Effect of preparing and loading multiple insemination guns on conception rate in two large commercial dairy herds

In large herds, inseminators frequently thaw multiple straws of semen and prepare several insemination guns at once. The aim of this study was to measure the effect of breeding order, the order that thawed straws are used, on conception rate in commercial dairy herds. A single professional inseminator, utilizing semen from five suppliers, performed 2629 inseminations over 30 months. Up to four straws were thawed at one time with the restriction that straws were used within 20 min of thawing. Straws were thawed per supplier's recommendations, with 66.4% of the straws pocket thawed and the remainder warm-water thawed. Conception was determined by a pregnancy check at 42 days. Data were modeled by multiple logistic regression analysis, which included herd, breeding order, lactation number, times bred, month bred and year bred. Breeding order had no significant effect on the probability of conception: Cows 1-4 achieved adjusted conception rates of 0.36, 0.41, 0.37, and 0.39, respectively. Odds ratios (and 95% confidence intervals) were 1.00 (1.00-1.00), 1.22 (0.99-1.49), 1.04 (0.82-1.32), and 1.12 (0.86-1.45), respectively. Associated laboratory studies, which evaluated the effect of post-thaw holding time on percentage of sperm with progressive motility, found mean values at 20 min holding time to be largely unchanged from mean values at 5 min. Thawing temperatures were 6, and 35 degrees C and holding temperatures were 6, 22, and 35 degrees C. The length of the trial and the wide use of semen from multiple suppliers with differing thawing methods suggests that under similar conditions, a careful and experienced inseminator can thaw multiple straws of semen and prepare insemination guns sufficient to breed up to four cows within 20 min, without an adverse effect on conception.     

Bull influences on conception percentage and calving date in Angus Hereford, Brahman and Senepol single-sire herds

Bull breeding soundness parameters, semen characteristics and sexual behavior were evaluated for effects on reproductive performance in single-sire beef herds. A total of 155 cow herds (Angus, 50 herds; Hereford, 40 herds; Brahman, 46 herds; and Senepol, 19 herds) bred to bulls of the same breed were observed for 8 yr. All bulls produced adequate quality semen and had scrotal circumference (SC) >/= 30 cm. Reproductive performance was evaluated by the conception rate (CON), conception rate during the first 21 d of the breeding season (21dCON), mean calving date (MCD), and mean calving date of the first half of the herd to calve (HHCD). Correlations were determined between breeding soundness parameters and reproductive performance for all bulls combined, by breed, and by age. The Cp statistic was used to select models for the effects of parameters on CON, 21dCON, MCD and HHCD. Breeding season length and breed had significant effects. The percentages of normal cells, proximal droplets, detached heads and the semen score (motility plus percentage of normal cells) had a significant effect on CON when all bulls were considered. After the effect of season was deleted, the most significant parameter affecting CON in the Brahman was the percentage of detached sperm heads. In the Angus, motility was significantly correlated with all reproductive performance indices. In the Hereford, breeding soundness examination score (BSE) was positively correlated with 21dCON.     

Evaluation of a contract breeding management program in Ohio dairy herds: test day summary and economic measures

A field study was conducted to assess the impact of a contract breeding program that was offered by a breeding co-operative and featured tail chalking and daily evaluation of cows for insemination by co-operative technicians; dairy employees no longer handled estrous detection and insemination activities. From early 2002 until mid-2004, herd-level test day summary records related to production and reproduction were obtained for 32 herds identified as well-managed client herds of the breeding co-operative. Using analyses that controlled for other predictors and random herd-level effects, average days to first service were less by 13 days (P=0.0037) and estrous detection rate was greater by 12% (P=0.0011) for program than for non-program herds. Although first service conception rate was slightly less and the program herds used 0.34 more services per conception (P=0.1488) than non-program herds, the program herds averaged 16 fewer days before pregnancy (P=0.028). Test day summary information and representative estimates of feed, milk, and semen prices were used in a spreadsheet-based model to estimate a partial budget annuity value for an average cow in each herd on each test day. Value of an average cow from a contract herd did not significantly differ from a non-contract herd, even though the analyses suggested an economic benefit for the program herds; the modeling did not, however, account for costs of the program implementation. Additional analyses did not find any significant associations between technician and on days to first service, first service conception rate, estrous detection rate, services per conception, or days open.     

