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1.
Studies were conducted to determine the effects of lysocellin on growth performance and metabolism of steers fed forage-based diets. Treatments in all experiments consisted of 1) control, 2) 100 mg lysocellin/d, 3) 200 mg lysocellin/d and 4) 200 mg monensin/d. In each of two 90-d performance studies, 24 Hereford steers were individually fed greenchop (fungus-free tall fescue and Coastal and Tifton-44 bermudagrass) ad libitum and .91 kg/d of a corn-trace mineral salt supplement. In Exp. 1, tall fescue was fed from d 1 to 45 and bermudagrass from d 46 to 90. Bermudagrass was offered during d 1 to 45 and tall fescue during d 46 to 90 in Exp. 2. Lysocellin improved gain (Exp. 1, P less than .01) and feed conversion (Exp. 1 and 2 combined, P less than .05), decreased total VFA concentrations (P less than .05), increased molar proportions of propionate, isobutyrate and isovalerate (P less than .01), decreased molar proportions of acetate and butyrate (P less than .01) and lowered acetate:propionate (P less than .01). Two metabolism studies involving a total of 16 Hereford steers were conducted. Steers were fed tall fescue greenchop and .91 kg/d supplement for a 34-d adjustment period followed by a 5-d total collection period. Lysocellin increased N digestibility (P less than .01) and N retention (P less than .06) but did not (P greater than .05) affect DM, NDF or ADF digestibility. Data indicate that lysocellin results in major alterations in ruminal fermentation and can increase growth performance and N retention in steers fed forage-based diets.  相似文献   

2.
Seeds of the tall fescue ( Festuca arundinacea Schreb .) cultivars Kentucky 31 and an experimental ryegrass X tall fescue hybrid derivative strain (G1-307), and orchard grass (OG) seed were fed in a carrier diet to calves in controlled environmental rooms (31 to 32 C). Both tall fescue varieties produced symptoms of summer toxicosis in dairy steers. Total feed intake (P less than .01) and water intake (P less than .01) of calves were reduced by the tall fescue seed diets when compared with orchard grass. Steers fed G1-307 and Kentucky 31 tall fescue lost (NS) 17.5 and 7.8 kg of body weight, respectively, while those consuming orchard grass gained (P less than .01) 6.2 kg during the experiment. Rectal temperatures were lower (P less than .05) in the calves fed OG (39.4 C) when compared with those fed G1-307 (40.6 C) and Kentucky 31 (40.8 C) tall fescue seed, respectively. In a second trial Kentucky 31 seed was fed in a carrier diet to Holstein steers at graded levels of 0, 350, 700 and 1,050 g seed/d. Consumption of 700 and 1,050 g seed/d adversely affected performance of steers. Total feed intake was lower and water intake was reduced (P less than .05), with rectal temperatures being elevated (P less than .01) in these two groups when compared with 0- or 350-g treatments. No significant differences were detected in body weight changes in this trial. Respiration rates were not significantly affected in either trial. Results of these trials with the young bovine indicate that a toxic substance(s) is present in tall fescue seed.  相似文献   

