Plasma, follicular, and uterine levels of prostaglandins in chickens laying soft-shelled and shell-less eggs.

Not all eggs produced by chickens are laid at the expected time of oviposition. Some eggs are laid prematurely, which result in inadequate shells. These uncollectible eggs are referred to as soft-shelled (partial calcification) or shell-less (no calcification) eggs. Of all soft-shelled or shell-less eggs that were laid in the present study, 57% were expelled prematurely. To determine whether prostaglandins were correlated with the expulsion of soft-shelled or shell-less eggs, prostaglandin F2alpha (PGF2alpha), 13,14-dihydro-15 keto prostaglandin F2alpha (PGFM), and 13-14-dihydro-15 keto prostaglandin E2 (PGEM) were measured in the peripheral plasma and follicular and uterine tissues of hens laying soft-shelled eggs and shell-less eggs. Controls were represented by hens laying hard-shelled eggs (normal calcification). Plasma concentrations of PGFM increased (P less than .01) upon the premature oviposition of soft-shelled eggs but not shell-less eggs. The source of the peripheral PGFM may have been the preovulatory follicle, because PGF2alpha levels were higher (P less than .07) in the soft-shelled or shell-less egg layers when compared with the controls. Plasma and tissue levels of PGEM did not differ between hens laying soft-shelled or shell-less eggs versus hard-shelled eggs. These results suggest that PGF2alpha and PGFM are involved in the premature oviposition of some chicken eggs.

Gas chromatographic analysis of shell membrane amino acids from hard-shelled, soft-shelled, and shell-less eggs.

The amino acid composition of shell membranes from hard-shelled (HS), soft-shelled (SS), and shell-less (SL) eggs produced by 62-wk-old hens was analyzed by gas chromatography using N-acetyl n-propyl ester derivatives. This technique succeeded in identifying tryptophane and ornithine as shell membrane components. There were no significant differences in the concentrations of any of the 17 amino acids analyzed among HS and SS eggs, HS and SL eggs, or SS and SL eggs. Stepwise discriminant analysis of the amino acid ratios correctly classified all of the amino acid chromatograms of shell membranes from HS/SL and SS/SL egg pairs, and 92.9% of the HS/SS and 90.0% of the HS/SS/SL amino acid chromatograms were classified correctly (F = 1.0). Higher F values reduced the percentage of correct classifications to 75.0%, 85.0%, and 67.5% (F = 2.0) for the HS/SL, SS/SL, and HS/SS/SL egg groups, respectively, and to 78.6% (F = 3.0) for the HS/SS egg group. Stepwise discriminant analysis also identified specific amino acid ratios that were most efficient at classifying the amino acid chromatograms according to shell type. This process identified three amino acid ratios for the HS/SS egg group (F = 3.0), two ratios for the HS/SL egg group, four ratios for the SS/SL egg group, and four ratios for the HS/SS/SL egg group (F = 2.0). Based on the number of times they appeared as efficient discriminating variables at higher F values, alanine, proline, and isoleucine seemed to be the most important amino acids for correctly classifying shell membranes by egg type.

Relationship of high intensity step-up lighting to bone ash and growth plate closure of the tarso-metatarsus in turkeys.

The reduced lameness observed in turkeys reared in a high intensity step-up (HISU) lighting programme as compared to a low intensity step-down (LISD) lighting regimen cannot be explained by differences in the inorganic matrix of the bone, because the proportions of bone ash, bone ash calcium, and bone ash phosphorus did not differ between lighting programmes. At 17 weeks of age, there was a significant difference in the proportion of closed growth plates in males reared on the HISU programme rather than on LISD lighting. These results support the hypothesis that HISU lighting reduces lameness by promoting earlier growth plate closure of long bones.

Comparison of two lighting regimens and drinker cleaning programmes on the performance and incidence of leg abnormalities in turkey males.

Turkey males subjected to a low intensity step-down (LISD) lighting programme showed significantly heavier body weights after 20 weeks of age and significantly better feed conversions after 14 weeks of age compared with males reared in a high intensity step-up lighting (HISU) programme. Although both nonchilled and chilled carcase weights were higher, the dressing percentages were lower for males of the LISD lighting regimen. Males of the HISU lighting programme had significantly fewer leg abnormalities, shorter tarso-metatarsi, lighter drumstick weights, and lighter tibia weights. Males on the HISU lighting programme from 15 to 19 weeks of age had larger testes; however, after 20 weeks of age they were larger in males on the LISD lighting regimen. Cleaning and disinfecting the drinking troughs daily rather than weekly had no effect on any production variable measured.

Phosphorus phase feeding and uterine and isthmus mucosal enzymes and minerals in relation to soft-shelled and shell-less egg production.

