Biomedical subjects

V L Christensen

Publications and source records attributed to V L Christensen.

At least 73 records · Page 4Linked to original sources

PubMed1989

Efficacy of fertilization in artificially inseminated turkey hens.

Research was conducted to develop an artificial insemination protocol optimizing the use of spermatozoa by turkey breeder hens. Large White turkey hens were inseminated on Days 14 and 17 postphotostimulation with 200 million spermatozoa from one male phenotype to fill the oviductal storage sites. Artificial inseminations were then performed weekly for 20 wk with different spermatozoa numbers of another male phenotype. Fertility and phenotype of each poult were determined at hatch to ascertain which insemination, initial or subsequent, was responsible for fertility. Inseminating weekly with 200 million viable spermatozoa cells resulted in better fertility but did not optimize the hen's utilization of spermatozoa from the initial inseminations. When fewer spermatozoa were inseminated weekly (50 million cells), more progeny were fertilized by spermatozoa already residing in the oviduct than would be expected. When the number of spermatozoa inseminated weekly was increased at intervals during a laying cycle, spermatozoa from the initial inseminations were utilized more efficiently, but fertility was depressed at times during the laying cycle. Gradually increasing weekly inseminated numbers of spermatozoa from 50 to 200 million viable cells/hen as the hens age results in nearly equivalent fertility to that resulting from insemination by 200 million cells each week. This represents a savings of 1.4 billion spermatozoa/hen over a 20-wk laying period.

Animals↗

PubMed1989

Effect of different protein levels fed during the prebreeder period on performance of turkey breeder hens.

An experiment was conducted to examine the effects of prebreeder protein intake on subsequent reproductive performance and to examine body weight, feed consumption, and body composition changes due to aging in Large White turkey breeder hens. One hundred twenty-nine Hybrid Large White turkey breeder hens were fed either 12, 15, or 18% CP diets (2,882 kcal ME/kg) during the prebreeder period from 24 to 32 wk of age. All hens were photostimulated with 15.5 h light/day and fed a standard 16% protein breeder ration from 32 to 55 wk of age. Prebreeder protein intake increased linearly as dietary protein increased. Treatments did not affect body weight, body composition, egg production, feed consumption, fertility, hatch of fertile eggs, or percentages of early or late dead. Body weight increased from 24 to 55 wk in a cubic response to age. Percentage of carcass moisture decreased, whereas percentage of carcass fat increased from 24 to 55 wk in a quadratic response to age. Prebreeder and breeder feed consumption were not significantly affected by treatment or age. This experiment is evidence that a 12% protein prebreeder ration is adequate for subsequent reproductive performance; observed effects of age on body characteristics agree with published data.

Animal Feed↗

PubMed1988

Improved hatchability of turkey eggs at high altitudes due to added oxygen and increased incubation temperature.

Turkey egg hatchability at high altitudes was examined at two different oxygen tensions and two incubation temperatures. Incubating turkey eggs in a 149-torr oxygen environment at 37.7 C gave significantly better hatchability than a 109-torr oxygen environment at 37.5 C. Embryonic mortality data indicated that the higher incubation temperature in combination with increased oxygen tension decreased embryonic mortality during the 3rd and 4th wk of incubation and resulted in higher hatchability. The data suggest that hatchery managers at high altitudes should supplement with oxygen and incubate turkey eggs at higher temperatures than employed at lower altitudes.

Altitude↗

PubMed1987

The posthatch physiology of the turkey poult--I. Growth and development.

Daily body, heart, liver, spleen, pancreas and bursa of Fabricius weights of developing turkey poults were measured. Neither organ nor body weight was affected by sex of the poults during the first 10 days posthatch. Decreases in growth were apparent between days 3 and 6 or 7 and 9 posthatch and coincided with peaks in early mortality.

Aging↗

PubMed1987

The posthatch physiology of the turkey poult--II. Hematology.

