J. G. Berardinelli

The time required for the presence of bulls to alter the interval from parturition to resumption of ovarian activity and reproductive performance in first-calf suckled beef cows.

This experiment was designed to determine 1) if exposure of firstcalf suckled beef cows to mature bulls in the first 30 days, after 30 days, or continuously post partum reduces the postpartum anestrous period and 2) if exposure to bulls alters the first service pregnancy rate. Postpartum first-calf suckled crossbred (Angus x Hereford; Hereford x Angus) cows were randomly assigned to be 1) exposed continuously to mature, epididectomized bulls (BE; n = 18); 2) exposed to bulls for the first 30 days post partum (BE/NE; n = 17); 3) exposed to bulls after the first 30 days post partum (NE/BE; n = 16); or not exposed to bulls (NE; n = 18). Blood samples were collected weekly to be assayed for progesterone to determine resumption of ovarian cyclic activity. All the cows were bred for 21 days by AI while under their respective treatment regimens and were then exposed to fertile bulls for an additional 35 days. The postpartum interval to resumption of ovarian cyclic activity did not differ (P>0.10) among the 3 (BE, BE/NE, and NE/BE) treatment groups, but it was 15.4 d shorter (P<0.05) than for cows in the NE group. The overall pregnancy rates did not differ (P>0.10) among the treatment groups. The AI pregnancy rates for the BE/NE and NE/BE treatment groups were higher (P<0.05) than for the NE group. The AI pregnancy rates for the BE and NE treatment groups did not differ (P>0.10). The results showed that all three treatments (BE, BE/NE and NE/BE) similarly decrease the postpartum interval and that exposure to bulls may improve the reproductive performance of first-calf suckled beef cows.

Characterization of the vaginal microbiota of ewes and cows reveals a unique microbiota with low levels of lactobacilli and near-neutral pH

Although a number of common reproductive disorders in livestock involve bacterial infection, very little is known about their normal vaginal microbiota. Therefore, we sought to determine the species composition of sheep and cattle vaginal microbiota. Twenty Rambouillet ewes and twenty crossbred cows varying in age and reproductive status were sampled by ectocervicovaginal lavage. We amplified and sequenced the V3–V4 region of the 16S ribosomal RNA (rRNA) contents yielding a total of 907,667 high-quality reads. Good’s Coverage estimates indicated that we obtained data on 98 ± 0.01% of the total microbial genera present in each sample. Cow and ewe vaginal microbiota displayed few differences. Cow microbiota exhibited greater (P ≤ 0.05) α-diversity compared to the ewe microbiota. Both livestock species differed (P ≤ 0.05) from all previously reported vaginal communities. While bacteria were numerically dominant, Archaea were detected in 95% of cow and ewe samples, mainly of the order Desulfurococcales. Both ewes and cows were predominately colonized by the bacterial phyla Bacteroidetes, Fusobacteria, and Proteobacteria. The most abundant genera were Aggregatibacter spp., and Streptobacillus spp. Lactobacillus spp. were detected in 80% of ewe and 90% of cow samples, but only at very low abundances. Bacteria previously described from culture-based studies as common to the cow and ewe vaginal tract, except for Escherichia, were variably present, and only in low abundance. Ewe and cow pH differed (P ≤ 0.05), with means (±SD) of 6.7 ± 0.38 and 7.3 ± 0.63, respectively. In conclusion, 16S rRNA sequencing of cow and ewe vaginal ectocervicovaginal lavages showed that cow and ewe vaginal microbiota differ from culture-led results, revealing a microbiota distinct from previously described vaginal ecosystems.

Cortisol and prolactin concentrations during three different seasons in relocated Brahman and Hereford bulls

The objective of this study was to evaluate seasonal changes of cortisol and prolactin (PRL) concentrations in Brahman and Hereford bulls moved to locations that differ in geographical and environmental conditions. Postpubertal Hereford bulls from Montana (n = 15) and Nebraska (n = 15) and Brahman bulls from Texas (n = 18) were located in or relocated to Montana, Nebraska or Texas so that each location had 5 Montana Herefords, 5 Nebraska Herefords and 6 Texas Brahman bulls. Blood samples were collected at 20-minute intervals for 8 hours in November (Fall 1), April (Spring) and November (Fall 2) of the next year. These dates corresponded to 6, 12 and 18 months, respectively, after relocation in May of the first year. Cortisol concentrations were higher (P<0.05) in Fall 1 than in Fall 2 and were higher (P<0.05) for bulls in Montana than for bulls in Texas. The decrease in cortisol concentrations from Fall 1 to Fall 2 was negatively related (P<0.05) to age and weight. There was a three-way interaction (P<0.05) of breed-type origin, location and season for PRL concentrations. Seasonal patterns of PRL concentrations differed between relocated Texas Brahman and Hereford bulls, and patterns for relocated bulls differed from those of the nonrelocated bulls. Seasonal patterns of PRL were influenced to a greater extent by relocation in Texas Brahman bulls than in Hereford bulls.

