Biomedical subjects

R J Lien

Publications and source records attributed to R J Lien.

11 recordsLinked to original sources

PubMed1998

Peanut hulls as a litter source for broiler breeder replacement pullets.

Broiler breeder pullets were reared on either peanut hulls or pine shavings to determine effects of litter type on growth performance and litter characteristics. Pullets were reared to 20 wk of age in rooms initially bedded with 8 cm of clean shavings or hulls. Heating and ventilation were standardized in all rooms. Restricted skip-a-day feeding was used to attain recommended growth curves. Water was continuously provided for ad libitum consumption. Litter and environmental variables were measured throughout rearing and 2 wk after pullets were removed from the litter materials. Feed consumption, BW, mortality, and uniformity at 20 wk were not affected by litter type; however, gizzard weights were decreased in pullets reared on hulls. Litter bulk density increased with use and was greater for shavings through 11 wk, but not thereafter. Particle size decreased with use in both litter types. Through 11 wk, there were more particles in the > 4 mm range and less in the < 1.7 mm range with hulls. Litter moisture increased with use but was not affected by litter type. Litter pH was greater in unused shavings, but during and after use was generally greater in hulls. With both litter types, litter and environmental ammonia levels increased to 11 wk then decreased; however, this effect was more pronounced for hulls. Bacteria populations were not affected by litter type; however, greater fungal populations were observed in shavings at 7 and 15 wk. Aflatoxins were detected in unused hulls but not shavings. Because aflatoxin levels decreased during use and Aspergillus flavus and Aspergillus parasiticus populations were not detected in samples collected during use, aflatoxins observed were presumed to have been formed prior to use. Peanut hulls performed similarly to pine shavings as a litter source for breeder pullets; however, the specific influence of the aflatoxins contained in this litter source on bird performance deserves further study.

Aflatoxins↗

PubMed1994

Plasma concentrations of corticosterone and thyroid hormones in broilers provided various lighting schedules.

The purpose of this study was to measure plasma corticosterone and thyroid hormone concentrations in broilers exposed to various photoschedules. Day-old male broilers were placed on litter floors in light-controlled chambers. Four chambers were randomly assigned to each of four light treatments: 1) 23 h light (L):1 h dark (D) from 1 to 56 d of age (designated extended, E); 2) 1L:3D from 1 to 56 d (intermittent, I); 3) 6L:18D from 1 to 14 d and 1L:3D from 15 to 56 d (brief-I, BI); and 4) 6L:18D from 1 to 14 d and 23L:1D from 15 to 56 d (brief-E, BE). Blood samples were collected 0, 4, and 20 h after lights-on (1200 h) at 13, 41, and 55 d of age. Corticosterone concentration did not differ among light treatments or collection times and was decreased at 41 d compared with 13 d (.65 vs 2.11 ng/mL). Triiodothyronine (T3) increased and thyroxine (T4) decreased with age. At 13 d, there were light treatment by sampling time interactions for T3 and T4. Plasma T3 was elevated in Treatments BI (3.11 ng/mL) and BE (3.40 ng/mL) compared with Treatments E (2.39 ng/mL) and I (2.30 ng/mL) at 0 h; the former two treatments showed decreased T3 concentrations at 4 and 20 h compared with 0 h. Plasma T4 showed reciprocal changes to T3. There were no differences in T3 or T4 for light treatments or sampling times at 41 and 55 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Effects of increased rearing period body weights and early photostimulation on broiler breeder egg production.

Broiler breeder pullets were subjected to photostimulation (PS) at either 14, 17, or 20 wk of age after attaining greater than recommended BW during rearing in order to determine effects on age at onset of lay, egg weight, and egg production. During rearing, feed was consumed ad libitum (AL) or provided in allotments resulting in growth to projected BW of 2.8 (heavy, HV) or 2.3 kg (light, LT) at 20 wk. Rearing period feeding and age at PS treatments made up a 3 x 3 factorial arrangement. A single restricted feeding program was provided during lay. Although age at first egg in the AL treatment was earlier than in HV and LT treatments, total production by HV and LT birds was greater because peak and postpeak production by AL birds were depressed. Relative to PS at 20 wk, PS at 14 and 17 wk advanced age at first egg and increased cumulative production to 30 wk. However, early PS decreased peak production and, therefore, did not affect total production. Mean egg weight and settable egg production (egg weight > 50 g) were increased in HV and LT treatments. Egg weight and settable egg production were not affected by age at PS. These results indicate that the onset of lay by broiler breeders can be advanced by early PS and that increased BW facilitates this. However, allowing greater BW during rearing does not compensate for reduced early egg weights and results in decreased total production and mean egg weights when feed is provided at recommended levels during lay.

