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1.
Groups of Hereford weaners carrying naturally acquired infestations of L. vituli were allocated to a factorial experiment to examine the effect of lice treatment, sex and nutrition on growth rate during winter and early spring. Plane of nutrition was the only factor influencing growth rate over this period. In untreated groups of cattle, the plane of nutrition influenced the lice score but lice score did not influence growth rate.  相似文献   

2.
Two experiments were conducted to examine the consequences of attempting to control dystocia in Hereford heifers by restricting nutrition during late pregnancy. Nutritional level was controlled by varying feedlot rations in experiment 1 and by varying pasture availability in experiment 2. In neither experiment was the incidence of dystocia or stillbirths significantly affected by level of nutrition during late pregnancy. Calf birthweight was reduced and dam pelvic growth was retarded when the feed intake of heifers was restricted prior to calving. Clear evidence of the dangers associated with allowing heifers to lose too much weight in late pregnancy was provided by these experiments. The loss of around 0.5 kg/day during the last trimester of pregnancy was associated with weak labour, increase dystocia rates, increased perinatal mortality, reduced calf growth rate, prolonged post partum anoestrus and a reduced pregnancy rate (not all statistically significant differences). These effects were not evident in heifers which were maintaining or gaining weight at a moderate rate during late pregnancy. On the basis of this work it is suggested that heifers should be fed to allow modest rates of bodyweight gain (0--0.5 kg/day) during late pregnancy.  相似文献   

3.
Two experiments were done to evaluate the effectiveness of a slow-release, morantel tartrate, anthelmintic bolus for controlling parasitic gastroenteritis in replacement dairy heifers. In experiment 1, good control of nematode contamination of pasture was indicated by lower worm burdens in tracer calves that grazed with 15 heifers treated orally with a single bolus and by significantly decreased numbers of nematode eggs in the feces of the 15 treated heifers, as compared with numbers of eggs in the feces of 15 nontreated control calves. Significant differences in weight gain were not seen between treated and nontreated heifers, probably due to low amounts of larval exposure, the small number of heifers evaluated, and parasitic resistance in the heifers, which may have developed as a result of prestudy exposure to contaminated pasture. In experiment 2, done 1 year after the 1st experiment, using the same pastures that were used in experiment 1, young heifers were used. Many of the heifers were parasite naive at the beginning of the experiment (ie, nematode eggs were not found before the experiment). Treatment with the bolus was effective in controlling parasitic gastroenteritis in the heifers and in controlling nematode contamination of pasture. Compared with nontreated heifers, treated heifers had significantly higher cumulative weight gains, a significant decrease in plasma pepsinogen concentrations, and a significant decrease in worm egg excretion. The number of worms acquired by tracer calves that were grazed with treated heifers was significantly less than for tracer calves that were grazed with nontreated heifers.  相似文献   

4.
A 3-yr study was conducted to evaluate the effects of calving system, weaning age, and postweaning management on growth and reproduction in beef heifers. Heifer calves (n = 676) born in late winter (average birth date = February 7 +/- 9 d) or early spring (average birth date April 3 +/- 10 d) were weaned at 190 or 240 d of age, and heifers born in late spring (average birth date May 29 +/- 10 d) were weaned at 140 or 190 d of age. Heifers were managed to be first exposed to breeding at approximately 14 mo of age. After weaning, the calves were randomly assigned to treatments. Heifers on the constant gain treatment were fed a corn silage- and hay-based diet. Heifers on delayed gain treatments were placed on pasture but were fed grass hay or a supplement, or both, depending on the forage conditions. Three months before their respective breeding seasons, delayed gain heifers were moved to drylot and fed a corn silage- and barley-based diet (late winter or early spring) or moved to spring rangeland (late spring). The data were analyzed using mixed model procedures with calving system, weaning age, and postweaning management options creating 12 treatments. Average daily gain was 0.36 +/- 0.05 (SED) kg/d less (P < 0.001) for delayed gain heifers during the initial phase, whereas these heifers gained 0.44 +/- 0.03 kg/d more (P < 0.001) than constant gain heifers during the last 90 d before breeding. Body weights at the beginning of the breeding season did not differ (P = 0.97) between constant gain and delayed gain heifers but were affected by calving system and weaning age, reflecting some of the differences in initial BW. Prebreeding BW for heifers weaned at 190 d of age were 36 +/- 6.4 kg heavier (P < 0.001) for those born in late winter and early spring compared with late spring and were 388, 372, and 330 kg for heifers weaned in October at 240, 190, or 140 d of age (linear effect, P < 0.001). The proportion of heifers exhibiting luteal activity at the beginning of the breeding season was not affected (P = 0.57) by treatment. Approximately half of the heifers were randomly selected for breeding. Treatment had no effect (P = 0.64) on pregnancy rates. In conclusion, heifers from varied calving systems and weaning strategies can be raised to breeding using either constant or delayed gain strategies without affecting the percentage of heifers cycling at the beginning of the breeding season. These results suggest that producers have multiple options for management of heifer calves within differing calving systems.  相似文献   

