Depressed Egg Production Research Articles

Nutrient stability in mould-infested feed and mitigating effect of dietary supplemental vitamins in brown laying hens.

A 10-week study was conducted to assess the impact of mould infestation on nutrient stability of feed and the mitigating effect of supplemental tocopherol, retinol or a multivitamin on performance and hepatic histology of ISA Brown laying chickens. Two batches of corn were obtained: the aflasafe corn used in preparing control diet and corn with physical evidence of mould used in preparing diets 2 to 5 containing no supplemental vitamin, tocopherol, retinol or a branded multivitamin supplementations respectively. One hundred and fifty (150) laying chickens used were completely randomized into five dietary treatments with three replicates of 10 birds each. Results showed that there was gross instability in the nutrients of mouldy maize. The activities of the fungi depleted both protein and lipid contents by 11.54% and 12.72% respectively while crude fibre content rose by 31.7%. There was substantial drop in both retinol and tocopherol while aflatoxin content rose to 267μg in mouldy corn and 118μg in the mouldy diets. Feed intake was significantly (P < 0.05) reduced and consequently depressed (P < 0.05) egg production and feed efficiency. Egg quality differs (P < 0.05) in shell thickness and yolk colour. Proliferation of biliary duct epithelium, hepatic degeneration, cellular infiltration, hyper-cellularity or dilation of the sinusoidal spaces characterized livers of birds on mouldy corn diets while supplementation with vitamins subverted mycosis and aflatoxicosis as evidenced by normal-to-mild congestion of hepatocytes. It was concluded that mould contamination in feed compromised feed nutritive values, reduced bird performance and adversely impaired the liver of the experimental birds while tocopherol, retinol or a multivitamin supplementation relapses the damaging potential of mould and mycotoxin differently.

Small-scale egg production centres increase children's egg consumption in rural Zambia.

Animal source foods can efficiently enhance dietary quality, but they remain inaccessible and unaffordable for many women and young children in remote, low-income communities. We piloted an intervention in which 20 groups established egg production centres (EPCs) in their rural Zambian communities to increase the availability of eggs in the local food system. In a repeated cross-sectional design over 1year (midline [4months after the start of egg production] and endline [11months]), we evaluated programme impact on household egg acquisition within those communities and on egg consumption and height-for-age z score (HAZ) among young children (6-36months) using multilevel linear, logistic, and truncated negative binomial regression techniques. At midline, households in project areas were significantly more likely to consume eggs than those in control areas (OR 2.08, 95% CI [1.56, 2.78]), particularly those located within 250m of the EPC. Similarly, children living in project communities were significantly more likely to consume eggs at midline than those in control areas (OR 5.53, 95% CI [2.90, 10.58]). Although increased over baseline, egg acquisition and consumption decreased by endline because of depressed egg production over time. There was no impact on children's HAZ, likely because of the short follow-up time and relatively modest "dose" of egg consumption. Although productivity can be improved, the EPC programme offers a novel approach to improving access to eggs in rural communities, and optimization of the production practices and marketing is needed to ensure that egg consumption translates to improved dietary quality, growth, and health.

Effects of rearing systems on reproductive hormones secretion and their receptors gene expression in Xianju chickens under summer conditions.

Previous study in our lab showed that indigenous Xianju chickens from free-range system (FRS) under summer conditions had lower egg production than those from conventional cage rearing system (CRS). The objective of this study was to preliminarily determine the FRS-dependent mechanism of depressing laying performance according to determining the effect of rearing systems on reproductive hormones secretion and their receptors mRNA expression in Xianju chickens reared under summer conditions. A total of 360 indigenous Xianju chickens were randomly allocated to CRS and FRS groups, each of which included 5 replicates of 36 hens. The experiment lasted between 21 and 29 wk of age. We found that the ovarian weight, numbers of small yellow follicles, and large white follicles in the FRS group were lower than those in the CRS group (P < 0.05). Changing from CRS to FRS increased serum concentrations of prolactin and decreased serum-luteinizing hormone and progesterone levels (P < 0.05). Gene expressions in the preovulatory follicles from FRS hens were upregulated for prolactin receptor and downregulated for luteinizing hormone receptor and progesterone receptor, compared to those from CRS hens (P < 0.05). It can be concluded that changing from CRS to FRS in the current experimental conditions depressed egg production traits in Xianju chickens by inducing a synergistic activity of reproductive hormones and the gene expressions of their receptors.

