Economic evaluation of breeding strategies for improvement of dairy cattle in Kenya

Cost-benefit analysis using net present value (NPV) as the economic evaluation criterion was used to investigate the economic merits of four breeding strategies used for genetic improvement of dairy cattle in Kenya. The breeding strategies were evaluated over a 25-year period. The costs involved in setting up and running each strategy were obtained from large-scale dairy cattle farms, and government and private institutions involved in genetic improvement of dairy cattle. Only benefits from genetic improvement were considered. The impact on NPV due to changes in genetic and economic parameters was investigated. The ranking of the breeding strategies greatly differed with genetic ranking. Among the local selection programs, a strategy utilizing young bulls, sons of local bulls, was more profitable than one utilizing old progeny tested bulls. Continuous semen importation was not an economically viable alternative. The strategy utilizing young bulls progeny of imported bulls (PIB) was only viable if imports were from countries which are >2.00 SD in genetic merit above the local dairy cattle population. The ranking of strategies was not sensitive to changes in genetic parameters but to economic parameters. The use of local semen from young bulls progeny of local proven bulls is recommended. Alternatively, PIB can be utilized but the semen will have to be imported from countries which are >2.00 SD above the local dairy cattle population or the cost of imported semen should be?≤?US$40 per straw.     

Genetic evaluation of breeding strategies for improvement of dairy cattle in Kenya

Cost-benefit analysis using net present value (NPV) as the economic evaluation criterion was used to investigate the economic merits of four breeding strategies used for genetic improvement of dairy cattle in Kenya. The breeding strategies were evaluated over a 25-year period. The costs involved in setting up and running each strategy were obtained from large-scale dairy cattle farms, and government and private institutions involved in genetic improvement of dairy cattle. Only benefits from genetic improvement were considered. The impact on NPV due to changes in genetic and economic parameters was investigated. The ranking of the breeding strategies greatly differed with genetic ranking. Among the local selection programs, a strategy utilizing young bulls, sons of local bulls, was more profitable than one utilizing old progeny tested bulls. Continuous semen importation was not an economically viable alternative. The strategy utilizing young bulls progeny of imported bulls (PIB) was only viable if imports were from countries which are >2.00 SD in genetic merit above the local dairy cattle population. The ranking of strategies was not sensitive to changes in genetic parameters but to economic parameters. The use of local semen from young bulls progeny of local proven bulls is recommended. Alternatively, PIB can be utilized but the semen will have to be imported from countries which are >2.00 SD above the local dairy cattle population or the cost of imported semen should be ≤ US$40 per straw.     

Putative urinary pheromone of bulls involved with breeding performance of primiparous beef cows in a progestin-based estrous synchronization protocol

