Doctor of Philosophy / Department of Animal Sciences and Industry / KC Olson / The objective of this series of studies was to develop and improve methods of production in cow/calf operations of the Great Plains. Ultrasound measures of longissimus muscle depth (LMD) and intramuscular fat (IMF) of Angus × heifers were used to predict lifetime cow productivity. IMF and LMD were categorized into high, medium, and low groups (IMFG and LMDG, respectively). Cows in the high and medium LMDG had greater (P < 0.05) pregnancy rates than cows in the low LMDG. Calf BW at weaning increased (P < 0.05) as dam IMF increased. Angus crossbred cows grazing native range were used to evaluate the effects of pre-partum ruminally-protected choline (RPC) supplementation on postpartum beef cow and calf performance. Under the conditions of our study, RPC supplementation had minimal (P > 0.05) effects on pregnancy rates and performance of beef cows and calves. Lactating crossbred cows with calves and non-pregnant, non-lactating Boer-cross nannies were used to evaluate the effects of co-grazing on herbivory patterns and animal performance while grazing native tallgrass rangeland infested heavily by sericea lespedeza (SL). The proportion of individual SL plants that had been grazed at the end of the trial was greater (P < 0.01) in co-grazed pastures than in single-species pastures. Grazing cows and goats in combination increased (P < 0.01) grazing pressure on SL without negatively affecting beef cow performance, beef calf performance, or residual forage biomass. Angus × cows and heifers grazing native range were used to evaluate the effects of pre-partum corn steep liquor supplementation on postpartum beef cow and calf performance. Under the conditions of our study, CSL supplementation did not generally promote beef cow and calf performance that was equivalent to supplementation with an isonitrogenous, dry, corn-soy alternative. Cow calf pairs were used to evaluate the effects of grazing system (GS) and stocking rate (SR) on cow and calf performance. Late season rest-rotation (LSRR) was compared with continuous (CONT) grazing at low, moderate, and high SR. Under the conditions of our study, CONT produced consistently better (P < 0.01) late-season cow and calf performance than LSRR. Season-long effects of SR on animal performance were minimal; moreover, GS and SR treatments produced equivalent pregnancy rates.

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Production records for dairy cows were first based on the yield of butter for a seven day period any time during the lactation. Later, 365- day records based on production for one day in each calendar month came into general use. The records preferred at present are 305- day records based on monthly test day production, but calculated using the centering date method. The centering date estimate is based on milk and butterfat production from two consecutive milkings per month. The sampling day is centered as nearly as possible in the test month period which need not coincide with the calendar month. The reason for the general acceptance of the 305- day records is the desire of the dairyman to freshen the dairy cow annually, which means milking for ten months and dry for two months. Records calculated by the centering date method more nearly represent actual production than records calculated by other methods that have been used. It is generally accepted that if the present testing program is used properly it can be of great value to the dairy farmer from the standpoint of herd improvement and for selecting animals for a breeding program. However, only a small percentage of the dairymen take advantage of a testing program. One of the limiting factors has been the cost of testing and record keeping. It has been suggested that bimonthly or trimonthly test periods might provide as much information as the monthly testing interval and at the same time reduce the cost to the individual dairymen. It is reasonable to speculate that with reduced costs there would be an increased number of herds tested. This would help compensate the testing supervisor and data processing center for lost income resulting from less frequent testing, and at the same time provide more information for national sire proving programs. However, bimonthly or trimonthly testing have not been accepted because of the possiblilty of larger error being involved in individual records. This larger error occurs because the curvelinear shape of the lactation is not taken into account and a cow is given credit for the same production over the entire testing period, resulting in either under or over estimation of the record. Tho objective of this study is to measure the relative accuracy of estimating 305- day production of dairy cows by using different testing intervals and different methods to estimate production. Monthly, bimonthly, and trimonthly intervals are studied. Methods include the centering date method and three methods using factors designed to extend production from each test day to a 305-day estimate with the test day estimate averaged to determine the final estimate of production for 305 days.