3.
Fall weaned Angus calves grazed stockpiled 1) tall fescue (Festuca arundinacea Schreb.), 2) tall fescue-red clover (Trifolium pratense L.), or 3) tall fescue-alfalfa (Medicago sativa L.) or were barn-fed, 4) tall fescue hay, 5) orchardgrass (Dactylis glomerata L.)-alfalfa hay, or 6) tall fescue silage from late October to early April during each of 5 yr. Infection of the fescue with Acremonium coenophialum ranged from 0 to 55%. There were two replications each of steers and heifers for each forage system in a completely random design. Each replicate was grazed by three Angus stockers, except for System 1, which was grazed by six stockers, for a total of 420 stockers. Each pasture replicate contained .8 ha (except System 1, which was 1.6 ha), and the stocking rate was one stocker per .27 ha. Fescue hay and silage were harvested each spring for barn-fed systems from the area stockpiled for grazing by cattle in System 1. Nitrogen fertilizer (90 kg/ha) was applied in early spring and again in early August, before stockpiling; no N was applied to stockpiled fescue grown with legumes. Daily gains by calves grazing stockpiled fescue-alfalfa were greater (P less than .01) than by calves grazing stockpiled fescue-red clover or N-fertilized stockpiled fescue (.50, .33, and .34 kg/d, respectively), but fescue-alfalfa calves required more days (P less than .01) of supplemental hay feeding (105, 60, and 36, respectively). Calves fed fescue hay in the barn gained more (P less than .01) than those fed fescue silage.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
Livestock grazing endophyte (Acremonium coenophialum)-infected tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31) at high ambient temperatures may suffer from fescue toxicosis. Adult Angus cows (Bos taurus) were fed 0 to 1 kg/d of 70% infected tall fescue seed containing about 4.4 g of loline alkaloids in factorial combination with thiamin at 0 or 1 g/d. Cows assigned to the zero level of tall fescue seed received a supplement of equivalent energy and protein. Ingestive behavior was measured at 1330 to 1430 EDT during two 4-d periods in two consecutive weeks in August on alfalfa (Medicago sativa L.) pastures using a tethered grazing system. Alfalfa intake per measured grazing session of cows given tall fescue seed declined linearly (P less than .01) as air temperatures during grazing increased above 25 degrees C, largely because of shorter grazing meals. Thiamin increased alfalfa intake per measured grazing session by extending grazing time. Alkaloids in ingested endophyte-infected tall fescue induce thiamin deficiencies in cattle that result in symptoms of tall fescue toxicosis.  相似文献   

5.
Two experiments were conducted to determine the effects of frequency of offering and type of supplemental forage on intake and digestion in calves consuming endophyte-infected fescue hay (I). In Exp. 1, five Holstein steers, averaging 128 kg body weight (BW), were used in a 5 X 5 Latin square experiment. All steers were given free access to I in the afternoon. Morning meals consisted of 1) ad libitum access to I daily (control), 2) .5% BW of Bermuda-grass hay (BG) daily, 3) 1.0% BW of BG every 2nd d, 4) 1.5% BW of BG every 3rd d and 5) 2.0% BW of BG every 4th d. Steers receiving BG consumed less (P less than .01) I and more (P less than .01) total dry matter (DM) than did steers given I alone. Within treatment, I intake was similar (P greater than .10) among days of the feeding cycle without BG. Organic matter (OM) digestion was lower (P less than .05) with than without BG. In Exp. 2, 12 beef calves (Angus and Hereford X Angus; 6 mo of age, 155 kg initial BW) were used in a completely randomized-design experiment. Calves were given ad libitum access to I daily (control) or to BG or wheat hay (WH) on d 1 and I the following 3 d. Hay (I, BG or WH) intake d 1 of the feeding cycle was higher for BG and WH than for the control treatment (16 and 45%, respectively) and higher for WH than BG (25%; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

6.
Seaweed (Ascophyllum nodosum) is a known source of plant growth regulators, and application to turfgrasses has increased activity of the antioxidant superoxide dismutase (SOD) and specific vitamin precursors. Increased antioxidant activity in both plants and animals diminishes oxidative stress. Two pasture experiments investigated effects of Tasco-Forage (a proprietary seaweed-based product) applied to tall fescue (Festuca arundinacea) on antioxidant activity in plants and in ruminants that grazed the forage. In Exp. 1, fescue was 70 to 100% infected with the endophyte fungus Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin). Twenty-four wether lambs (initial BW 41 kg; SD = 5) grazed fescue treated with 0, 1.7, or 3.4 kg Tasco/ha applied in April and July, 1994, with four replications per treatment. Grazing occurred for 26 d beginning April 21 and for 22 d beginning July 19. In July, there was a linear increase in daily gains (P < 0.05), and serum vitamin A (P < 0.13) and whole-blood Se (P < 0.10) tended to increase in lambs grazing Tasco-treated fescue. In Exp. 2,48 Angus and Angus x Hereford steers (initial BW 245 kg; SD = 20) grazed infected or uninfected tall fescue in Virginia that was treated (3.4 kg/ ha) or untreated with Tasco in April and July, 1995. Steers that grazed infected tall fescue had lower (P < 0.02) serum vitamin A and E and tended (P < 0.07) to have lower whole-blood Se in September compared with steers that grazed uninfected tall fescue. Tasco decreased (P < 0.06) serum vitamin E but tended to increase whole-blood Se (P < 0.10) in September and serum vitamin A in July (P < 0.12). During 1996 and 1997, the experiment was repeated in Virginia with Angus steers and was replicated at Prairie, MS, where 1/4 Brahman x 3/4 Angus steers were used. Forty-eight steers were included at each location in each year (n = 192 total steers for 1996 and 1997). Steers that grazed infected tall fescue in Mississippi had lower (P < 0.05) serum vitamin E by the end of the grazing season. At both locations Tasco increased (P < 0.05) activity of superoxide dismutase in both infected and uninfected fescue. The endophyte in tall fescue seemed to decrease antioxidant activity in grazing steers, whereas Tasco seemed to increase antioxidant activity in both the forage and the grazing ruminant. Tasco may provide opportunities to reduce oxidative stress in plants and animals.  相似文献   