Effect of prostaglandin F2α dosage and stage of estrous cycle on the estrous response and corpus luteum function in beef heifers

Ninety-five normal cyclic crossbred beef heifers were used to determine if the proportions of heifers showing estrus, intervals to estrus and corpus luteum (CL) function were influenced by PGF2alpha dosage and (or) the stage of luteal phase when PGF2alpha was administered. Heifers were assigned randomly to treatments in a 4x3 factorial arrangement. Treatments were 5, 10, 25 or 30 mg PGF2alpha injected either in early (5 to 9 d), mid (10 to 14 d) or late (15 to 19 d) stages of the luteal phase. Jugular samples were taken at 0 h and at 8 h-intervals for 48 h and again at 60 h after PGF2alpha treatment for progesterone assay. Heifers were observed for estrus continuously for 120 h PGF2alpha treatment. The proportion of heifers showing estrus was dependent upon (P<0.05) both dosage of PGF2alpha and stage of luteal phase. Heifers given 5 mg of PGF2alpha showed estrus only if treated during the late stage, while those given 10 mg of PGF2alpha showed a progressive increase of heifers in estrus as stage of luteal phase advanced. The proportion of heifers showing estrus after 25 and 30 mg of PGF2alpha increased from 56% for the early stage to 100% for the mid and late stages. Interval to estrus in heifers showing estrus within 120 h after PGF2alpha treatment did not differ (P>0.05) among dosages but tended (P=0.10) to be longer in heifers treated during the mid luteal stage (67 h) than in heifers treated in the two other stages (56 h). A greater proportion of heifers (P<0.05) showed estrus by 60 h after PGF2alpha when treated during the early and late luteal stages (75.5%) than for heifers treated during the mid luteal stage (30.4%). Patterns of progesterone concentrations were influenced (P=0.08) by the three way interaction of dosage, stage and time. In heifers that showed estrus, rate of decline in progesterone tended (P=0.07) to be slower during the mid luteal stage than during the early and late stages. Progesterone did not drop below 1 ng/ml until 32 h in heifers treated during the mid luteal stage; whereas progesterone dropped below 1 ng/ml by 24 h in heifers treated during the early and late stages. These data may be useful in designing more efficient systems for using PGF2alpha or its analogues in estrus synchronization of beef cattle.

Lipid levels and digesta viscosity of rats fed a high-fiber barley milling fraction

Abstract Forty adult rats were used in an experiment to evaluate the effect of feeding a high viscosity barley milling fraction on plasma and liver lipids and intestinal content viscosity. Shonkin barley was milled into 14 fractions utilizing an 8-roller dry mill. The fraction selected for this experiment was classified as break shorts containing 8.4% β-glucan. Rats were randomly allotted to diets containing 0.5% cholesterol and barley shorts at either 0% (control), 30, 60, or 90% of the diet. Experimental duration was 21 d at which time rats were sacrificed, small intestine contents removed and viscosities determined. The animals were not fasted prior to sacrifice. Response criteria measured were plasma lipids and glucose, liver lipids, wet digesta weight and viscosity of intestinal contents. Plasma lipids and glucose were not different (P > .05) for rats fed any of the diets. There were no differences in liver weights among groups. Rats fed different levels of shorts had significantly lower (P

Duration of daily bull exposure on resumption of ovulatory activity in postpartum, primiparous, suckled, beef cows.