Effectiveness of frozen boar semen under practical conditions of artificial insemination

A technique of boar semen deep-freezing and frozen semen use was tested in practice. 338 sows and 43 gilts belonging to small herds with less than 10 females each were inseminated without oestrus detection by a teaser boar. About 58 % of the inseminated females produced 9.3 piglets per litter. But there were differences between parities. The sows had the highest fertility rate, whereas the gilts showed a significantly lower farrowing rate (59.8% vs 41.9%; P < 0.05). The standing reaction of the female to the back pressure test made by the inseminator and the behaviour of the female during insemination had an effect on the farrowing rate. The best result was obtained after a standing reaction and a behaviour score of 1 (64.5% and 9.6 piglets for farrowing rate and litters size respectively). Farrowing rate for inseminators ranged from 44.3% to 62.4% among inseminators. Farrowing rate for females inseminated with frozen semen from Large-White, Landrace, Pietrain boars was not different, but there were significant differences between the boars. Results showed that insemination with deep-frozen boar semen could be used under practical conditions as an additional technique to the use of fresh semen.     

Effect of sequence of insemination after simultaneous thawing of multiple semen straws on conception rate to timed AI in suckled multiparous Nelore cows

The objective was to determine the effect of sequence of insemination after simultaneous thawing of multiple 0.5 mL semen straws on conception rate in suckled multiparous Nelore cows. The effect of this thawing procedure on in vitro sperm characteristics was also evaluated. All cows (N = 944) received the same timed AI protocol. Ten straws (0.5 mL) of frozen semen from the same batch were simultaneously thawed at 36 °C, for a minimum of 30 sec. One straw per cow was used for timed AI. Frozen semen from three Angus bulls was used. Timed AI records included sequence of insemination (first to tenth) and time of semen removal from thawing bath. For laboratory analyses, the same semen batches used in the field experiment were evaluated. Ten frozen straws from the same batch were thawed simultaneously in a thawing unit identical to that used in the field experiment. The following sperm characteristics were analyzed: sperm motility parameters, sperm thermal resistance, plasma and acrosomal membrane integrity, lipid peroxidation, chromatin structure, and sperm morphometry. Based on logistic regression, there were no significant effects of breeding group, body condition score, AI technician, and sire on conception rate, but there was an interaction between sire and straw group (P = 0.002). Semen from only one bull had decreased (P < 0.05) field fertility for the group of straws associated with the longest interval from thawing to AI. However, the results of the laboratory experiment were unable to explain the findings of the field experiment. Sperm width:length ratio of morphometric analysis was the single sperm characteristic with a significant interaction between sire and straw group (P = 0.02). It was concluded that sequence of insemination after simultaneous thawing of 10 semen straws can differently affect conception rates at timed AI, depending on the sire used. Nevertheless, the effects of this thawing environment on in vitro sperm characteristics, remain to be further investigated.     

Reproductive performance in Ohio dairy herds in the 1990s

The objective of this study was to evaluate trends in reproductive performance in Ohio dairy herds during the 1990s. Stringent criteria for herd inclusion were applied to DHI records to ensure high quality and reliability of the data. The final data set contained 44,425 monthly herd summary records from 1772 herds from years 1992, 1994, 1996 and 1998. Outcomes of interest were calving interval length, calving-to-conception interval, days to first breeding, services per conception and first service conception rate. PROC MIXED in SAS (version 8.1) was used and the monthly records were treated as repeated measures nested within years and herds. First-order autoregressive covariance structure was used to model the covariance between the repeated measures within herds. The data were analyzed for the entire herd as well as for the first lactation cows separately. During the 1990s reproductive performance declined in Ohio dairy herds. Herd average calving interval lengthened from 13.6 to 14.1 months and calving-to-conception interval increased from 136 to 150 days between 1992 and 1998, respectively. Days to first service and number of services increased while first service conception rate declined on a herd level. The reproductive performance of first lactation cows, however, remained constant during this same period. Overall herd reproductive performance was associated with herd size and fat-corrected rolling herd average milk production (FCM). As milk yield increased, first service conception rate decreased and services per conception increased. Larger herds had lower first service conception rate and needed more services per conception, but they started breeding their cows earlier resulting in a slightly shorter calving interval and calving-to-conception interval compared to smaller herds.     

