Comparison between the coat temperature of the eland and dairy cattle by infrared thermography

Little is known about the thermoregulatory response of the eland, a tropical animal often raised in temperate climate. We compared the surface temperature (T_s) of the eland with that of similarly sized Holstein–Friesian dairy cattle at three different ambient temperatures (T_a) to get better evidence about thermal response. The T_s of all body areas (neck, dewlap, trunk, body forepart, barrel, body hind part, forelimb and rear limb) did not differ at T_a 29.2 °C, but at T_a 12.5 °C all the areas of the eland (except the neck) had lower mean T_s than those areas in cattle. At T_a 0.4 °C, only the eland dewlap had a lower T_s and the eland neck had a higher T_s than that in cattle.     

Circulating progesterone dynamics after intravaginal instillation of prostaglandin-F2α to lactating dairy cows

Our objectives were to evaluate circulating progesterone (P4) concentration dynamics and test the feasibility of inducing luteal regression after intravaginal (IVG) instillation of the PGF2α analogue dinoprost (PGF) in lactating dairy cows. In two experiments, cows were synchronized using the Ovsynch protocol to induce the formation of a corpus luteum (CL). Cows with at least one functional (P4 ≥1 ng/mL) CL ≥15 mm 7.5 days after Ovsynch remained in the studies. In experiment 1, cows (n = 31) were stratified by parity group and received 5 mL of saline IVG (SAL-IVG, n = 6), 25 mg of PGF intramuscular (IM) (PGF25-IM, n = 7), 25 mg of PGF IVG (PGF25-IVG, n = 6), 50 mg of PGF IVG (PGF50-IVG, n = 6), and 125 mg of PGF IVG (PGF125-IVG, n = 6). Experiment 2 was conducted to test the hypothesis that IVG instillation of two 25 mg doses of PGF 12 hours apart would be more effective than a 25- or 50-mg dose in a single application. Cows (n = 32) were stratified by parity and received SAL-IVG (n = 7), PGF25-IM (n = 7), PGF25-IVG (n = 6), and PGF50-IVG (n = 6) as in experiment 1, whereas another group received two IVG instillations of 25 mg of PGF 12 hours apart (PGF25-2X-IVG, n = 6). Blood was collected at −1 hour, every 6 hours from 0 hour to 24 hours, and every 12 hours up to 96 hours after treatment (trt). In experiment 1, there was an effect of trt (P < 0.01), time (P < 0.001), and an interaction between trt and time on P4 concentrations (P < 0.001). All PGF-treated groups had lower (P < 0.05) concentrations of P4 than cows in the SAL-IVG group from 12 to 96 hours after trt. Although an initial decline in P4 concentrations was induced in all PGF-treated cows, some cows in the IVG-treated groups presented a rebound in plasma P4, indicating CL recovery. More cows in the PGF25-IVG and PGF125-IVG groups than in the PGF50-IVG and PGF25-IM groups presented CL recovery, suggesting that greater doses of PGF may not necessarily improve CL regression. In experiment 2, there was an effect of trt (P < 0.001), time (P < 0.001), and an interaction between trt and time on P4 concentrations (P < 0.001). All PGF-treated groups had lower (P < 0.05) P4 than the SAL-IVG group from 12 to 96 hours after trt. Cows in the PGF25-2X-IVG group had a P4 profile that was similar to that of cows in the PGF25-IM group and the lowest P4 concentrations after treatment among the IVG-treated groups, and all cows presented complete CL regression (defined as P4 <0.4 ng/mL). We conclude that CL regression can be induced through IVG instillation of PGF in lactating dairy cows and that instillation of two IVG doses of 25 mg of PGF 12 hours apart was the most effective strategy.     

