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PubMed1982

Use of boar spermatozoa for artificial insemination. II. Fertilizing capacity of fresh and frozen spermatozoa in gilts inseminated either at a fixed time or according to Walsmeta readings.

A fertility trial was conducted comparing two methods of defining the optimum time to inseminate frozen boar semen. One hundred sixty-four gilts were inseminated, one-half at a fixed insemination time of 32 to 34 h after calculated onset of estrus and the remainder were inseminated on the basis of changes in the vaginal mucosal electrical resistance. Inseminations were made when the instrument (an inversely scaled ohmmeter) reading fell between 54 to 64 on a scale of 1 to 100. Both fresh and frozen boar semen were used. Pregnancy rates and live embryos/gilts from inseminations made at the fixed time and inseminations made on the basis of ohmmeter readings did not differ significantly for either fresh of frozen-thawed spermatozoa. Pregnancy rates and number of live embryos/gilt were significantly higher for gilts inseminated with fresh spermatozoa than for those inseminated with frozen-thawed spermatozoa (82%, 11.6 vs 61%, 8.2, respectively). Inseminations were conducted from January to September. Pregnancy rates were significantly higher for inseminations made for the first quarter or the year (January, February and March) than for inseminations made for the third quarter (July, August and September). No benefit was derived from using an ohmmeter to time insemination with frozen-thawed boar spermatozoa.

Animals↗
PubMed1984

Radiographic evaluation of bovine artificial inseminating technique among professional and herdsman-inseminators using .5- and .25-ml French straws.

Using radiography, inseminating syringe tip location and inseminate distribution in excised bovine reproductive tracts were described for 20 professional and 20 herdsman-inseminators using .5- and .25-ml French straws. Inseminations (20 by each participant) were performed in tracts placed on a device that stimulated the anatomical position of the reproductive organs in vivo. A computer-coupled graphics information digitizer was used to quantitate the precise location of the syringe tip and to estimate the distribution of radiopaque inseminate within the tract from each pair of radiographs. Neither category of inseminator (professional or herdsman) nor volume of inseminate (.5 vs .25 ml) influenced (P greater than .05) syringe tip placement or subsequent distribution of the radiopaque inseminate within the tract. The proportion of syringe tip placements in various anatomical locations (586 attempts) were: uterine body, 39%; cervix, 25%; left uterine lumen, 13% and right uterine lumen, 23%. The variability among inseminators was high, with the ability to position the syringe tip in the uterine body ranging from 0 to 85% of the 20 attempts. Among all inseminators, 82% were unable to place the syringe in the uterine body greater than 60% of the time. When averaged across all inseminations (n = 666), 40% of the inseminate was located in the uterine body and(or) equally distributed in the uterine lumina. The remainder of the inseminate was located in the cervix (17%) or disproportionately in one uterine lumen (43%). Syringe tip placement in the uterine body was correlated (r = .73; P less than .05) with the proportion of inseminate located in the uterine body and(or) equally distributed to the lumen of both uterine horns. Measurements of various anatomical components of the reproductive tract were made from the first radiograph. The means were: cervical diameter, 5.9 cm; length from internal cervical os to external uterine bifurcation, 16.4 cm; uterine body length, 1.7 cm and uterine body surface area, 3.6 cm2. There was no relationship between the palpable anatomical components and uterine body size.

Animals↗
PubMed1981

Rates of conception by artificial insemination of dairy cattle.

Over 41 mo, 1004 first and second service inseminations were evaluated in Holstein cows and heifers of breeding age. Cattle were inseminated either at the end of the heat check in which they were observed in heat (0 h) or at the end of the next heat check (12 h). Rate of conception was affected by estrous behavior at 12 h, site of semen placement in the reproductive tract, sire, and environmental temperature the day after insemination. Service number, time of day at which insemination occurred, inseminator, and timing of insemination in relation to the onset of estrus had no effect on fertility. With twice daily heat checks, a single daily service produced acceptable rates of conception.

Animals↗
PubMed1989

Use of B-mode, linear array ultrasonography for evaluating the technique of bovine artificial insemination.