Buffalo Herd Structure and its Repercussions for Condition of Individual African Buffalo Cows

The African buffalo Syncerus caffer was studied in Lake Manyara National Park, Tanzania. Emphasis was placed on the study of (individual) buffalo cows, which live in mixed herds. Buffalo herds are discrete social units and females were never observed in another herd than their own. The herd showed a structure with respect to the distribution of sex-age classes. Individual cows generally kept the same location within the herd. The location in the herd appeared to be coupled to food intake and was strongly related to physical condition. The best location (highest intake and best condition) was between the front and the centre of the herd, the worst location was the rear of the herd (when moving or grazing). Females with calves appeared to have the highest position in the hierarchy as determined from the rate of displacement over food; adult bulls did not interact with cows. Few births were observed during the late dry season and it appears that there is a calving peak at the end of the long rains. Conception rate increased when cows increased in condition and dropped when cows lost condition. Cows showed a strong seasonality in condition but bulls on average hardly changed in condition, except for a loss in condition during the inferred conception peak. Buffalo herds in Manyara showed a fusion-fission pattern independent of season but strongly influenced by the size of the herd: large herds split more often than smaller ones. In large herds, buffalo grazed closer together than in small herds and it appeared likely that competition was more severe in large herds. Animals in the rear of a large herd lost condition faster during the dry season than animals in the best location in the herd, and especially cows in the rear split off most frequently from the herd to graze in a smaller fragment. From the literature on cattle, it is inferred that the reproductive success of cows in the rear of the herd will be lower than of cows in the best location, and this differential is confirmed by the behaviour of adult bulls. It is as yet unclear what the advantage is for adult cows in the rear of a large herd to stay in that herd but the sharing of information with more successful individuals seems a good candidate.     

Biomarkers of in vivo fertility in sperm and seminal plasma of fertile stallions

The global proteome of sperm and seminal plasma of fertile stallions was investigated to determine whether associations with relative in vivo fertility exist. Seven stallions at stud in a commercial breeding station were collected throughout the breeding season and bred to a total of 164 mares to determine conception rates. On three occasions during the breeding season, raw semen was obtained from a regular collection for proteomic analysis using two-dimensional electrophoresis and also assessed for routine semen quality end points. First cycle conception rate was negatively related to ejaculate volume (r = −0.43, P = 0.05) and total IGF1 content (ng) per ejaculate (r = −0.58, P = 0.006), whereas overall pregnancy rate was positively related to sperm concentration (r = 0.56, P = 0.01). The abundance of three proteins known to be involved in carbohydrate metabolism in sperm was positively related to fertility. Furthermore, the abundance of four seminal plasma proteins were identified as being negatively related to fertility; these were identified as kallikrein-1E2 (KLK2), clusterin, and seminal plasma proteins 1 (SP1) and 2 (SP2). Abundance of cysteine-rich secretory protein 3 (CRISP3) was positively related to first cycle conception rate (r = 0.495, P = 0.027) and may provide a good marker of fertility. Based on stepwise regression analysis, clusterin and SP1 in seminal plasma together with sperm citrate synthase were predictive of fertility (r = 0.77, P < 0.0001). This study identified proteins within sperm and seminal plasma that could serve as biomarkers of semen quality and fertility in stallions.     