The decline in fertility in dairy cows is of international concern. Since 1950, milk production demands have increased while first service rates of conception have decreased. It is unclear why fertility has decreased, however current dairy management practice requires cows to be kept on a tight yearly calving schedule to ensure maximum milk production over the lifetime of the cow. The current postulate suggests that this regime places a high metabolic burden on the cows, which in turn requires the breakdown of tissues such as fat and muscle to provide substrates to meet the increased energy demands of lactation. Immediately after calving, dairy cows enter a state of negative energy balance (EB), as they cannot consume enough energy to sustain lactation. During this period of negative EB, fat is mobilised in the form of non-esterified fatty acids to help supply the body with the extra energy it needs, but fat mobilisation decreases after four weeks while cows remain in a state of negative EB for several more weeks. It is unclear whether or not muscle breakdown occurs and plays a role in the restoration of EB in lactating cows during peak lactation. I hypothesized that the breakdown of muscle does occur in cows during peak lactation, and that it occurs to a greater extent in cows producing higher amounts of milk. Dairy cows from three strains, NZL, NZH and OSH, representing cows with differing milk production abilities (low, intermediate and high, respectively), were studied for 12 weeks postpartum. Blood was drawn at weekly intervals and muscle biopsies taken at -1, 1, 4, 8, and 12 weeks postpartum. Analysis of plasma revealed an increase in the abundance of troponin I-fs (a marker of muscle breakdown) over the period of study, suggesting that breakdown of skeletal muscle was occurring. Real-time polymerase chain reaction analysis showed that expression of the ubiquitin-proteasome (UbP) ligases atrogin-1 (atro1) and muscle ring finger protein 1 (murf1) increased initially, but returned to normal levels by four weeks postpartum. Concentration of mRNA of the lysosomal proteases, cathepsin B, D, H and L, did not change over the period of study. Therefore, the UbP pathway may contribute to the breakdown of muscle detected by troponin I-fs in plasma. Proteins involved in translation initiation were examined by Western blotting. The ratio of phosphorylated over total eIF2alpha and 4E-BP1 remained unchanged throughout the study, indicating that the breakdown of muscle was not a result of decreased protein synthesis. However, there was a greater ratio of phosphorylated to total eIF2alpha in NZL cows compared with NZH and OSH, suggesting that protein synthesis was less overall in NZL cows than other strains. Measurement of myosin heavy chain composition indicated there was no change in the abundance of type I and type IIx muscle fibres and plasma myostatin levels did not change over the period of study. However, the OSH cows had less myostatin in their plasma than the NZL and NZH cows, suggesting that there may be inhibition of muscle growth occurring in this strain. The results of this study suggest that breakdown of muscle could be important in restoring the EB in high-producing dairy cows during peak lactation. Upregulation of the UbP pathway during the first four weeks of lactation may contribute to this muscle breakdown. However, it remains unclear what processes then continue to regulate breakdown of skeletal muscle to maintain the elevated abundance of troponin I-fs in plasma from four to 12 weeks postpartum in lactating dairy cows.

No description available.