7.
Lactating Hereford and Hereford X Angus cows, 2 to 6 yr old, and their calves were used in two trials to study the effects of energy intake on the postpartum interval (PPI) and the adequacy of the cow's milk production for calf growth. In trial 1, 23 cows were fed either 120 (high energy, HE) or 100% (adequate energy, AE) of National Research Council energy recommendations. Cow weights, calf weights and milk production were determined 1 wk after calving and every 2 wk until 17 wk postcalving . One-half of the calves received creep feed from the start of the study, whereas the other half did not receive creep feed until their average daily gain was below .23 kg/d. In trail 2, 19 cows were fed energy levels of 100 (AE) or 85% (low energy, LE). Estimated percentage body fat ( EPBF ) was estimated twice during the study; other variables were determined as in trial 1. In trial 1, the HE cows gained more weight (P less than .01) and produced more milk (P less than .01). In trial 2, the AE cows gained more weight (P less than .01) and produced calves 17 kg heavier (P less than .01) at the end of the study than did the LE cows. Milk production was not influenced by energy treatment (P greater than .2). It required 7.5 kg of milk and 2.3 kg of creep feed to produce 1 kg of calf gain in trial 1.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

8.
Two experiments were conducted to compare Mg bioavailability from Mg oxide (MgO) vs Mg hydroxide (Mg(OH)2) fed in either a completely mixed diet or a mineral supplement. In Exp. 1, these Mg sources were incorporated into completely mixed diets and offered to 15 steers (282 kg) allotted to three treatments: control diet containing .19% Mg, control plus .2% added Mg as MgO, or control plus .2% added Mg as Mg(OH)2. Each calf was fed 5 kg/d of the respective diet during 10-d adjustment and 7-d collection periods. Blood samples were collected on d 1, 3 and 7. Mg supplementation increased (P less than .01) fecal and urinary Mg excretions, whereas apparent Mg absorption (%) and retention were similar (P greater than .10) for all treatments. Plasma Mg concentrations were similar (P less than .10) for calves supplemented with MgO and Mg(OH)2 but were higher (P less than .05) for Mg supplemented than for control calves on d 7. In Exp. 2, these Mg sources were incorporated into mineral supplements and offered free choice to 30 spring-calving beef cows gazing tetany-inducing pastures from March 6 to May 1. Each of three groups of 10 cows was assigned to a 5.7-ha tall fescue pasture and offered either a control supplement or a supplement containing 40% MgO or Mg(OH)2. Blood samplers were collected on d 0, 7, 14, 28, 42 and 56. Plasma Mg concentrations were not different (P greater than .10) for cows offered MgO and Mg(OH)2 but were higher (P less than .01) for Mg-supplemented than for control cows on d 28, 42 and 56.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