The objective of this study was to determine if factors associated with the biostimulatory effect of bulls alter breeding performance of primiparous, suckled beef cows using a progestin-based estrous synchronization protocol. We tested the hypotheses that the estrous synchronization response and AI pregnancy rates differ among cows exposed to bulls, continuously exposed to bull urine, and exposed to fence-line contact with bulls or cows not exposed to bulls or bull urine. Data were collected from 3 experiments performed over consecutive years. Cows were assigned to the following treatments: bull exposure (BE; n = 26) or no bull exposure (NB; n = 25) in Exp. 1, bull urine exposure (BUE; n = 19) or steer urine exposure (SUE; n = 19) in Exp. 2, and fence-line contact with bulls (BFL; n = 26) or no bull exposure (NB; n = 26) in Exp. 3. Synchronization protocols in each experiment included the use of a controlled internal drug release device (d -10), PGF(2alpha) (d -3), and GnRH and fixed-time AI (TAI; d 0). Cows that were observed in estrus by 60 h after PGF(2alpha) were inseminated 12 h later. Cows not observed in estrus by 60 h after PGF(2alpha) were TAI at 72 h and given GnRH (100 mug). Pregnancy was determined by ultrasonography 35 d after TAI. In Exp. 1, 2, and 3, cows were exposed directly to bulls, bull urine, or bull fence-line contact for 35, 64, and 42 d, respectively. Data were analyzed between treatments within each experiment. The proportion of estrous cycling cows did not differ between treatments at the beginning of each experiment; however, more (P < 0.05) BE and BFL cows were estrous cycling at the beginning of the estrous synchronization protocol than NB cows in Exp. 1 and 3. The proportion of cows that showed estrus and interval to estrus after PGF(2alpha) did not differ between treatments in Exp. 1 and 3. However, in Exp. 2, more BUE cows tended (P = 0.09) to have shorter intervals to estrus and to exhibit estrus after PGF(2alpha) than SUE cows. Overall, AI pregnancy rates were greater (P < 0.05) for BE and BUE cows than for NB and SUE cows in Exp. 1 and 2, respectively. There was no difference in AI pregnancy rates between BFL and NB cows in Exp. 3. The presence of bulls and exposure to bull urine appeared to improve breeding performance of primiparous beef cows using a progestin-based estrous synchronization protocol, whereas fence-line bull exposure was insufficient to cause this biostimulatory effect. We propose that a novel urinary pheromone of bulls may be responsible for the enhancement of fertility in the primiparous, postpartum cow.     

Cost-benefit evaluation of artificial insemination for genetic improvement of wool-producing sheep

SUMMARY The financial costs and benefits associated with the use of artificial insemination (AI) in commercial flocks are evaluated. Benefits are calculated in terms of net present values after summing the discounted value of benefits over 20 years. Two breeding strategies are evaluated. With the first, AI is used to produce flock ewes and wethers. The method is unlikely to be profitable unless high breeding value rams are available for AI programs with fresh semen. With the second, AI is used to produce home-bred rams, which in turn sire flock ewes and wethers. This approach is more likely to be profitable. The cost of AI per lamb weaned from laparoscopic AI programs is about $100. Benefits exceed this cost for rams of very high merit when wool prices are moderate or higher. Flock structure has a significant effect on the benefits. Flocks with low wether retention rates have benefits half that of flocks that retain most wethers to 6 years of age. AI with purchased semen also provides benefits to risk management for owners of commercial flocks who wish to breed their own replacement flock rams.     

Genetic Parameters for Semen Production Traits in Austrian Dual-Purpose Simmental Bulls

Genetic parameters were estimated for semen production traits collected in an Austrian AI centre in the years 2000-2004. In total, 12,746 ejaculates from 301 Austrian dual-purpose Simmental (Fleckvieh) AI bulls were examined considering different effects on ejaculate volume, sperm concentration, percentage of viable spermatozoa in the ejaculate, total spermatozoa per ejaculate and motility. The model for genetic parameter estimation included the fixed effects age of bull, collection interval, number of collections on collection day, bull handler, semen collector, year and month of collection, a random additive genetic component and a permanent environmental effect. Correlations between estimated breeding values for semen traits and male fertility from the routine evaluation were calculated. The fertility trait considered in the routine evaluation is non-return rate 90 for the first insemination. All semen production traits were moderately heritable. Heritabilities for volume, concentration, percentage of viable spermatozoa, total number of spermatozoa and motility were 0.18, 0.14, 0.10, 0.22 and 0.04, respectively. Correlations between breeding values for semen quality traits and routinely estimated breeding values for male fertility were low and ranged from 0.08 to 0.17 indicating that semen production traits are rather poor predictors of male fertility.     

Inherited progressive spinal myelinopathy in Murray Grey cattle

In a breeding experiment conducted to determine the mode of inheritance of progressive spinal myelinopathy, semen from a Murray Grey bull which had previously sired affected calves was used to inseminate 120 cows. Female progeny were then inseminated with semen from the same bull. Of the 51 calves born, six (11.8%) had spinal cord lesions consistent with progressive spinal myelinopathy. From analysis of pedigrees and the results of the breeding experiment it was concluded that the condition was inherited as an autosomal recessive condition in Murray Grey cattle.     

