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The effect of energy and protein intake on serum insulin-like growth factors I and II (IGF-I and IGF-II) concentrations in lactating cows was determined. Lactating cows were assigned in diets of either high or low crude protein and net energy intake. Serum concentrations of IGF-I and IGF-II were determined before and after bovine somatotropin (bST) administration. Plasma IGF-I and IGF-II levels were not affected by the type and amount of diet. However injection with bST resulted in a differential increase in both IGF-I and IGF-II levels correlated with the differential increase in milk production depending on the type of diet.

Implants containing the hormone 17-beta-estradiol (E2) were administered to gonadectomized cows and bulls to determine the influence of E2 on the serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations and patterns. Low E2 doses enhanced LH and FSH concentrations. However, higher concentrations significantly reduced the circulating concentrations of the LH and FSH. Estradiol effect on FSH levels was found to be greater in bulls than in cows.

The inability of naloxone in helping to increase the production of oxytocin in dairy cows, with little experience of suckling activities, is discussed.

The change in levels of oxytocin in dairy cows while machine milking in the presence or absence of the calves is studied.

The author examines human-animal similarities and differences while recounting her experiences learning veterinary medicine. Topics include identity, social ethics, objectification, and the navigation of self and other.

The objective of the current study was to evaluate the effect of unrepresentative sampling of digesta particulate matter entering the omasal canal on the accuracy of fiber flow measurements. The experimental design comprised one period, one diet, and three cows as experimental units. Within each cow, the physical and chemical composition of digesta particulate matter was assessed at seven sites within the digestive tract. Three Finnish Ayshire dairy cows, equipped with ruminal and simple-T duodenal cannulas, in extended lactation were offered grass silage twice daily on an ad libitum basis. Digesta samples were collected from the rumen (dorsal and ventral sac), reticulum, omasal canal, omasum, duodenum, and rectum to determine particle size distribution in digesta, chemical composition of various particle size fractions, and distribution of two flow markers (Cr-labeled straw and indigestible NDF [INDF]) among particle size fractions. Digesta samples were wet-sieved using sieves of 2.50, 1.25, 0.630, 0.315, 0.160, and 0.080 mm. Particulate matter was analyzed for OM, NDF, and Cr concentrations, and INDF concentration was determined based on 12-d ruminal incubation. The particle size of digesta entering the omasal canal was larger compared with the omasum or the duodenum, suggesting that omasal canal samples were not representative of particle size distribution truly escaping the rumen. The concentration of potentially digestible NDF (PDNDF) decreased with decreasing particle size. The PDNDF concentration of particulate matter retained on all sieves was greatest in the rumen and gradually decreased along the digestive tract. From the reticulorumen to the omasum, the decrease was associated with decreased particle size, reflecting selective passage of particulate matter. In contrast, from the omasum to the duodenum and rectum, the PDNDF concentration decreased within each particle size fraction without effect on particle size, indicating a nonselective passage of particulate matter between these sites. Variation between particle size fractions was slightly greater for Cr concentration than for INDF concentration, indicating that unrepresentative sampling of particulate matter had a greater effect on Cr concentration compared with that of INDF. Owing to unrepresentative sampling, NDF entering the omasal canal was overestimated by 5% using INDF and underestimated by 7% using Cr as a particle phase marker. Of total NDF digestibility, proportionally 0.90, 0.07, and 0.03 occurred in the reticulorumen, omasum, and intestines, respectively. The current results indicate that, despite unrepresentative sampling of digesta particulate matter entering the omasal canal, the errors in determined NDF flow were small. The omasum may have a greater role in postruminal NDF digestion than the intestines. Key Words: Cows, Digestibility, Fiber, Markers, Omasum, Rumen

