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Biomedical subjects

J D Garlich

Publications and source records attributed to J D Garlich.

At least 19 recordsLinked to original sources
PubMed1998

Dietary threonine responses in growing turkey toms.

A study was conducted to evaluate Thr responses in Large White (British United Turkeys) male turkeys during three time periods: 0 to 3, 3 to 6, and 6 to 9 wk of age. The Thr-deficient diets, fed in 3-wk intervals, were composed primarily of corn, peanut meal, poultry meal, and soybean meal as intact protein sources and supplemented with amino acids. Graded levels of L-Thr were added to the Thr-deficient diets. Another group of turkeys received a corn-soybean-poultry meal control diet in each time period. Diets were formulated to meet a minimum of 110% of suggested amino acid specifications (NRC, 1994) for all essential amino acids, except Thr. Feed intake, BW gain, and feed:gain responses were measured. Average environmental temperatures for Weeks 1, 2, and 3 were 29, 27, and 24 C, respectively. From 4 to 9 wk of age, average environmental temperatures varied between 24 and 35 C. Turkeys in each time period responded to Thr in a curvilinear manner with responses at the asymptote being equivalent to turkeys fed the corn-soybean meal control diets. Adequate dietary Thr levels for gain and feed:gain for the 0 to 3 wk period were 0.93% (3.21 g Thr/Mcal ME) and 0.97% (3.34 g Thr/Mcal ME) of diet, respectively. From 3 to 6 wk of age, the level of dietary Thr needed to support adequate BW gain and feed:gain was 0.88% of diet (2.81 g Thr/Mcal ME). The level of dietary Thr needed to support adequate BW gain and feed:gain from 6 to 9 wk of age was 0.77% of diet (2.30 g Thr/Mcal ME). These results indicate that the NRC (1994) estimations of Thr needs up to 9 wk of age are more than adequate.

Animal Feed↗
PubMed1998

Vitamin D deficiency alters the immune responses of broiler chicks.

Three experiments were conducted to test the hypothesis that a vitamin D deficiency alters the immune responses of female broiler chicks. The control diet contained 800 IU of cholecalciferol (vitamin D3)/kg and the deficient diet was the same except without supplemental vitamin D3. The vitamin D deficiency status was established on the basis of a significantly lower blood ionized calcium or total serum calcium (75 to 85% of the control). Vitamin D-deficient chicks also had lower growth rate and bone ash. In Experiment 1 at 8 d of age, and Experiment 2 at 23 d of age, the cutaneous basophil hypersensitivity response as determined by the increase in interdigital skin thickness 20 h after a single injection of 100 microg phytohemagglutinin-P was significantly depressed in vitamin D-deficient chicks (62 to 64% of the control). Thymus weight, adjusted for body weight, was significantly lower in the vitamin D-deficient chicks at 24 d of age (61% of the control). Primary and secondary antibody responses against SRBC in vitamin D-deficient chicks were not different from the control. In Experiment 3, in 17-d-old chicks, vitamin D deficiency decreased the number of abdominal macrophages phagocytizing SRBC in vitro within 45 min from 14.7 to 10.1%. These results indicate that vitamin D deficiency depresses the cellular immune responses in young broiler chicks.

Animal Feed↗
PubMed1996

Dietary Spirulina platensis enhances humoral and cell-mediated immune functions in chickens.

Cornell K-strain White Leghorns and broiler chicks were raised to 7 wks and 3 wks of age respectively, with diets containing various levels (0, 10, 100, 1,000 and 10,000 ppm) of Spirulina platensis from day of hatch. Chicks in all treatment groups had comparable body weights. While bursal and splenic weights did not change, the K-strain chicks had larger thymuses (P < or = .05) over the controls (0 ppm group). No differences were observed in anti-sheep red blood cells antibodies during primary response. However, during secondary response, K-strain chicks in all Spirulina-dietary groups had higher total anti-SRBC titers with 10,000 ppm group being the highest (6.8 Log2) versus the 0 ppm (5.5 Log2) group. In broiler chicks, a one Log increase in IgG (P < or = .05) was observed in 10,000 ppm group over the controls. Similarly, chicks in 10,000 ppm Spirulina group had a higher PHA-P-mediated lymphoproliferative response over the 0 ppm controls. Macrophages isolated from both K-strain (10,000 ppm group) and broilers from all Spirulina groups had higher phagocytic potential than the 0 ppm groups. Spirulina supplementation at 10,000 ppm level also increased NK-cell activity by two fold over the controls. These studies show that Spirulina supplementation increases several immunological functions implying that a dietary inclusion of Spirulina at a level of 10,000 ppm may enhance disease resistance potential in chickens.