正交优化法建立奶牛基因组DNA RAPD-PCR最佳反应体系

从 36头荷斯坦奶牛血样中提取基因组DNA ,以相同DNA浓度混成DNA池。以其为模板 ,通过正交设计试验 ,建立了RAPD PCR最佳反应体系。     

Toll-Like Receptor 2 Gene Polymorphism and its Relationship with SCS in Dairy Cattle

Toll-like receptor 2 (TLR2) plays an important role in the innate immune response to a variety of pathogens. In this study, bovine TLR2 gene was taken as a candidate gene for mastitis resistance. Through PCR-SSCP analysis and sequencing, three missense mutations at T385 G, G398A, and G1884A were detected in the coding region that encoded extracellular domain. Altogether 240 dairy cattle of three breeds (Holstein, Simmental, and Sanhe cattle) were genotyped and allele frequencies were determined. The effects of TLR2 polymorphisms on somatic cell score (SCS) were analyzed and significant association was found between T385 G and SCS. The mean of genotype GG was significantly lower than those of genotype TT and TG. No significant associations were found with SCS for G398A and G1884A. Information provided in this research will be useful in further studies to determine the role of TLR2 gene in the mastitis resistance.     

流式细胞仪原理及其在奶牛性别控制上的应用

流式细胞仪分离得到的定性奶牛精子,借助人工授精技术或其他相关技术已经生产出许多预知性别的后代奶牛。流式细胞仪分离精子的原理是基于携带有X或Y性染色体精子的DNA含量不同。高性能的流式细胞仪可以达到每小时分离1.5～2×108个精子,并且准确率可达到90%。该项技术的应用使得奶牛的人工授精和低温保存技术更为便利,并且该项技术也可以用于其他养殖动物X、Y精子的分离。     

Expected early genetic gain from selection for milk yield in dairy cattle

Summary A matrix program to predict short term genetic gain from single trait selection for milk yield was developed. Rate of genetic gain was calculated as the annual change in the mean breeding value of all producing females. Several parameters sets representing various selection policies were used to examine situations pertinent to dairy populations of the United States. Approach to the asymptotic rates of genetic gain within the model varied with the choice of parameters, but even with consistent selection policies, predicted total genetic gain in the first 10 years was only half of the expected from classical theory. Considerable year to year variation in the rate of gain occurred. Early gains were more dependent on female selection decisions than gains during the steady state. In a two-phase model, the approach to the linear rate of gain in the second phase was accelerated by starting with an ongoing improvement program, but considerable delays still existed. Selection for sex- limited traits such as milk yield, which require pedigree selection and a waiting time for progeny test results reached asymptotic rates more slowly than previously assumed.     

Timed embryo transfer programs for management of donor and recipient cattle

Currently, timed ovulation induction and fixed-time artificial insemination (FTAI) in superstimulated donors and synchronization protocols for fixed-time embryo transfer (FTET) in recipients can be performed using GnRH or estradiol plus progesterone/progestin (P4)-releasing devices and prostaglandin F_2α (PGF2α). The control of follicular wave emergence and ovulation at predetermined times, without estrus detection, has facilitated donor and recipient management. However, because Bos taurus cows have subtle differences in their reproductive physiology compared with Bos indicus cattle, one cannot assume that similar responses will be achieved. The present review will focus on the importance of orchestrating donor and recipient management to assure better logistics of procedures to achieve more desirable results with embryo collection and transfer. In addition, this will provide clear evidence that the use of FTAI in superstimulated donors and FTET in embryo recipients eliminates the need to detect estrus with satisfactory results. These self-appointed programs reduce labor and animal handling, facilitating the use of embryo transfer in beef and dairy cattle.     

Effect of intrauterine administration of gonadotropin releasing hormone on serum LH concentrations in lactating dairy cows