The objective of this experiment was to determine if duration of daily bull exposure influences length of postpartum anestrus in primiparous, anovular, suckled, beef cows. The null hypotheses were that intervals from calving or the start of bull exposure (D 0) to resumption of ovulatory activity (OA), and proportions of cows that resumed OA during the experiment does not differ among cows exposed to bulls for 0h, 6h, or 12h daily, and that there is no relationship between the duration of bull exposure and interval to resumption of OA in cows exposed to bulls for 0h, 6h, or 12h daily. At 51.5+/-2.3d (+/-SE) after calving, cows were assigned randomly to be exposed for 12h (BE12; n=15) or 6h daily (BE6; n=14) to bulls, or not exposed to bulls (NE; n=10) for 45 d. Interval from calving or from D 0 to resumption of OA was shorter (P<0.05) and the proportion of cows that resumed OA during the experiment was greater (P<0.05) for BE12 than for NE cows. Interval from D 0 to resumption of OA did not differ (P>0.10) between BE6 cows and either BE12 or NE cows. However, interval from calving to resumption of OA was shorter (P<0.05) for BE6 than NE cows. The proportion of cows that resumed OA did not differ (P>0.10) between BE6 cows and BE12 cows; however, the proportion of cows that resumed OA during the experiment tended (P=0.08) to be greater for BE6 cows than for NE cows. There was a linear relationship between intervals from calving (b(1)=-7.64 d/h; P<0.05) and D 0 (b(1)=-3.3 d/h; P<0.05) to resumption of OA and duration of daily bull exposure. Thus, the duration of bull-pheromone stimuli that cows perceive each day is related to when primiparous, postpartum, anestrous, suckled cows respond to this stimulus and undergo the physiological changes necessary to resume ovulatory activity.

Seasonal differences in spermatogenesis, testicular mass and serum testosterone concentrations in the grizzly bear

Abstract The objectives of this study were to determine whether there are seasonal changes in spermatogenesis for pre-pubertal and post-pubertal grizzly bears (Ursus arctos horribilis), and investigate the seasonal association between testis mass and serum testosterone (T) concentrations for post-pubertal grizzly bears from the continental US from May through October. Testes from 25 grizzly bears were collected from bears killed by federal and state wildlife personnel in Montana and Wyoming from 1978 to 1995. Fifty blood samples were obtained from wild, post-pubertal (≥5.5 years) male grizzly bears from May through October in Montana and Wyoming from 1993 through 1995. In pre-pubertal bears, the seminiferous tubules were small and surrounded by abundant interstitial tissue in May. Tubules were enlarged and closely packed July through September. Tubules began to degenerate in November. Although spermatogonia and spermatocytes were present from May through September, spermatids never occurred within seminiferous tubules. The epididymal tubules in pre-pubertal bears were well organized from May through September, although they never contained spermatozoa. In post-pubertal bears, spermatogenesis changed seasonally: the entire spermatogenic population from spermatogonia through spermatids was present May through August, and spermatogonia and spermatocytes were present in October and November. The seminiferous epithelium began to deteriorate in July. The epididymal tubules contained spermatozoa May through August only. Both testis mass and T concentrations peaked in June. Mean T concentrations during May and June were greater (P = 0.02) than those during July through October. These results suggest that in grizzly bears in the continental US, seasonal changes in spermatogenesis are accompanied by changes in testis mass and T concentrations and both are associated with photoperiod.

Testosterone and luteinizing hormone response to GnRH in yearling bulls of different libido

Abstract This study was conducted to evaluate pituitary and testicular responsiveness to gonadotropin releasing hormone (GnRH) as measured by luteinizing hormone (LH) assay and by testosterone assay, respectively, in bulls that had previously exhibited either high or low libido based on a libido test. Eighty-four purebred Angus bulls were tested for libido during 1988 and 1989. Blood samples were collected from four bulls that had the highest and lowest libido scores in each year by indwelling jugular cannula at 15 min intervals for 2 h before and for 5 h after GnRH (10 ng/kg body weight, i.v.) administration. The samples were assayed for LH, testosterone and cortisol. Low libido bulls had higher (P

Characteristics of temporal patterns of cortisol and luteinizing hormone in primiparous, postpartum, anovular, suckled, beef cows exposed acutely to bulls