9.
Endophyte (Acremonium coenophialum)-infected Kentucky 31 tall fescue was fertilized in mid-August, stockpiled, harvested November 4 to 6 and stored in a concrete stave silo. Ninety-six growing calves (189 kg) were assigned to the following treatments (24 calves/treatment): 1) corn silage (CS) plus .4 kg/d of soybean meal (SBM; 2) fescue haylage plus .4 kg/d of SBM; 3) fescue haylage plus 1.6 kg/d of corn and 4) fescue haylage plus 1.6 kg/d of corn and .4 kg/d of SBM. Daily gains and dry matter (DM) intakes during the 91-d trial were .52, 4.58; .51, 5.22; .59, 6.06; and .63, 6.18 kg for treatments 1 through 4, respectively. Daily gains of calves fed corn silage plus SBM and fescue haylage plus SBM were not different (P greater than .05). However, a difference (P less than .05) existed between treatments 1 and 2 vs 3 and 4. Feed conversion was improved (P less than .05) in calves fed corn silage. Calves in a metabolism trial were fed either 1) 6.2 kg November-ensiled fescue haylage or 2) 6.2 kg November-ensiled fescue haylage plus 1.6 kg/d of corn. Digestibility of DM, N-free extract (NFE) and TDN did not differ (P greater than .05) between treatments. Ether extract digestibility was greater (P less than .05) for the added corn diet, while that of CP was greater (P less than .05) for the fescue haylage diet. Nitrogen retained was higher (P less than .05) for calves fed added corn. A follow-up trial with 96 growing calves (190 kg) compared September- and November-harvested fescue haylages supplemented with either 1.3 or 2.6 kg corn/d.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

10.
Mature Charolais x Angus rotational cross cows were adjusted to moderate body condition by d 190 of gestation then randomly blocked to a maintenance (ME) or low-energy (LE) diet. At parturition, the 128 cows were randomly allotted within prepartum (PRP) diet to a high-energy (HE) or LE diet. At d 30 postpartum (PP), cows were randomly blocked to two treatments in which calves were weaned early (EW) or normally (NW) at 7 mo of age. Cows receiving a LE PRP diet had lighter calves at birth (34.7 vs 39.0 kg) and 105 d (127.9 vs 144.6 kg). Prepartum and PP energy interacted to affect postpartum anestrous interval (PPI, d) and cycling activity (%), respectively (LE-LE = 72.6, 33.3; LE-HE = 54.3, 56.3; ME-LE = 65.7, 52.9; ME-HE = 68.4, 54.3). High PP energy averaged over PRP diet increased (P less than .10) pregnancy rate by 22.7% and 105-d calf weight by 15.1 kg. Early weaning reduced PPI by 24.3 d (P less than .01) and first service conception rate by 21.7% (P less than .10). Cycling activity within 60 d PP was affected (P less than .01) by PRP diet and suckling status (LE-EW = 62.5, LE-NW = 26.7, ME-EW = 88.9, ME-NW = 13.3%). Thin cows had a longer PPI but had a higher first service conception rate than moderate and fleshy cows. Higher pregnancy rates were observed in cows approaching or maintaining average body condition from parturition to conception than for cows moving away from moderate body condition. Results suggest that fleshy and thin cows at parturition should be managed to approach moderate body condition before the breeding season to optimize reproductive performance and preweaning calf gain.  相似文献   

11.
Two experiments were conducted to evaluate the influence of a yeast-derived cell wall preparation (YCW) on forage intake and digestibility, ruminal fermentation characteristics, serum prolactin and prolactin stores, and milk production in beef cattle consuming high-alkaloid tall fescue straw. In Exp. 1, 16 ruminally cannulated Angus x Hereford steers (200 +/- 6 kg of BW) were blocked by BW and within block were assigned to 1 of 4 treatments containing YCW at 0, 20, 40, or 60 g/d. Tall fescue straw (579 mug of ergovaline/ kg of DM) was provided at 120% of the previous 5-d average intake, with soybean meal used as a CP supplement. In the 29-d digestion study, total DM, OM, and NDF intakes and DM, OM, and NDF digestibilities were not affected by YCW supplementation (P > 0.13). Linear decreases in ruminal indigestible ADF outflow (P = 0.10) and liquid dilution rate (P = 0.03) were noted as YCW increased. Weekly serum prolactin was not affected by treatment (P > 0.50), but prolactin stores increased linearly as YCW increased (P = 0.05). In Exp. 2, 60 Angus x Hereford cows (517 +/- 5 kg of BW; approximately 200 d of gestation) were stratified by BCS (5.0 +/- 0.1) and randomly assigned to the same 4 YCW treatments as in Exp. 1 (447 microg of ergovaline/kg of DM, high-alkaloid straw), but with the addition of a low-alkaloid straw (149 microg of ergovaline/kg of DM; no YCW supplementation) as a control. Cows were provided ad libitum access to straw, and diets were supplemented with soybean meal daily. One cow was removed from the 40 g/d treatment because of clinical signs of fescue foot. No differences (P > 0.20) were observed in pre-or postcalving BCS change or postcalving BW change. Control cows gained more BW (P = 0.02) precalving compared with cows given 0 g/d of YCW. A linear increase (P = 0.04) in milk production at 60 d postpartum was observed as YCW increased. Serum prolactin post-calving and the change from initial to postcalving increased linearly (P = 0.02 and P = 0.06, respectively) with increasing YCW supplementation. In addition, postcalving serum prolactin was less for 0 g/d of YCW compared with the control (P = 0.003) and 20 g/d of YCW (P = 0.04). The YCW seemed to alleviate the prolactin depression normally associated with fescue toxicosis and therefore has the potential to be used successfully with other management practices when feeding or grazing high-alkaloid tall fescue.  相似文献   

