Egg Production Period Research Articles

Níveis de cálcio em rações de poedeiras comerciais no segundo ciclo de postura

The experiment was carried out to evaluate the effects of calcium levels in commercial laying hen performance in the second period of egg production. 192 laying hens - 68 weeks of age were used. The experimental design was randomly in a 3x2 factorial arrangement: (0.5; 2.0 and 3.5% of calcium during the pause period and 2.0 and 3.6% of calcium during egg laying period). The variables studied were: ration consume production, weight and mass of egg, feed conversion, albumen quality and external quality of eggs. Egg weight, feed conversion and internal quality of the eggs were not influenced by the treatments in the pause period and in the egg production period. The external quality characteristics of the eggs were influenced by the treatments and the best results were obtained with the 2.0% calcium level at the pause period and 3.5% at the egg production period

Effect of a Chelated Calcium Proteinate Dietary Supplement on the Reproductive Performance of Large White Turkey Breeder Hens

Researchers have reported that organic mineral complexes can have increased availability compared with inorganic sources. This work was conducted to examine the inclusion of a small amount of chelated calcium proteinate (CalKey) into turkey breeder hen diets and its effect on turkey breeder hen performance. Two studies were conducted, one each in Minnesota (A) and North Carolina (B). Typical corn and soybean meal diets without animal by-product meals were used as the control diets. Hens in the first study were photostimulated at 30 wk of age in December with 15L:9D for a 24-wk lay period, and hens in a second study were photostimulated after an induced molt in January with 15.5L:8.5D for a 24-wk lay period. In study A, hatchability of fertile eggs was improved during the last 4 wk of production for hens fed calcium proteinate. During 1 period, hens fed calcium proteinate had lower daily feed intake and increased incidence of soft-shelled eggs. In study B, hatchability of fertile eggs was improved for hens fed dietary calcium proteinate for 19 and 20 wk of lay. This result was associated with improved embryo livability for wk 3 and 4 of development. It was concluded that feeding 500 ppm calcium from chelated calcium proteinate improved hatchability of turkey eggs during the later period of egg production, which was associated with decreased late embryo mortality.

Secondary production of Calanus helgolandicus in the Western English Channel

The objective of this study was to investigate the production of Calanus helgolandicus off Plymouth, Western English Channel, from April to August 1998 comparing a range of different methods. The abundance of all developmental stages from NI to adult was determined. Body carbon and nitrogen and length were measured on individual NVI to adults. Female egg production was also monitored. All developmental stages were generally represented but four main periods of recruitment were determined. Two periods of low egg production were observed on the 13th and on the 27th of July: (i) the first was due to the arrival of newly moulted or not yet fertilised females in the population and (ii) the second low period was possibly due to the senescence of the females. Finally, the total production of C. helgolandicus was estimated using four different methods: the weight increment, the egg production, Huntley and Lopez and Hirst and Lampitt methods. Depending on the methods used, the production accumulated over the period from May 14 to August 10 ranged between 12 and 45 mg C m −3.

Lethal and sublethal effects of two insect growth regulators on adult Delphastus catalinae (Coleoptera: Coccinellidae), a predator of whiteflies (Homoptera: Aleyrodidae)