Dietary intervention to reduce methane emissions from lactating dairy cattle is both environmentally and nutritionally desirable due to the importance of methane as a causative agent in global warming and as a significant loss of feed energy. Reliable prediction systems for methane production over a range of dietary inputs could be used to develop novel dietary regimes for the limitation of feed energy loss to methane. This investigation builds on previous attempts at modeling methanogenesis and involves the development of a dynamic mechanistic model of whole-rumen function. The model incorporates modifications to certain ruminal fermentation parameters and the addition of a postruminal digestive element. Regression analysis showed good agreement between observed and predicted results for experimental data taken from the literature ([r.sup.2] = 0.76, root mean square prediction error = 15.4%). Evaluation of model predictions for experimental observations from five calorimetry studies (67 observations) with lactating dairy cows at the Centre for Dairy Research, in Reading, U.K., shows an underprediction (2.1 MJ/d) of methane production ([r.sup.2] = 0.46, root mean square prediction error = 12.4%). Application of the model to develop diets for minimizing methanogenesis indicated a need to limit the ratio of lipogenic to glucogenic VFA in the rumen and hindgut. This may be achieved by replacing soluble sugars in the concentrate with starch or substituting corn silage for grass silage. On a herd basis, the model predicted that increasing dietary energy intake per cow can minimize the annual loss of feed energy through methane production. The mechanistic model is a valuable tool for predicting methane emissions from dairy cows. Key Words: Methane, Animal Models, Dairy Cows

The objective was to test the efficacy of an intravaginal progesterone insert and injection of [PGF.sub.2[Beta]], for synchronizing estrus and shortening the interval to pregnancy in cattle. Cattle were assigned to one of three treatments before a 31-d breeding period that employed artificial insemination. Control cattle were not treated, and treated cattle were administered [PGF.sub.2[Beta]] or an intravaginal progesterone-releasing insert (CIDR) for 7 d and treated with [PGF.sub.2[Beta]] on d 6. The treatments were applied in one of three experiments that involved postpartum beef cows (Exp. 1; n = 851; 56 [+ or -] 0.6 d postpartum), beef heifers (Exp. 2; n = 724; 442.5 [+ or -] 2.8 d of age), and dairy heifers (Exp. 3; n = 260; 443.2 [+ or -] 4.5 d of age). Luteal activity before treatment was determined for individual cattle based on blood progesterone concentrations. In Exp. 1, there was a greater incidence of estrus during the first 3 d of the breeding period in CIDR+[PGF.sub.2[Beta]]-treated cows compared with [PGF.sub.2[Beta]]-treated or control cows (15, 33, and 59% for control, [PGF.sub.2[Beta]], and CIDR+[PGF.sub.2[Beta]], respectively; P [is less than] 0.001). The improved estrous response led to an increase in pregnancy rate during the 3-d period (7, 22, and 36% for control, [PGF.sub.2[Beta]], and CIDR+[PGF.sub.2[Beta]], respectively; P [is less than] 0.001) and tended to improve pregnancy rate for the 31-d breeding period for cows treated with CIDR+[PGF.sub.2[Beta]], (50, 55, and 58% for control, [PGF.sub.2[Beta]], and CIDR+[PGF.sub.2[Beta]], respectively, P = 0.10). Improvements in rates of estrus and pregnancy after CIDR+[PGF.sub.2[Beta]] were also observed in beef heifers. Presence of luteal activity before the treatment period affected synchronization and pregnancy rates because anestrous cows (Exp. 1) or prepubertal heifers (Exp. 2) had lesser synchronization rates and pregnancy rates during the first 3 d of the breeding period as well as during the entire 31-d breeding period. The [PGF.sub.2[Beta]] and CIDR+[PGF.sub.2[Beta]] but not the control treatments were evaluated in dairy heifers (Exp. 3). The CIDR+[PGF.sub.2[Beta]]-treated heifers had a greater incidence of estrus (84%) during the first 3 d of the breeding period compared with the [PGF.sub.2[Beta]]-treated heifers (57%), but pregnancy rates during the first 3 d or during the 31-d breeding period were not improved for CIDR+[PGF.sub.2[Beta]] compared with [PGF.sub.2[Beta]]-treated heifers. In summary, the concurrent treatment of CIDR and [PGF.sub.2[Beta]] improved synchronization rates relative to [PGF.sub.2[Beta]] alone or control. Improved estrus synchrony led to greater pregnancy rates for beef cows and beef heifers but failed to improve pregnancy rates for dairy heifers. Key Words: Estrus, Progesterone, Prostaglandins, Synchronization