ASAS centennial paper: Contributions in the Journal of Animal Science to the development of protocols for breeding management of cattle through synchronization of estrus and ovulation

American Society of Animal Science members, publishing in Journal of Animal Science (JAS), completed research that resulted in understanding the estrous cycle of cattle, which led to the ability to inseminate cattle on a given day with pregnancy rates similar to those achieved by 21-d breeding by a fertile and sound bull. Research published in JAS led to understanding estrus, ovulation, the estrous cycle, and postpartum interval for cattle (1930s through 1960s) and hormonal factors affecting corpus luteum lifespan of cattle (1950s through 1980s). Research during the 1940s to 1960s, using gonadotropins and progesterone to manage the estrous cycle of cattle, established the concepts for estrous synchronization and stimulated commercial research directed at developing cost-effective progestogen estrous synchronization products, leading to commercially available products from 1967 through today (Repromix, melengestrol acetate, Syncro-Mate-B, controlled internal drug release). Prostaglandin F(2alpha) products were approved for estrous synchronization (1970s, 1980s), and GnRH products were approved for use in cattle to treat ovarian follicular cysts (1970s, 1980s). Research published in JAS was essential for understanding the biology of and potential value of both PGF(2alpha) and GnRH and contributed both to new knowledge and scientific bases for future Food and Drug Administration Center for Veterinary Medicine approval of those products. Research during the1980s through 2000s led to understanding ovarian follicular waves and described the timing of follicular recruitment, selection, dominance, and atresia; this research was essential for the ability to effectively manage follicles to achieve success with timed AI. The knowledge gained through research published in JAS resulted in development of the numerous estrous synchronization and breeding management protocols that are cost-effective and meet the breeding management needs of most beef and dairy enterprises.     

价格变动对目标性状经济值及育种效果的灵敏性分析

基于鲁西牛育种、生产和市场体系,通过构建与目标性状相联系的遗传变量和经济变量的利润函数,采用偏微分预算法和基因流动法分析价格与目标性状经济值,以及目标性状经济值与育种效果之间关系的稳健性和灵敏性。结果表明,目标性状的经济值和育种效果随着市场体系的变化而变化,且育种效果的变化和目标性状经济值的变化相关联。以上结果说明,当前市场价格体系下获得的目标性状经济权重随着市场价格变化应做适宜的调整。     

法系夏洛来牛的引进繁育(上)

1986年后我站相继从国内、外引进法国夏洛来牛9头,在4头母牛基础上开始纯繁自育发展牛群。截至2003年6月,繁殖犊牛87头,存栏62头,其中成年公、母牛45头。4岁龄纯繁公、母牛平均体尺体重与同龄原种牛比,均有所提高。纯繁公牛20月龄采精调教,平均利用年限为61.73月龄,生产冻精71 074剂,淘汰年龄平均为84.6月龄。母牛平均初孕年龄为25.16月龄,平均淘汰年龄为95.71月龄,终生产犊4.8头。为社会创造巨大经济效益。     

Reducing bias in the dairy cattle single‐step genomic evaluation by ignoring bulls without progeny

The number of genotyped animals has increased rapidly creating computational challenges for genomic evaluation. In animal model BLUP, candidate animals without progeny and phenotype do not contribute information to the evaluation and can be discarded. In theory, genotyped candidate animal without progeny can bring information into single‐step BLUP (ssGBLUP) and affect the estimation of other breeding values. We studied the effect of including or excluding genomic information of culled bull calves on genomic breeding values (GEBV) from ssGBLUP. In particular, GEBVs of genotyped bulls with daughters and GEBVs of young bulls selected into AI to be progeny tested (test bulls) were studied. The ssGBLUP evaluation was computed using Nordic test day (TD) model and TD data for the Nordic Red Dairy Cattle. The results indicate that genomic information of culled bull calves does not affect the GEBVs of progeny tested reference animals, but if genotypes of the culled bulls are used in the TD ssGBLUP, the genetic trend in the test bulls is considerably higher compared to the situation when genomic information of the culled bull calves is excluded. It seems that by discarding genomic information of culled bull calves without progeny, upward bias of GEBVs of test bulls is reduced.     