Reproductive performance of lactating dairy cows following estrus synchronization regimens with PGF2alpha and progesterone

The objective of this study was to evaluate the reproductive performance of lactating cows in seasonal dairy herds after estrus synchronization with PGF2alpha (PG) with or without supplementation with progesterone (P4). In Trial 1, synchronized cows (S1; n = 521) were compared with untreated control cows (C; n = 518) in 5 herds. Estrus of cows in the S1 group was synchronized with 2 treatments of PG (Lutalyse) 13 d apart. The breeding season started 2 d after the second PG. Cows were first bred by AI for 7 wk and then herd sires were used. Compared with C cows, estrus synchronization in the treated cows reduced the conception rate to first AI (61.1 vs 70.5%; P < 0.01) and the intervals from start of the breeding season to conception for cows conceiving to AI (11.0 vs 14.6 d; P < 0.05) or to both AI and natural mating (16.5 vs 18.4 d; P < 0.05). There was no effect on conception rate to second AI (68.8%), on pregnancy rate by Day 24 (72.3%) or Day 49 (86.3%) of the breeding season, or on the percentage of cows not pregnant at end of the breeding season (5.0%). In Trial 2, effects of P4 supplementation before the second PG on reproductive performance were evaluated in 4 herds. Estrus of each cyclic cow was synchronized with PG as in Trial 1. Half of the cows in each herd were treated with an intravaginal P4 device (CIDR) for 5 d before the second PG (S2+P4, n = 608), whereas the remaining half received no CIDR treatment (S2, n = 593). Compared with S2 cows, P4 treatment increased the estrous response rate to the second PG (89.6 vs 82.9%; P < 0.01), the conception rate to first AI (65.1 vs 59.7%; P = 0.07), the pregnancy rate by Day 6 of the breeding season (59.3 vs 49.0%; P < 0.001), and reduced the intervals from start of the breeding season to conception for cows conceiving to AI (8.6 vs 10.4 d; P < 0.10) or to both AI and natural mating (12.7 vs 16.4 d; P < 0.01). Treatment with a used CIDR from Days 16 to 21 after start of breeding to re-synchronize returns to service had no effect on conception rate to first or second AI but may decrease the conception rate to second AI in cows previously treated with CIDR. In conclusion, estrus synchronization with the double PG system can reduce fertility, while P4 supplementation for 5 d before the second PG can improve estrous response and overall reproductive performance. Stage of the estrous cycle at the time of the second PG can affect fertility following synchronization.     

Field fertility with exported boar semen frozen in the new flatpack container

The present study tested the field fertility of frozen-thawed (FT) Swedish boar semen packaged in flat plastic containers (FlatPacks) and exported for artificial insemination (AI) to overseas nucleus herds. Semen from 47 Swedish boars of Landrace (L), Yorkshire (Y), and Hampshire (H) breeds was frozen using a lactose-egg yolk-based extender with 3% glycerol and 10(9) spermatozoa/ml in 5 ml FlatPacks. For all breeds, FT sperm membrane intactness averaged 60%, while mean FT sperm motility ranged from 49 to 53%. A total of 308 litters resulted from 421 overseas inseminations with FT semen, with a mean farrowing rate (FR) of 73% and 10.7 mean number total piglets born. In a within-sow analysis for the purebred L and Y breedings, the FR and litter size of FT semen were compared with natural matings (NM) and on-farm AI with liquid semen (NW/AI breedings) at the same farms. Farrowing rate was 72.3 and 78.8% (P = 0.23), total piglets 11.3 and 11.6 (P = 0.44), and live piglets 10.1 and 10.2 (P = 0.77), for the FT semen and NM/AI breedings, respectively. The present results suggest that this freezing protocol and FlatPack container maintains high sperm viability post-thaw. Further the fertility levels when inseminated at overseas nucleus herds seem to be similar to those achieved with (NM/AI breedings) at the same farms. This freezing method may be a reliable alternative for the freezing/thawing of boar semen under commercial AI conditions.     

