Summer and Winter Defoliation Impacts on Mixed-Grass Rangeland

Combined growing- and dormant-season pasture use has potential to increase herbage harvest without causing the undesirable shift in species composition that occurs with excessive utilization. The objective of this study was to determine the effect of summer clipping on winter pastures and winter clipping on summer pastures regarding standing crop, plant community composition, and forage quality. The study was conducted from 2003–2006 at the Antelope and Cottonwood Research Stations located in the mixed-grass prairie of western South Dakota. At each location, the experimental design was a randomized complete block with three replications that included 18 clipping treatments arranged as a split-split plot. Whole plots consisted of four summer clipping dates (May–August). Subplot treatments were two clipping intensities (clipped to residual height to achieve 25% or 50% utilization). Sub-subplots consisted of two winter clipping intensities (unharvested or clipped to a residual height to achieve a total utilization of 65%). Two winter control treatments were arranged in the subplot and split into two clipping intensities of 50% and 65% utilization. Winter biomass for the May 25% clipping treatment was similar to winter biomass for winter-only clipping. No increase in forage quality resulted from summer clipping compared with winter clipping. Three consecutive yr of combined growing-season and dormant-season defoliation to 65% utilization resulted in no change in functional group composition compared with ≤ 50% utilization treatments. Clipping in June resulted in reduced midgrass biomass at both stations and increased shortgrass biomass at Cottonwood. Results suggest that producers could combine growing and dormant-season grazing to increase the harvest of herbage on mixed-grass prairie, but should change season of use periodically to avoid an undesirable shift in plant composition.     

Effect of bandaging on second intention healing of wounds of the distal limb in horses

Objective   To evaluate the effect of a non-occlusive dressing incorporated in a 3-layer bandage on second intention healing of wounds of the distal portion of the limb.
Study Design   Untreated wounds in 33 adult horses used in four studies using the same wound-healing model conducted over 5 years.
Methods   Standardised, full-thickness wounds were made in the skin overlying the dorsomedial aspect of the mid-metacarpus; 17 horses were bandaged with a non-occlusive dressing covered by gauze-coated cotton wool that was compressed with adhesive tape; 16 horses were left unbandaged. Wounds were photographed weekly for 9 weeks and the images were analysed electronically.
Results   There were significant effects associated with bandage (P < 0.0001), week (P < 0.001), and bandage by week interaction (P < 0.0001). There was no difference in wound area at the first time-point after wound creation (P = 0.38). After week 1, there was a difference between bandaged and unbandaged wounds in wound area at each measurement until the end of the study. Bandaged wounds showed greater and more prolonged retraction. Unbandaged wounds retracted for 2 weeks before beginning to contract, whereas bandaged wounds continued to retract for 3 weeks. In bandaged wounds excess granulation tissue required regular trimming, but not in unbandaged wounds. There was no difference between groups in the total days to healing or the overall rate of healing.
Conclusions   These results should be treated with caution until validated with contemporaneous, controlled studies. Covering a wound with a non-occlusive dressing in a 3-layer bandage led to greater wound retraction, modulated the rate of wound contraction and promoted excessive granulation tissue. If excessive granulation tissue is excised regularly, bandaging has no effect on total time to healing.     