The objective of this study was to determine primiparous heifer performance following three different heifer development strategies that were the result of timed nutrient limitation. Two hundred eighty-two spring-born MARC III heifers were weaned at 203 [+ or -] 1 d of age and 205 [+ or -] 1 kg BW. The experiment was conducted on two calf crops with 120 heifers born in 1996 and 162 heifers born in 1997. Treatments consisted of different quantities of the same diet being offered for a 205-d period. Heifers in the HIGH treatment were offered 263 kcal ME/[([BW.sub.kg]).sup.0.75] daily. Heifers in the MEDIUM treatment were offered 238 kcal ME/ [([BW.sub.kg]).sup.0.75] daily. Heifers in the LOW-HIGH treatment were offered 157 kcal ME/[([BW.sub.kg]).sup.0.75] daily the first 83 d and 277 kcal ME/[([BW.sub.kg]).sup.0.75] daily for the remainder of the 205 d. Treatments differed in total ME intake (P [is less than] 0.001); heifers on the HIGH treatment consumed 3,072 [+ or -] 59 Mcal/heifer, those on the MEDIUM treatment consumed 2,854 [+ or -] 21 Mcal/heifer, and those on the LOW-HIGH treatment consumed 2,652 [+ or -] 19 Mcal/ heifer. At the beginning of breeding, heifers on the HIGH treatment were taller at the hips (P = 0.01) and weighed more (P [is less than] 0.001) than heifers in the other two treatments. The percentage of heifers that calved expressed as a fraction of the cows exposed did not differ among treatments (89.7%; P = 0.83). The age of heifer at parturition (P = 0.74) and the time from first bull exposure to calving (P = 0.38) did not differ among treatments. Birth weight of calves (P = 0.80) and the calves' weaning weight (P = 0.60) did not differ among the treatments. Calf survival rate on the LOW-HIGH treatment (73%) was lower than that on the moderate treatment (89%; P = 0.007) but did not differ from that on the HIGH treatment (81%; P = 0.26). The second-calf pregnancy rate (92.8%) for cows with a nursing calf at the start of breeding did not differ between treatments (P = 0.83). These findings suggest that as long as heifers are growing and meet a minimal BW before mating, patterns of growth may be altered in the postweaning period without a decrease in the ability of the heifer to conceive or a decrease in calf growth potential. However, limit-feeding heifers may decrease first-calf survival. These alterations in postweaning gain through monitoring the amount of feed offered can be used to optimize feed resources. Key Words: Cattle, Development, Growth, Weight Gain

The influence of transport stress on the secretion of adrenocorticotropin (ACTH) from peripheral bovine lymphocytes was evaluated by exposing cows to short- (30 min) or long-term (14 h) transport. After transporting animals for 14 h they were given a mandatory rest for 24 h in two different situations, either by off-loading them and allowing them to rest in a stall or by keeping them in the truck. Blood samples were withdrawn before and after transport and after the rest period in long-term transported cows and before and after transport in cows transported for 30 min. Peripheral blood lymphocytes were separated and cultured for 72 h in serum-free medium. Adrenocorticotropin was measured using highly sensitive and specific immunoradiometric assay in culture supernates. We noticed no effect of short-term transport on ACTH secretion from lymphocytes. The ACTH concentration in animals transported for 14 h increased (P [is less than] 0.01) from 4.72 [+ or -] 0.48 pg [multiplied by] [mL.sup.-1]/2 x [10.sup.6] lymphocytes before the transport to 8.24 [+ or -] 1.40 pg [multi[lied by] [mL.sup.-1] directly after the transport. When animals were off-loaded and rested in a stall for 24 h, ACTH secretion from cultured lymphocytes returned to the basal value of 4.24 [+ or -] 0.31 pg [multiplied by] [mL.sup.-1], whereas the animals rested in the truck had ACTH levels of 8.9 [+ or -] 1.43 pg [multiplied by] [mL.sup.-1]. Phytohemagglutinin, a plant lectin that stimulates lymphocytes, did not affect the lymphocytic ACTH secretion in this study. Heart rate and rectal temperature measured telemetrically increased in cows directly after 14 h of transport but decreased to pretransport values in cows rested for 24 h in cows rested in stalls and those rested inside the truck. This experiment is the first to show lymphocytic ACTH secretion in cows, and the results indicate that ACTH secretion from peripheral lymphocytes could be used as a reliable measurement in stress studies. Key Words: Bovidae, Corticotropin, Lymphocytes, Stress, Transport