Effect of centrifugal fractionation protocols on quality and recovery rate of equine sperm

Centrifugal fractionation of semen is commonly done to improve quality of human semen in assisted-reproduction laboratories, allowing sperm separation based on their isopycnic points. Sperm with morphologic abnormalities are often more buoyant, promoting their retention above defined density media, with structurally normal sperm passing through the media following centrifugation. Three experiments were conducted to evaluate the effects of density-medium type, centrifuge-tube size, sperm number, and density-medium volume (column height) on stallion sperm quality and recovery rate in sperm pellets following centrifugation. In all three experiments, equine semen was initially centrifuged to increase sperm concentration. In Experiment 1, semen was layered over continuous or discontinuous gradients. For Experiment 2, semen was layered over three column heights of continuous gradients in 15- or 50-ml conical-bottom tubes. For Experiment 3, increasing sperm numbers were layered over continuous gradient in 15- or 50-ml conical-bottom tubes. Following centrifugation, sperm pellets were evaluated for sperm morphologic quality, motility, DNA integrity, and recovery rate. Centrifugal fractionation improved (P < 0.05) sperm morphology, motility, and DNA integrity, as compared to controls. The continuous gradient increased (P < 0.05) sperm recovery rate relative to the discontinuous gradient, whereas sperm processed in 15-ml tubes yielded higher velocity and higher recovery rates (P < 0.05 for each) than that processed in 50-ml tubes. Sperm recovery rate was not affected (P > 0.05) by column height of gradient. Increasing sperm number subjected to gradient centrifugation decreased (P < 0.05) sperm recovery rate when 15-ml tubes were used.     

Influence of centrifugation or low extension rates prefreezing on the fertility of ram semen after cervical insemination

We compared the fertility of thawed ram semen, frozen according to different prefreezing semen handling protocols and previously well-defined in vitro, after cervical artificial insemination (AI) during natural estrus in Corriedale sheep. Following primary extension 1 + 1, we adjusted the final sperm concentration before packaging (200 x 10(6)/straw) either by centrifugation, in order to reconcentrate the extended semen (Protocol 1: P1), or without centrifugation, by adjusting the final sperm number by stepwise extension (Protocol 2: P2). We evaluated sperm motility (assessed both subjectively and with a computer-assisted sperm analysis instrument [CASA]), membrane integrity (SYBR-14/PI), and capacitation status (chlortetracycline [CTC]) in vitro in three pooled straws of frozen-thawed semen. Three hundred Corriedale ewes, having shown spontaneous estrus during the breeding season (i.e., April, in the southern hemisphere) under extensive management conditions in Uruguay, were cervically inseminated with thawed semen from the same freezing operations as studied in vitro. The semen evaluation in vitro yielded higher percentages (P < 0.05) of damaged spermatozoa in the samples where sperm numbers were adjusted by extension before freezing (P2), compared with when adjustment was done by centrifugation (P1). However, due to the higher sperm concentration finally achieved by P2, the calculated total number of viable spermatozoa was almost equal in the two AI doses. We observed no differences in fertility between P1 and P2 for either nonreturn rates (NRRs) 21 (30.8 vs. 29.7%) and 36 (28.5 vs. 27.8%) days after AI or lambing rate (21.9 vs. 21.4%), respectively. Fertility did not differ significantly between the two different procedures of adjusting sperm numbers prior to freezing. This may indicate that the simplified protocol with adjusted extension of the semen, resulting in higher numbers of viable spermatozoa, should be the procedure of choice when freezing ram semen under field conditions. Further studies aimed at improving the modified protocol need to be performed.     

Effect of cryopreservation methods and precryopreservation storage on bottlenose dolphin (Tursiops truncatus) spermatozoa