The probiotic Bacillus licheniformis ameliorates heat stress-induced impairment of egg production, gut morphology, and intestinal mucosal immunity in laying hens

We investigated the effect of a 12-d exposure to 34°C plus dietary inclusion of the probiotic Bacillus licheniformis on the egg production, gut morphology, and intestinal mucosal immunity of laying hens. Ninety-six commercial hens (Hy-Line Brown) at the age of 60 wk were randomly allocated to 4 groups. After a period of laying rate adjustment (14 d), all the hens were subjected to 2 temperature treatments (12 d). Birds in 1 group were raised at 21°C and fed a basal diet, and birds in the other 3 groups were raised at 34°C and fed a basal diet supplemented with 0, 106, or 107 cfu of B. licheniformis per gram of feed, respectively. Rearing at 34°C depressed egg production and feed intake (P < 0.05). Compared with birds kept at 21°C, birds kept at 34°C had elevated serum levels of tumor necrosis factor-α (d 6), IL-1 (d 6 and 12), and corticosterone (d 6); decreased villus height (ileum: d 6; cecum: d 6 and 12) and ratio of villus height to crypt depth (ileum: d 6; cecum: d 6 and 12); fewer intraepithelial lymphocytes (ileum: d 6; cecum: d 6) and IgA-secreting cells (ileum: d 6; cecum: d 6 and 12); and more mast cells (ileum: d 6; cecum: d 6 and 12; P < 0.05). The number of goblet cells in the cecum increased at d 6 in heat-treated birds, and then deceased at d 12 (P < 0.05). Moreover, morphological examination showed injury to the villi of birds kept at 34°C. In general, inclusion of 107 cfu/g of B. licheniformis in the diet of heat-stressed hens was effective in overcoming the observed decline in egg production and feed intake, restoring the impaired villus structure, and sustaining a balanced mucosal immune response. Therefore, the probiotic B. licheniformis may be useful for ameliorating the adverse influence of heat on the egg production and gut health of laying hens.

Constant and Changing Photoperiods in the Laying Period for Broiler Breeders Allowed [Corrected] Normal or Accelerated Growth During the Rearing Period

Broiler breeder pullets were grown on 8-h photoperiods to 2.23 or 2.42 kg of BW at 20 wk, and then transferred abruptly to 11- or 16-h photoperiods. Subsequently, some of the 11-h photoperiod birds were given 15-min increases in day length weekly or a 1-h increase every 4 wk to reach 16 h of light at 54 wk. The birds transferred abruptly to a 16-h photoperiod at 20 wk matured 4 d earlier than 11-h photoperiod birds, required 500 g less feed to reach 50% lay, but, because of a 3% lower rate of lay after peak, produced 5 fewer eggs to 60 wk. However, the number of settable eggs was similar for the 2 groups because the 11-h photoperiod birds laid more eggs on the floor, resulting in more cracked and dirty eggs. The 11-h photoperiod birds converted feed into egg more efficiently, and were 100 g heavier at end of lay. Increasing the photoperiod in 15-min or 1-h increments from 11 to 16 h during the laying cycle depressed egg production. Mean egg weight and mortality were similar for all lighting groups. The heavier BW birds at 20 wk reached maturity 1 d earlier, but used 1 kg more feed to reach maturity, laid 5 fewer total eggs (because of a 3% lower rate of lay after peak), produced 7 more unsettable eggs (because more eggs were laid on the floor), and converted feed into egg less efficiently than did the lighter BW birds. Mean egg weight, BW at 57 wk, and mortality were similar for both groups. There was no significant light × growth interaction for any performance parameter. It is concluded that there is no benefit to egg production from extending the photoperiod to 16 h when broiler breeders are kept in light-proofed housing, especially if they have access to illuminated nest boxes.