The objectives were to compare: (1) preovulatory serum LH concentrations, and (2) synchronization of ovulation, after im or iu administration of the second GnRH treatment of Ovsynch in lactating dairy cows. Lactating cows (N = 23) were presynchronized with two injections of PGF_2α given 14 days apart (starting at 34 ± 3 days in milk), followed by Ovsynch (GnRH-7 d-PGF_2α-56 h-GnRH) 12 days later. At the time of the second GnRH of Ovsynch (Hour 0), cows were blocked by parity and randomly assigned to 1 of 3 groups: (1) control group (CON; N = 7) were given 2 mL sterile water im; (2) intramuscular group (IM; N = 8) received 100 μg of GnRH im; and (3) intrauterine group (IU; N = 8) had 100 μg GnRH infused in the uterus (2 mL). Blood samples for serum LH concentrations were collected at Hours 0, 0.5, 1, 1.5, 2, 3, and 4. Furthermore, ultrasonography was performed twice daily (12-h intervals) from Hours 0 to 60 to confirm ovulation. The LH concentrations were greater (P < 0.05) in the IM than IU and CON groups at Hours 0, 0.5, 1, 1.5, 2, 3, and 4. Although LH concentrations were numerically higher in the IU group, LH concentrations within the IU and CON groups did not change over time. More cows ovulated in the IM (8/8) and IU (7/8) groups within 60 h after the second GnRH administration compared with the CON (2/7) group. In summary, serum LH concentrations were lower in the IU versus IM group, but the proportion of cows that ovulated within 60 h was similar between these two groups. Therefore, iu administration of GnRH may be an alternative route of delivery to synchronize ovulation in beef and dairy cattle.     

Effect of supplementation with different fat sources on the mechanisms involved in reproductive performance in lactating dairy cattle

Supplementary fat positively influences reproductive performance in dairy cattle, although the mechanisms involved are not clearly defined. Our objective was to determine the effects of four different fat supplements on follicle development, plasma steroid hormone concentrations and prostaglandin (PG) synthesis in lactating dairy cattle. Forty-eight early lactation Holstein-Friesian cows (21 primiparous, 27 multiparous) were used in a completely randomized block design. Cows were fed the same basal TMR diet and received one of four fat supplements: (i) palmitic acid (18:0 fatty acid; Control), (ii) flaxseed (rich in 18:3 n-3 fatty acid; Flax), (iii) conjugated linoleic acid (a mixture of cis-9, trans-11 and trans-10, cis-12 isomers; CLA), and (iv) fish oil (rich in 20:5 and 22:6 n-3 fatty acids; FO). All lipid supplements were formulated to be isolipidic; palmitic acid was added as necessary to provide a total lipid supplement intake of 500 g/day. Cows were synchronized to be in estrus on Day 15 of dietary treatment. All antral follicles were counted, and dominant follicles, subordinate follicles and corpora lutea were measured daily via transrectal ovarian ultrasonography for one complete estrous cycle. Blood samples were collected daily, and selected samples were analyzed for progesterone, estradiol, insulin-like growth factor-1, insulin, cholesterol and non-esterified fatty acids. Estrus was synchronized a second time, and liver and endometrial biopsies were collected on Day 7 of the estrous cycle. Gene expression was evaluated for a number of genes involved in prostaglandin synthesis (endometrium) and fatty acid uptake and utilization (liver). Fat supplementation had little effect on follicle development. Cows receiving supplementary n-3 fatty acids had lesser plasma progesterone (P4) and smaller corpora lutea than cows receiving the CLA or Control supplements. Effects of fat supplementation on the endometrial expression of genes involved in PG synthesis were minor. Hepatic expression of SREBF1, ASCL1 and FABP1 was reduced by FO supplementation. Reduced plasma P4 in n-3 supplemented cows may lead to a suboptimal uterine environment for embryo development and hence reduced fertility compared to cows receiving the control or CLA supplements.     

Influence of somatic cell count, body condition and lameness on follicular growth and ovulation in dairy cows

The objective of this study was to investigate the effect of somatic cell count (SCC), body condition score (BCS) or lameness score on ovarian follicular growth and ovulation in dairy cows. Seventy four animals 30-80 days post-partum were monitored for all three conditions before synchronization of ovarian follicular phases by administration of gonadotrophin releasing hormone (GnRH) followed seven days later with prostaglandin F2alpha (PG). Ultrasonography of both ovaries twice daily throughout the follicular phase revealed that fewer animals with combined high SCC and lameness (4/9) ovulated compared to healthy animals (19/21; P = 0.006) or animals with only high SCC (11/11; P = 0.004) or only lameness (21/27; P = 0.06). Overall, regardless of the presence of other concurrent conditions, fewer lame cows ovulated than Non Lame animals (30/42 and 30/32; P = 0.015). Mean follicular growth and maximum follicular diameter were unaffected by any of the three conditions. However, dominant follicle growth and maximum diameter were greater in the 60 animals that ovulated compared to the 14 that did not; 1.83 ± 0.16 versus 0.96 ± 0.26 mm/day (P = 0.014) and 19.4 ± 0.4 versus 16.4 ± 1.2 mm (P = 0.003), respectively. In conclusion, lameness reduced the proportion of cows that ovulated and the synergistic effect of high SCC and lameness reduced that proportion further. However, follicular growth and maximum follicular diameter were unaffected by high SCC, low BCS or lameness.     

