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Bhupender Singh Fernando Saravia Renée B?ge Heriberto Rodríguez-Martínez 《Acta veterinaria Scandinavica》2005,46(1):1-12
Hormonal asynchronies during oestrus, related to the presence of suprabasal plasma-progesterone (P4) concentrations and a delayed ovulation, interfere with the fertility of repeat-breeder heifers (RBH). Since tubal dysfunction can occur in connection with hormonal asynchronies and constrained availability of fertile spermatozoa at the time of ovulation, the present study tested the hypothesis that frequent sperm deposition from onset of oestrus to ovulation may improve pregnancy rates in RBH. Five RBH and five virgin heifers (VH; controls) were repeatedly artificially inseminated (AI) at 6 h intervals from onset of oestrus to spontaneous ovulation. Hormone analyses revealed suprabasal P4 concentrations and a delay in the occurrence of the luteinising hormone (LH) surge, but a normal cortisol profile in RBH. Compared with controls, RBH presented longer interval from onset of oestrus to ovulation, and therefore, received more AIs. Pregnancy rates in RBH reached control levels (60%; NS), indicating that the hypothesis might be correct. Pregnancy rates in VH were below the expected range, presumably attributed to a deleterious influence of the frequent handling. The study suggests that pregnancy rates can be improved in RBH by frequent AI in relation to spontaneous ovulation. However, this practice of repeated manipulations, while seeming not to show adverse effects, lacks practicality for routine use. 相似文献
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Anki Roxström Erling Strandberg Britt Berglund Ulf Emanuelson Jan Philipsson 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(1):7-14
The main objective of this study was to estimate genetic correlations between fertility and production traits in first, second and third lactations as well as between fertility traits measured in the same way at different ages. The fertility traits studied were: number of inseminations per service period, number of treatments for reproductive disturbances, interval between first and last inseminations, interval between calving and first insemination, and interval between calving and last insemination. Early milk production was measured as the average of the energy-corrected milk yield at the second and third monthly testdays in a lactation. The number of records was approximately 450 000, 350 000, 180 000 and 75 000 in the heifer period, first, second, and third lactations, respectively. A linear, trivariate model that included the effects of herd-year, year, month, age and sire of the cow was applied. To reduce the effect of ongoing selection, 305-days kg protein production in first lactation was included as a variate in all of the analyses. Correlations between the herd-year effects indicated that factors of herd-year level conducive to increased production had a tendency to increase the number of inseminations as well as the number of reproductive treatments, although there was an earlier start and termination of the insemination period. Genetic correlations between fertility traits and production were in the range of 0.2-0.4, all of them unfavourable and higher at later parities. The genetic correlations between fertility traits in the heifer period and the same traits in first lactation were 0.7. Genetic correlations between the first and second lactation varied between 0.7 and 0.9, and between the second and third lactation they were all 0.9 or higher. In conclusion, fertility and production traits need to be selected for simultaneously if fertility is going to be maintained along further genetic improvement on production, and such selection should include fertility results from lactating cows. 相似文献
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实验探讨了重复超排对育成牛繁殖力的影响。结果表明:(1)经1～3次重复超排后14～16月龄育成荷斯坦牛自然发情后人工授精(3次以内),超排1次组、超排2次组和超排3次组妊娠率分别为96.25%、91.67%和95.29%,与对照组(未超排组)妊娠率为94.74%均无显著差异(P>0.05)(;2)超排处理后恢复期为5～10d组的妊娠率为50.0%,低于恢复期为30～40d组66.67%和恢复60～80d组60.47%的移植妊娠率,但差异不显著(P>0.05);(3)不同超排次数胚胎移植妊娠率分别为超排1～2次组63.27%、3～4次组61.11%、5～6次组57.14%,差异不显著(P>0.05)。重复超排后奶牛胚胎移植妊娠率随超排次数的增加有下降趋势,但与对照组(未超排组)62.50%的妊娠率无显著差异。 相似文献