牛精子冷冻损伤研究进展

人工授精技术是目前通过冷冻精液进行牛遗传改良而应用最为广泛的生物技术。虽然如此,由于精液产品的质量而导致人工授精的遗传影响被限制,在精液的冷冻－解冻过程中40%~50%的活精子失去完整性或功能受到损伤。作者在参阅国内外相关文献的基础上,通过阐述冷冻－解冻对精子细胞的损伤作用及机理、精浆对牛冷冻精液质量的影响、冷冻－解冻过程中精子的过氧化损伤,以及冷冻－解冻后精子相关基因与蛋白质的变化等,以期为牛高质量冷冻精液的研究提供一定参考,进一步提升冷冻精液质量。     

Artificial insemination in pigs: predicting male fertility

Efficient artificial insemination (AI) is essential for future challenges in the pig industry. Knowledge on the exact relation between semen quality characteristics and fertility can have a major impact on both the genetic merit of future animals and the efficiency of AI. Variation in fertility is caused not only by farm- or sow-related parameters but also by boar- and semen-related parameters. In pig AI there is no gold standard concerning semen quality assessment. Assessing semen quality characteristics objectively and relating them to large field fertility datasets leads to an efficient production of insemination doses, which results in an efficient dissemination/descent of the breeding program required genes. Overall, this contributes to the development of semen quality assessments, which improves the prediction of porcine male fertility. Knowing which semen characteristics, and to what extent, contribute to male fertility and makes the field fertility more predictable.     

Transmission of bovine virus diarrhoea virus (BVDV) by artificial insemination (AI) with semen from a persistently-infected bull

Twelve heifers that did not have antibodies to bovine virus diarrhoea virus (BVDV) were inseminated with semen from a bull that was persistently infected with the virus and contained 10(4.0)-10(6.5) TCID50 0.1 ml-1. All 12 became infected, as indicated by seroconversion within 2 weeks of insemination. Four control heifers were inseminated with virus-free semen. The virus was not transmitted to these animals in spite of close contact with the heifers inseminated with the infected semen. All the heifers became pregnant and gave birth to clinically normal calves at term. However, one calf was born persistently infected with BVDV. After the birth of this persistently-infected calf the control heifers and their calves seroconverted. The study demonstrates that BVDV may be transmitted in cattle by artificial insemination (AI). Therefore entry of persistently-infected animals into AI centres should be prevented.     

补饲与犊牛断乳对产后母牦牛发情周期恢复的影响研究

为了提高当年产犊母牦牛的发情率,我们对选定的120头怀孕母牦牛进行补饲,同时在犊牛产后3个月对犊牛进行隔离断奶,补饲试验于2010年3月初开始：100头母牦牛随机分为两组,试验组Ⅰ 50头母牦牛隔离断奶后进行同期发情和定时授精处理;Ⅱ组50头母牦牛隔离断乳.不进行同期发情处理,发情母牛进行人工授精。人工授精冻精液为荷斯坦和野牦牛冻精。配种45d后进行怀孕诊断。Ⅰ组发情39头,发情率为78%（39/50）,怀孕34头妊娠率为68%（34/50）;Ⅱ组发情31头,发情率为62%（31/50）,怀孕27头,妊娠率为54%（27/50）。相同草场放牧50头适配母牦牛作为对照。对照组母牛和犊牛不进行隔离和短期断乳;对照组发情率为12%（6/50）,妊娠率为6.32%（3/50）。试验结果表明,通过对带犊的母牦牛实施隔离断奶,能够明显提高当年产犊母牦牛的发情率和妊娠率。     