The objective of this study was to evaluate the influence of cow age on grazing distribution relative to mountain riparian areas. In each of two years, sixty cow-calf pairs were stratified by age into the following treatments: 1) thirty first calf heifers (442 kg, body condition score (BCS)=4.5), and 2) thirty mature cows (5-7 years of age; 569 kg, BCS=5.0). From late July to early September, treatments were randomly assigned to four pastures with treatments reversed in Year 2. Analysis of hourly cattle locations observed during 4-d periods early (d 15 to d 18) and late (d 36 to d 39 in Year 1; d 29 to d 32 in Year 2) during the grazing bout revealed a three-way interaction between cow age, time of day, and grazing bout (P<0.01). In the morning hours of the early grazing bout, mature cows distributed farther from the stream (P<0.10), and occupied the riparian vegetation type less (P<0.10) than first calf heifers. No differences (P>0.10) in distribution occurred between age classes from 1300 h until dark. Similarly, during the late grazing bout, no differences were observed (P>0.10) between the distribution of the age classes. While no difference (P=0.20) occurred between age classes in total minutes spent grazing, first calf heifers foraged longer during the morning and evening bouts (P<0.10). The forage utilization pattern and the fecal deposits within 1-m of the stream were not different (P>0.10) between age classes. While mature cows tended (P=0.17) to have higher dry matter intake (DMI), first calf heifers consumed more feed per unit of body weight (BW) (P=0.08). Though first calf heifers tended (P=0.13) to gain more BW, no differences occurred between age classes in BCS change (P=0.69), or calf average daily gain (ADG) (P=0.34). In summary, mature cows distributed farther from water and spent more time outside the riparian vegetation zones during the morning hours early (d 15 to d 18) in the trial compared to first calf heifers. / Graduation date: 2003

Two experiments were designed to study endometritis in postpartum dairy cows. In the first experiment, 30 cows 28 to 41 days in milk (DIM) and without evidence of clinical endometritis were sampled using cytobrush cytology. Cytobrush sampling provided sufficient endometrial material to prepare cytologic specimens and to extract endometrial mRNA. Pro-inflammatory cytokines were analyzed in harvested endometrial tissue taken from cows with and without endometritis. Cytokine expression varied between experimental groups with 30-fold higher IL-6 expression levels (P=0.01), greater than 50-fold higher IL-8 expression levels (P=0.0001), and 20-fold higher TNF-α expression levels (P=0.001) in endometritis-positive versus negative cows. Regression analysis of cytokine expression levels (Ct) and the percentage of PMNs in subclinical endometritis-positive cows showed that for each additional threshold cycle required for IL-8 detection, which corresponded to two-fold less mRNA, the percentage of PMN decreased by 3.3% (P=0.00001). Similarly, for each additional threshold cycle required to detect IL-6 and TNF-α, the percentage of PMNs in endometritis-positive cows decreased by 2.3% (P=0.015) and 2.4% (P=0.054), respectively. Cows with > 18% PMNs required significantly fewer amplification cycles to detect IL-6 (P = 0.01), IL-8 (P =0.0001) and TNF-α (P=0.053) mRNA than cows with <18% PMNs (endometritis-negative). There was a highly significant positive correlation between the expression of individual pro-inflammatory cytokines when comparing IL-8 and IL-6 (P=0.0001), IL-8 and TNF-α (P=0.00001), and finally IL-6 and TNF-α (P=0.0002). In the second experiment, 340 cows 28 to 41 days in milk were examined using cytobrush cytology and transrectal ultrasonography of the uterus and ovaries. One-half of the cows were treated with benzathine cephapirin uterine infusion to determine the lowest PMN percentage where a significant improvement in reproductive performance occurred. Subclinical endometritispositive (>15%) cows in this study were defined as those with the lowest percentage of PMNs that was associated with a significant positive treatment effect. Treated cows with >15% PMNs required 31 fewer days (P=0.041) to become pregnant and had 2.5 times fewer services per conception (P=0.0001) than untreated cows with >15% PMNs. The likelihood of there being CLs at the time of examination in cows with >15% PMNs in endometrial cytobrush cytology was 2.3 times significantly higher (P=0.04). The treatment of cows with ultrasonographically detectable fluid in the uterine lumen with benzathine cephapirin had no effect on days open compared to treatment of cows without fluid in the uterus (P=0.39). Cervical diameter and endometrial thicknesses did not differ between groups of cows with >, < 15%PMNs (P=0.46, P=0.36, respectively). In summary, based on the response to a single treatment with benzathine cephapirin, and the analysis of pro-inflammatory cytokine gene expression, we recommend that a threshold of >18% PMNs be used to define endometritis-positive disease status in cows 28 to 41 DIM. Cervical diameter, ultrasonographic evidence of uterine fluid and ultrasonographic measurement of endometrial thickness were not useful for diagnosing benzathine cephapirin responsive endometritis.