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Growth rates during rearing affect the age and body weight (BW) of replacement heifers at first calving. Diet and disease can affect growth via altered metabolic hormone concentrations, but are difficult to monitor accurately on commercial farms. This study investigated the effect of management and metabolic indices (IGF-I, insulin, glucose and urea) on the growth rate of 509 Holstein-Friesian heifers on 19 UK dairy farms. Size (BW, heart girth, height and crown-rump length) was measured at approximately 1, 6 and 15 months. The mean daily weight gain up to 6 months for all calves was 0.77 kg/day, with extreme variability both between cohorts of calves (range 0.49–1.02 kg/day) and between individual calves within farms (range 0.45–1.13 kg/day). Growth was enhanced by supplemental colostrum, by milk replacer as opposed to whole milk and by ad libitum milk feeding and was reduced by gradual weaning and dehorning after weaning. Larger group size slowed growth before weaning (>6 calves) but increased it post-weaning (>20 calves). These management differences were reflected in altered plasma IGF-I concentrations, which were positively associated with growth throughout the rearing period. Larger calves at 1 month had a greater weight gain up to 6 months. Sub-optimum growth of some heifers within each cohort was established at an early age and resulted in animals reaching the start of breeding at an inadequate size (BW range 209–498 kg at 15 months). This could be alleviated by altered management strategies and improved monitoring of growing heifers. 相似文献
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M.E. Drewnoski E.J. Oliphant M.H. Poore J.T. Green M.E. Hockett 《Livestock Science》2009,125(2-3):254-260
A three-year study was conducted to investigate the effects of endophyte-free (E−), endophyte-infected (E+) and novel endophyte-infected (EN) tall fescue on the growth and pregnancy rate of beef heifers during the spring. Each year, 48 beef heifers were strip-grazed on stockpiled fescue from December through February, fed fescue hay during late February to early April and then rotationally grazed on spring growth of fescue until June. At the end of the trial, heifers had been maintained on E+, E− or EN (pasture or hay) for a total of 152, 188 and 191 d in years 1, 2, and 3, respectively. In late March, heifers were synchronized using a controlled intravaginal drug-releasing device, (CIDR®) for 7 d followed by injection with PGF2α (Lutalyse®). Heatmount detectors (Kamar®) and observation for behavioral estrus were used to detect estrus for 63 d. Heifers were artificially inseminated 8 to12 h after the onset of standing estrus. Conception was determined by transrectal ultrasonography at approximately 30, 60 and 90 d after synchronization. Reproductive performance did not differ among treatments (P ≥ 0.20). Pregnancy rate was 54, 65, and 65% for E+, E− and EN, respectively. However, during the spring, growth and prolactin were decreased (P < 0.01) for heifers on E+. Gains on spring pasture were 0.24, 0.75, and 0.71 kg/d (SEM ± 0.03) for E+, E− and EN, respectively. Based on these results, the wild type endophyte-infected fescue can be used in production systems as a source of winter forage but producers should consider placing heifers on alternative forage (such as the novel endophyte-infected fescue) in the spring. 相似文献
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An experiment was performed on 113 heifers born during three successive autumns (1987, 1988, and 1989) and aimed to study the effect of rearing strategy on performances and longevity. From 4–12 mo of age, heifers were grazing (G) or fed indoors with two levels of a corn-silage based diet (CS) with a high (CSH) or low (CSL) level concentrate. Age at first calving was 24 months (AFC24), but, because of seasonal calving management, some animals calved at 36 months of age (AFC36). From 4–12 mo of age, average daily weight gain (ADG) of G, CSL and CSH heifers was 874, 736 and 890 g/d, respectively. G and CSH heifers had the same ADG from 4–12 mo of age, whereas G and CSL heifers had the same ADG from 4 mo of age until puberty. Puberty was detected for 106 heifers, occurring at 269 (SD = ± 28) d of age at a weight of 286 (± 36) kg. On average, CSH heifers were 28 d younger at puberty (P < 0.001). In AFC24 heifers, fertility after one insemination was higher for CS heifers than for G heifers (77 and 55%, respectively). When heifers were adults, it corresponded to 77 and 96%, respectively. During their 1st lactation, AFC24 (G and CSL) heifers tended to have a higher milk peak than CSH heifers (27.3, 28.8 and 24.7 kg/d, respectively). On average, each cow completed 2.64 lactations (range = 0–7), but this parameter varied significantly (P < 0.05): 2.81 (G), 2.67 (CSL), 2.30 (CSH). Productive life was 852 d long, with significant differences between groups (945, 890 and 663 d for G, CSL and CSH groups, respectively). Culling rate during the first four lactations was around 38%. A deleterious effect of an excessive growth rate between 120 and 300 d, corresponding to body weight varying between 150 and 260 kg, was noted. In practice, this indicates that growth rates should be controlled before puberty, but a high growth rate is possible between puberty and first insemination without major problems. 相似文献
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[目的]为研究杏鲍菇菌糠对9～12月龄生长期荷斯坦奶牛生长性能和经济效益的影响。[方法]选择9～12月龄生长期荷斯坦奶牛60头,随机分为2组,分别饲喂原日粮和添加杏鲍菇菌糠全混合日粮,试验期60 d,分别测定采食量、日增重、体高、体长等生长指标,并分析经济效益。[结果]结果表明,菌糠饲料适口性好,试验组采食正常,两组间采食量无显著差异(P0.05);生长性能指标间无显著差异(P0.05);试验组饲料成本较对照组减少5.87元/(头·d)。[结论]杏鲍菇菌糠替代部分粗饲料饲喂9～12月龄生长期荷斯坦牛对其生长性能无影响,且显著降低饲料成本,具有现实推广价值。 相似文献