5.
An experiment was conducted to evaluate the effects of breed, sex and plane of nutrition on the growth response to zeranol in Angus and crossbred calves prior to weaning. Eighty-eight heifers and 118 steers received either a high or low plane of nutrition using a first and last grazing technique. Half of the calves in each nutrition group received a zeranol implant (36 mg) at an average age of 3.4 mo. Both zeranol and the higher level of nutrition increased (P less than .001) growth rate prior to weaning (7.4 mo of age). Zeranol did not affect hip height at weaning (P greater than .1), but calves on the higher plane of nutrition were taller (P less than .01) than calves on the lower plane of nutrition. The zeranol x nutrition interaction was not significant (P greater than .1) for growth rate or hip height. Steers grew faster (P less than .01) preweaning and were taller (P less than .01) at weaning than heifers. Crossbred calves gained more rapidly (P less than .001) preweaning and were taller (P less than .001) at weaning than Angus calves were. Neither sex nor breed interacted with zeranol to influence any of the traits examined. Based on these results we conclude that preweaning growth was affected by zeranol and this effect was consistent across sexes, breeds and planes of nutrition tested.  相似文献   

6.
SUMMARY Groups of White Shorthorn calves, stanchioned to prevent self-grooming and given high or low levels of nutrition, were exposed to artificial infestations of the cattle louse, Linognathus vituli. Undernutrition caused a significant (P = 0.03) increase in lice numbers. Lice did not significantly affect percentages of packed cells, lymphocytes, polymorphs and eosinophils or the number of red and white cells. Calves were always able to control lice infestations without self-grooming.  相似文献   

7.
The relationship between lice infestation in calves during their first winter and damage to the leather produced was investigated in a trial involving 500 calves, 100 of which were treated with a pour-on endectocide during the first winter. All the calves received routine lice treatment in the second winter and were reared to slaughter weight. The hides were removed at the abattoir, tanned, inspected for lice-related damage, and graded according to their suitability for the production of high quality leather. The untreated group developed natural infestations of the chewing louse (Bovicola bovis) during the first winter but none was observed in the second winter. Hides from cattle infested with lice in their first winter had higher levels of lice damage than hides from those treated with eprinomectin, at both the chrome-tanned and dried dyed-crust stages of leather production.  相似文献   

8.
Two experiments were conducted to determine the effect of an antioxidant (AGRADO®; Solutia Inc., St. Louis, MO) on the growth, gain to feed ratio, and health of receiving calves. In Experiment 1, 96 mixed breed heifer calves (206 ± 1.4 kg initial BW) were purchased at sale barns and delivered as a single group to the research facility near Fayetteville. All heifers were fed a total mixed diet containing 30% cottonseed hulls, 53% cracked corn, and 11% soybean meal for 42 d with either 0 or 150 mg AGRADO®/kg diet. Fewer (P<0.05) of the heifers fed supplemental AGRADO® were treated for respiratory disease (73% vs 83%), and medication cost was lower (P<0.05) for heifers fed supplemental AGRADO ($6.33 vs $9.49 per pen). Supplemental AGRADO® did not affect (P>0.10) ADG, daily feed intake, and gain to feed ratio. In Experiment 2, 86 bull and steer calves (237 ± 2.2 kg initial BW) were managed and fed as in Experiment 1 for a 41-d study. In this trial, supplemental AGRADO® had no significant effect on the number of sick calves or medication costs, but gain to feed ratio was improved (P<0.05) during the first 28 d of the trial. These results indicate that supplemental AGRADO® may improve the health or growth performance of newly received feedlot cattle.  相似文献   