Age Factors↗

PubMed1993

The relationship of plasma thyroid hormone and prolactin concentrations to egg laying, incubation behavior, and molting by female turkeys exposed to a one-year natural daylength cycle.

To determine relationships to egg laying, incubation behavior and molting, plasma thyroxine (T4), triiodothyronine (T3), and prolactin levels of 20 female domestic turkeys were determined throughout a one-year cycle of natural daylengths. Endocrine changes were analyzed relative to periods of reproductive and molting cycles. Data were also analyzed relative to termination of lay after division into two groups based on the presence (I, n = 7) or absence (NI, n = 13) of incubation behavior. Plasma T4 levels of the flock increased to a peak and subsequently decreased during the onset of lay period from February to April. Plasma T4 generally increased throughout the decline of lay period from April to July and molting period from July to October, and then reached greatest levels at the end of the molting period. Plasma T3 reached a peak early in the onset of lay and decreased rapidly during the remainder of that period. Plasma T3 remained depressed during the decline of lay, increased throughout molting, and attained greatest levels as molt was completed. Prolactin was low throughout the prelay period and sharply increased midway through the onset of lay. Prolactin increased to a marked peak during the decline of lay, and then rapidly decreased as egg laying was terminated. Relative to NI birds, egg laying was terminated earlier and prolactin levels were markedly greater during and following the termination of lay in I birds. Plasma T4 and T3 were generally lower in I birds during the molting period which followed the termination of lay and their molt was delayed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effects of short-term thyroxine administration during the laying period on egg production and moulting by turkeys.

1. Effects of thyroxine (T4) administration on egg production, moulting and photorefractoriness in laying turkeys were determined. Thyroxine dosages of 0.075 to 2 mg/bird/d were injected IM for periods of either 2 or 3 weeks following 10 weeks of photostimulation. Control groups were administered saline vehicle. 2. Plasma T4 concentrations were increased in a dose dependent manner by T4 administration, while triiodothyronine (T3) was decreased. 3. Egg production and percentage of hens in production were transiently decreased in a dose dependent manner by T4 administration, but returned to levels similar to controls within 4 weeks of T4 treatment termination. Moulting was stimulated in a dose-dependent manner by T4 administration, but was similar to controls after T4 treatment termination. Only dosages of 2 mg/bird/d resulted in cessation of egg production and complete moulting. 4. Results indicate that although short term elevation of plasma T4 causes cessation of egg production and moulting these effects are transient and not indicative of photorefractoriness.

Animals↗

PubMed1991

Influence of thyroidectomy on reproductive responses of male domestic turkeys (Meleagris gallopavo).

1. The influence of age at thyroidectomy on reproductive activity of male turkeys was investigated. 2. Thyroidectomy of 53-week-old male domestic turkeys that had been reproductively active for 25 weeks resulted in undetectable plasma thyroxine concentrations, termination of semen production and testicular regression. Daily light-dark treatment was 14L:10D before and after thyroidectomy. 3. Thyroidectomy of 28-week-old, reproductively inactive, males maintained on a daily light-dark cycle of 8L:16D resulted in increased semen volumes following photostimulation with 14L:10D at 32 weeks of age. Semen quality was not affected, while plasma thyroid hormone concentrations were undetectable. The moult and termination of semen production that occurred in response to changing the daily light-dark cycle from 14L:10D to 8L:16D near the end of the study were inhibited by thyroidectomy. 4. The requirement for the thyroid glands in the reproductive processes of male turkeys changes either with age or after an extended period of reproductive activity.

Animals↗

PubMed1991

Live performance and yields of broilers provided various lighting schedules.

The purpose of the present study was to measure performance and carcass yield from broilers maintained on photoschedules that may influence incidence of leg disorders. Day-old male broilers were placed on litter floors of light-controlled chambers. Four chambers were randomly assigned to each of four light treatments: 1) 23 h light (L): 1 h dark (D) from 1 to 56 days of age (designated extended, E); 2) 1L:3D from 1 to 56 days (intermittent, I); 3) 6L:18D from 1 to 14 days and 1L:3D from 15 to 56 days (brief-I, BI); and 4) 6L:18D from 1 to 14 days and 23L:1D from 15 to 56 days (brief-E, BE). Mean (+/- SEM) light intensity was 5.4 +/- .26 lx for all light treatments. At 13, 21, and 42 days of age, Treatments BI and BE had lower BW than Treatment E. The percentage of birds with leg abnormalities among treatments was greater at 56 days than at 42 days. The BI birds had significantly fewer leg abnormalities than E birds. There was an age by treatment interaction for the frequency of tibial dyschondroplasia (TD), with BI showing better recovery from TD at 56 days than other treatments. At 42 days of age, split breast yield (percentage of BW) was greater in E than I, and breast yield (percentage of lean carcass) was greater in E and BI compared with I. At 56 days of age, yield (percentage of BW) of tenders was lower in I and BI compared with E and BE.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Effects of thyroidectomy on egg production, molt, and plasma thyroid hormone concentrations of turkey hens.