Research was conducted to develop an effective method for cryopreserving bottlenose dolphin (Tursiops truncatus) semen processed immediately after collection or after 24-h liquid storage. In each of two experiments, four ejaculates were collected from three males. In experiment 1, three cryopreservation methods (CM1, CM2, and CM3), two straw sizes (0.25 and 0.5 ml), and three thawing rates (slow, medium, and fast) were evaluated. Evaluations were conducted at collection, prefreeze, and 0-, 3-, and 6-h postthaw. A sperm motility index (SMI; total motility [TM] x % progressive motility [PPM] x kinetic rating [KR, scale of 0-5]) was calculated and expressed as a percentage MI of the initial ejaculate. For all ejaculates, initial TM and PPM were greater than 85%, and KR was five. At 0-h postthaw, differences in SMI among cryopreservation methods and thaw rates were observed (P < 0.05), but no effect of straw size was observed. In experiment 2, ejaculates were divided into four aliquots for dilution (1:1) and storage at 4 degrees C with a skim milk- glucose or a N-tris(hydroxymethyl)methyl-2-aminoethane sulfonic acid (TES)-TRIS egg yolk solution and at 21 degrees C with a Hepes-Tyrode balanced salt solution (containing bovine albumin and HEPES) (TALP) medium or no dilution. After 24 h, samples were frozen and thawed (CM3, 0.5-ml straws, fast thawing rate) at 20 x 10(6) spermatozoa ml(-1) (low concentration) or at 100 x 10(6) spermatozoa ml(-1) (standard concentration). The SMI at 0-h postthaw was higher for samples stored at 4 degrees C than for samples stored at 21 degrees C (P < 0.001), and at 6-h postthaw, the SMI was higher for samples frozen at the standard concentration than for samples frozen at the low concentration (P < 0.05). For both experiments, acrosome integrity was similar across treatments. In summary, a semen cryopreservation protocol applied to fresh or liquid-stored semen maintained high levels of initial ejaculate sperm characteristics.     

Insemination factors affecting the conception rate in seasonal calving Holstein-Friesian cows

Differences in conception rate to first service between artificial inseminations (AI) carried out by commercial AI operators (CAI) or do-it-yourself operators (DIY), between natural service (NAT) and AI, between different AI sires, and between fresh and frozen-thawed semen, on Irish commercial dairy farms, were studied using logistic regression. The study comprised 12,933 potential first inseminations from 77 spring-calving dairy herds. The data were recorded during 1999 and 2000. Amongst the total, 4,394 cows had repeated records across the two years. Adjustment variables included: herd, year, parity, calving period, calving to service interval, herd size, proportion of North American Holstein-Friesian genes, peak milk yield, semen fresh or frozen-thawed status, AI sire and a cow history variable to account for the correlation structure that may exist between performance records of cows present in both years of the study. Interactions of interest were tested but were non-significant. No significant association was observed between the category of AI operator and the likelihood of conception rate to first service (PREG1). The variation in PREG1 observed within the category of operator (CAI and DIY) was investigated using the Levene test for homogeneity of variance. There was no difference between the level of variation observed within CAI and DIY operators. There were significant differences in the likelihood of PREG1 between different AI sires. Amongst the 40 most commonly used AI sires, 3 sires had a lower likelihood of PREG1 (P < 0.05) when compared to the reference AI sire (sire with PREG1 similar to the mean of the group). There was a tendency for a reduced likelihood of PREG1 with the use of fresh semen compared to frozen-thawed semen (OR = 0.80, P = 0.067). Amongst the adjustment variables in the model, those significantly associated with the likelihood of PREG1 included the herd, calving period, calving to first service interval and peak milk yield. No significant difference in the likelihood of PREG1 was observed between AI and NAT.     

Danish A.I. field data with sexed semen

The objective of this study was to compare conception rates, non-return rates and sex ratios of sexed and conventional semen from the same sires in commercial dairy herds in Denmark. The semen was produced from three bulls from each of the three major dairy breeds in Denmark: Holstein, Jersey and Danish Red Dairy Breed (nine bulls total), in order to answer questions on breeds differences in field results. AI was performed by trained technicians using a minimum of 150 doses of sorted sperm and 50 control doses from each bull. During the trial, a total of 2087 doses were used in 63 herds.The trial showed that the conception rate using sorted semen was 5% points lower than with conventional doses for Danish Reds, 7% points for Jerseys, and 12% points for Holsteins. Translating this into non-return rate revealed differences of 10-20% points among bulls. These differences are thought to be a good indicator of what to expect from commercial use of sexed semen.The sex ratios varied from 89% to 93% female calves among breeds, which on average is consistent with the theoretical average sex ratio of 93% females considering the low number of inseminations.     