Glycemic index of starch affects nitrogen retention in grower pigs

Three studies were performed to examine the effect of starch and protein digestion rates on N retention in grower pigs. In Exp. 1, the glycemic index (GI) of corn, a malting barley, and a slow-rumen-degradable barley (SRD-barley) were measured using 6 barrows (BW = 18.0 ± 0.5 kg). The GI of malting barley was greater (P < 0.05) than that of SRD-barley (71.1 vs. 49.4), and the GI of both barley cultivars was less (P < 0.05) than that of corn (104.8). In Exp. 2, the standardized ileal digestibility of AA and DE content of the 3 ingredients were determined using 5 ileal-cannulated barrows (BW = 20.7 ± 2.3). The apparent total-tract energy digestibility values of corn (86.1%) and malting barley (85.7%) were greater (P < 0.05) than that of SRD-barley (82.3%). The standardized ileal digestibility of Lys was 94.0, 92.6, and 92.4% for corn, malting barley, and SRD-barley, respectively, and did not differ among grains. In Exp. 3, 6 diets were formulated to equal DE (3.40 Mcal/kg), standardized ileal digestibility of Lys (8.6 g/kg), starch (424.9 g/kg), and digestible CP (180.0 g/kg) using the values obtained in Exp. 2. Three GI [high (corn), medium (malting barley), and low (SRD-barley)] and 2 rates of protein digestion [rapid (soy protein hydrolysate) and slow (soy protein isolate)] were tested in a 3 × 2 factorial arrangement with 36 barrows (BW = 32.2 ± 2.5 kg). Pigs were fed 3.0 times the maintenance energy requirement daily in 2 meals for 2 wk and were housed in metabolic crates to collect feces and urine separately. At the end of the study, intestinal contents were collected from 4 equal-length segments of the small intestine. The percentage of unabsorbed CP in segment 1 relative to dietary CP was greater (P < 0.05) for the soy protein isolate diet than for the soy protein hydrolysate diet (170.3 vs. 116.5%). The percentages of unabsorbed starch in segments 1 and 2 were greater (P < 0.05) for the SRD-barley diet than for the malting barley or corn diet. Nitrogen intake and fecal N excretion were greater (P < 0.05) for pigs fed the malting barley and SRD-barley diets than for pigs fed the corn diet. Urinary N excretion was greater (P < 0.05) for pigs fed the SRD-barley diet than for pigs fed the corn or malting barley diet. Pigs fed slowly digestible starch (SRD-barley; 46.6%) had less (P < 0.05) net N retention than pigs fed corn or malting barley (54.7 and 54.1%, respectively). In conclusion, slowly digestible starch sources such as SRD-barley may not be suitable to support maximum protein deposition in restricted-fed grower pigs.     

一例犬细小病毒病的诊断与治疗

犬细小病毒病是由犬细小病毒引起的以出血性肠炎或非化脓性心肌炎为主要特征的一类疾病.根据发病情况、临床特征、剖检变化、实验室诊断等情况,对一例犬细小病毒病临床病例进行了诊断并采取了相应的治疗措施,取得了较好的效果.     

Effect of ovulatory follicle size and expression of estrus on progesterone secretion in beef cows

Induced ovulation of small dominant follicles (SF, < 12 mm; CO-Synch protocol) in postpartum beef cows resulted in formation of corpora lutea (CL) that exhibited a delayed rise in progesterone (P4) compared with CL from large dominant follicles (LF, > 12 mm). Experiment 1 characterized P4 concentrations from ovulation to subsequent estrus among GnRH-induced or spontaneously ovulated SF (or= 12 mm) to determine if P4 secretion by CL formed from GnRH-induced SF remains lower postovulation in nonlactating beef cows. Nonlactating beef cows were induced to ovulate 48 h after PGF(2alpha) (CO-Synch; GnRH on d - 9, PGF(2alpha) on d - 2, and GnRH on d 0) or exhibited estrus and spontaneously ovulated after PGF(2alpha). Follicle size was measured at the second GnRH in cows induced to ovulate or approximately 3 h after the onset of estrus for cows that ovulated spontaneously. Cows were classified into 1 of 4 groups: 1) GnRH-induced ovulation-SF (or= 12 mm; Ind-LF; n = 16); 3) spontaneous ovulation-SF (or= 12 mm; Spon-LF; n = 22). Serum concentrations of P4 from d 3 to 15 were reduced in the Ind-SF compared with the Ind-LF (P = 0.05), Spon-SF (P = 0.07), and Spon-LF (P = 0.03). Experiment 2 characterized P4 concentrations (0 to 60 d postAI) among GnRH-induced or spontaneously ovulated SF (or= 13 mm) to determine if P4 secretion by CL formed from GnRH-induced SF remained lower during early gestation. Ovulation was induced with GnRH 48 h after PGF(2) (CO-Synch) or occurred spontaneously, and ovulatory follicle size was measured at AI. Lactating cows were classified into 1 of 3 groups: 1) GnRH-induced ovulation-SF (or= 13 mm; Ind-LF; n = 43); or 3) spontaneous ovulation-LF (>or= 13 mm; Spon-LF; n = 27). The increase in P4 concentrations was greater (P = 0.06) in pregnant (d 2 to 12) compared with nonpregnant cows. Also, the increase in P4 from d 2 to 12 was greater (P = 0.01) in the Ind-LF compared with the Ind-SF groups, but there was no difference (P = 0.94) among groups in P4 from d 14 to 60 in pregnant cows. Follicle size at AI influenced the increase in P4 in cows that failed to conceive (P = 0.007), but not among cows that became pregnant (P = 0.32) to AI. In summary, P4 secretion after GnRH-induced ovulation of SF was decreased from d 2 to 12 compared with that of LF, but was similar among pregnant cows from d 14 to 60 postAI (d 0).     