Statistical Methods to Produce "Good" Bovine Frozen Semen

A "good" bovine frozen semen must have: high fertility, low costs, good genetic values. The genetic value is associated to the sire and the Artificial Insemination (AI) centre can only optimize the management of the progeny test program. The high fertility and the low costs are strictly linked to the qualitative level of the technical management of the AI centre. The optimization of the management of an AI centre can be done by the choice of the best systems of semen handling and analysis, using the methods of the Statistical Quality Control (SQC). To support the production in an AI centre, it becomes important to set up some statistical instruments aiming to performing a Statistical Quality Control. These instruments (such as Control Charts) should allow the monitoring of the production because the various lots, produced by the same centre, should have a basically constant number of motile spermatozoa after thawing (the quality parameter with the better correlation with the fertility). Moreover, this number should range within the tolerance limits established by the centre. Only in this way the production activity of an AI centre may become of industrial type. The system that aims to maximize the production level, in an AI centre, as a function of the number of motile spermatozoa after thawing, consists of predicting forward motility and concentration, after thawing, of a batch of semen and using these values to compute the correct number of straws to produce for the batch (for each bull). The ARIMA models can be used to forecast the percentage of motile sperms after thawing for bulls with continue production, while to forecast the concentration it is necessary to verify the loss of spermatozoa during the semen handling.     

National genetic improvement programs for dairy cattle in the United States

Rate of genetic improvement for milk yield has been increasing in recent years. Cows born in 1986 were about 135 kg superior in breeding value for milk yield to those born in 1985. Over 2.2 million cows contribute new data to genetic evaluations for production traits annually. These evaluations are computed with an animal model that provides best linear unbiased predictions of transmitting abilities for milk, fat, and protein yields and fat and protein percentages. The model includes effects of management group, permanent environment, herd-sire interaction, and animal genetic merit. Unknown-parent groups represent the genetic merit of base populations defined by birth year and sex. Type appraisal data are collected by breed associations and are evaluated with a sire model. Holstein cow evaluations are computed using scores from all appraisals and a multitrait model; evaluations for other breeds are computed using all appraisal scores, a repeatability model, and a single-trait system. Dystocia data are collected by individual AI organizations and dairy records processing centers; they are analyzed by a categorical-trait sire model at Iowa State University with support from the National Association of Animal Breeders. The AI organizations have been extremely important in increasing rate of genetic progress by increasing numbers of young bulls sampled, increasing selection intensity of bull dams through multiple ovulation and embryo transfer, and shortening generation interval through the use of younger cows and some virgin heifers as bull dams. (ABSTRACT TRUNCATED AT 250 WORDS)     

Impact of trichomoniasis on the cow-calf producer's profitability

Using current knowledge of bovine trichomoniasis, a computer spreadsheet simulation model was developed to contribute to the understanding of the disease dynamics and the disease's impact on calf crop, weaner calf production, and revenue returns. Two disease prevalence simulations were generated with the model. In each simulation, 200 susceptible cows were confined with 5 fertile bulls. In simulation 1, one bull was infected with Tritrichomonas foetus (prevalence, 20%); in simulation 2, 2 bulls were infected (prevalence, 40%). The remaining bulls in these groups were designated noninfected. The disease simulation outcomes for breeding and calving variables were compared with a similar but noninfected model group, simulation 0. The disease model predicted a reduction of 14 to 50% in annual calf crop, a prolonged breeding season, a reduction of 5 to 12% in the suckling/growing period, a reduction of 4 to 10% in pounds of marketable calf crop at weaning, a reduction of 4 to 10% in monetary return per calf born, and a substantial reduction of 5 to 35% in the return per cow confined with a fertile bull.     