Packed cell volume, total leukocytes, total erythrocytes, hemoglobin, mean cell volume and mean corpuscular hemoglobin concentration of the poult were analyzed daily for the first 10 days posthatch. Sexually dimorphic effects on hematological parameters were not apparent, but there was a sex X day interaction for all parameters except hemoglobin indicating that males were slower to develop/respond to critical stimuli. The study revealed a latency in production of erythrocytes and leukocytes in posthatch males and females which coincided temporally with early poult mortality.

Aging↗

PubMed1987

Controlled egg weight loss during incubation of turkey eggs.

Weight loss (12%) of turkey eggs in a commercial incubator by a weekly adjustment of relative humidity (RH) was compared in four independent trials with the industry standard of maintaining 58% RH. Trials 1 and 2 were conducted with eggs from one flock of recycled hens during their 14th and 20th week of lay, respectively. Trials 3 and 4 were conducted with first cycle hens during their 3rd and 10th week of lay, respectively. Hatch of eggs was significantly better when eggs were incubated to lose an optimum amount of weight. Hatch of fertile eggs was significantly improved (P less than .05) in all except Trial 2. Hatchability was best when loss of egg weight was not greater than 11.5% at 25 days of incubation.

Animals↗

PubMed1987

Increasing hatchability of turkey eggs with biotin egg injections.

At 25 days of incubation, eggs from Large White turkey hens in two field trials were injected with 87 micrograms of exogenous d-biotin per egg. Hatchability of fertile biotin-injected eggs was significantly higher than that of control (noninjected) eggs. Hatchability values of fertile eggs were 4 and 5% higher for exogenous d-biotin-injected eggs than for control eggs for December 1985 and May 1986 trials, respectively.

Animals↗

PubMed1987

Water balance in incubating turkey eggs.

The eggshell water vapor conductance capable of maintaining constant water content in incubating turkey eggs was determined for three different egg weight classifications. Metabolism of the developing turkey embryos was altered by increasing or decreasing eggshell permeability. Eggshell permeability accommodated metabolic water in large eggs very well. Both relative poult weights and relative water content of embryos in large eggs at the plateau stage in oxygen consumption decreased or increased allometrically to the permeability treatment. However, among small and medium eggs, if eggshell permeability was increased, relative poult weights at hatching were much less than expected. This occurred despite the fact that relative water content of the eggs at 25 days of incubation was not similarly affected. The data suggest a biological asynchrony for egg size, metabolism, and water content of turkey eggs.

Animals↗

PubMed1986

Effect of sperm numbers per insemination following early or late initial inseminations in turkeys.

Large White turkey hens were used in this study to investigate sperm storage in the hen throughout a 20-week breeding cycle. Hens were initially inseminated early or late and subsequently at 7-day intervals with either 20, 50, or 100 million sperm each time. Early inseminations (EI) were performed on Days 14 and 17 postlighting, and the late inseminations (LI) were performed on Days 21 and 24 postlighting. Fertility (percent) was calculated weekly for 20 weeks following the second initial insemination in each group. Fertility was greatest in EI hens for the 20-week period; the largest difference occurred between EI and LI treatments of the 50 million sperm/insemination group. A significant interaction was observed between time of initial insemination and sperm numbers per insemination. Overall fertility was improved with each increase in sperm numbers/insemination.

Animals↗

PubMed1986

Physiological characteristics of a molt and second cycle of egg laying in turkey breeder hens.

Large White turkey hens were housed in light-controlled pens in molting experiments. In each experiment, a group of hens was molted (MO) and nonmolted control hens (CON) were maintained in an adjacent room. Body weight and absolute and relative weights (g organ weight/100 g body weight) of the ovary with ova, oviduct, and liver were observed in MO and CON throughout the molting period and after photostimulation. Further determinations were made of the percentage of liver dry matter (PLDM) and ash (PLA). The MO hens lost body weight during feed deprivation but regained it and continued to gain body weight until they were heavier at the beginning of the second cycle than at the end of the first cycle. Hematocrit and body temperature of MO hens exhibited significant (p less than or equal to .05) changes during molt. Hen-day egg production averaged 44.7% +/- 1.3 during the second cycle. Mean value for eggs per hen-housed was 62.6 +/- 1.8. Egg weight remained constant (96.8g +/- .2 g) and egg specific gravity averaged 1.076 +/- .0001 in MO hens. The molt was characterized by significantly (P less than or equal to .05) reduced relative liver weight during feed deprivation, decreased relative ovary and oviduct weights that did not begin to increase until after photostimulation. No consistent differences were observed in PLDM or PLA.