BackgroundThe physiological mechanism by which bulls stimulate resumption of ovarian cycling activity in postpartum, anovular, suckled cows after calving may involve the concurrent activation of the hypothalamic-hypophyseal-ovarian (HPO) axis and hypothalamic-hypophyseal-adrenal (HPA) axis. Thus, the objectives of this experiment were to determine if characteristics of temporal patterns of cortisol and luteinizing hormone (LH) in postpartum, anovular, beef cows are influenced by acute exposure to bulls. The null hypotheses were that daily, temporal characteristics of cortisol and LH concentration patterns do not differ between cows exposed acutely to bulls or steers.MethodsSixteen cows were assigned randomly 67 +/- 4 (+/- SE) after calving to be exposed to bulls (EB, n = 8) or steers (ES, n = 8) 5 h daily for 9 d (D 0 to 8). Blood samples were collected daily from each cow via jugular catheters at 15-min intervals for 6 h from 1000 to 1600 h each day. The 5-h exposure period began 1 h after the start of the intensive bleeding period. Characteristics of cortisol and LH concentration patterns (mean, baseline, pulse frequency, pulse amplitude, and pulse duration) were identified by PULSAR analyses.ResultsMean cortisol concentrations decreased (P < 0.05) in cows in both treatments from D 0 to D 2. Thereafter, mean cortisol concentrations stabilized and did not differ (P > 0.10) between EB and ES cows. The decrease in mean cortisol concentrations in EB and ES cows from D 0 to D 2 was attributed to cows acclimatizing to intensive blood sampling and handling procedures. Consequently, analyses for characteristics of cortisol and LH concentration patterns included D 2 through 8 only. Cortisol mean and baseline concentrations, and pulse amplitude did not differ (P > 0.10) between EB and ES cows. However, cortisol pulse duration tended to be longer (P = 0.09) and pulse frequency was lower (P = 0.05) in EB than ES cows. LH pulse frequency was greater (P = 0.06) in EB than ES cows. All other characteristics of LH concentration patterns did not differ (P > 0.10) between EB and ES cows. Characteristics of cortisol concentration patterns were not related to characteristics of LH concentration patterns for ES cows (P > 0.10). However, as cortisol pulse amplitude increased, LH pulse amplitude decreased (b1 = -0.04; P < 0.05) for EB cows.ConclusionsIn conclusion, exposing primiparous, postpartum, anovular, suckled cows to bulls for 5-h daily over a 9-d period did not alter mean concentrations of cortisol or LH compared to mean concentrations of cortisol and LH in cows exposed to steers. However, exposing cows to bull in this manner altered characteristics of temporal patterns of both LH and cortisol by increasing LH pulse frequency and decreasing cortisol pulse frequency. Interestingly, in cows exposed to bulls, as amplitude and frequency of cortisol pulses decreased, amplitudes of LH pulses increased and frequency of LH pulses tended to increase. Thus, the physiological mechanism of the biostimulatory effect of bulls may initially involve modification of the HPA axis and these changes may facilitate activation of the HPO axis and resumption of ovulatory cycles in postpartum, anovular, suckled cows.

Effects of supplemental safflower and vitamin E during late gestation on lamb growth, serum metabolites, and thermogenesis.

Twin-bearing Targhee ewes (Exp. 1, 1 yr, n = 42) and 1,182 single- and twin-bearing whiteface range ewes (Exp. 2, n = 8 experimental units over 2 yr) were used in a 2 x 2 factorial arrangement of treatments to determine the effect of supplemental energy source and level of vitamin E supplement on lamb serum metabolites and thermogenesis (Exp. 1) and on lamb growth (Exp. 2). During late gestation, ewes were individually fed (Exp. 1) or group-fed (Exp. 2) a daily supplement. Supplements were 226 g/ewe of daily safflower seed (DM basis; SS) with either 350 IU/ewe daily (VE) or no added supplemental (VC) vitamin E; or 340 g/ewe daily of a barley-based grain supplement (DM basis; GC) and either VE or VC. One hour postpartum in Exp. 1, twin-born lambs were placed in a 0 degrees C dry cold chamber for 30 min. Lamb rectal temperature was recorded every 60 s and blood samples were taken immediately before and after cold exposure. In Exp. 2, lambs were weighed at birth, at turnout from confinement to spring range (32 d of age +/- 7; turnout), and at weaning (120 d of age +/- 7). Ewes were weighed at turnout and weaning. In Exp. 1, a level of vitamin E x energy source interaction was detected (P < 0.10) for body temperature and change in NEFA and glucose concentrations. Lambs from SSVC ewes had the lowest (P = 0.01) body temperature and had decreased (P = 0.08) NEFA concentration. The SS lambs tended to have decreased (P < 0.11) concentrations of blood urea N (BUN) and thyroxine at 0 min than did lambs born to GC ewes. After 30 min of cold exposure, SS lambs had increased and GC lambs had decreased BUN, triiodothyronine, and triiodothyronine:thyroxine concentrations (P < 0.10). In Exp. 2, kilograms of lamb per ewe at turnout and weaning and lamb survival at weaning were greater (P < 0.07) for GC than SS lambs. Based on the decreased body temperature in SSVC lambs at birth, the greater change in BUN during the cold exposure for SS than GC lambs, and the decreased survival rate for SS than GC lambs, SSVC-supplemented ewes appeared to give birth to lambs with an apparently decreased energetic capacity. This may compromise the ability of the newborn lamb to adapt to extreme environmental conditions.