Two experiments were designed to study endometritis in postpartum dairy cows. In the first experiment, 30 cows 28 to 41 days in milk (DIM) and without evidence of clinical endometritis were sampled using cytobrush cytology. Cytobrush sampling provided sufficient endometrial material to prepare cytologic specimens and to extract endometrial mRNA. Pro-inflammatory cytokines were analyzed in harvested endometrial tissue taken from cows with and without endometritis. Cytokine expression varied between experimental groups with 30-fold higher IL-6 expression levels (P=0.01), greater than 50-fold higher IL-8 expression levels (P=0.0001), and 20-fold higher TNF-α expression levels (P=0.001) in endometritis-positive versus negative cows. Regression analysis of cytokine expression levels (Ct) and the percentage of PMNs in subclinical endometritis-positive cows showed that for each additional threshold cycle required for IL-8 detection, which corresponded to two-fold less mRNA, the percentage of PMN decreased by 3.3% (P=0.00001). Similarly, for each additional threshold cycle required to detect IL-6 and TNF-α, the percentage of PMNs in endometritis-positive cows decreased by 2.3% (P=0.015) and 2.4% (P=0.054), respectively. Cows with > 18% PMNs required significantly fewer amplification cycles to detect IL-6 (P = 0.01), IL-8 (P =0.0001) and TNF-α (P=0.053) mRNA than cows with <18% PMNs (endometritis-negative). There was a highly significant positive correlation between the expression of individual pro-inflammatory cytokines when comparing IL-8 and IL-6 (P=0.0001), IL-8 and TNF-α (P=0.00001), and finally IL-6 and TNF-α (P=0.0002). In the second experiment, 340 cows 28 to 41 days in milk were examined using cytobrush cytology and transrectal ultrasonography of the uterus and ovaries. One-half of the cows were treated with benzathine cephapirin uterine infusion to determine the lowest PMN percentage where a significant improvement in reproductive performance occurred. Subclinical endometritispositive (>15%) cows in this study were defined as those with the lowest percentage of PMNs that was associated with a significant positive treatment effect. Treated cows with >15% PMNs required 31 fewer days (P=0.041) to become pregnant and had 2.5 times fewer services per conception (P=0.0001) than untreated cows with >15% PMNs. The likelihood of there being CLs at the time of examination in cows with >15% PMNs in endometrial cytobrush cytology was 2.3 times significantly higher (P=0.04). The treatment of cows with ultrasonographically detectable fluid in the uterine lumen with benzathine cephapirin had no effect on days open compared to treatment of cows without fluid in the uterus (P=0.39). Cervical diameter and endometrial thicknesses did not differ between groups of cows with >, < 15%PMNs (P=0.46, P=0.36, respectively). In summary, based on the response to a single treatment with benzathine cephapirin, and the analysis of pro-inflammatory cytokine gene expression, we recommend that a threshold of >18% PMNs be used to define endometritis-positive disease status in cows 28 to 41 DIM. Cervical diameter, ultrasonographic evidence of uterine fluid and ultrasonographic measurement of endometrial thickness were not useful for diagnosing benzathine cephapirin responsive endometritis.