12.
A 2-yr study was conducted to evaluate the effects of a high-energy creep feed, preweaning zeranol implants and breed type on calf and cow performance. Two hundred calves sired by Brahman and Romana Red bulls out of Angus and Angus x Brown Swiss reciprocal crossbred (F1) dams were stratified by breed type and sex to three creep treatments: no creep feed (NC); long-term creep (LC), creep-fed from 56 to 210 d of age (weaning); and short-term creep (SC), creep-fed from 146 to 210 d of age. Alternate calves within sex, breed type and creep treatment were implanted with 36 mg of zeranol at an average of 56 d and reimplanted 90 d later. The LC and SC calves had heavier (P less than .001) 210-d weights than NC calves (264 and 257 vs 231 kg, respectively), and the LC calves were heavier (P less than .001) at 146 d than NC calves. The LC calves had higher (P less than .001) ADG from 118 to 210 d of age and higher 146 and 210-d condition scores than did NC calves. Pregnancy rate was not affected (P greater than .46) by creep treatment of calf. Zeranol implants increased (P less than .01) 146- and 210-d weights (184 vs 175 kg and 259 vs 243 kg) and ADG during all periods to weaning. Brahman-sired calves had higher (P less than .005) 146- and 210-d weaning weights and frame scores than Romana Red-sired calves.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

13.
Two experiments were conducted to investigate the effect of feeding endophyte (Acremonium coenophialum)-infected fescue (Festuca arundinacea Shreb.) seed on LH secretion in postpartum beef cows and in cycling heifers and cows. In Exp. 1, spring-calving primiparous Angus cows (n = 16) were pair-fed for 75 d diets that contained endophyte-free or endophyte-infected (95%) fescue seed that contained 1.3 micrograms/g of ergovaline and 5.2 mg/g of saturated pyrrolizidines. Serial blood samples for basal and GnRH-stimulated serum LH analysis were obtained on d 7, 28, 42, and 56 of the study. The endophyte had no effect on LH secretion (basal, pulse frequency, and amplitude) or milk production. Average daily gain was decreased (P < .05) in cows that consumed infected fescue seed compared with controls (-.20 vs -.01 kg, respectively). Basal serum prolactin concentrations were reduced (P < .01) in treated compared with control cows (8.9 vs 25.4 ng/mL, respectively) on d 70. In Exp. 2, cycling Angus heifers (n = 8; age = 2 yr) and cows (n = 8; age = 4 yr) stratified by age were pair-fed for 40 d diets that contained the noninfected or the highly infected fescue seed. Estrus was synchronized by prostaglandin F2 alpha (d 18 and 28). Serial blood samples for serum LH analysis were obtained on d 28 (luteal phase) and d 30 (follicular phase). The endophyte did not affect LH (P > .28) or prolactin (P > .16) secretion, whereas ADG was decreased (P < .05) in treated compared with control animals (.32 vs .70 kg/d, respectively).  相似文献   