Effect of semen collection method (artificial vagina vs. electroejaculation), extender and centrifugation on post-thaw sperm quality of Blanca-Celtibérica buck ejaculates

The aim of this study was to evaluate the effect of semen collection method (artificial vagina compared to electroejaculation), season in which the semen was collected (breeding season compared to non-breeding season), freezing extender (Biladyl(?), Andromed(?) and skim milk based extender) and pre-treatment procedure (washing compared to non-washing) on post-thaw semen quality in buck. Ejaculates from seven bucks of the Blanca-Celtibérica breed were collected by artificial vagina and electroejaculation during the breeding (July to December) and non-breeding season (January to June). Samples were split in two aliquots and one of them was washed. Three freezing extenders were evaluated on washing and non-washing sperm samples. Ejaculates collected by artificial vagina had a greater sperm quality after thawing, with greater values (P≤0.05) for SM (sperm motility), NAR (acrosome intact), YO-PRO-1-/PI- (intact spermatozoa), and Mitotracker+/YO-PRO-1- (spermatozoa with active mitochondria) and lower % DFI (DNA fragmentation index). Thawed sperm samples which were collected during the breeding season had greater values (P≤0.05) for NAR, intact spermatozoa and spermatozoa with active mitochondria, than those semen samples obtained during the non-breeding season. Semen freezing with Biladyl(?) and Andromed(?) resulted in a greater sperm quality (P≤0.05) after thawing in relation to milk-based extender. Washing procedure had no effect on sperm parameters assessed at thawing. Results from the present study suggest that the success of semen cryopreservation in Blanca-Celtibérica goat depends on semen collection method and season, as well as on the extender used. Thus, the post-thaw sperm quality will be greater (P≤0.05) when samples are collected by artificial vagina during the breeding season and when Biladyl(?) or Andromed(?) are used as freezing extenders.     

Assessment of the post partum Reproductive Performance of the Icelandic Dairy Cow During a 3 Year Period

The time of ovulation, artificial insemination (AI), conception and conception rate were studied in 412 Icelandic dairy cows from 2 different areas during a period of 3 years. To assess these parameters the progesterone level was measured in sequential samples of milk and the status of the genital organs evaluated by monthly rectal palpations. The time and number of AI was recorded and the conception rate calculated and compared with the other parameters. Furthermore, the length of the calving interval and gestation period were determined. The effects of year, season, area, age, herd and parity on these parameters were evaluated. The overall mean for the time of first post partum ovulation was 42 days and varied from 29 to 49 days between herds. This is a considerably longer time than recorded for many other breeds of dairy cows. The effects of season, area and herd were significant for the time of first post partum ovulation. The overall time of first post partum AI and conception were 74 days and 97 days, respectively. In spite of late onset of ovarian activity in Icelandic dairy cows, these two pararmeters are comparable to those of other breeds of cattle. The effects of season, parity and herd were significant for these two parameters. The conception rate to first post partum AI was 59% and the number of AI per conception was 1.6. The time of conception correlated closely (r = 0.5) with the time of first post partum AI, but the conception rate to first AI increased and the number of AI per conception decreased with increasing time of first post partum AI. The calving interval was 382 days and the gestation period was 287 days.     

