionally, the data implied that none of the diets were limiting in RAC and RAP for vigorous microbial activity. Fat-corrected (3.5%) milk production was greatest (P<.05) when alfalfa-corn silage based diets contained supplements providing intermediate (69 % RAe) carbohydrate availability (corn and barley) and low (60 % RAP) ruminal protein availability (BM and SBM). The increase in fat-corrected milk was consistent with the predicted milk production response in the previous study when RAP exceeded 62% of CP. However, the ruminal parameters, nutrient flow, and nutrient digestibility measurements did not adequately explain the increased milk production when diets contained increased concentrations of BM. / Ph. D.

Increasing feeding costs has led many dairy farmers to use pasture for lactating cows to reduce their production cost. Little is known about the efficiency of nutrient utilization by lactating cows under grazing conditions. The objective of this study, therefore, was to investigate ruminal turnover, intake and site and extent of nutrient digestion in grazing lactating cows. Four dual cannulated (rumen and proximal duodenum) cows were randomly assigned to two groups to graze permanent pasture with no supplement or with 6.4 kg/d corn-mineral mix in a switchback design with three periods of two wk each. Solid and liquid markers (chromic oxide and CoEDTA), used to estimate duodenal flow, fecal output, and ruminal turnover, were administered through the rumen cannula twice daily at 1100 and 2300 h. The supplemented cows had greater milk production (23.7 kg/d) than those on pasture only (19.5 kg/d) with an increase of .66 kg of milk production per kg of concentrate. Corn, however, depressed milk fat percentage resulting in a similar milk fat yield between the two diets. Supplemental corn reduced rumen ammonia-N (22 vs 17 mg/dl) and increased N recovery at the duodenum (86 vs 75% of N intake). True Nitrogen digestibility averaged 72% and microbial N flowing to the duodenum was 67% of the total N flow. This results indicated that grazing cows may benefit from concentrates containing undegradable protein. Daily OM intake was not different, but when cows were fed the supplemented diet, pasture OM was lower than when fed pasture only. Organic matter, NDF and ADF digestibility in the rumen and whole digestive tract were greater when cows were fed. Cellulolytic activity may have been reduced by grain supplementation due to decreased ruminal pH (6.4 vs 6.2). The reduction in fiber digestibility may explain the decrease in forage intake when cows were fed supplemental grain. Ruminal rates of passage (kp) for solid (7.3 %/h) and liquid (18.2 %/h) markers were similar for both diets. The kp values observed for solid and liquid indicate that grazing cows may have a faster ruminal turnover than cows fed diets containing primarily hay or silage. / Master of Science

The present study was designed to measure levels of oxytocic activity in the blood of cows before, during, and after physical stimulation to the teats and udder. It was also designed to determine the relationship between these levels and intramammary pressure. Knowledge in both these areas has been lacking up to the present. Some information in these areas was obtained as a result of this study. It was found that a wide variation existed in the levels of oxytocic activity between cows. In most cows, a bulk of oxytocic activity was detected in the interval of one to four minutes after stimulation began. The activity rapidly declined to low levels, with some exceptions, between the third and fourth minute post-stimulation. This information indicates that no specific changes need to be made in the present milking procedures. / Master of Science

Three milk, fat yield and final score type records were simulated for each cow in 20 herds of 200 cows over 13 years. At completion of the simulation, cows were ranked by different selection methods and the top 2% were chosen to be bull dams. Preferential treatment was simulated by increasing milk and fat yields by 8, 16, 32, and 48% in separate copies of the simulation. Preferential treatment was given to a limited number of cows in copies of the original herds based on 8 strategies. Cows were chosen to receive preferential treatment for 2nd and 3rd records based on phenotypic records and ETA’s alone and in combination with a phenotypic minimum for final score type. Cows were also chosen to be biased in all records based on phenotypic records of dam, parent average ETA, maternal line and final score type. Bull dam selection methods compared used 2:2:1 milk:fat:type indexes of cow Predicted Transmitting Abilities (PTA), first lactation PTA, (PTA-F), PTA after requiring phenotypic minimums, (PTA-P), 3-generation Pedigree Index (PI-3) and PTA after preselection on 3-generation Pedigree Index (PI-3/PTA). Comparison criterion was average merit on a 2:.2:.1 weighting of true transmitting abilities for milk, fat and type for cows selected in each of 3 replicates of the cow population that were started with different random number seeds. Selection methods PTA and PTA-F gave the highest average true breeding values when no bias was present, and both methods were robust to bias levels of 8 and 16% mean response, and continued to give the best results at these levels for all bias patterns studied. In general, selection on PI-3 and PTA-P gave poor results and should not be considered viable selection methods. Selection ability of PTA was greatly decreased at the 32 and 48% bias levels. Selection on PTA-F continued to be effective when bias did not occur in the first lactation or when bias was based on type score, while selection on PI-3PTA was unaffected by bias at any level. Requiring a high level of 3-generation Pedigree Index before selection on PTA appears useful for selecting bull dams when very high levels of bias are present. / Master of Science

Maternal performance of reciprocal two-breed cross cows between Angus, Herefords and Shorthorns was compared in 249 matings over a four year period. These cows were mated to bulls of the same three breeds to produce three-breed and baekcross calvea. Shorthorn x Angus cows (sire breed first) weaned l7.S~ fewer calve. and Hereford x Angus cows 10.31 fewer calves than their respective reciprocal crosses. Thete differencea while large were not statistically significant presumably due to the small numbers involved. There was little difference between Shorthorn x Hereford and Hereford x Shorthorn cows in percentage calf crop_ The calves from Shorthorn x Angua cows were significantly heavier at birth than the calves from their reciprocals. Birth weight differences of calves from the other two sets of rec1proc41 eros. cows were not significantly different. Differences in average daily gain from birth to weaning were highly significant in calves from Angus x Hereford cows over calves from Hereford x Angus cows as well as Shorthorn x Hereford over Hereford x Shorthorn. The third set of reCiprocal crossea, Angus x Shorthorn versus Shorthorn x Hereford, did not show significant differences in average daily gains. / Master of Science