Effects of Dietary Zinc Supplementation on Hen Performance, Ammonia Volatilization, and Nitrogen Retention in Manure

This investigation was undertaken to evaluate the effects of dietary ZnSO4 supplementation on ammonia volatilization and nitrogen retention in hen manure. One hundred twenty, 45-wk-old commercial Leghorn laying hens were sequentially fed diets with 1000, 2000, and 3000 ppm Zn as ZnSO4 (Zn-1000, Zn-2000, and Zn-3000), then followed by two control dietary periods with 114 ppm Zn (Control-1 and Control-2) for a total of five consecutive eight-day experiment periods, respectively. When hens were fed the 1000 and 2000 ppm Zn treatment diets, room ammonia levels were significantly reduced compared to the control diets. Dietary Zn treatments reduced the decomposition of uric acid, resulting in an increase in manure total-N retention compared to the control fed birds. The 1000 ppm Zn supplement had no adverse effects on hen body weight, feed consumption, egg production, egg weight, albumen height, or shell thickness. However, hens fed the diet containing 3000 ppm Zn had significantly depressed body weight, feed consumption, egg production, egg weight, and shell thickness. Zinc levels of egg contents increased linearly as dietary Zn levels increased. These levels in eggs would not be a problem for human consumption because these are much less than the daily Zn recommended dietary allowance. Although land application of such manure will not cause environmental problems or crop toxicity, proper monitoring of soil and crop Zn levels and effective nutrient management planning would be well advised.

Hy-Line W-36 and Hy-Line W-98 laying hens respond similarly to dietary phosphorus levels

Two experiments were conducted to determine if 2 laying hen strains, Hy-Line W-36 and Hy-Line W-98, would respond similarly to being fed corn-soybean meal diets (17% CP and 3.8% Ca) deficient in nonphytate P (NPP). In experiment 1, 3 diets with varying NPP levels (0.10, 0.14, and 0.45%) were fed to 6 replicate groups of 12 hens of each Hy-Line strain from 20 to 50 wk of age. Body weight, egg weight, egg mass, feed intake, and NPP intake were higher for W-98 hens compared with W-36 hens throughout the 30-wk period. The 0.10% NPP dietary treatment was terminated for both strains at 35 wk of age due to similar low egg production. Within each strain, there was no significant difference in egg production performance for hens fed 0.14% NPP compared with hens fed 0.45% NPP. In experiment 2,3 diets with varying levels of NPP (0.10, 0.13, and 0.45%) were fed to 5 replicate groups of 12 hens of each Hy-Line strain from 95 to 112 wk of age. The 0.10% NPP treatment rapidly and severely depressed egg production and was terminated at 99 wk of age for both strains. In addition, egg production and egg mass were depressed similarly in both strains fed 0.13% NPP. In conclusion, this research indicates that Hy-Line W-36 and Hy-Line W-98 hens responded similarly to dietary NPP deficiency, suggesting that both strains have similar NPP requirements.

Effect of a Single Short-Term Reduction in Photoperiod on Photorefractoriness in Turkey Hens

In a prior study, we reported that a high proportion of hens in a winter-laying flock became relatively photorefractory (rPR) early in the reproductive cyand that successive short-term reductions in photoperiod in such hens each initially depressed egg production but then caused a rebound in rate of lay to briefly exceed that of hens that did not exhibit rPR. The present study was conducted to assess rPR in a summer-laying flock and to determine whether a single short-term reduction in day length early in the reproductive cycle might enhance egg production and delay the onset of absolute photorefractoriness (aPR). Control hens received a photoperiod of 16L:8D throughout the experiment. Experimental hens were photostimulated with 16L:8D, received a reduced (but still stimulatory) photoperiod of 11.5L:12.5D for 2 wk beginning 8 wk after photostimulation, and then were returned to 16L:8D for the remainder of the 23-wk test period. Results showed that a single 2-wk reduction in day length shortly after the hens reached peak egg production did not significantly reduce overall flock egg production, but it also did not improve late-season egg production or retard the onset or incidence of aPR. The incidence of rPR was substantially less in this study than we had observed with a winter-laying flock (32.9 vs. 67.1%), but similar proportions of treated hens exhibited the most severe rPR response (a brief but complete cessation of egg production) in both studies (21.1 vs. 24.0%), and all treated hens that subsequently became aPR had shown this severe rPR response to the test photoperiod. We concluded that a core proportion of hens (approximately one-fifth) exhibited a strong rPR response when presented with a reduced photoperiod early in the reproductive cycle, regardless of season of the year, and that such hens were more likely to subsequently exhibit poor egg production or become aPR than flockmates that did not exhibit rPR. Therefore, some indication of the incidence of rPR early in the lay period may have a predictive value for the overall egg production of the flock.