Matrix metalloproteinases (MMP) responsible for degradation of connective tissue are found in most tissues. The MMP are regulated at the levels of transcription, zymogen activation by plasmin or membrane-type- (MT) MMP, and control of enzyme activity by tissue inhibitors of metalloproteinases (TIMP). Whole bovine skeletal muscle showed multiple MMP activities on gelatin zymography and also expressed mRNA encoding MMP-1, -2, -9, -14, and -16, tissue inhibitors of metalloproteinase (TIMP)- 1, -2, and -3 and plasminogen activator and its receptor. Purified intra-muscular fibroblasts and myogenic cell culture derived from satellite cells expressed most or all of these elements. Statistical analysis (n = 35) revealed a strong positive correlation among the mRNA levels of several elements of the MMP system, including MMP-2, MMP-14, TIMP-1, -2, and -3 (r - 0.614 to 0.930, P [is less than] 0.0001). Our results provide an extensive profile of an extracellular proteolytic cascade involving MMP in skeletal muscle and suggest that 1) the activation cascades of muscle MMP may be initiated by both plasmin and membrane-type MMP; 2) a group of genes involved in the same 'arm' of zymogen activation are coexpressed in this tissue; and 3) skeletal muscle cells, in addition to the intramuscular fibroblasts, express an extensive complement of MMP and related proteins. Key Words: Connective Tissue, Fibroblasts, Metalloproteinases, Satellite Cells, Skeletal Muscle

Signal transducer and activator of transcription (Stat)5 has been implicated in the signal transduction pathways of several factors that are lactogenic or galactopoeitic in mammary cells, including prolactin, GH, and IGF-I. Data from cell or explant culture support the concept that Stat5 may represent part of a common route by which different extracellular signals converge and are transduced into the cell. There are few data on Stat5 activity and level in vivo, and we set out to determine whether physiological stimuli of milk synthesis, including GH, GH-releasing factor, and milking frequency, would be associated with alterations in Stat5 activity or protein. We measured Stat5 DNA binding activity using electrophoretic mobility shift assay and Stat5 protein by Western blot in bovine mammary tissue obtained by biopsy or slaughter. Stat5 activity was absent in nonlactating, nonpregnant cows and was present in late pregnancy and throughout lactation. Stat5 activity varied considerably among cows at similar stages of lactation. Mammary Stat5 activity and protein were determined in hormone-treated lactating cows and mammary quarters of cows milked at different frequencies. Infusion of GH and GH-releasing factor for 2 mo significantly raised levels of milk production and depressed mammary Stat5 activity without influencing Stat5 protein abundance. Mammary Stat5 was also influenced by milking frequency; once-daily milking reduced milk production, Stat5 activity, and protein abundance compared with twice-daily milking. Analysis of mammary Stat5 in relation to milk protein concentration in pooled data from lactating cows indicated that Stat5 activity was correlated (r = 0.505, P [is less than] 0.05) with average milk protein concentration and not related to milk protein yield (P [is less than] 0.05). These results show that both Stat5 protein and Stat5 activity are modulated by different physiological signals in vivo and suggest that Stat5 lies within in the zone where signal transduction cascades from a variety of factors are convergent. Further work is required to clarify the role of Stat5 in relation to other factors in regulation of milk protein gene expression. Key Words: Cows, Lactation, Milk, Protein, Somatotropin, Transcription Factors

The objectives of this study were to determine 1) the effect of intramammary infection on calf weaning weight, milk somatic cell count, and milk composition, and 2) the effect of parity on percentages of infected cows, infected quarters, and blind quarters. The number of infected quarters, milk somatic cell counts, milk components, and intramammary infection were studied at weaning in 164 beef cows. The percentage of infected cows ranged from 61.9% at first parity to 66.7% at fifth to ninth parities. Cows with three or four infected quarters had higher (P [is less than] .01) milk somatic cell counts than cows with zero, one, or two infected quarters. Among bacterial isolates, Staphylococcus aureus-infected quarters had the highest (P [is less than] .01) milk somatic cell count. Percentages of butterfat and lactose were lower (P [is less than] .01) in milk from infected quarters than from uninfected quarters. Infections by S. aureus and coagulase-negative staphylococci were the most common and accounted for 67 to 78% of the infections. Percentages of infected quarters and infections caused by S. aureus increased with parity (P [is less than] .01). Intramammary infections did not affect (P [is greater than] .10) calf weaning weight. In conclusion, intramammary infection had no effect on calf weaning weight but increased milk somatic cell count and decreased the percentage of protein, lactose, solids-not-fat, and butterfat. The number of infected and blind mammary quarters increased with parity. Key Words: Beef Cows, Infection, Mastitis, Somatic Cell Counts