9.
Forty heifer calves, 27 yearling heifers, and 64 yearling steers with naturally occurring infections of nematode parasites were treated with levamisole HCl or morantel tartrate or were not treated. Although heifer calves had much larger worm egg counts before treatment than yearling heifers, necropsies showed a smaller average number of nematodes in the calves. Both anthelmintics significantly reduced the egg counts. At the end of the experiments, 98 to 240 days after treatments, there was no significant difference among groups of cattle in respect to necropsy worm counts. An advantage of 5% in rate of gain in body weight was shown in each experiment or phase of an experiment in favor of the treated groups of cattle. Overall, an advantage of 6% in feed efficiency was calculated for the treated groups of cattle.  相似文献   

10.
SUMMARY The calving performance of 268 two-year-old Hereford heifers was studied in 2 commercial herds and at a research station to compare supervision and non-supervision during calving. Supervision in the 3 herds involved twice-daily paddock inspections of calving heifers using a vehicle and the provision of obstetrical aid to those in difficulty. The unsupervised controls were inspected once weekly and were not assisted. The supervised heifers experienced a higher incidence of live-natural births and fewer dead calves compared with the unsupervised heifers. Dam survival rates were significantly (p < 0.05) increased in all supervised treatments. Calving supervision was justified by higher survival of both heifers and calves as well as humane considerations. It was endorsed as a worthwhile management practice in commercial herds with significant levels of dystocia in calving heifers.  相似文献   

11.
A worm control programme in which heifers were treated with anthelmintic on three occasions during autumn, was tested in the Mediterranean-type climatic environment of south-west Western Australia. The experiment aimed to determine if the treatments would prevent the heifers contaminating their pastures with worm eggs during autumn, thereby improving their growth performances the following winter. An attempt was made to measure the availability of infective larvae of abomasal worms on the heifers' pastures during early winter by counting the worms in steers, previously of low worm status, that grazed with the heifers from late autumn until the start of mating in mid-winter.

The anthelmintic treatments reduced the contamination of pasture for most of autumn. The treated heifers that grazed these pastures grew faster, and by the start of mating two months after the last treatment were about 22 kg heavier, than untreated heifers grazing contaminated pasture. At the end of mating six weeks later the difference was 45 kg in favour of the treated heifers. At this time half the heifers grazing contaminated pasture were treated with anthelmintic. The following month these heifers grew faster than those left untreated, but by late November they had not attained the wieght of the heifers grazing uncontaminated pasture.

The heifers that grazed uncontaminated pasture produced more calves the following autumn than did those grazing contaminated pasture. The abomasal worm counts of the steers, with a mean of about 46 000 worms, failed to reveal any difference between treatments in the availability of larvae of abomasal worms on pasture. However, it was concluded that the treatments probably exerted their effect on growth rates by reducing the number of infective larvae ingested by heifers grazing the uncontaminated pasture during winter.  相似文献   