Relating the reproductive toxicity of five ingested metals in calanoid copepods with sulfur affinity

The sublethal toxicity of dietary Ag, Cd, Hg, Mn, and Zn to marine copepods, measured as depressed egg production, was evaluated as a function of ambient metal concentrations and metal concentrations in copepod tissues. All metals were toxic following 4-h feedings on metal-contaminated phytoplankton food, but there was a four order of magnitude difference between the inhibitory concentration in copepod tissues of the most toxic (2.4 nmol g −1 dry wt. for Hg) and least toxic (13.4 μmol g −1 dry wt. for Mn) metals. Metal concentrations in copepods that elicited a toxic response were about 3 times higher than background concentrations for Ag and 9 times higher for Hg, about 2 times higher for Cd, two orders of magnitude higher for Mn, and only 5% higher for Zn. Copepods exposed to lower concentrations of Zn for longer periods (1 week), resulting in tissue Zn concentrations similar to those in the short-term exposures, were not affected, suggesting that copepods were capable of adjusting to slowly increasing Zn by sequestration of this metal. Toxic metal concentrations in copepod tissues were directly proportional ( r 2=0.85) to the affinity of the metals for sulfur, as indicated by the solubility products of the metal sulfides. This relationship, together with protein analysis of eggs, published recently, suggests that metals affect egg production by binding to enzymes involved with vitellogenesis.

Vitamin E can alleviate the depressed egg production of heat-stressed laying hens

Vitamin E can alleviate the depressed egg production of heat-stressed laying hens

Effect of dietary organic arsenicals and cupric sulfate on copper toxicity, liver accumulation and residue in eggs and excreta of laying hens

A trial was conducted to examine the effects of the interaction of an organic arsenical compound (roxarsone): 3-nitro-4-hydroxy-phenylarsonic acid and copper sulfate on the egg production, liver function, and the copper content of the liver, eggs and excreta of laying hens. The experiment was a 2×3 factorial design with three replications. Ninety 38-weeks-old layer hens were selected from a commercial flock, and placed into six dietary treatments, i.e. two levels of roxarsone (0, 50 mg kg −1) and three levels of supplementary copper (400, 500, 600 mg kg −1), with five layer hens in each cage. Feeding was undertaken for four weeks. The interaction between copper and roxarsone in the diet significantly influenced the feed intake, egg production, and copper content in the liver and excreta ( P<0.05). Increasing the supplementation of copper from 400 to 600 mg kg −1 significantly depressed feed intake and egg production in both groups receiving diets with or without added roxarsone ( P<0.05). Increasing the supplement of copper from 400 to 500 mg kg −1 significantly depressed feed intake and egg production only in the diet including roxarsone. Adding roxarsone to the low copper supplemented diet (400 mg kg −1) significantly depressed egg production ( P<0.05). The copper content in liver significantly increased with an increasing level of copper supplement ( P<0.05) in the diet without roxarsone inclusion. With the addition of roxarsone, the level of copper supplement did not significantly influence the copper concentration in the liver ( P>0.05). With all supplement levels of copper, the copper concentration in both the liver and egg were significantly depressed by adding roxarsone to the diet. Without the roxarsone supplement, increased levels of copper supplements also significantly depressed the copper content in the eggs ( P<0.05). In all diets, both with and without roxarsone, the copper content in excreta of layers significantly increased as the level of supplemental copper increased ( P<0.05). The rate of copper excretion increased significantly more with the diet containing added roxarsone as supplemental copper increased from 400 to 500 mg kg −1. The response of serum aspartate aminotransferase (AST) and creatine kinase (CK) to the dietary supplement of copper and roxarsone was inconsistent. However, lactate dehydrogenase (LDH) activity increased significantly ( P<0.05). High dietary copper (500 or 600 mg kg −1) diets increased the serum LDH activity significantly ( P<0.05) with the roxarsone inclusion in the diet at the end of the first week of feeding. With the dietary inclusion of roxarsone, the LDH enzyme activity also significantly ( P<0.05) raised in the high copper diet of 500 mg kg −1 on the third week, and in all levels of copper on the forth week. Liver damage was also observed with the bile duct proliferation and hepatocyte degeneration.