Oike, Masahiro, Chiwaka Kimura, Tetsuya Koyama, Miyuki Yoshikawa, and Yushi Ito. Hypotonic stress-induced dual [Ca.sup.2+] responses in bovine aortic endothelial cells. Am J Physiol Heart Circ Physiol 279: H630-H638, 2000.--We have investigated the effects of hypotonic stress on intracellular calcium concentration ([[[Ca.sup.2+]].sub.i]) in bovine aortic endothelial cells. Reducing extracellular osmolarity by 5% to 40% elicited a steep [Ca.sup.2+] transient both in normal Krebs and [Ca.sup.2+]-free solutions. The hypotonic stress-induced [Ca.sup.2+] transient was inhibited by phospholipase C inhibitors (neomycin and U-73122), a [P.sub.2]-receptor antagonist (suramin), and an ATP-hydrolyzing enzyme (apyrase), suggesting that the hypotonic stress-induced [Ca.sup.2+] transient is mediated by ATP. A luciferin-luciferase assay confirmed that 40% hypotonic stress released 91.0 amol/cell of ATP in 10 min. When the hypotonic stress-induced fast [Ca.sup.2+] transient was inhibited by neomycin, suramin, or apyrase, a gradual [[[Ca.sup.2+]].sub.i] increase was observed instead. This hypotonic stress-induced gradual [[[Ca.sup.2+]].sub.i] increase was inhibited by a phospholipase [A.sub.2] inhibitor, 4-bromophenacyl bromide. Furthermore, exogenously applied arachidonic acid induced a gradual [[[Ca.sup.2+]].sub.i] increase with an [ED.sub.50] of 13.3 [micro]M. These observations indicate that hypotonic stress induces a dual [Ca.sup.2+] response in bovine aortic endothelial cells, i.e., an ATP-mediated fast [Ca.sup.2+] transient and an arachidonic acid-mediated gradual [Ca.sup.2+] increase, the former being the predominant response in normal conditions. mechanical stress; adenosine 5'-triphosphate; arachidonic acid.

The aim of the present study was to determine the effect on; FSH increase, follicle wave emergence, estrus and ovulation in cattle that were in various stages of follicular wave development at the time of estradiol benzoate (EB) (2.5 mg) and progesterone (P4) (200mg) treatment. At the time of EB and P4 treatment (EB and P4 treatment = h 0; Group 1 (n = 10) had 4-7 mm follicles, Group 2 (n = 9) had 7-9 mm follicles, Group 3 (n = 9) had a dominant follicle and Group 4 (n = 10) had a persistent follicle. Examinations of ovarian structures via ultrasonography commenced five d prior to EB and P4 treatment and continued daily until estrus was detected following treatment. Blood samples for FSH analysis were collected 12 h prior to EB and P4 treatment and taken every six h thereafter until follicular wave emergence was detected 4 to 6 d following treatment. Size of the largest follicle at the time of EB and P4 treatment was different among groups (P < 0.05). The variance in interval to follicular wave emergence following EB and P4 treatment was less in Group 4 (67.4 h) than Groups 1 (297.6 h) or 2 (689.1 h) (P < 0.05), but not Group 3 (118.6 h) (P > 0.10). Variability in interval to estrus and ovulation following EB and P4 treatment was less for Group 4 (72.3 h and 109.7 h, respectively) than Groups 1 (250.4 h and 422.1 h) and 2 (548.4 h and 820.5 h)(P < 0.05), but not Group 3 (189.8 h and 186.0 h)(P > 0.10). Mean interval to estrus was less in Group 4 (55.6 h [+ or -] 2.5) than Groups 1 (76.7 h [+ or -] 6.5) and 2 (88.1 h [+ or -] 8.7) (P < 0.05), but not Group 3 (66.4 h [+ or -] 4.1) (P > 0.10). Mean interval to ovulation was less for Group 4 (83.8 h [+ or -] 3.3) than Groups 1 (113.1 h [+ or -] 6.8) and 2 (124.8 h [+ or -] 10.1) (P < 0.05), but not Group 3 (95.5 h [+ or -] 4.8) (P > 0.10). In conclusion, cows that have a persistent follicle at the time of EB and P4 treatment have a more synchronous interval to follicle wave emergence, estrus and ovulation then cows with ovarian follicles in recruitment or selection stages of development. Key Words: Cattle, Ovarian follicles, Estradiol benzoate