Pyriproxyfen, a juvenile hormone analog, and buprofezin, a chitin synthesis inhibitor, are two insect growth regulators (IGRs) considered as selective and effective insecticides for controlling whiteflies. Delphastus catalinae (Horn) is a commercially produced whitefly predator considered to be a valuable biological control agent of whiteflies, especially of Bemisia tabaci (Gennadius) ( B. argentifolii Bellows & Perring) in greenhouses. The compatibility of these two control strategies was tested by evaluating the lethal and sublethal effects resulting from ingestion of insect growth regulator (IGR) residues on treated B. tabaci eggs by adult lady beetles in the laboratory. Feeding on pyriproxyfen-treated whitefly eggs caused no significant decrease in longevity of either male or female beetles, whereas feeding on buprofezin-treated eggs reduced longevity significantly. Likewise, preoviposition period was not affected by pyriproxyfen, but was lengthened 3–6 days by buprofezin. Buprofezin reduced D. catalinae egg production and oviposition periods while a 28-day treatment with the low rate of pyriproxyfen actually increased these parameters. Both IGRs reduced D. catalinae egg fertility, especially the higher rate of pyriproxyfen and both rates of buprofezin. However, the process was largely reversed in the case of pyriproxyfen by a transfer of D. catalinae to water-treated whitefly eggs. Because D. catalinae fecundity was actually increased by 28 day exposure to the low rate of pyriproxyfen, there was no net effect on viable egg production. Thus, while both growth regulators negatively impacted D. catalinae , fewest side effects were observed with pyriproxyfen, and the worst of these, egg sterility, was reversible following removal of treated eggs.

HABITAT USE AND PREFERENCES OF BREEDING FEMALE WOOD DUCKS

Abstract Female wood ducks (Aix sponsa) feed primarily on plant foods in the prelaying period and switch to a diet of mostly invertebrates during egg production. If nutrient acquisition is habitat-specific, then selection and use of habitats may differ between these reproductive stages. A better understanding of these processes is needed to assist future habitat conservation and management efforts. In January–May 1999 and 2000, we monitored movements and habitat use of radiomarked females (n = 47) during the prelaying and egg-production periods of first nests. Home-range size averaged 367 ha and did not vary with reproductive period, year, or female age. Habitat use did not differ between periods of prelaying and egg production; consequently, data were combined. Habitat use varied between years, female age, and periods of nest initiation (i.e., early vs. late). Use of beaver ponds (BP), temporary wetlands (TW), managed impoundments (MI), and lake habitats (LK) declined in 2000 compared to 1999, possibly d...

Influence of photoperiod and age of photostimulation on the incidence of polycystic ovarian follicle syndrome in turkey breeder hens

An arrest in egg laying associated with a polycystic ovarian follicle syndrome (PCOF) has been recently reported early in the egg production period in turkey hens photostimulated at 30 wk of age (WOA) with continuous light. When autopsied 2 to 3 wk after laying ceased, the ovaries of PCOF hens contained an increased number of mature size (F1) yolky follicles in comparison with normally laying hens plus several larger cystic follicles, while their oviducts were equal in weight to oviducts of hens laying normally. Four experiments were conducted to examine effects of age at photostimulation and photoperiod [14L:10D (14L) or continuous lighting 24L:0D (24L)] on the incidence of the PCOF syndrome. Turkey hens of the egg line were given short-day photostimulation of 6L:18D at 16 WOA and then photostimulated with either 14L or 24L at various ages between 26 to 70 WOA. Egg production was followed for 6 to 8 wk, and hens that stopped laying eggs during this period were autopsied 2 to 3 wk later to determine presence and incidence of the PCOF syndrome. At 26 WOA, the PCOF incidence was 80% with 24L lighting and 31% with 14L lighting (P = 0.006). At 28 WOA, the PCOF incidence was 56% with 24L lighting and 25% with 14L lighting (P = 0.072). At 31, 34, and 41 WOA, there were no differences (P > or = 0.10) in incidence of the PCOF syndrome between the 24L and 14L treatments. Within the 24L treatment, the PCOF incidence at 26 and 28 WOA (80 and 56%) were greater than at 31 WOA and older ages (< or = 20%; P < or = 0.025). Within the 14L lighting treatment, the PCOF incidence was not different among ages (26 WOA, 31% to 48 WOA, 0%; P > or = 0.05). It was concluded that the incidence of the PCOF syndrome is greater when photosensitive Egg line turkey hens are photostimulated at relatively young ages (less than 31WOA) and with 24L in comparison to 14L lighting.

Interval between preovulatory surges of luteinizing hormone increases late in the reproductive period in turkey hens.