Adjuvants, Immunologic↗
PubMed1995

Fusarium proliferatum culture material alters several production and immune performance parameters in White Leghorn chickens.

White Leghorn Cornell K-strain chicks (3 replicates of 16 per pen) were started at Day 7 on feed amended with Fusarium proliferatum culture material containing fumonisin B1, fumonisin B2, and moniliformin at 61, 10.5, and 42.7 ppm, respectively. Observed effects on performance of treated birds included reduced feed conversion at 2 wk, and reduced body weight of males and females up to 6 wk (P < or = .05). Splenic, thymic, and liver weights, normalized for body weight, were reduced (P < or = .05) with no change in bursa of Fabricius. No significant changes were observed histologically in the spleen, bursa, kidney, heart, liver, cecal tonsils, colon, or tibia. Significant suppression in total Ig and IgG levels occurred. Macrophages from treated chicks exhibited a 34% reduction in phagocytic activity. Natural killer cell activity was not affected. These findings, which showed that Fusarium toxins alter performance and immune end points in chickens, imply that chickens exposed to mycotoxins may be more susceptible to infectious diseases.

Animals↗
PubMed1995

Potassium chloride improves the thermotolerance of chickens exposed to acute heat stress.

Experiments were designed to test the hypothesis that chicks that drank an electrolyte solution containing K prior to and during an acute exposure to heat would have greater thermotolerance than chicks that consumed only water. In three experiments, 5- or 7-wk-old male chickens drank distilled water (control), or .3, .6, or .9% KCl solutions (Experiments 1 and 2), and .6 or .9% KCl or .8% KHCO3 solutions (Experiment 3) for 48 h before acute heat stress (HS) and during HS. Body temperature (Tb), blood pH, partial pressure of blood carbon dioxide (pCO2), ionized Ca (Ca2+), plasma Na, K, Cl, total Ca, inorganic P (Pi), and osmolality (Osm), and water consumption were determined. Water intake increased with the concentration of KCl. Before HS, .6% KCl increased plasma K and Ca2+, whereas .9% KCl resulted in a marked increase in K, Ca2+, Na, Cl, and Osm and a decrease in pH. During HS, .6% KCl-birds had lower hyperthermic Tb and pH values and higher Ca2+ and K concentrations than controls. Plasma Na and Osm of .6% KCl birds decreased whereas those of the control birds remained unchanged. Providing K as KHCO3 aggravated respiratory alkalosis and failed to influence either Tb or plasma electrolytes, suggesting that the beneficial effect of .6% KCl may in part be attributed to the accompanying Cl. Hyperthermic Tb and Ca2+ values were highly correlated. The results showed that .6% KCl solution reduced HS-related responses and indicated a relationship among supplemental KCl, blood Ca2+, and Tb.

Acid-Base Equilibrium↗
PubMed1995

Tolerance of turkeys to diets high in trypsin inhibitor activity from undertoasted soybean meals.