Variants of smooth Salmonella enterica serovar Enteritidis that grow to higher cell density than the wild type are more virulent.

Salmonella enterica serovar Enteritidis that grows to a higher cell density (SE-HCD) than wild type while retaining O-chain lipopolysaccharide was isolated by transforming wild type serovar Enteritidis with the cell density sensor plasmid pSB402 and selecting for bioluminescence. A luminescent strain, SE-HCD, that emitted light in proportion with cell density and opacity through stationary phase was isolated. After a peak cell density of 1.5 x 10(11) CFU/ml was observed, luminescence decreased, although opacity continued to increase. Scanning electron microscopy revealed that changes in luminescence and opacity past peak cell density were associated with lysis of a swarming hyperflagellated coccobacillary cell type and emergence of a 10-to-30-fold-elongated rod cell type that lacked cell surface structures. Vigorous aeration was required to induce this dramatic cellular differentiation. The virulence of two isogenic variants with different patterns of light emission at an opacity of 0.2 after the culture was diluted 10-fold (1/10 OD) was assessed in animal models. Whereas SE-HCD1 killed 70% of 6-day-old chicks challenged subcutaneously, the same dose of SE-HCD2 did not kill any chicks. Conversely, subcutaneous challenge of hens with SE-HCD2 contaminated eggs five and seven times more often, respectively, than did SE-HCD1 or wild type serovar Enteritidis. Intravenous challenge with SE-HCD2 contaminated 22% of eggs versus 0. 5% with wild type, depressed egg production for 4 weeks, and caused clinical signs of Gallinarum Disease (Fowl Typhoid) in hens. SE-HCD2 produced no contaminated eggs following oral infection, whereas wild type contaminated 1.3% of eggs. Thus, SE-HCD2 is better at contaminating eggs than wild type, but only by parenteral challenge. These results suggest that it may be possible to separate luminescent serovar Enteritidis into groups that infect different age groups and organs and contaminate eggs.

Ahemeral lighting of turkey breeder hens. 2. Early age at lighting and reproductive performance

An experiment was conducted to determine whether ahemeral lighting (AH) could be used to obtain increased egg weight and poult weight and otherwise normal reproductive performance in Large White turkey hens lit as early as 26 wk of age. The experimental design utilized a 2 x 2 factorial arrangement of treatments that evaluated two light cycle lengths (24 h, control and 28 h, ahemeral) at two hen ages (26 and 30 wk). Treatments were continued for 24 wk and the following variables were measured: BW, feed intake, onset and rate of lay, fertility, hatchability, incidence of floor eggs, egg weight, poult production, and poult weight. As compared to the response of hens in the control lighting treatment, ahemeral lighting increased egg weight and poult weight early in the lay period only and resulted in delayed onset of lay (+3.4 d) and depressed egg production (-7 eggs to 54 wk of age). Percentage fertility and hatchability were similar between ahemeral and control treatment groups. However, ahemeral lighting decreased the number of poults per hen when started at 26, but not 30, wk of age. Hens photostimulated early at 26 wk of age were delayed in onset of lay by 5.9 d but produced more eggs per hen to 54 wk of age (95.8) than hens photostimulated at 30 wk (89.7); however, during equivalent lay periods, egg production was similar between the two groups. Early lighting did not have an adverse effect on fertility, hatchability, or poults per hen but egg weight and poult weight were depressed. It was concluded that although ahemeral lighting increased egg weight and poult weight in turkey hens photostimulated early, continuous application of ahemeral lighting throughout the lay period had adverse effects on some components of reproductive performance.