Turkey hens were thyroidectomized at different ages and phases of their reproductive cycles. Egg production, primary remige molting, and plasma thyroxine (T4) and triiodothyronine (T3) concentrations were monitored during each of three experiments. Thyroidectomy of hens (26 and 30 wk of age) prior to photoinduction of egg production prevented subsequent egg production and molting. Thyroidectomy of adult hens (36 wk of age) early in the egg production cycle caused a gradual termination of egg laying without the occurrence of molting. Thyroidectomy of mature hens (66 wk of age) during the light restriction period prior to their second egg production cycle prevented subsequent egg laying and molting. All successful thyroidectomies reduced plasma T4 and T3 to concentrations below the sensitivity levels of the assays. Feeding 1 ppm T4 to thyroidectomized hens resulted in resumption of normal egg production and molting. These results indicate that the thyroid is essential for the initiation and maintenance of egg production and for molting in turkey hens.

Animals↗

PubMed1989

Turkey plasma thyroid hormone and prolactin concentrations throughout an egg laying cycle and in relation to photorefractoriness.

Plasma concentrations of thyroxine (T4), triiodothyronine (T3), and prolactin were determined weekly through an egg laying cycle induced with 30 wk of 14 h light:10 h dark. Egg production, primary remige molting, and occurrence of photorefractoriness were monitored. Hens were assigned to one of two groups; those that exhibited photorefractoriness (PR) and those that remained photosensitive (PS). Weekly plasma T4 concentrations relative to the time of initiation of photostimulation did not differ between PR and PS groups; concentrations peaked prior to the onset of egg production, were lowest during peak egg production, and increased between Weeks 6 and 30 of photostimulation. Plasma T4 levels of PR hens peaked 3 wk prior to the onset of photorefractoriness. Plasma T3 concentrations of PS and PR hens were similar until increases occurred in PR hens at the onset of photorefractoriness. Plasma prolactin levels in PS and PR hens increased after photostimulation, declined sooner in PR hens, and were generally greater in PS than PR hens during the last 20 wk of the study. Mean time of onset of photorefractoriness in PR hens was 23.0 wk (range = 18 to 28 wk) after initiation of photostimulation. Egg production of PS hens was greater than that of PR hens after 20 wk of photostimulation, and PR hens molted a greater number of primary remiges than PS hens. Results indicated that 1) elevated plasma T4 may be involved in development of photorefractoriness in turkey hens, 2) increases in plasma T3 may be involved in gonadal regression and molting, and 3) elevated plasma prolactin was associated with persistence of photosensitivity.

Animals↗

PubMed1987

Effects of dietary and parenteral estrogens on bobwhite reproduction.

Bobwhites were fed one of several doses (.01 to 1,000 micrograms/day) of estriol (E3), beta-estradiol-3-benzoate (E2B), diethylstilbestrol (DES), or biochanin-A (BA) during two 10-week trials. The initial 2 weeks of each trial were short day length (10L:14D) followed by 8 weeks of long day length (16L:8D). In addition, female bobwhites were given daily injections containing dosages (.01 to 10 micrograms/day) of E2B, E3, and DES while housed on the same light regimen. Reproductive performance as assessed by onset of lay, egg production, and egg fertility was depressed in a dose-dependent manner and was inhibited by dietary dosages of 1,000 micrograms/day of E3, DES, and E2B. No consistent effects on reproductive performance were observed in bobwhites fed up to 1,000 micrograms/day of the phytoestrogen BA. Injected estrogens appeared approximately 100 times more potent than dietary estrogens. It was concluded that both dietary and parenteral estrogen can inhibit reproduction, but in order for phytoestrogen (BA) in natural feedstuffs to impair reproduction in bobwhites it would have to be consumed in excess of 1 mg/day.

Animal Feed↗

PubMed1985

The influence of exogenous estradiol on bobwhite quail (Colinus virginianus) reproductive systems.

Mean plasma 17-beta-estradiol (E2) concentrations of nonphotostimulated adult bobwhite quail were less than 31.2 and 119.9 pg/ml for males and females, respectively. Dietary beta-estradiol-3-benzoate (E2 beta) dosages of 10, 100 or 500 micrograms/bird/day caused mean plasma E2 concentrations of females to increase by 1.2, 2.0 or 5.6 times. Oviduct weights were significantly increased in females fed E2 beta dosages of greater than 100 micrograms/bird/day for five days. Gonad weights were not significantly effected in either sex. Ten- to fifty-fold greater doses of dietary E2 beta were required to induce oviduct growth responses equivalent to those produced by injected E2 beta.

Animals↗