Animals↗

PubMed1985

Magnesium, calcium, and phosphorus content of shells from hatching and nonhatching turkey eggs.

Shells of hatching and nonhatching Large White turkey eggs were examined for magnesium, calcium, and phosphorus content. Eggshells containing embryos that hatched contained significantly (P less than .05) more magnesium than shells from nonhatching eggs. No differences were seen in their calcium content. Eggshells from pipped eggs contained significantly (P less than .05) more phosphorus than shells from eggs that were not pipped or those that hatched. Calcium and magnesium in turkey eggshells declined as time in lay increased. Injections of exogenous magnesium both at setting and transfer significantly (P less than .05) depressed hatchability, whereas exogenous calcium injected at transfer significantly (P less than .05) improved hatchability. Injections of exogenous calcium at the time of setting significantly (P less than .05) depressed hatchability. It was concluded that the mineral content of turkey eggshells may influence embryo physiology and hatchability.

Animals↗

PubMed1985

Effect of initial insemination and insemination interval on fertility in turkey hens.

Large White turkey hens were used to observe fertility through a 20-week laying cycle (31 to 51 weeks of age), following early initial inseminations (EI) and late initial inseminations (LI). Early initial inseminations were made on Days 13 and 15 following photostimulation with subsequent artificial insemination (AI) every 7 (EI + 7) or 14 (EI + 14) days. Late initial inseminations were made on Days 20 and 22 postlighting with subsequent AI every 7 (LI + 7) or 14 (LI + 14) days. Percent of egg production, fertility, and hatch of fertile eggs were measured following the initial AI in each treatment. No significant differences in egg production were seen between treatments. Percent of fertility was greatest in Weeks 6 to 20 with 7-day AI intervals as compared to 14-day intervals. Early inseminations resulted in higher fertility than LI with 14-day AI intervals, but no difference was observed with 7-day intervals. Greater fertility in EI + 14 hens through 20 weeks of egg production, as compared to LI + 14 hens, seems to lend further support to the concept of enhanced oviduct receptiveness to spermatozoa before egg production commences.

Animals↗

PubMed1985

Supplemental thyroid hormones and hatchability of turkey eggs.

Fertile turkey eggs were injected with thyroid hormones to test the effects of exogenous hormones on hatchability. Physiological doses of thyroxine (T4) and triiodothyronine (T3) of 50 and 25 ng, respectively, injected at setting, depressed hatchability. Conversely, injections of T4 and T3 at 25 days of incubation significantly (P less than .05) improved hatchability. Injections with thyroid-stimulating hormone (TSH) or tyrosine had no significant effect on hatchability when injected at setting or at 25 days of incubation. Injections of thyroid-releasing hormone (TRH) had no effect on hatchability when injected at setting but significantly (P less than .05) improved hatchability when injected at 25 days of incubation. Because T4 and T3 significantly (P less than .05) depressed hatchability when injected whereas TSH and TRH had no effect on hatchability when injected at setting, these data suggest classic negative feedback mechanisms function very early in the embryonic turkey. The improvement in hatchability observed when thyroid hormones were injected at 25 days of incubation offers further evidence that hypothyroidism may be a cause of poor hatchability among turkey eggs.

Animals↗

PubMed1984

Vital gas exchange and hatchability of turkey eggs at high altitude.