14.
Twelve growing Angus heifers averaging 282 kg in weight were fed a tall fescue hay-based diet in a completely randomized design experiment to determine sulfur (S) and nitrogen (N) metabolism and bioavailability of different forms of supplemental S:elemental S (E), sodium sulfate (SU) and DL-methionine (M). The study included a 72-h adaptation phase that was followed immediately by a 5-d retention phase. Control (C) heifers were fed a ground fescue hay diet twice daily throughout the study. Supplementation with .15% S from E, SU or M to the basal diet began at h 0. Differences in total blood S, plasma S and ruminal NH3 N were dependent on sampling time in the 72-h adaptation phase. Urinary S excretion during 0 to 72 h was greater for S-supplemented calves than for C. Mean molar proportions of acetate, butyrate, isobutyrate and valerate were affected by form of S supplementation. No treatment differences (P greater than .10) were noted in total VFA concentrations. Sulfur supplementation increased daily urinary sulfate (P less than .01), total urinary S (P less than .01) and fecal S (P less than .01) excretion during the retention phase. Methionine and SU heifers had the greatest urinary S losses, and fecal S was highest for E (P less than .01). No differences (P greater than .10) in DM digestion occurred among treatments. N retention (g/d) and N retention as a percentage of intake averaged 5.9, 8.5; 13.2, 18.7; 13.8, 20.5; and 11.3, 19.2, respectively, for C, E, SU and M. Sulfur retention (g/d) was increased (P less than .10) by S supplementation. Sulfur supplementation of a basal fescue hay diet increased S retention transitorily, although much of the added S was lost through excretory routes. Supplementing S as E, SU or M appeared to be equally beneficial, despite differences in route and extent of S excretion among the three S sources.  相似文献   

15.
As part of a 2-yr study documenting the physiologic impact of grazing endophyte-infected tall fescue on growing cattle, 2 experiments were conducted to characterize and evaluate effects of grazing 2 levels of toxic endophyte-infected tall fescue pastures on vascular contractility and serotonin receptors. Experiment 1 examined vasoconstrictive activities of 5-hydroxytryptamine (5HT), α-methylserotonin (ME5HT; a 5HT(2) receptor agonist), d-lysergic acid (LSA), and ergovaline (ERV) on lateral saphenous veins collected from steers immediately removed from a high-endophyte-infected tall fescue pasture (HE) or a low-endophyte-infected mixed-grass (LE) pasture. Using the same pastures, Exp. 2 evaluated effects of grazing 2 levels of toxic endophyte-infected tall fescue on vasoconstrictive activities of (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), BW 723C86 (BW7), CGS-12066A (CGS), and 5-carboxamidotryptamine hemiethanolate maleate (5CT), agonists for 5HT(2A),( 2B), 5HT(1B), and 5HT(7) receptors, respectively. One-half of the steers in Exp. 2 were slaughtered immediately after removal from pasture, and the other one-half were fed finishing diets for >91 d before slaughter. For Exp. 1, maximal contractile intensities were greater (P < 0.05) for steers grazing LE pastures than HE pastures for 5HT (73.3 vs. 48.9 ± 2.1%), ME5HT (52.7 vs. 24.9 ± 1.5%), and ERV (65.7 vs. 49.1 ± 2.6%). Onset of contractile response did not differ for 5HT (P = 0.26) and ERV (P = 0.93), but onset of ME5HT contraction was not initiated (P < 0.05) in HE steers until 10(-4) compared with 10(-5) M in LE-grazing steers. For Exp. 2, maximal contractile intensities achieved with DOI were 35% less (P < 0.05), whereas those achieved with 5CT were 37% greater (P < 0.05), in steers grazing HE pastures. Contractile response to CGS did not differ between pasture groups, and there was an absence of contractile response to BW7 in both groups. There were no differences between endophyte content in contractile responses after animals were finished for >91 d. Experiment 1 demonstrated that grazing of HE pastures for 89 to 105 d induces functional alterations in blood vessels, as evidenced by reduced contractile capacity and altered serotonergic receptor activity. Experiment 2 demonstrated that grazing HE pastures alters vascular responses, which may be mediated through altered serotonin receptor activities, and these alterations may be ameliorated by the removal of ergot alkaloid exposure as demonstrated by the absence of differences in finished steers.  相似文献   