In turkey hens, the egg production rate is relatively high early during a reproductive period, but declines as the period progresses. Among lines with different egg production potential, the interval between preovulatory surges of LH is the primary determinant of the egg production rate. The main objective of this study was to determine whether the decline in egg production rate late during an egg production period is also associated with a difference in the interval between LH preovulatory surges. A group of photosensitive turkey hens (Early) were photostimulated with continuous light (24L:0D) at 40 wk of age to induce egg laying, and serial blood samples were collected after about 3 wk of egg production. A second group of hens (Late) were housed in floor pens and photostimulated with 14L:10D at 40 wk of age for a normal 36-wk reproduction period and were then switched to 24L:0D lighting for 2 wk before collection of serial blood samples. Continuous light photostimulation was used for at least 2 wk before and during serial blood sampling to avoid potential masking effects of diurnal lighting on the interval between LH surges. The Early (n = 12) and Late (n = 16) hens were cannulated 3 days before being serially bled hourly for 10 days. The mean interval between preovulatory surges of LH was shorter in the Early hens than in the Late hens (26.1 +/- 2.5 h and 34.7 +/- 3.9 h, respectively). The intra-hen LH surge interval coefficient of variation was lower in the Early hens than in the Late hens (7.2% and 18.6%, respectively). The inter-hen LH surge interval coefficient of variation was similar in the Early and Late hens (9.5% and 11.2%, respectively). The incidence of blind surges of LH (those not retrospectively associated with ovipositions) was not different between Early and Late laying hens (8.4% +/- 15.2% and 7.3% +/- 14.6%, respectively). In conclusion, in turkey hens, longer intervals and greater intra-hen variation between LH surges were associated with a poorer rate of egg production late in the reproductive period relative to early in the reproductive period.

Effect of Extreme Light Regime on Production and Characteristics of Egg in Laying Geese

The objective of this study was to investigate the effect of long light regime (20 h light and 4 h dark, 20L:4D) and short light regime (4 h light and 20 h dark, 4L:20D) on egg production and egg characteristics of laying geese. Thirty-six laying birds, 4 replicates of 3 birds per treatment were allotted to three light regimes, i.e., 20L:4D, 4L:20D, and natural light (NAT) from March 7 to June 20. Results showed that the geese in 20L:4D consumed 54 g less feed per goose daily and laid 17.5 less eggs per goose (p<0.05) comparing to those in 4L:20D. The number of days from initiation of light treatment till cease of laying was 22 days shorter (p<0.05) in 20L:4D comparing to that in NAT. Five geese (41.7%) in 4L:20D kept laying by the end of applying light regime. Weight and surface area of the eggs in 4L:20D were greater (p<0.05) comparing to those in the other two light regimes. It is concluded that the period of egg production in goose could be manipulated by light regime in the ways such as using short light regime of 4 h light daily to prolong egg production through summer and using long light regime of 20 h light daily to induce cease of egg production. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 8 : 1182-1185)

Mating and fecundity of Dermatophagoides farinae.

Studies of the life cycle of cultured Dermatophagoides farinae found that after an initial mating D. farinae females lived for 63.3+/-64.6 (SD) d after their egg production period ended (Arlian and Dippold 1996). The long period after cessation of egg production for D. farinae suggested D. farinae females could mate multiple times and produce eggs continuously for a longer period. The purpose of this study was to determine if female D. farinae could mate at least two times, and subsequently increase the production of viable eggs over a longer period of time compared to a single mating. Female D. farinae were randomly selected from thriving cultures and isolated in cages. When the females had ceased to lay eggs a male was added to the cage. Fifty-seven percent of the isolated females mated again and produced a second batch of viable eggs. In natural or culture populations, females have continuous availability of males. Therefore, in another experiment, females that emerged from the tritonymphal stages were continuously exposed to fresh males and fecundity and lengths of the reproductive and post reproductive periods were determined. These females had a 11 d longer reproductive period and produced 30.7% more eggs compared to females that only mated one time after they emerged from the tritonymphal stage. However, the post reproductive period was still long (58.6+/-11.4 [SE] d) the significance of which is not clear. In conclusion, this study revealed that D. farinae females are capable of more than one successful mating that results in increased egg production compared to that of a single mating. It is likely that females mate multiple times in natural and culture populations. It was observed that females actively attract males during the reproductive period but not afterward even though she continues to live a long time.