Characterizing homozygosity across United States,New Zealand and Australian Jersey cow and bull populations

Background

Dairy cattle breeding objectives are in general similar across countries, but environment and management conditions may vary, giving rise to slightly different selection pressures applied to a given trait. This potentially leads to different selection pressures to loci across the genome that, if large enough, may give rise to differential regions with high levels of homozygosity. The objective of this study was to characterize differences and similarities in the location and frequency of homozygosity related measures of Jersey dairy cows and bulls from the United States (US), Australia (AU) and New Zealand (NZ).

Results

The populations consisted of a subset of genotyped Jersey cows born in US (n = 1047) and AU (n = 886) and Jersey bulls progeny tested from the US (n = 736), AU (n = 306) and NZ (n = 768). Differences and similarities across populations were characterized using a principal component analysis (PCA) and a run of homozygosity (ROH) statistic (ROH45), which counts the frequency of a single nucleotide polymorphism (SNP) being in a ROH of at least 45 SNP. Regions that exhibited high frequencies of ROH45 and those that had significantly different ROH45 frequencies between populations were investigated for their association with milk yield traits. Within sex, the PCA revealed slight differentiation between the populations, with the greatest occurring between the US and NZ bulls. Regions with high levels of ROH45 for all populations were detected on BTA3 and BTA7 while several other regions differed in ROH45 frequency across populations, the largest number occurring for the US and NZ bull contrast. In addition, multiple regions with different ROH45 frequencies across populations were found to be associated with milk yield traits.

Conclusion

Multiple regions exhibited differential ROH45 across AU, NZ and US cow and bull populations, an interpretation is that locations of the genome are undergoing differential directional selection. Two regions on BTA3 and BTA7 had high ROH45 frequencies across all populations and will be investigated further to determine the gene(s) undergoing directional selection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1352-4) contains supplementary material, which is available to authorized users.     

Prediction of response with overlapping generations accounting for multistage selection

Summary A generalization of Hill's equations predicting response to selection is developed that accounts for multiple stage selection in either or both sexes. The method accounts for the flow of genes for animals selected at later stages. This allows for the use of genetic gains from later stages, which explains the reduction in variance due to previous selection. Genetic gains from different selection differentials in each reproductive pathway are incorporated into the equations. The asymptotic response to a single cycle of selection is shown to agree with classical selection theory.The method is applied to a dairy progeny testing scheme representative of an artificial insemination organization in the USA. Two models were compared: (1) the first model accounted for two-stage selection of males, the first stage being based on pedigree information and the second stage on both pedigree and progeny test information; and (2) the second model assumed single-stage male selection. Selection was based on milk volume, milk fat, and milk protein yields. The predicted asymptotic rates for a single cycle of selection were overestimated by 6% and the cumulative response to continuous selection over 20 years was overestimated by 8% by assuming singlestage male selection.Journal Paper No. J14146 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa; Project No. 1053     