Resistance to glyphosate in Lolium rigidum

Annual ryegrass (Lolium rigidum) is a widespread and important weed of Australia and populations of this weed have developed resistance to most major herbicides, including glyphosate. The possible mechanisms of resistance have been examined in one glyphosate-resistant Lolium population. No major differences were observed between resistant and susceptible biotypes in respect of (i) the target enzyme (EPSP synthase), (ii) DAHP synthase, the first enzyme of the target (shikimate) pathway, (iii) absorption of glyphosate, or (iv) translocation. Following treatment with glyphosate, there was greater accumulation of shikimate (derived from shikimate-3-Pi) in susceptible than in resistant plants. In addition, the resistant population exhibited cross-resistance to 2-hydroxy-3-(1,2,4-triazol-1-yl)propyl phosphonate, a herbicide which, although structurally similar to glyphosate, acts at an unrelated target site. On the basis of these observations we speculate that movement of glyphosate to its site of action in the plastid is involved in the resistance mechanism. © 1999 Society of Chemical Industry     

Role of Tumour Necrosis Factor α in Stimulation of Prostaglandins F2α and E2 Release by Cultured Porcine Endometrial Cells

The present studies were undertaken to examine the effect of tumour necrosis factor (TNF) alpha on prostaglandins (PGs) F(2alpha) and E(2) release by cultured porcine endometrial cells harvested on days 13-16 after oestrus in comparison to stimulation with oxytocin (OT) and luteinizing hormone (LH). A time-dependent effect of TNFalpha (10 ng/ml) on PGF(2alpha) release was observed in stromal and luminal epithelial cells. Moreover, TNFalpha increased PGF(2alpha) secretion from both endometrial cell types with effective concentrations of 1 (p < 0.05), 10 and 50 ng/ml (p < 0.01). The effect of TNFalpha (10 ng/ml) on endometrial PGF(2alpha) and PGE(2) release was compared with OT (100 nmol/l) and LH (100 ng/ml). All factors affected PGF(2alpha) secretion from stromal cells, however, the stimulation tended to be more potent after OT and LH (p < 0.01) than after TNFalpha (p < 0.05) treatment. In epithelial cells, only TNFalpha was able to stimulate PGF(2alpha) release (p < 0.001). PGE(2) secretion from stromal cells increased after incubation with TNFalpha and OT (p < 0.05). Only LH stimulated PGE(2) release from epithelium (p < 0.001), and its action was very effective when compared with TNFalpha or OT (p < 0.01). Summarizing, TNFalpha induces both PGs secretion from cultured porcine endometrium, but preferentially stimulates PGF(2alpha) release from luminal epithelial cells. Therefore, similarly to OT and LH, TNFalpha may be considered as a potential modulator of endometrial PGF(2alpha) production during luteolysis in the pig.