Preovulatory Luteinizing Hormone Surge Interval in Old and Young Laying Turkey Hens Early in the Egg Production Period

Egg production rate normally declines with duration of the reproductive period, but hen age and duration of the reproductive period are usually confounded. Initiation of egg production can be delayed in turkey hens with short-day lighting, allowing hen age to be separated from duration of the reproductive period. The objective of the present report is to determine if the interval between luteinizing hormone (LH) surges is different between old and young laying turkey hens during the peak of egg production. Turkey hens were given short-day lighting [6 h light (L):18 h darkness (D)] at 16 wk of age, and were photostimulated with 24L:OD (constant light) at 30 (young hens) or at 70 (old hens) wk of age. Egg production in the young hens started about 2 wk after they were photostimulated, but some of the old hens had started laying at 64 wk of age while under short-day lighting, and all old hens were laying after 1 wk of photostimulation. To monitor the interval between plasma LH surges at peak of production, hens were serially bled hourly for 240 h, starting about 6 wk after photostimulation. The interval of LH surges was not different between young (n = 5) and old (n = 10) laying hens. Not all LH surges were coincident with oviposition of eggs 1 to 2 d later (blind LH surges), and the percentage of young hens with at least one blind LH surge was higher than for old hens (60% of young hens and 10% of old hens). The baseline concentration of LH was not different between the young and old laying hens. In conclusion, the interval between LH surges, baseline concentration of LH, and amplitude of LH surges were not related to age of the hens during the peak rate of lay.

The effect of adding exogenous phytase to nutrient-reduced corn- and wheat-based diets on performance and egg quality of two strains of laying hens

A laying trial was conducted in which ISA-Brown and ISA-White hens were fed diets based on corn or wheat that had been pelleted to eliminate endogenous phytase. Control diets were formulated to contain adequate levels of all nutrients. Nutrient-reduced diets were formulated to account for nutrients released by the phytase. To formulate these diets, phytase was entered into the matrix with a value, on a weight basis, of 1,173% for CP (60.5% for lys, 29.4% for met plus cys, 40.0% for thr), 39 900 kcal kg–1 for AME, 666% for Ca, and 333% for available P. A negative control diet was based on the modified formulation but did not include phytase. Differences between diets were observed for tibia ash, and Ca and P in the ash, as well as for BW and measures of egg quality. Egg production likely provided the best measure of the adequacy of P nutrition. In the final period of production, feed intake and egg production of hens fed the nutrient-reduced corn-based diet without enzyme was lower (P &lt; 0.05) than that of hens on the control diet. Egg production of hens fed the nutrient-reduced diet with phytase was similar to that of hens fed the control diet, showing that inclusion of phytase permits formulation of corn-based diets with reduced levels of energy, CP, Ca, and P. No major effect of diet was seen for the hens fed wheat-based diets indicating that the formulation changes used may not have been appropriate for evaluating a response to exogenous phytase in wheat-based diets. Key words: Phytase, layers, corn, wheat, phosphorus

Ultrastructural analysis of the eggshell: Contribution of the individual calcified layers and the cuticle to hatchability and egg viability in broiler breeders