When is a cow in estrus? Clinical and practical aspects

Good detection of estrus is critically important in dairy husbandry. Incorrect detection of estrus is related to loss of profit due to extended calving intervals, milk loss, veterinary costs, etc. Detection of estrus remains a major problem despites enormous progress in the knowledge of reproductive physiology of the cow and in development of estrus detection aids. To achieve good estrus detection, many factors have to be taken into account. On one hand a cow has to express estrus and on the other hand the farmer has to detect it. Combined action of several hormones causes physiological changes that lead to ovulation and an environment in the uterus that allows sperm to fertilize the egg. Besides these internal actions, a number of external changes can be observed. When using visual observations, time of the day and time spend on observation have a great impact on detection rates. Many devices are available to aid in estrus detection, such as pedometers, mount devices, temperature, and hormone measurements.Expression of estrus can be influenced by many factors. Heritability, number of days postpartum, lactation number, milk production, and health are known to influence estrus expression. Environmental factors like nutrition, season, housing, herd size, etc. also play a role in estrus expression. To evaluate estrus detection, record keeping is very important; a number of formulas can be used to assess detection efficiency. Besides the farmer, the veterinarian and inseminator can play an important role in estrus confirmation and good insemination strategy. In the end, the time of ovulation and the age of the egg at sperm penetration is critical for conception. Therefore, emphasis in research needs to be on the timing of insemination relative to ovulation, and thus on the detection of ovulation.     

Influence of lameness on follicular growth, ovulation, reproductive hormone concentrations and estrus behavior in dairy cows

The objective of this study was to examine the effect of a chronic stressor, lameness, on reproductive parameters. Seventy cows 30-80 days post-partum were scored for lameness and follicular phases synchronized with GnRH followed seven days later by prostaglandin (PG). Fifteen Lame animals did not respond to GnRH ovarian stimulation. Milk progesterone for 5 days prior to PG was lower in the remaining Lame cows than Healthy herdmates. Fewer Lame cows ovulated (26/37 versus 17/18; P = 0.04) and the interval from PG to ovulation was shorter in Lame cows. In Subset 1 (20 animals), the LH pulse frequency was similar in ovulating animals (Lame and Healthy) but lower in Lame non-ovulators. An LH surge always preceded ovulation but lameness did not affect the interval from PG to LH surge onset or LH surge concentrations. Before the LH surge, estradiol was lower in non-ovulating cows compared to those that ovulated and estradiol concentrations were positively correlated with LH pulse frequency. In Subset 2 (45 cows), Lame ovulating cows had a less intense estrus than Healthy cows, although Lame cows began estrus and stood-to-be-mounted earlier than Healthy cows. In conclusion, we have identified several parameters to explain poor fertility in some chronically stressed animals. From 30 to 80 days post-partum, there was a graded effect that ranged from 29% Lame cows with absence of ovarian activity, whereas another 21% Lame cows failed to express estrus or ovulate a low estrogenic follicle; in 50% cows, many reproductive parameters were unaffected by lameness.     

Factors affecting pregnancy loss for single and twin pregnancies in a high-producing dairy herd

Our objective was to determine the magnitude of, and factors affecting, pregnancy loss for lactating Holstein cows on a commercial dairy farm when diagnosed with twin (n = 98) or single (n = 518) pregnancies using transrectal ultrasonography. Pregnancy losses were assessed with records of non-viable embryos at first pregnancy examination and embryo losses between the first (25-40 d after AI) and second (48 and 82 d after AI) post-breeding pregnancy examinations. Among cows diagnosed with single pregnancies, 3.7% were diagnosed with a non-viable embryo at first pregnancy examination, and 4.6% of those diagnosed with a viable embryo underwent pregnancy loss by the second examination. A total of 11.2% of cows diagnosed with twins experienced a single embryo reduction, whereas 13.3% lost both embryos. Overall, the total proportion of cows experiencing pregnancy loss or experiencing embryo reduction was greater for cows diagnosed with twin than single pregnancies (odds ratio; OR = 3.6), resulting in an embryo survival rate of 91.9% for cows diagnosed with single compared to 75.5% for cows diagnosed with twin pregnancies. Season of breeding and milk production were associated with pregnancy loss for single pregnancies, whereas CL number was associated negatively with embryo reduction and pregnancy loss for twin pregnancies. The risk of twinning and double ovulation among pregnant cows increased with days in milk (DIM), and the risk of double ovulation was greater for cows diagnosed with ovarian cysts and lacking a CL at initiation of an Ovsynch protocol. We concluded that in this herd, embryo reduction and pregnancy loss during early gestation was greater for lactating Holstein cows diagnosed with twin compared to single pregnancies. In addition, cows diagnosed with ovarian cysts and lacking a CL had an increased risk for double ovulation.