Records of embryo production in Red Brahman donor cows (n=50) and F1 recipients (n=531) were evaluated from the collection day to the birth of the embryo produced. The effects of the sire of the donor and the embryo, protocol, season-protocol, and body condition of the donor on the total number of good, degenerated, unfertilized, and total embryos were evaluated. The number of donors collected for protocols 1, 2, and 3 were 50, 39, and 46 respectively. The production of good transferable embryos, and embryos/collection for protocols 1, 2, and 3 were 171 (4.6), 152 (4.6), and 208 (6.3) respectively. The final status of each recipient was recorded as non-pregnant, resorption, abortion, and live calf. The model used to analyze pregnancy state was: protocol, embryo stage, embryo quality, corpora lutea size, and season. The effects of sire of the embryo, season-protocol, protocol, embryo stage, embryo quality, body condition score, and corpora lutea size on gestation length and birth weight were analyzed. Season-protocol affected (P<0.05) the number of degenerated embryos. Mean number of degenerated embryos were higher (P<0.05) during winter for protocols 2 and 3 than during other seasons. The ratio for good embryos differed (P<0.01) by sire of donor. The final status of recipients was affected (P<0.01) by protocol. The maximum percentage of live calves and the minimum percentage of non-pregnant recipients were achieved for protocol 3. Gestation length differed (P<0.01) by sire of the embryo, season-protocol, protocol, and body condition score. Spring-protocol 3 resulted in the shortest while Fall-protocol 2 resulted in the longest mean gestation length. Calf birth weight differed (P<0.05) by season-protocol and by embryo quality. The lightest birth weights resulted from embryo quality grade 2 and from spring-protocol 3. These results indicate that using protocols that combine 17??-estradiol, FSH and GnRH (protocol 3) during the spring in conjunction with selection for sire of donor can increase embryo production by Red Brahman cows. Use of protocol 3 with donors in the spring, selection of embryo sire for short gestation length and transfer of quality grade 2 embryos can be used to minimize the incidence of dystocia in recipients.

Two experiments were designed to study endometritis in postpartum dairy cows. In the first experiment, 30 cows 28 to 41 days in milk (DIM) and without evidence of clinical endometritis were sampled using cytobrush cytology. Cytobrush sampling provided sufficient endometrial material to prepare cytologic specimens and to extract endometrial mRNA. Pro-inflammatory cytokines were analyzed in harvested endometrial tissue taken from cows with and without endometritis. Cytokine expression varied between experimental groups with 30-fold higher IL-6 expression levels (P=0.01), greater than 50-fold higher IL-8 expression levels (P=0.0001), and 20-fold higher TNF-&#945; expression levels (P=0.001) in endometritis-positive versus negative cows. Regression analysis of cytokine expression levels (Ct) and the percentage of PMNs in subclinical endometritis-positive cows showed that for each additional threshold cycle required for IL-8 detection, which corresponded to two-fold less mRNA, the percentage of PMN decreased by 3.3% (P=0.00001). Similarly, for each additional threshold cycle required to detect IL-6 and TNF-&#945;, the percentage of PMNs in endometritis-positive cows decreased by 2.3% (P=0.015) and 2.4% (P=0.054), respectively. Cows with > 18% PMNs required significantly fewer amplification cycles to detect IL-6 (P = 0.01), IL-8 (P =0.0001) and TNF-&#945; (P=0.053) mRNA than cows with 15%) cows in this study were defined as those with the lowest percentage of PMNs that was associated with a significant positive treatment effect. Treated cows with >15% PMNs required 31 fewer days (P=0.041) to become pregnant and had 2.5 times fewer services per conception (P=0.0001) than untreated cows with >15% PMNs. The likelihood of there being CLs at the time of examination in cows with >15% PMNs in endometrial cytobrush cytology was 2.3 times significantly higher (P=0.04). The treatment of cows with ultrasonographically detectable fluid in the uterine lumen with benzathine cephapirin had no effect on days open compared to treatment of cows without fluid in the uterus (P=0.39). Cervical diameter and endometrial thicknesses did not differ between groups of cows with >, < 15%PMNs (P=0.46, P=0.36, respectively). In summary, based on the response to a single treatment with benzathine cephapirin, and the analysis of pro-inflammatory cytokine gene expression, we recommend that a threshold of >18% PMNs be used to define endometritis-positive disease status in cows 28 to 41 DIM. Cervical diameter, ultrasonographic evidence of uterine fluid and ultrasonographic measurement of endometrial thickness were not useful for diagnosing benzathine cephapirin responsive endometritis.