Economics of selecting for sex: the most important genetic trait

Over 20,000 calves have resulted from artificial insemination (AI) of cattle with sexed, frozen/thawed sperm in the course of experimentation in several countries, and from commercial sales in the United Kingdom. This technology likely will become commercially available in many countries within a few years. Accuracy of the process is about 90% for either sex, and resulting calves appear to be no different from non-sexed controls in birthweight, mortality, rate of gain, and incidence of abnormalities. The main determinants of the extent of use of sexed sperm will be pregnancy rate and cost. Fertility of low doses (1.5 x 10(6)-2 x 10(6)) of sexed, frozen sperm for AI of heifers usually has been in the range of 70-80% of unsexed sperm at normal doses (10 x 10(6)-20 x 10(6) sperm) in well managed herds; it has been lower in poorly managed herds, and likely will be lower with lactating dairy cows. It is expected that fertility of sexed sperm will increase significantly due to very recent improvements in the hydrodynamics of the sexing process and potential improvements in cryopreservation procedures. It is unclear how sexed sperm will be priced; the cost of sexed sperm for cattle will likely be more than double the cost of unsexed sperm in most markets. The economic benefit of using sexed sperm also will depend on the baseline fertility of the herd since at lower fertility, it takes more doses of semen per calf produced. It is noted that for a small percentage of elite cattle, the economics of using sexed sperm do not depend primarily on increased production or efficiency of producing meat or milk, but rather on factors such as scarcity, tradition, cattle show winnings, and biosecurity during herd expansion. Until sorting efficiencies improve and costs decline, sales likely will be limited primarily to these niche markets. With near normal fertility and a premium for sexing in the range of US$ 10 per insemination dose, sexed sperm likely would become economically and environmentally beneficial for many, if not most populations of cattle being bred by AI.     

Site of semen deposition in cattle: a review

The breeding of cattle using conventional artificial insemination methods involves the deposition of semen in the uterine body. However, it has been recently proposed by several authors that the site of semen deposition be changed to the uterine horns. This suggestion is based on 2 facts: the acceptance that the major preovulatory sperm reservoir may be the uterotubal junction rather than the cervical canal, and the lack of accuracy by inseminators in depositing semen. In over 50% of cases, inseminators were not sufficiently trained to deposit semen into the uterine body, so that intracervical insemination was often performed resulting in reduced fertility. The advantage of deep uterine insemination, whether bicornual or unicornual, is that it favors the deposition of semen nearer to the uterotubal junction and thus reduces the incidence of cervical deposition. This review updates the literature on the ideal site of semen deposition, including cervical, uterine body, cornual and intraperitoneal. Also analyzed are the effects of right vs. left side activity of the female reproductive tract on the optimum site of semen deposition as it affects fertilization. Finally, the question of whether the clinical training of inseminators should be reevaluated is discussed.     

The effect of straw size, freezing rate and thawing rate upon post-thaw quality of dog semen

Optimal freeze-thaw processes for dog semen will yield a maximal number of insemination doses from an ejaculate. The objectives of this study were to compare the effects of two straw sizes (0.25- and 0.5-mL French), two freezing rates (straws suspended 3.5 and 8 cm above liquid nitrogen) and two thawing rates (in water at 37 and 70 degrees C) upon post-thaw quality of dog semen, and to determine the best treatment combination. Quality was expressed in terms of the percentage progressively motile sperm 5 and 60 min after thawing and the percentage of abnormal acrosomes 5 min after thawing. One ejaculate from each of eight dogs was frozen. Two straws from each ejaculate were exposed to each of the eight treatment combinations. Data were analyzed by means of a repeated measures factorial analysis of variance and means compared using Bonferroni's test. Dog affected each response variable (P < 0.01). Neither straw size, nor freezing rate, nor thawing rate affected motility 5 min after thawing (P > 0.05). Half-milliliter straws resulted in 5.7% more progressively motile sperm 60 min after thawing and 6.5% fewer abnormal acrosomes than 0.25-mL straws (P < 0.05, n = 64). The percentage progressively motile sperm 60 min after thawing tended to be higher for semen thawed at 70 degrees C compared to 37 degrees C (P < 0.06, n = 64). Semen thawed in water at 70 degrees C had 6.6% fewer abnormal acrosomes than semen thawed in water at 37 degrees C (P < 0.05, n = 64). Freezing rate interacted with thawing rate (P < 0.05) in their effects upon acrosomal morphology and freezing 8 cm above liquid nitrogen and thawing in water at 70 degrees C was best. Dog semen should be frozen in 0.5-mL straws, 8 cm above liquid nitrogen and thawed in water at 70 degrees C.