1. Scanning electron microscopy was used to assess the relationship between the layers of the eggshell and egg viability. The relative thickness (absolute and %) of the mammillary, palisade, vertical crystal and cuticle layers relative to the total eggshell were measured over a 30-week laying period in 2 broiler breeder lines having different hatchability rates. 2. A significant difference in hatchability of 5.5% between the breeder lines was observed. However, there was no significant difference in either egg viability or fertility between lines. 3. The relative thickness of the individual calcified layers and the cuticle did not differ between lines. Therefore, variations in the thickness of the individual eggshell layers are unlikely to explain the 5.5% difference in hatchability rate between lines. 4. The thickness of the calcified region did not alter as the broiler hen aged. However, the percent contribution of each calcified layer significantly differed over the egg production period. 5. The cuticle was significantly thinner at the beginning and at the end of the laying period compared to 38 weeks of age. 6. No significant correlation was observed between egg viability and the relative thicknesses of the mamillary, palisade or cuticle layers. In contrast, there was a positive relationship between egg viability and the thickness of the vertical crystal layer. 7. The percent contribution of the mammillary and palisade layers was similar in the thinnest and thickest eggshells, suggesting conservation of the proportions of these layers independent of eggshell thickness.

The use of step-down and modified constant protein feeding systems in developing pullets reared in hot climates

The effect of using varied levels of dietary protein with high energy levels in rearing diets on pullet development and on subsequent layer performance in hot climates, was studied using 160 Lohmann White Leghorn pullets. Five replicate groups of 16 pullets, 1 day of age were randomly assigned to each of two series of rearing diets. Pullets in both treatments were fed a 190 g crude protein (CP)/kg starter diet in the first week. Dietary protein level series used during Weeks 2–6, 7–14, and 15–18 were 190, 160, and 135 g CP/kg, respectively, for the decreasing protein series treatments and 160, 160, and 135 g CP/kg, respectively, for the semi-constant series. Energy level used during the rearing period in all diets was 12.55 MJ AME/kg. Pullets were reared under a natural cyclic hot temperature ranging as low as 27°C measured at 07:00 hours and as high as 34°C measured at 13:00 hours. At the beginning of Week 19, pullets were transferred to laying cages and fed two isocaloric layer diets for 20 weeks. Diet 1 used 190 g CP/kg and 4 g methionine/kg and Diet 2 used 160 g CP/kg and 3.4 g methionine/kg. Each diet was fed to half of the pullets within each rearing treatment program. During the rearing period, body weight of pullets in both treatment programs was similar, as was feed intake during Weeks 7–14 and 15–18. However, pullets fed diets with 160 g CP/kg had significantly ( p<0.05) higher feed intake than those fed the 190 g CP/kg diet during Weeks 2–6. Hen-day egg production, days to 50% egg production, egg weight and Haugh unit values were not affected by dietary protein treatments during the rearing period. Reducing protein levels from 190 to 160 g CP/kg in laying hen diets significantly increased egg production during Weeks 27–30 and 35–38, but reduced egg weight during Weeks 23–30 period of egg production. In addition, the results of this study showed that when birds were given adequate pullet development, very few differences in egg production parameters resulted due to feeding 160 or 190 g CP/kg during the early production period under this climatic condition.

Spawning in the nick of time? Effect of adult demographics on spawning behaviour and recruitment in Chesapeake Bay striped bass

Striped bass (Morone saxatilis) is an iteroparous anadromous species that spawns dispersive offspring into freshwater habitats and exhibits a high fecundity and high embryo and larval mortality rates. Field studies indicate that temperature differentially affects spawning behaviour and larval survival, and periods of high egg production are often mis-timed for optimal larval survival. I hypothesize that age structure of females may be an important determinant in reducing variability in recruitment through its influence on spawning behaviour. Age diversity of Chesapeake Bay female striped bass is indexed according to expectations of age-specific reproductive values in an unexploited population. The age diversity index was positively correlated to spawning dispersion (egg presence ratio) and 0+ juvenile abundance during the recent period of population recovery (1985–1995). Diversity in age structure and spawning behaviour may contribute to a storage effect, because in most years minority behaviours would result in sustained recruitment. A diverse age structure may thus contribute to an accumulation of spawning stock biomass and increase the future likelihood of dominant year classes.