Effects of high levels of vitamin e supplementation in heat stressed laying hens

It was investigated in a small-scale study using a climate-controlled room at IAPGR, Roslin, that the effects of feeding a high level of supplemental vitamin E (500 mg/kg) on egg production and plasma concentrations of egg-associated metabolites in laying hens subjected to a short exposure (7 days) to a moderate heat stress (temperature of 32°C). The study showed, on small group sizes (12 birds / group), that in control birds (fed 30 mg supplemental vitamin E/kg), this degree of heat stress depressed egg production by about 30%. In the birds receiving the high level of vitamin E, egg production was maintained at levels very close to those prior to the heat stress. The objective of this experiment was to confirm in a larger scale the effects of high levels of dietary vitamin E on egg production of hens exposed to a chronic heat stress and during a period of recovery at thermoneutral temperatures.

Effects of high levels of vitamin e supplementation in heat stressed laying hens

It was investigated in a small-scale study using a climate-controlled room at IAPGR, Roslin, that the effects of feeding a high level of supplemental vitamin E (500 mg/kg) on egg production and plasma concentrations of egg-associated metabolites in laying hens subjected to a short exposure (7 days) to a moderate heat stress (temperature of 32°C). The study showed, on small group sizes (12 birds / group), that in control birds (fed 30 mg supplemental vitamin E/kg), this degree of heat stress depressed egg production by about 30%. In the birds receiving the high level of vitamin E, egg production was maintained at levels very close to those prior to the heat stress. The objective of this experiment was to confirm in a larger scale the effects of high levels of dietary vitamin E on egg production of hens exposed to a chronic heat stress and during a period of recovery at thermoneutral temperatures.

Effects of Ascorbic Acid on Plasma Thyroxine Concentrations and Eggshell Quality of Leghorn Chickens Treated with Dietary Thiouracil

Because ascorbic acid (AA) and the thyroid hormones are known to influence eggshell formation, the effects of AA on body weight, total plasma thyroxine (T4), egg production, and eggshell quality of Single Comb White Leghorn (SCWL) hens concurrently and previously treated with thiouracil (TU) were determined. Hens were provided feed containing either 0 or 100 ppm AA from 47 to 67 wk of age and either 0 or .1% TU from 47 to 57 wk of age. A three-way split-plot analysis was employed to test for the effects of AA, TU, and time, and their interactions.Dietary TU increased body weight between 53 and 59 wk, and increased thyroid weight at 67 wk; however, TU only depressed plasma T4 level at 51 wk. Dietary TU depressed egg production from 50 to 56 wk and egg weight at 49, 51, and 57 wk. Dietary TU depressed eggshell weight per unit surface area at 49 wk. There was no significant effect due to AA and no AA by TU interaction for any of the parameters examined. It was concluded that .1% dietary TU from 47 to 57 wk of age did not alter eggshell quality and that dietary AA at the 100 ppm level did not influence the effects of .1 % TU on body weight, egg production, or egg weight of SCWL hens.

Effect of Dietary Boron Supplementation on Egg Production, Shell Quality, and Calcium Metabolism in Aged Broiler Breeder Hens

Three experiments were conducted using aged broiler breeder hens (>60 wk) to investigate the effects of supplemental B on egg production (EP), shell quality, and Ca metabolism. Experiment 1 had a 2 × 2 factorial arrangement of treatments: 1) high Ca (3.5%); 2) high Ca plus B; 3) low Ca (1.5%); and 4) low Ca plus B; using 32 60-wk-old hens. The B levels were basal and 100 ppm supplemental for the first 2 wk of the experiment and reduced to 60 ppm for the remaining 3 wk. Egg production, shell thickness (ST), and egg specific gravity (SG) were recorded weekly. In Experiment 2, 40 60-wk-old hens were divided into two groups: high and low shell quality. Each group was further divided into two subgroups and fed a low-Ca basal diet with or without supplemental B. The level of B supplementation and the experimental period was the same as in Experiment 1. In Experiment 3, 52 75-wk-old hens were force-molted. After molting, 36 hens were fed a commercial layer diet with the remaining 16 hens fed the control diet supplemented with 100 ppm B. Blood samples were taken during the nonlaying and laying periods, respectively.The results showed that B significantly (P<.05) depressed EP in Experiment 1 but not in Experiments 2 and 3. Supplemental B decreased plasma Ca when hens were fed a diet containing high Ca levels (3.5%). Supplemental B did not affect SG, ST, or Ca retention, but did significantly increase tibial bone ash percentage (P<.05). The results of these studies indicate mat pharmacological B supplementation of laying diets is not warranted.