B-Mode, linear array ultrasonography was used to evaluate the site of semen deposition in live cows. The insemination sheath was modified to hold a brass bead that was deposited at the simulated site of semen deposition. The position of the bead was identified by ultrasonography and the bead was recovered by pulling a nylon line that was attached to the bead. An ultrasound technician identified placement of the bead in the site designated for semen deposition by a skilled inseminator in 24 of 25 cases. This procedure improves methods for inseminator training by providing a method of evaluating insemination technique using live animals rather than excised reproductive tracts. The ultrasound equipment used for inseminator evaluation is affordable, portable, and does not pose a human health risk.

Animals↗
PubMed1992

Estimates of genetic trend in an artificial insemination progeny test program and their association with herd characteristics.

Individual lactation records from Holstein cows in 3449 herds participating in an AI stud's young sire sampling program from 1971 to 1987 were used to characterize the sampling program and to estimate genetic merit and trend. Average genetic merit of cows in sampling program herds was consistently superior to the average genetic merit of cows in the US population. Genetic trend of sires of first-crop cows was 58 kg of milk and 1.5 kg of fat/yr from 1971 to 1978 and 176 kg of milk and 5.5 kg of fat/yr from 1979 to 1987. The average genetic merit of sires of first-crop cows born after 1983 was equivalent to or exceeded the genetic level of sires of other cows in the herd. Within-herd-year means and standard deviations of yield, genetic evaluation, and management traits (herd-year characteristics) were computed for a subset of 341 herds contributing first-crop daughters for at least 10 yr. The average of each herd-year characteristic during 10 or more years was used to predict within-herd genetic trend. Herd characteristics explained up to 51% of differences in within-herd genetic trends. Average sire genetic merit of daughters other than first-crop daughters accounted for up to 80% of the explained differences. Other herd characteristics suggested that herds with larger within-herd standard deviation milk yields, a larger number of young sires represented, younger cows, and greater percentage of cows sired by AI sires made greater genetic improvement. Results indicated that the average genetic merit of cows and the rate of within-herd genetic improvement are higher in herds that participate in a young sire sampling program.

Animals↗
PubMed1994

Use of milk progesterone and prostaglandin F2 alpha in a scheduled artificial insemination program.

We tested the efficacy of monitoring progesterone in dairy cows using a commercially available milk progesterone test as a determinant for administration of PGF2 alpha to induce estrus in cows before first AI. Holstein cows milked twice daily were assigned randomly for AI at their first estrus after d 42 postpartum (control) or to receive PGF2 alpha after a milk progesterone test. Milk progesterone was assessed in samples from the Monday morning milking in both groups of cows, but only those in the treatment received PGF2 alpha when milk progesterone tested high. Blood was collected before injection of PGF2 alpha on Monday afternoon to verify retrospectively the accuracy of the milk progesterone test. Agreement of serum concentrations of progesterone was 87% for high milk progesterone tests and 63% for low tests. Use of milk progesterone plus PGF2 alpha reduced days to first AI, calving intervals, rate of reproductive culling, and cost per pregnancy and increased the proportion of cows inseminated within 21 d of the beginning of breeding. As a management tool in an AI program, PGF2 alpha use is warranted and cost effective. However, the milk progesterone test is not justifiable unless the cost is significantly lower than the cost of a weekly injection of PGF2 alpha.

Animals↗
PubMed1994

Timing of artificial insemination of dairy cows: fixed time once daily versus morning and afternoon.

Nonreturn rates to professional technician service of 7240 first AI Holstein cows were calculated to evaluate differences between once daily and a.m.-p.m. AI. To determine whether management practices affected nonreturn rates, participating herd owners were surveyed for methods used for detection of estrus. Nonreturn rates for once daily and a.m.-p.m. AI were 64.6 and 65.6% for 60-d, 60.1 and 60.6% for 75-d, and 58.4 and 57.8% for 90-d nonreturn periods. Signs of estrus for AI and interval from detection of estrus to AI were related to nonreturn rates. Nonreturn rate was highest, 63.4%, when cows were in standing estrus. Nonreturn rates were lowest, 36%, when cows were bred after treatment with PGF2 alpha without being detected in estrus or bred strictly on veterinary advice based on palpation. Nonreturn rates were similar for different times of the day when once daily AI was practiced. However, AI in the midmorning may have some advantages. The highest nonreturn rate for a 3-h period was 68.2% for 0800 and 1100 h; the lowest was 54.7% for 1300 to 1600 h. Movement before observation for estrus and an observation period > 15 min improved nonreturn rates for once daily AI. Once daily AI can be used effectively with no difference from the traditional a.m.-p.m. system; results are best when AI is based on standing estrus and performed between 0800 and 1100 h.