Scheduled breeding of gilts after estrous synchronization with altrenogest

Fertility of 104 gilts artificially inseminated (AI) at a predetermined time (scheduled AI) after estrous synchronization with altrenogest (15 mg X gilt-1 X d-1 for 18 d) was compared with that of 103 gilts checked for estrus (estrus checked) and inseminated after altrenogest. Scheduled-AI gilts were inseminated once on d 5, 6 and 7 after the last altrenogest feeding (d 0). Estrus-checked gilts were exposed to a boar twice daily at 0830 and 1630 h and inseminated after the second and third estrous detection period following first detected estrus. Percentage of gilts assigned to treatment that farrowed (72.8 vs 67.3%), total pigs farrowed (11 +/- .4 vs 11.3 +/- .4) and pigs born alive (10.1 +/- .4 vs 10.5 +/- .4) were similar for estrus-checked and scheduled-AI gilts, respectively. We conclude that scheduled AI can be used with estrous synchronization for gilts and may have advantages in breeding herd management and the use of AI in swine.     

Laparoscopic artificial insemination in sheep

The goal of any AI program is to create improved offspring, and the achievement of this objective will depend on the breeding value of the ram and ewe selected. Laparoscopic AI is being utilized in the sheep industry to extend the use of superior rams, and it offers the producer the opportunity to maximize the reproductive potential of superior sheep. Rapid genetic trait infusion of known superior stud rams into the flock is the primary economic benefit of laparoscopic AI. The success of laparoscopic AI depends on events and factors that interrelate in a complex way. Once the selection and preparation of the ewe have been accomplished, one of the more important steps in the program is the successful synchronization of the ewe to deliver the necessary ova to the site of fertilization at a specific time. One of the best methods of synchronization for laparoscopic AI is the use of a progesterone product for a controlled time period and the administration of PMSG upon its removal. Detecting the onset of estrus is critical, and the addition of sterile (e.g., vasectomized) males is helpful, even essential, to accurately determine when each ewe begins her estrus. The ram effect has been shown to stimulate ovulation and estrus. Ewes must be inseminated within a narrow window of time after the synchronization product is removed. Ewes should be inseminated in the order in which they begin to exhibit signs of behavioral estrus, but age, stage of lactation, duration of behavioral estrus, and breed must be taken into account when this order is established. Fresh-extended semen works well throughout this preferred time frame established for laparoscopic AI, but frozen semen gives best results when used near the end. Advancement in manufacturing technology today removes equipment as a variable factor. It is important, therefore, that the inseminator develop a level of expertise in laparoscopy to ensure maximum fertilization rates. If available, fresh-extended semen is preferred over frozen semen, using at least the minimal number of spermatozoa necessary for fertilization. Evaluation of the post-thaw frozen or fresh semen is necessary to determine motility, morphology, and concentration, all of which help determine the volume of the insemination dose. The minimum necessary for laparoscopic AI in fine-wooled breeds is 20 X 10(6) normal motile spermatozoa; however, the more seasonal and less fertile American sheep need approximately 40 to 50 X 10(6) normal motile sperm to achieve acceptable fertility rates.(ABSTRACT TRUNCATED AT 400 WORDS)     

Optimal replacement and ranking of dairy cows determined by a hierarchic Markov process

A dairy cow replacement model based on the notion of a hierarchic Markov process is presented. A hierarchic Markov process is a series of Markov decision processes built together in one Markov decision process, called the main process.In the model a cow is described in terms of lactation number, stage of lactation, the level of milk yield during the previous and present lactation, the length of the calving interval, and the genetic class defined from the breeding value of the father. The criterion of optimality is the maximization of the present value under an infinite planning horizon. Revenues from milk, calves, and replaced cows, feed costs and costs of replacement heifers are considered.The future profitability calculated from the optimal solution is used for ranking of the cows in the herd. The genetic class makes it possible to include the heifers available for replacement in the ranking and to let the replacement decision depend on the genetic class of the heifers.It is concluded that the milk yield of previous lactation is not needed as a state variable when the other variables are present in the model.