Primiparous (n = 76) and multiparous (n = 328) lactating Angus cows were randomly assigned to receive either a 50 g or 100 g dose of GnRH at either the first or second GnRH injection of the CO-Synch estrus synchronization protocol to evaluate the efficacy of a reduced dosage in inducing a fertile ovulation. The result was four separate treatment groups: 50:50, 50:100, 100:50 and 100:100. The CO-Synch protocol traditionally consists of GnRH on d 0, followed by an injection of PGF2a on d 7. On d 9 cows were injected with another GnRH injection and mass inseminated. On d -10, and again on d 0, blood samples were obtained to examine progesterone levels and determine the proportion of anestrous cows. Calves were removed for a 48 h period on d 7 and were put back with the cows immediately after breeding. Clean-up bulls were turned in with the cows on 14 d following AI. Cows were pregnancy checked via transrectal ultrasonography 68 d after AI. Serum progesterone levels indicated that 34.9% of the cows were estrual at the start of breeding. All treatments were equally effective (P>0.05) in inducing anestrus cows to ovulate and become pregnant. There was no difference in pregnancy rates among the treatment groups (50:50=50.7%; 50:100=49.3%; 100:50=50.3%; and 100:100=44.6%, P>0.05), thus indicating that a reduced dosage of GnRH is effective in inducing fertile ovulation in the CO-Synch timed insemination protocol. We conclude that using a lower dose of GnRH is an effective method of reducing cost of synchronization with the CO-Synch protocol. Key Words: Estrous synchronization, Beef cows, Fixed-time AI

Synchronization of estrus is a management tool for producers who perform artificial insemination in their beef and dairy cattle. Through the Iowa Beef Center, a Synchronization Planner originally developed in 1998 by Iowa State University Extension has been revised to a web-based platform that incorporates many emerging techniques for synchronization of estrus and synchronization of ovulation in cattle. The revised Synchronization Planner is still available as a stand-alone program. The major enhancements to this program include the expansion of user-selected synchronization options from seven to eleven and the addition of a cost analysis. Users supply the following inputs: desired breeding date, number of females, desired synchronization system, and estimated costs of sychronization products and AI breeding. Outputs from the Synchronization Planner include a daily work schedule that users should follow, a cost analysis and sensitivity table which illustrates the cost per pregnancy with varying expected pregnancy rates, and a list of assumptions. The web-based Extension Synchronization Planner may be found on the home page of the Iowa Beef Center (http://www.iowabeefcenter.org). Key Words: synchronization of estrus, synchronization of ovulation, computerized scheduling

Near infrared reflectance spectroscopy (NIRS) has been used to identify differences in fecal chemistry between cows differing in reproductive status. Eight mature ovariectomized Brahman cows were utilized in an experiment to determine the efficacy of fecal NIRS in predicting serum P4. Treatment consisted of P4 delivery via either 0, 1, or 2 CIDR intravaginal devices. Cows were randomly assigned to treatments in one of three trials such that each cow received each treatment in a switch-back design. CIDR devices were placed at 0 hrs and removed at 72 hrs. Blood and fecal samples were collected at 6 hr intervals from 0 to 48 hrs, then at 12 hr intervals until 72 hrs. The same regimen was followed after CIDR removal. Blood samples were processed to yield serum and frozen until analyzed for P4 by RIA. Fecal samples were stored frozen, then dried 12 hrs at 60 [degrees] C, and ground to a 1mm particle size. Fecal spectra (1108-2492 nm) were obtained by NIRS. P4 concentration was 0.61 [+ or -] 0.09 ng/ml for all treatments at 0 hrs and was 13.94 [+ or -] 1.97 ng/ml for treatment 1 and 20.85 [+ or -] 1.88 ng/ml for treatment 2 (P 5.0 ng/ml in treatment 1 until CIDR removal and returned to pre-treatment values (0.67 [+ or -] 0.80 ng/ml) by 18 hrs post-CIDR removal. Treatment 2 P4 concentration was > 13.0 ng/ml until CIDR removal, and did not return to pre-treatment values (0.60 [+ or -] 0.10 ng/ml) until 42 hrs post-CIDR removal. Serum P4 in the 0 treatment was < 1.0 ng/ml throughout sampling. NIRS predictive equations for P4, utilizing modified partial least squares procedures, were derived from a calibration set of serum P4 values (hr = n) paired with fecal spectra at hr = n + 18 due to the estimated time for serum P4 to be metabolized and appear in the feces. Performance of the equation thus derived (n=295, [R.sup.2]=0.63, SE calibration=2.52 ng/ml) was validated against two data sets with known P4 concentrations: 1) 50 random samples selected from the calibration set, and 2) 20 samples from estrous cycling Brahman x Hereford heifers. Neither 1 ([R.sup.2]=0.11, SE prediction=7.7 ng/ml) nor 2 ([R.sup.2]=0.15, SE prediction=13.9 ng/ml) yielded results indicating reliability of fecal NIRS to predict P4 of exogenous origin. Key Words: Near Infrared Reflectance Spectroscopy, Progesterone, Feces