Genetic relationship among lines and smooth muscle and ovarian follicular development within lines of Japanese quail in two long-term selection studies

Smooth muscle tumor and ovarian follicular development were studied in lines of Japanese quail selected for increased 4-wk BW (HW, P, and T) and their randombred controls (C and R1). The lines studied were from long-term selection studies at The Ohio State University (HW and R1) and The University of Georgia (P, T, and C). To study the genetic relationship among the lines in the two selection studies, the C, P, HW, and R1 lines were DNA-fingerprinted by digestion of the DNA with the HaeIII restriction enzyme and using Jeffreys' 33.6 probe. The BW of females at 4 wk of age and at the end of a 240-d egg production period were similar for the C and R1 lines. The BW of the selected lines was ranked P > T > HW for both measurements. Smooth muscle tumors were found in the oviducal ligaments adjacent to the magnum. A greater percentage of hens from the BW-selected lines had smooth muscle tumors of greater weight than the randombred control lines, which did not differ in tumor incidence or weight. The P and T lines had a greater incidence of multiple-lobed tumors than the HW line. Based on bandsharing (BS) of DNA fingerprints, the Georgia and Ohio lines did not appear to be closely related, suggesting that, perhaps, the smooth muscle tumors in the BW-selected lines in the two studies might have resulted from pleiotrophic effects of genes affecting growth or to genes closely linked to the growth genes. The BW-selected lines in both selection studies had more ovarian follicles in rapid development, which were of greater weight, than the randombred control lines. The HW line had a larger number of ovarian follicles in rapid development than the P and T lines. The percentage of hens with atretic follicles was greater in the BW-selected lines. The results of the present study suggest that the effect of BW selection on ovarian follicular development may occur early in selection (within the first 30 generations) and is not influenced by additional genetic changes in BW.

Time of Day of Ovulation by Three Duck Species in Subarctic Alaska

I examined variation in ovulation times of Northern Pintails (Anas acuta), American Wigeon (A. americana), and Lesser Scaup (Aythya affinis) breeding in subarctic Alaskan wetlands. Ovulation times and, by extension, egg-laying times were highly variable in all three species, with ovulations occurring during all hours of the day. Only Lesser Scaup demonstrated a morning peak in ovulations, within a broad range of ovulation times. Lack of a distinct time of day of ovulation suggests that fitness is not related to egg-laying time for these species, particularly at subarctic latitudes with nearly perpetual daylight. Egg-laying interval may have more adaptive significance than egg-laying time for these species. Ovulation intervals were estimated to be approximately 24 hr, which is short relative to the range of intervals documented in birds, despite high energetic and nutritional costs of egg formation in these species. Evidence of approximately 24-hr ovulation intervals, particularly in the absence of a distinct time of day for egg laying, supports hypotheses that a shortened period of egg production in waterfowl may have selective advantage due to reduction in the period of nest exposure to predation, earlier hatch dates, reduced hatch asynchrony, or improved viability of early-laid eggs.

The effect of divergent selection for total plasma phosphorus in Japanese quail on fearfulness and selected blood and heart parameters

A selection experiment utilizing Japanese quail was initiated to study the genetic relationship of growth and reproduction traits. In this study, lines were selected for increased (HP line) and decreased (LP line) total plasma phosphorus at the beginning of lay. The HP and LP lines were derived from a randombred control population (R1 line) that was maintained with the selected lines to remove environmental variation over generations. During the course of selection, it was observed that blood from HP line females was more viscous than that of the LP and R1 females. In later generations of selection, mortality of females during a 120-d egg production period was higher in the HP line than in the LP and R1 lines. The purpose of this experiment was to identify possible factors contributing to the increased mortality in the HP line. Fearfulness, as measured by tonic immobility, was greater in the HP and LP lines than in the R1 line. Indirect blood pressure measurements were made near the beginning and near the end of the 120-d egg production period. No significant line differences were observed in either measurement. Weight of the heart at the end of the laying period was higher in the HP and LP lines than in the R1 line. Histological study of the hearts of the HP and R1 lines indicated significant increases in the HP line in collagen content of the coronary arteries and in myocardial fibrosis. The data suggest that the increased mortality of females of the HP line relative to the R1 line during the laying period may be related to increased fearfulness and changes in the coronary structure leading to heart abnormalities.