Research Note: The Effect of Feeding Lovastatin and Colestipol on Production and Cholesterol Content of Eggs

The purpose of the present study was to determine whether feeding lovastatin or colestipol, or both, to laying hens would decrease the concentration of cholesterol in eggs. Forty-eight White Leghorn hens (69 wk of age) were allocated randomly to one of four groups. For 5 wk, the birds were fed: 1) a control diet; 2) diets supplemented with 35 mg of lovastatin per kg of feed; 3) 11.7 g of colestipol per kg of feed; or 4) both 35 mg of lovastatin and 11.7 g of colestipol per kg of feed. Drug feeding did not affect egg production or the concentration of cholesterol in the yolk, muscle, or liver. Lovastatin residue was found in liver samples from hens receiving lovastatin, but no lovastatin residue was found in the muscle, egg-white, or egg-yolk samples from hens on any treatment. These findings suggest that lovastatin or colestipol, or both, fed at relatively low amounts do not decrease the concentration of cholesterol in egg yolk and do not depress egg production.

Effects of sediment-bound residues of the pyrethroid insecticide fenvalerate on survival and reproduction of meiobenthic copepods

Pure, microcosm-cultured populations of benthic copepods were established from pristine or pesticide-impacted Spartina marsh creeks and used as efficient bioassay groups to assess lethal and sublethal effects of sediment-bound pesticide residues. Naturally-weathered sediments contaminated with the synthetic pyrethroid insecticide fenvalerate were collected by traps moored in a tidal creek receiving major pesticide-laced runoff from an agricultural watershed, and used as dosing material. Silty sediments with fenvalerate residues reaching 100 ppb were trapped and then diluted with uncontaminated sediments to achieve an exposure range of 0, 25, 50 and 100 ppb (i.e. no dilution). Despite a broad database showing extreme sensitivity to water-solubilized fenvalerate by many marine invertebrates and fishes, a 7-day exposure to sediment-bound residues as high as 100 ppb caused no significant mortality for any life stages (i.e. nauplii, copepodites or adults) of the benthic harpacticoid copepods Microarthridion littorale or Paronychocamptus wilsoni, and no mortality for adults of Enhydrosoma propinquum. However, sediment-bound residues as low as 25 ppb significantly depressed egg production (50–100% reduction) and mean clutch sizes (40–100% reduction) of fertile M. littorale and P. wilsoni. If sedimenting fenvalerate depresses copepod reproduction in the field, then lowered recruitment of new individuals will lead inevitably to a decline in population growth.

Pineal Gland and Ocular Influences on Turkey Breeder Hens.: 1. Reproductive Performance

The influence of the pineal gland and the eyes on reproductive performance of turkey hens was examined. Photosensitive, yearling Large White turkey breeder hens underwent pinealectomy (PX) or bilateral ocular enucleation (EX) or both while held on 8 hr of light per day (8L:16D) and were then photoinduced into a typical 20-week egg laying period by exposing the birds to 16 hr of light per day (16L:8D). Data were obtained for the time to first egg (sexual maturation), rate of egg laying, percent fertility, percent hatchability, weight of poults at hatching, and plasma melatonin levels. A significant interaction between PX and EX treatments occurred in the sexual maturation data only.Pinealectomy significantly delayed (P<.05) the onset of egg laying (by 4.1 to 7.4 days) compared with the other treatment groups. No other significant differences in onset of lay occurred. Pinealectomy significantly depressed egg production during weeks 11 to 20 of lay and this resulted in fewer eggs per PX hen over the 20-week study (85.4 vs. 93.3 eggs in the PX and pineal intact groups, respectively). Enucleation did not significantly affect egg production. Neither the PX nor the EX treatment significantly affected fertility or hatchability determined at 4-week intervals over the 20-week study. However, poult weights were significantly greater as a result of either PX (P<.01) or EX (P<.05 ) treatment. Nocturnal elevation of plasma melatonin was significantly reduced by PX but not by EX. It was concluded that an extraretinal, extrapineal photoreceptive mechanism is operative in turkey breeder hens but both the pineal gland and the eyes can influence certain reproductive parameters.