Animals↗
PubMed1996

Optimal size of progeny groups for progeny-testing programs by artificial insemination firms.

A semi-stochastic model for the simulation of genetic improvement in a dairy cattle population was used to evaluate and optimize progeny-testing programs for AI firms that operate in a competitive market for semen from progeny-tested bulls with regard to number of bulls sampled and size of progeny groups. The population was serviced by four firms. The competition for market share and semen sales was determined by the relative rank of progeny-tested bulls from a firm based on EBV for a trait with a heritability of 25%. For a fixed total number of daughters from young bulls for an AI program (test capacity), optimal size of the progeny groups was highly dependent on the objective to be maximized. The rate of genetic gain was maximized with a progeny group of 57 to 61 daughters per bull, but was relatively robust to changes in size of progeny groups. The number of marketable bulls was maximized with progeny groups between 20 and 40 daughters, depending on the test capacity. However, when a relationship between price per dose of semen and EBV of marketable bulls was considered, returns from semen sales were maximized at 49 and 82 daughters per bull, respectively, for linear and quadratic functions for semen price. The critical objective, net returns from semen sales, subtracting costs of sampling bulls, was maximized for progeny groups of between 95 and 105 daughters. Optimal size of progeny groups was robust to changes in economic parameters and the breeding programs of competitors. For economic parameters that were typical for Canadian AI firms, net returns per annual cohort of young bulls were 40% higher for the optimal size of the progeny groups than for sampling with 60 daughters per bull.

Animals↗
PubMed1997

Relationship between body condition scores and conception at first artificial insemination in a large dairy herd of high yielding Holstein cows.

This study investigated the relationship between changes in body condition during the dry period and early lactation and conception to first postpartum AI. Holstein cows (n = 720) on a commercial dairy farm were scored weekly for body condition beginning at dry-off and continuing until first AI. Occurrence of postpartum diseases was recorded. A multiple logistic regression model was a significant predictor of the success or failure of conception for multiparous cows, but not for primiparous cows. Principal component analysis reduced collinearity among independent variables and allowed the variables to be ranked based on their contribution to the interval from first AI to conception. The top three ranking variables were lactation number, milk yield at 120 d of lactation, and change in body condition score between parturition and wk 4 of lactation. Increased milk yield at 120 d of lactation was associated with an increased likelihood of conception, and decreased body condition during the 1st mo of lactation was associated with a decreased likelihood of conception. Health problems were less associated with conception than were body condition or milk yield in this herd. Body condition during the dry period and during the first 30 d of lactation is an important tool to identify cows at risk for failure to conceive at first AI.

Adipose Tissue↗
PubMed1997

Usability for genetic evaluations of records from herds participating in progeny test programs of artificial insemination organizations.

Thirteen AI organizations provided identification of herds that participated in their progeny test programs in 1989 and 1990; 15% of those herds participated in programs of more than one AI organization, but only 2.6% participated in programs of more than two AI organizations. Of the 19,589 participating herds, 82 and 76% were enrolled in DHI test plans that were considered to be usable for genetic evaluations during 1991 and 1992. For herds that had participated in AI progeny test programs, mean percentages of usable records were 77% in 1991 and 78% in 1992; the mean percentages of usable records for nonparticipating herds were 62% in 1991 and 60% in 1992. Participating herds had larger mean herd sizes, higher means and standard deviations of milk yields, younger cows, and a lower percentage of registered cows than did nonparticipating herds. Analysis of variance was used to explain the variation in the percentage of records that were usable for genetic evaluations. Herds that participated in AI progeny test programs or that had smaller herd sizes, higher mean milk yields, younger cows, or larger percentages of registered cows had higher percentages of records that were usable for genetic evaluations. Improved usability of records for genetic evaluations would increase the efficiency of AI progeny testing, and consideration of herd characteristics associated with higher percentages of usable records should aid AI organizations in evaluating prospective herds for progeny test programs.

Animals↗