The hypothesis that ovulation in response to short-term (48 h) calf removal(CR) is dependent on the developmental stage of the dominant follicle was tested in two studies. The objective of Exp. 1 was to characterize the fate of a dominant follicle following 48-h CR on d 2,4,or 8 of a postpartum follicular wave. Ovaries of 61 beef cows were examined daily by transrectal ultrasonography starting at d 20 to 21 postpartum. Treatments were no CR (n = 14) and CR on d 2 (n = 12), 4 (n = 16), or 8 (n = 10) of first detected follicular wave. Percentage of cows that ovulated a dominant follicle following treatment was not different among groups (P = 0.62). Maximum size of dominant follicles was larger in cows that ovulated (P = 0.002) than in cows that did not ovulate. The objectives of Exp. 2 were 1) to determine whether a follicular wave could be synchronized in anestrous cows following injection of 1 mg of estradiol benzoate (EB) and 200 mg of progesterone ([P.sub.4]); EB + ([P.sub.4]); 2) to characterize the fate of dominant follicles following 48-h CR at three stages of a synchronized follicular wave; and 3) to determine whether estrous cycles of normal length followed ovulation in cows pretreated with EB + ([P.sub.4]). Ovaries of 50 anestrous beef cows were examined daily as in Exp. 1. Treatments were sesame oil (SO) injected (i.m.) on d 25 postpartum and no CR (n = 9); EB + ([P.sub.4]) and no CR (n = 9); EB + ([P.sub.4]) and CR on 6 (n = 12), 8 (n = 9), or 12 (n = 11) d after injection. The EB and ([P.sub.4]) injections were given on d 25 postpartum. Variability in day of emergence of subsequent follicular waves was lower in cows receiving EB + P4 than in SO-injected cows (P Key Words: Beef Cattle, Calf Removal, Graafian Follicles, Ovulation, Suckling

Six cannulated lactating cows were used in two replicated, concurrently run 3 x 3 Latin square experiment to study the interaction between level of feeding and diets differing in ruminally undegraded protein (RUP) on bacterial protein synthesis, ruminal escape of dietary protein, and flow of total and individual amino acids (AA) to the small intestine. Treatments consisted of three diets formulated to contain 69 g (HL), 53 g (HH), and 48 g (LL) of RUP per kilogram of DM, respectively. Measurements were made in early lactation, at high feeding level (19.3 kg DM/d), and repeated at late lactation (9.8 kg DM/d, low feeding level) with the same animals and diets. Decreasing feed intake increased (P < .05) the apparent digestibility of OM, NDF, and ADF in the rumen and the total tract, decreased (P < .05) ruminal liquid and particulate passage rate and total ruminal VFA concentration, and increased ruminal Ph and ammonia concentration. Decreased level of intake reduced the (P < .05) efficiency of bacterial N synthesis (28.1 vs 23.7 g bacterial N/kg OM truly digested in the rumen) and decreased (P < .05) ruminal protein degradation rate measured with an in situ method. Duodenal flow of nonammonia nitrogen (NAN), and total AA were highest (P < .05) for the HL diet and lowest (P < .05) for the LL diet at the high feeding level. However, at the low feeding level, diet composition did not affect the amount of NAN or total AA passing to the small intestine. Diet HL increased the proportion of Met, His (P < .05), and Arg (P < .07) in the duodenal digesta at both feeding levels. When purines were used to calculate bacterial N synthesis, no differences between diets were detected. However, when diaminopimelic acid was used, highest bacterial N synthesis was detected for diet HH at the high feeding level. Diet HL supported the highest (P Key Words: Dairy Cows, Feeds, Protein, Amino Acids, Rumen Digestion