16.
The effects of dietary energy intake and somatotropin (STH) on growth and puberty were studied in 40 Angus heifers. At an average age of 7 mo (208 +/- 8 d), heifers were assigned to four treatment groups: 1) vehicle (V) + high energy (HE; 2.68 Mcal ME/kg DM), 2) recombinant DNA-derived STH (20.6 mg/d; s.c.) + HE, 3) V + low energy (LE; 2.22 Mcal ME/kg DM) or 4) STH + LE. Animals remained on treatments until 15.5 mo of age. Body weights (BW), hip heights (HH) and areas of pelvic openings (PA) were measured every 28 d and backfat thicknesses (BF) were measured every 56 d. Plasma progesterone was measured in blood samples taken three times per week beginning at 9 mo of age to determine age at first ovulation. Heifers fed HE were heavier (P less than .01), gained faster (P less than .01) and had greater BF (P less than .01) than those fed LE. Animals treated with STH gained faster (P less than .01) and were heavier (P less than .05) between 12 and 15 mo of age than V-treated heifers. Heifers treated with STH also had less BF (P less than .05) and a tendency for a greater (P = .08) increase in HH than in V-treated heifers. Somatotropin interacted with energy (P less than .05) and age (P less than .01) to influence PA. Somatotropin increased (P less than .01) PA in heifers fed the HE diet but not in those fed the LE diet.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
The effects of somatotropin (STH) and energy intake on serum concentrations of glucose (GLU), insulin (INS), nonesterified fatty acids (NEFA), urea nitrogen (UN) and insulin-like growth factor-I (IGF-I) were determined in 40 Angus heifers. At 7 mo (208 +/- 8 d) of age heifers were assigned to four treatment groups: 1) vehicle (V) + high energy (HE; 2.68 Mcal ME/kg DM), 2) recombinant DNA-derived STH (20.6 mg/d; s.c.) + HE, 3) V + low energy (LE; 2.22 Mcal ME/kg DM) or 4) STH + LE. Animals remained on treatments until an average of 15.5 mo of age. Blood samples were taken every 30 min for 4 h at 9, 11, 13 and 15 mo of age to determine circulating concentrations of metabolites and hormones. Serum IGF-I was increased (P less than .01) by STH injections, but this effect appeared to diminish with age (STH x age; P less than .01). Energy intake did not influence IGF-I levels. Somatotropin increased (P less than .01) serum GLU in heifers fed the HE diet but only tended (P = .08) to increase GLU in those fed the LE diet (STH x energy; P = .05). Although STH increased (P less than .01) serum INS in both energy groups, the response in heifers fed the HE diet was greater (P less than .02) than that in heifers fed the LE diet (STH x energy; P less than .05). Heifers fed LE had higher (P less than .01) concentrations of NEFA than heifers fed HE.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

18.
Reproductive traits and preweaning growth of progeny from young Hereford, Red Poll, Hereford X Red Poll, Red Poll X Hereford, Angus X Hereford, Angus X Charolais, Brahman X Hereford and Brahman X Angus dams were evaluated. First-calf heifers were mated with Red Angus bulls; Santa Gertrudis sires were used for each cow's second and third breeding season. Herefords, Red Polls and Hereford-Red Poll crosses were below average in percentage of calves weaned, whereas Angus-sired and Brahman-sired dams exceeded the overall mean. Angus X Charolais (P less than .10), Brahman X Hereford (P less than .01) and Brahman X Angus (P less than .10) dams weaned a higher percentage of calves than straightbred Herefords. None of these breed types differed from young Angus X Hereford females in reproductive performance. Angus X Charolais calves ranked highest in 180-d calf weight, exceeding progeny from both Hereford (P less than .01) and Angus X Hereford (P less than .10) dams. Brahman X Hereford dams weaned heavier (P less than .05) calves than Herefords, but their progeny did not differ at weaning from those reared by Angus X Herefords. Calves from Brahman X Angus dams weighed 12.7 kg less (P less than .01) than Angus X Hereford progeny. Analysis of the Hereford-Red Poll diallel showed evidence of (P less than .10) maternal heterosis in 180-d calf weight.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