12.
A 3-yr study was conducted with spring-born heifers (n = 240) to determine the effects of developing heifers to either 55 or 60% of mature BW at breeding on reproduction and calf production responses. A concurrent study was also conducted with summer-born heifers (n = 146) to examine effects of breeding heifers with the mature cow herd or 1 mo earlier on reproduction and calf production variables. Spring-born crossbred heifer calves were weaned and developed on two different levels of nutrition to achieve the desired prebreeding BW. Summer-born heifers were developed to similar target breeding BW (60% of mature BW) to begin calving either 1 mo before (May) or at the same time as the mature cowherd (June). Blood samples were taken before breeding to determine differences in estrous cyclicity. Pregnancy rates through the fourth pregnancy were determined. Cow and calf production variables were evaluated through the third gestation. Spring-born heifers reached 53 or 58% of mature BW at breeding and had similar reproduction and first calf production traits between the two, groups. Calving difficulty with the second calf was greater (P < 0.05) for heifers developed to 58% of mature BW at breeding. Subsequent second calf weaning weight and ADG were decreased (P < 0.05) for heifers developed to 58% of mature BW at breeding. Feed costs were $22/heifer less for heifers developed to 53% of mature BW. Summer-born first-calf heifers calving in June had less (P < 0.01) calving difficulty than did heifers calving in May; however, calf birth weights were similar. Breeding summer-born heifers 1 mo before the cowherd did not influence pregnancy rates over three calf crops; however, first calf adjusted weaning weights and ADG were greater for calves born earlier. Development costs were $11/heifer more for heifers developed to calve in May vs. June. Developing spring-born heifers to 53% of mature BW did not adversely affect reproduction or calf production traits compared with developing heifers to 58% of mature BW, and it decreased development costs. Breeding summer-born heifers before the cowherd increased heifer development costs, increased calving difficulty, and improved calf performance, but had no effect on pregnancy rates.  相似文献   

13.
Two experiments were conducted in consecutive years to determine the effects of prepartum nutrient level and postpartum ruminally undegraded protein intake on nutrient status, milk production, subsequent calf production, and reproductive performance of 126 crossbred, primiparous beef heifers. Prepartum treatments were low nutrient intake (LN) (approximately 2.5 kg of TDN, .5 kg of CP animal-1.d-1 and maintenance nutrient intake (MN) (5 kg of TDN, 1 kg of CP animal-1.d-1), which were fed for 75 d before parturition. Two postpartum protein supplements were formulated to provide 250 g/d of ruminally degradable protein (RD) and one to supply ruminally undegraded protein (UD) at 250 g/d of additional UD CP compared to the RD supplement. Cholesterol was lower (P less than .01) in heifers given UD than in heifers given RD. Blood urea nitrogen was higher (P less than .01) for UD-fed heifers than for RD-fed heifers and was higher in LN heifers (P less than .06) than in MN heifers. Milk production did not differ (P greater than .11) as a result of LN, MN, UD, or RD. Postpartum cow weight gain was greatest (P less than .01) for UD and LN heifers. The percentage of heifers bred during the first estrous cycle of the breeding season was greater (P less than .02) for UD than for RD. Overall, prepartum nutrition did not interact with postpartum protein supplement, nor did it have any effect on postpartum interval, whereas UD increased cow weight gain postpartum and reduced postpartum interval.  相似文献   

14.
Two experiments were conducted simultaneously to evaluate the effects of different concentrates to roughage ratios on growth performance and attainment of puberty in Friesian–Boran crossbred heifers. Weaned 50% Friesian–Boran crossbred female calves were used in both experiments with 25 and 20 calves in experiments I and II, respectively. In experiment I, the calves were offered diets with concentrate to roughage ratios of 50:50 (treatment 1) or 30:70 (treatment 2). In experiment II, the calves grazed for 8 h a day and supplemented with 2 kg hay and 1 kg concentrate per head per day (treatment 1) or only 2 kg hay per head per day (treatment 2). The concentrate mixture was composed of 34% wheat bran, 31% wheat middling, 31% noug cake, 3% limestone, and 1% salt. In experiment I, heifers fed a ration with 50% concentrate and 50% roughage had higher (P < 0.05) daily body weight gain (0.532 kg) and attained puberty at 221 kg (65% of the mature body weight) in 15 months, while heifers fed a diet with 30% concentrate and 70% roughage gained 0.434 kg/day and reached puberty at 247 kg (70% of the mature body weight), about 3 months later. Heifers in treatments 1 and 2 of experiment II reached puberty 5 and 12 months later, respectively, than those in experiment I. In experiment II, heifers given 1 kg of concentrate supplement had higher (P < 0.05) daily body weight gain (0.346 kg) than those given only 2 kg hay in addition to grazing (0.278 kg). Growth rate of crossbred heifers was enhanced and age at puberty was reduced by changing the rearing management from outdoor to indoor and with increasing level of concentrate in the ration. This helps to bring the dairy heifer into production earlier and enhance to the overall productivity of the dairy industry.  相似文献   