Experimental evaluation of an inactivated vaccine against chicken anaemia virus

Summary An assessment of the performance of an inactivated chicken anaemia virus (CAV) vaccine following administration to specific‐pathogen‐free (SPF) breeder hens before the egg production period is reported. Antibodies to CAV in adult hens and maternally‐derived antibodies to CAV in the progeny chicks were assayed by ELISA. Progeny of vaccinated chickens showed sufficient levels of maternally‐derived antibody to CAV for up to 3 to 4 weeks of age. Following challenge at 1, 10, 20 and 30 days of age of chicks from CAV‐vaccinated and non‐vaccinated hens with virulent CAV, haematocrit levels and weights of thymus in vaccinates remained within normal ranges. Chicks derived from non‐vaccinated hens developed anaemia and thymus atrophy following challenge. These results support the view that vaccination of breeder flocks with an inactivated vaccine to CAV could be an effective means of control of CAV‐induced clinical disease.

Microbiology of Sanitized Broiler Hatching Eggs Through the Egg Production Period

Nest-clean and dirty eggs were sampled monthly across the productive period of a commercial broiler breeder flock. Eggshells and membranes were examined for total aerobic bacterial and Enterobacteriaceae counts per egg. Paired nest-clean and dirty eggs were spray sanitized in a two-stage commercial egg sanitizing machine (a chlorine detergent wash followed by a quaternary ammonia sanitizing spray) and tested for bacterial contamination. As the flock aged, numbers of bacteria per nest-clean egg fluctuated without a noticeable trend (from log10 4.1 to 5.3 aerobic bacteria). Bacterial populations were significantly lower on sanitized eggs (log10 0.8 to 3.2 cells total aerobic bacteria and 2 to 5 cells Enterobacteriaceae per egg) regardless of hen age. Those eggs classified as dirty had visible fecal contanmination and higher bacterial numbers than nest-clean eggs (log10 5.9 to 7.6 cells total aerobic bacteria per egg). After sanitization, previously dirty eggs had bacterial populations comparable to those of sanitized nest-clean eggs. When eggs were examined in the hatchery at transfer, sanitized dirty eggs were still microbiologically indistinguishable from sanitized net-clean eggs, though both groups had higher bacterial contamination levels than had been observed in samples taken immediately following sanitization.

Effects of environmental and social factors on incubation behavior, endocrinological parameters, and production traits in turkey hens (Meleagris gallopavo)

Hens raised in three different environments were assessed for changes in egg production performance, the rate of incubation behavior expression, and plasma levels of luteinizing hormone (LH) and prolactin for 20 wk following the laying of the first egg. The environments were individual (IFP) or collective floor pens (CFP) and individual battery cages (Cp and Cnp). The hens from three experimental groups (IFP, CFP, and Cp) were transferred from a short (6 h) to a long (14 h) photoperiod, whereas the ones from the remnant (Cnp) were left under a short one. Increase of the photoperiod induced significant increases (P < 0.05) in levels of prolactin and LH after 1 d, and resulted in the onset of egg laying in a delay of 14 d in all groups. However, the overall egg laying performance was highest for the IFP hens. The CFP and IFP hens laid 98 and 24% of their eggs inside the nest boxes, respectively. The hens raised in battery cages did not express incubation behavior, whereas 50 and 33%, respectively, of the CFP and IFP hens did. During the 1st wk of egg laying, levels of prolactin increased for all photostimulated hens but to a greater extent for CFP hens. Higher increases in levels of prolactin were associated with the expression of incubation behavior; however, prolactin levels of nonincubating laying hens were also higher under the CFP treatment. It appears that the rate of expression of incubation behavior, as well as changes in the plasma levels of prolactin and LH throughout an egg production period, are dependent upon rearing conditions in turkey hens.