The relationships among phosphorus phase feeding, egg shell quality, and the activities and concentrations of several enzymes and minerals in the uterine and isthmus mucosae of hens at the time of oviposition were investigated. During the first 8 months of production (Phase 1), layer diets contained .3, .5, or .7% available phosphorus. Between 9 and 12 months of production (Phase 2), dietary available phosphorus was either increased or decreased by .2% phosphorus, or was left unchanged. No significant differences due to Phase 1 diets were demonstrated for hard-shelled (HS), soft-shelled (SS), or shell-less (SL) egg production, livability, egg weight, or specific gravity. Phase 2 diets had no significant effect on SS or SL egg production, livability, or egg specific gravity; however, decreasing dietary phosphorus reduced egg weight. Levels as high as .9% had no effect on specific gravity or HS egg production, while .1% dietary phosphorus was detrimental to HS egg production and feed consumption. No significant differences due to dietary available phosphorus or egg type (SS vs. HS) were demonstrated for uterine or isthmus mucosal enzyme activities or mineral contents, with one exception. Higher inorganic phosphorus concentrations were found in the uterus of HS egg layers when compared to levels in the uterus of SS egg layers and the isthmus of HS and SS egg layers. Acid phosphatase and carbonic anhydrase activities, and total calcium levels were significantly higher in the isthmus than the uterus, while alkaline phosphatase and pyrophosphatase activities, and inorganic phosphorus levels were significantly higher in the uterus than the isthmus.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of plasma corticosterone and adrenal cholesterol and corticosterone to the production of soft-shelled and shell-less eggs.

Two experiments were conducted to determine if plasma corticosterone and adrenal cholesterol and corticosterone levels differed among hens that laid soft-shelled (SS) or shell-less (SL) eggs when compared with hard-shelled (HS) egg layers. For Experiment 1, four groups of White Leghorn hens were bled at 22 to 34 weeks of age in the morning (0600 to 1200 hr) and at 66 to 74 weeks of age in the morning and evening (1500 to 1900 hr). Group 1 consisted of birds that had just laid SS or SL eggs, whereas Group 2 hens had SS or SL eggs in utero. Groups 3 and 4 represented hens with HS eggs in their uteri and hens that had just laid HS eggs, respectively. For Experiment 2, adrenal cholesterol and corticosterone levels were assayed in high (18+%) and low (0%) incidence SS plus SL egg layers at 73 and 78 weeks of age. Both younger and older hens that laid SS or SL eggs in the morning had similar plasma corticosterone concentrations when compared to HS egg layers. Morning plasma corticosterone levels were significantly higher among hens that laid an egg when compared to hens with eggs in utero, regardless of whether the egg was SS, SL, or HS. However, plasma corticosterone levels of hens producing SS or SL eggs in the evening were significantly higher than levels of hens that laid evening HS eggs. Evening HS egg layers demonstrated the oviposition related peak in plasma corticosterone, but concentrations were 1 ng/ml higher among the evening SS or SL egg layers. Adrenal cholesterol and corticosterone concentrations were similar between high and low incidence SS plus SL layers at either age. It is postulated that evening production of SS or SL eggs is a consequence of elevated plasma corticosterone.

The relationship of dietary levels of phosphorus to the production of soft-shelled and shell-less eggs.

The relationship among available levels of dietary phosphorus (.2, .3, and .4%) and the production of soft-shelled (SS) and shell-less (SL) eggs was investigated in 864 White Leghorns of a commercial strain. An 11-month performance profile included hen-day production of hard-shelled (HS), SS, and SL eggs, feed consumption, livability, egg weight, and specific gravity. Percent HS egg production and feed consumption were significantly lower and egg specific gravity was significantly higher among hens consuming the .2% available phosphorus diet when compared to hens consuming the .3 or .4% available phosphorus diets. The level of available phosphorus in this study did not affect significantly hen livability or the production of SS or SL eggs. Five hours (HS egg in uterus) or 15 hr (SL egg in uterus) prior to expected oviposition time, 1 ml of a 200 mM phosphate solution was injected into the brachial vein (i.v.) or the uterus (i.u.) of hens observed to lay consistently HS eggs. Injections i.v. did not alter expected oviposition time when either a HS or SL egg was in the uterus, but i.u. injections induced premature oviposition when a SL egg was in utero. The concentrations of inorganic phosphorus and total calcium in the plasma and uterine fluid of hens that laid a high or low incidence of SS + SL eggs were determined 5 hr after the egg entered the uterus. Uterine fluid inorganic phosphorus and total calcium and plasma inorganic phosphorus levels of the high and low incidence groups were not significantly different. However, plasma total calcium was significantly higher among high incidence SS + SL layers when compared to low incidence SS + SL layers at this time during the ovulatory cycle.

Effects of high intensity step-up and low intensity step-down lighting programs on the incidence of leg abnormalities in turkeys.

Two trials were conducted to determine if a high intensity (20 lx) step-up lighting program would decrease the incidence of leg abnormalities in turkeys. The step-up lighting regimen was compared to a low intensity (2.5 lx) step-down lighting program. Toms were used in Trial 1 and both sexes were employed in Trial 2. Body weight, feed/gain ratio, and mortality of toms of Trial 1 did not differ significantly between lighting regimens. The incidence of leg deformities and the length of the tarsometatarsal bone were significantly decreased, whereas plasma androgen and testes weights were increased for toms of Trial 1 in the high intensity step-up lighting. The same trends were apparent for toms of Trial 2 with the exceptions that feed/gain ratios were adversely affected and testes weights were significantly lower for toms of the high intensity step-up lighting program. The performance of hens in the high intensity step-up lighting program of Trial 2 was affected adversely; however, incidence of leg abnormalities and length and width of the tarsometatarsus responded in the same manner as with toms. The results of this study indicate that a high intensity step-up lighting program can significantly reduce leg weakness problems in turkeys. Possible explanations for light stimulation reducing the incidence of leg abnormalities are through increased exercise and shortening of long bones.