Conductance of turkey eggshells was observed to be significantly (P less than .01) greater at 2000 than at 200 m elevation. It was concluded that the increased conductance may have been due to the Chapman-Enskog relation. Eggshells of nonhatching eggs from the high altitude were examined, and it was determined that despite the increased conductance rate, eggshells with significantly (P less than .05) less functional pore area hatched poorly in both oxygenated and nonoxygenated environments. When oxygen was not supplemented to the incubators at high altitudes, eggshells required significantly (P less than .01) fewer pore concentrations to allow embryos to survive to late stages of embryonic development than eggs in oxygen supplemented environments. However, greater pore concentrations on the air space were required in both environments to complete hatching. Cuticle removal from eggshells incubated in oxygen supplemented incubators at high altitudes significantly (P less than .05) reduced late embryonic mortality. It was concluded that eggshell cuticle removal may be more advantageous to hatchability at high altitude than oxygen supplementation.

Altitude↗

PubMed1983

Influence of in vitro microwave radiation on the fertilizing capacity of turkey sperm.

Turkey sperm were exposed to 2.45-GHz microwave radiation in a temperature-controlled wave-guide apparatus. Temperature was maintained at either 25 or 40.5 degrees C. The sperm were exposed for 30 min at a specific absorption rate (SAR) of 10 or 50 mW/g. Following irradiation, the sperm were used to inseminate virgin turkey hens artificially. During the 9 weeks following the single insemination, the following were assessed: mean number of eggs, percentage of fertile eggs, rate of decrease in egg fertility, percentage of hatched eggs, and percentage of early and late deaths. These data demonstrate that, for the conditions used in these experiments, microwave radiation has no effect on the fertilizing capacity of turkey sperm.

Animals↗

PubMed1983

Anti-sperm antibodies and fertility of turkey hens.

Anti-sperm antibody titers increase with time in serum of turkey hens following a standard production schedule of artificial insemination (AI). In hens receiving intravenous (IV) or intraperitoneal (IP) additional AI, serum anti-sperm antibody levels increase more rapidly after a lag phase. A single injury to the oviduct also resulted in increased anti-sperm antibodies similar to IV and IP groups. This is a new observation that a single injury increased antibody titers to spermatozoa equal in IV and/or IP injections. A negative correlation between serum anti-sperm antibody titers for IV, IP and injury to oviduct and fertility of these groups was observed. Hens of IV and injury to oviduct groups with high levels of anti-sperm antibodies in the last 2 weeks of production had significantly lower fertility than hens with low levels of antibodies and control hens.

Animals↗

PubMed1983

Filling rates of the uterovaginal sperm storage glands in the turkey.

Large White turkey hens were assigned to two groups of 30 birds each and photostimulated at 32 weeks of age. Group 1 hens (nonlaying) were artificially inseminated (AI) three times prior to the onset of lay on Days 14, 15, and 16 postlighting. Group 2 hens (laying) were also inseminated three times as in Group 1, but the inseminations followed the onset of egg production on Days 23, 24, and 25 postlighting. Six hens from each group were sacrificed following the initial insemination at intervals of 1, 2, 3, 5, and 7 days. Histological sections of the uterovaginal (UV) junction from each hen were made to determine filling rates of the sperm storage glands. Sperm concentrations in the UV glands of the nonlaying hens did not increase significantly beyond 24 hr post-AI. There was a significant (P less than .05) peak, however, in the number of stored spermatozoa on Day 5 post-AI in the laying hens. These results indicate that inseminations performed in the absence of oviposition and ovulation enable the UV sperm storage glands to be filled nearer their capacity with fewer inseminations.

Animals↗

PubMed1982

Physiology of turkey embryos during pipping and hatching I. Hematology.

Blood samples were collected from turkey embryos during pipping and hatching, an age which corresponds to a time of elevated embryonic mortality. Samples were analyzed for erythrocyte counts (RBC), packed cell volume (PCV), hemoglobin concentration (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). An increase in RBC was significant (P less than .05) during piping and hatching. The PCV increased significantly (P less than .01) until pipping occurred and then declined significantly through hatching. The Hb concentration also increased significantly (P less than .05) as pipping and hatching occurred. The MCV declined significantly as development proceeded. Both MCH and MCH declined significantly (P less than .05) until the onset of pipping at which time both increased significantly (P less than .05) through hatching.

Animals↗