15.
Beef calves from 2 sources entering southern Alberta feedlots in the winters of 1997-98 and 1998-99, were surveyed for the presence of lice. A random sample of multiple source (MS), that is, auction market-derived, calves entering commercial feedlots and single source (SS) calves entering a backgrounding feedlot were examined for the presence of lice at entry to the feedlot. A standardized examination, which involved hair-part examination of 8 louse predilection sites, was conducted on each selected calf to determine prevalence and intensity of infestation. The long-nosed sucking louse, Linognathus vituli, was the most commonly encountered species. This species infested from 57.8% to 95.6% of the calves selected from both MS and SS calves during both winters. Louse index values, indicating intensity of infestation, for L. vituli ranged from 1 to 243 lice per animal. The chewing louse, Bovicola bovis, was present on MS and SS calves only in the winter of 1998-99. The louse index values for B. bovis ranged from 1 to 230 lice per animal. Mixed infestations of the L. vituli and B. bovis were common. The little blue cattle louse, Solenopotes capillatus, was present only on the SS calves in the winter of 1997-98. The short-nosed sucking louse, Haematopinus eurysternus, was present at very low intensities, 1-2 lice per animal, on 2.6% to 4.4% of the MS calves during both winters. Comparison of results from the current study with published literature suggests that efforts to determine the economic impact of louse infestations are confounded by the lack of a uniform method to assess louse population levels.  相似文献   

16.
In two experiments, 17-wk-old Holstein bulls exposed to 16 (Exp. 1) or 24 h (Exp. 2) of light daily were compared with bulls given 8 h of light. Blood was sampled at 30-min or 120-min intervals for 48 h at the beginning and again after 4 wk of light treatment. Melatonin concentrations varied episodically in serum, and means were 1.6-fold to 5.1-fold greater during darkness than during light periods. Continuous lighting abolished the nocturnal increase in concentrations of melatonin in three of four calves. Prolactin (PRL) was greater (P less than .05) in calves receiving 16 h (30.9 ng/ml of serum) than in calves receiving 8 h (7.0 ng/ml) of light daily. Prolactin was not different between calves receiving 24 or 8 h of light daily. In a third experiment, one pinealectomized (PX) and two sham PX (SPX) calves were exposed to continuous lighting and infused with melatonin for 16 h/d for 5 wk, and one PX and two SPX calves were infused for 8 h daily. Melatonin infusion increased average concentrations of melatonin in serum 7.2-fold to 18-fold above baseline concentrations. Duration of melatonin infusion did not affect PRL (21.0 vs 20.8 ng/ml of serum). Also, surgical treatment did not affect PRL concentrations. Similarly, in a fourth experiment, PRL in postpubertal heifers fed melatonin to mimic and 8L:16D photoperiod averaged 27.1 ng/ml of serum, which was not different from PRL in heifers receiving 16L:8D and fed vehicle (32.6 ng/ml). We conclude that PRL and melatonin are each affected by photoperiod but are not casually related in cattle.  相似文献   

17.
Field experiments were carried out for three consecutive years to study the influence of gastrointestinal nematodes in young cattle during their first grazing season. Free-living stages of Ostertagia ostertagi and Cooperia oncophora were found to survive the winter in the pasture in sufficient numbers to cause reduced weight gain and clinical disease, including deaths, in the calves. The symptoms were most pronounced during the first half of the grazing season.The mean weight gain of calves on parasite-free pastures was 48.3, 15.5 and 31.2 kg above those on contaminated pastures during the 3 years.Calves grazing contaminated pasture from the spring onwards, treated with thiabendazole and moved to aftermath in July, showed significantly better weight gain during the last part of the grazing season than calves which remained on the same contaminated pasture. It was, however, suggested that the better grazing conditions were the main cause of the improved weight gain on aftermath.  相似文献   