19.
Reproductive traits were evaluated in Bos taurus and Bos indicus crossbred heifers that were fed different diets during the postweaning period. The study was designed in a 2 x 2 x 2 factorial arrangement of treatments. Angus x Hereford (AH; n = 148) and Brahman x Hereford (BH; n = 148) heifers were sorted after weaning by body weight into light (LW) and heavy (HW) weight blocks. Heifers in each weight block were assigned to diets calculated to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weights by the start of the breeding season. Puberty was determined after a 160-d observation period and characterized by the following criteria: 1) behavioral estrus, 2) presence of a palpable corpus luteum (d 6 to 10; estrus = d 0), and 3) rise in serum progesterone above 1 ng/ml (d 6 to 10). A higher (P = .01) proportion of AH heifers than of BH heifers reached puberty by the breeding season (93% vs 67%). Interactions of breed x weight block and energy level x weight block also contributed to this difference. Weight at puberty was heavier (P = .001) among HE than among LE heifers and greater for heifers in HW than for those in LW blocks (P = .02). Differences in prebreeding weight, body condition, average daily gain, hip height, and pelvic area were influenced selectively by breed, energy level, or weight block. Pregnancy rates were higher (P = .01) among AH than among BH heifers. Incidence and severity of dystocia was influenced by the breed x energy level interaction (P = .01). Brahman x Hereford heifers had less (P = .01) dystocia than AH heifers, HE heifers had less (P less than .02) dystocia than LE heifers, and HE-AH heifers had less (P less than .01) dystocia than LE-AH contemporaries. Subsequent duration of the postpartum interval to estrus was shorter (P = .002) among AH than among BH females. Pregnancy rates at the end of the 2nd yr were higher (P = .02) among LW than among HW females and weights were heavier (P = .001) at weaning among calves weaned from BH dams.  相似文献   

20.
It is well established that grazing Neotyphodium coenophialum-infected forages results in reduced BW gain and serum prolactin concentrations of cattle. The objective of this study was to determine the potential effects of toxic endophyte-infected tall fescue consumption on blood metabolites, carcass characteristics, and content of proteins critical for AA metabolism in the liver, kidney, and LM tissue of growing steers. Steers grazed a low toxic endophyte (LE; 0.023 microg/g ergot alkaloids) tall fescue-mixed grass pasture (n = 9; BW = 266 +/- 10.9 kg; 5.7 ha) or a high toxic endophyte (HE; 0.746 microg/g of ergot alkaloids) tall fescue pasture (n = 10; BW = 267 +/- 14.5 kg; 5.7 ha) from June 14 through at least September 11 (> or =89 d). No difference was observed for BW (P < 0.10) for the overall 85-d growth period. Also, no differences were observed for ribeye area/100 kg of HCW (P > 0.91), backfat (P > 0.95), or backfat/100 kg of HCW (P > 0.67). However, ADG (P < 0.01), final BW (P < 0.05), HCW (P < 0.01), dressing percentage (P < 0.01), ribeye area (P < 0.01), whole liver wet weight (P < 0.01), and whole liver wet weight/100 kg of end BW (P < 0.01) were greater for LE steers than HE steers. After 85 d of grazing, serum concentrations of alkaline phosphatase (P < 0.05), alanine aminotransferase (P < 0.01), aspartate aminotransferase (P < 0.03), cholesterol (P < 0.01), lactate dehydrogenase (P < 0.01), and prolactin (P < 0.01) were less for HE than LE steers. At slaughter, hepatic content of cytosolic phosphoenolpyruvate carboxykinase (P < 0.01) was greater in HE steers than LE steers. Hepatic content of aspartate aminotransferase (P < 0.01) also was greater, whereas renal and LM content were not (P > or = 0.42). No differences (P > or = 0.15) were observed for hepatic, renal, and LM content of alanine aminotransferase, glutamate dehydrogenase, glutamine synthetase, and 3 glutamate transport proteins. These data indicate that the HE steers displayed classic endophyte toxicity symptoms for growth and blood variables, classic symptoms that were concomitant with novelly identified altered glucogenic capacity of the liver and decreases in carcass characteristics.  相似文献   

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