18.
Three experiments with five wether each were carried out in order to investigate the influence of various levels of flavomycin (0, 5 and 10 mg per animal and day) on apparent digestibility of artificially dried grass. A short time individual feeding experiment (42 days) with 9 bulls and a long term individual feeding experiment (225 days) with 52 heifers were conducted. Animals consumed 0 or 30 mg flavomycin per day. Parameters of rumen fermentation were investigated. Feed intake and weight gain were measured in the experiment with heifers. Flavomycin did not significantly influence the apparent digestibility of organic matter and crude nutrients as well as parameters of rumen fermentation. Flavomycin did not influence dry matter intake, but increased significantly weight gain (49 g per animal and day, 10.5%) and reduced feed and energy required per kg weight gain (10.6%) in heifers. The reasons of ergotropic effects of flavomycin are mostly unknown at present.  相似文献   

19.
A 3-yr study was conducted with heifers (n = 170) whose dams were used in a 2 x 2 factorial arrangement of treatments to determine the effects of late gestation (LG) or early lactation (EL) dam nutrition on subsequent heifer growth and reproduction. In LG, cows received 0.45 kg/d of a 42% CP supplement (PS) or no supplement (NS) while grazing dormant Sandhills range. During EL, cows from each late gestational treatment were fed cool-season grass hay or grazed sub-irrigated meadow. Cows were managed as a single herd for the remainder of the year. Birth date and birth weight of heifer calves were not affected (P > 0.10) by dam nutrition. Meadow grazing and PS increased (P = 0.02; P = 0.07) heifer 205-d BW vs. feeding hay and NS, respectively. Weight at prebreeding and pregnancy diagnosis were greater (P < 0.04) for heifers from PS dams but were unaffected by EL nutrition (P > 0.10). There was no effect (P > 0.10) of LG or EL dam nutrition on age at puberty or the percentage of heifers cycling before breeding. There was no difference (P > 0.10) in pregnancy rates due to EL treatment. Pregnancy rates were greater (P = 0.05) for heifers from PS dams, and a greater proportion (P = 0.005) of heifers from PS dams calved in the first 21 d of the heifers' first calving season. Nutrition of the dams did not influence (P < 0.10) heifers' average calving date, calving difficulty, and calf birth weight during the initial calving season. Weight at the beginning of the second breeding season was greater (P = 0.005) for heifers from PS dams but was not affected by maternal nutrition during EL (P > 0.10). Dam nutrition did not affect (P > 0.10) heifer ADG or G:F ratio. Heifers from PS dams had greater DMI (P = 0.09) and residual feed intake (P = 0.07) than heifers from NS cows if their dams were fed hay during EL but not if their dams grazed meadows. Heifers born to PS cows were heavier at weaning, prebreeding, first pregnancy diagnosis, and before their second breeding season. Heifers from cows that grazed meadows during EL were heavier at weaning but not postweaning. Despite similar ages at puberty and similar proportions of heifers cycling before the breeding season, a greater proportion of heifers from PS dams calved in the first 21 d of the heifers' first calving season, and pregnancy rates were greater compared with heifers from NS dams. Collectively, these results provide evidence of a fetal programming effect on heifer postweaning BW and fertility.  相似文献   

20.
The objective of this study was to examine whether susceptible calves grazing together with second-year resistant heifers are less exposed to trichostrongylid infection than are calves grazing on their own. Two groups of animals representing each age category were turned out onto pasture on 24 May 1997 and grazed at comparable stocking rates. The grazing of calves and heifers together was compared to groups of each age category grazing separately. The results indicated that herbage larval counts were significantly reduced in the second part of the grazing season on the plot grazed by the mixed group compared to the plot grazed by the first-season calves only. The mixed grazing strategy protected the young calves and no clinical signs were observed in this group, while most of the calves that grazed alone exhibited clinical signs. The availability of herbage was reduced towards the end of the season, with subsequent competition for the grass forcing all the animals to graze the tufts around the faecal pats, where the quality of the grass is poor and the numbers of infective larvae are high. The effect of this was visible in the form of increased parasite burdens in the calves that were grazed together with the heifers, confirmed by increased blood serum pepsinogen concentrations and reduced daily weight gains in the second part of the grazing season. The lower numbers of infective larvae on the pasture were probably achieved through the heifers ingesting many of the larvae but subsequently depositing relatively few eggs, since they had acquired some degree of resistance against trichostrongylid infections during their first grazing season. Thus they did not suffer any parasitological ill-effects during mixed grazing with first-season calves.  相似文献   

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