The objectives were to determine the responses of turkeys to soybean meals (SBM) differing in urease and trypsin inhibitor activity, to estimate the AME of diets containing these SBM, and to determine the responses to supplemental L-Met and L-Lys. Four experiments were conducted with poults 1 to 3 wk of age and one with turkeys 6 to 8 wk of age. In Experiment 1, the trypsin inhibitor activities (TI) were 1.8, 4.2, 5.4, 7.0, and 8.8 mg trypsin inhibited/g SBM (method of Hamerstrand et al., 1981). The corresponding urease indices were .02, .14, .51, .90, and 1.5 pH units. The SBM were 46% of the diet. Significant pancreatic hypertrophy occurred with dietary concentrations of TI of 3.2 mg/g and above. At 4.0 mg TI/g of diet, the feed:gain ratio was increased, but body weight gain and AME of the diet were reduced. In Experiments 2, 3, and 4, poults responded similarly to Met additions to diets containing 46% SBM with TI of 1.8 or 4 mg/g SBM, or to Met or Met plus Lys additions to diets containing 40.7 or 49.6% SBM with TI of 2 or 11 mg/g SBM. In Experiment 5, the SBM contained TI at 4.3, 6.1, 8.9, or 12.5 mg/g. The corresponding urease indices were .05, .27, 1.43, and 1.72 pH units. The SBM were 49.6% of the diet. Using 6 to 8 wk old turkeys, the AME of the four diets were determined to be 2.76, 2.71, 2.58, and 2.57 Mcal/kg. The AME of diets containing 4.4 and 6.2 mg TI/g of diet were reduced (P < .05). In conclusion, through 3 wk of age, turkeys can tolerate soybean TI concentrations of 2.5 mg TI/g of diet. Turkeys 6 to 8 wk of age can tolerate 3 mg of soybean TI/g of diet.

Animal Feed↗
PubMed1995

Dietary calcium and phosphorus effects on broiler performance and the incidence of sudden death syndrome mortality.

Three experiments were conducted with broiler chickens to determine the effect of dietary Ca and P on growth, feed conversion, bone ash, and the incidence of sudden death syndrome (SDS) mortality. Trial 1 tested three rations [100% NRC (1984) Ca and P; 140% NRC Ca and P; and 140% NRC Ca and P to 3 wk and 100% NRC from 4 to 7 wk] in Ross x Ross males to 7 wk of age. Dietary Ca and P had no effect on body weight, feed conversion, bone ash, or leg problems, but SDS mortality was significantly higher in the two groups fed 140% Ca and P for 3 or 7 wk (2.83 and 3.33% SDS mortality, respectively). Trial 2 tested three diets (85% NRC Ca and P, 100% NRC Ca and P, and 140% NRC Ca and P) in mixed sex Arbor Acres x Peterson chicks to 7 wk of age. The lower level of Ca and P (85% NRC) significantly improved feed conversion (7 wk) and decreased bone ash only at 3 wk and serum Ca (7 wk). There was no effect of diet on SDS in this trial. Trial 3 tested two diets (85% NRC Ca and P or 100% NRC Ca and 85% NRC P) in Ross x Ross males to 9 wk of age. Six-week body weight was significantly reduced in the 85% NRC Ca and P diet but body weight was equal by 9 wk of age. No effects were observed for feed conversion, leg disorders, bone ash, or serum Ca. The SDS mortality was significantly increased in the chicks fed the 100% NRC Ca and 85% P diet compared to the 85% NRC Ca treatment. The results of these trials indicate that even slight deviations in dietary Ca and P beyond the NRC recommendations can create a metabolic imbalance in certain strains of broilers (Ross x Ross), which possibly increases susceptibility to SDS mortality.

Animals↗
PubMed1994

Dietary electrolyte balance effects on performance and metabolic characteristics in finishing steers.

One hundred twenty Angus and Angus-hereford crossbred steers (337 +/- 3 kg) were used in a randomized complete block design to evaluate the effects of dietary electrolyte balance (DEB; Na + K - Cl) on performance, acid-base status, and plasma mineral concentrations in cattle consuming a high-concentrate, low-fiber (5% cottonseed hull) diet. The steers were blocked into six groups based on BW and pen location, with five steers per pen. The treatments consisted of 0, 15, 30, and 45 mEq of DEB/100 g of DM. Average daily DMI increased linearly (P < .01) with increasing DEB for the first 28 d then increased quadratically (P < .05) for the remainder of the study. Daily gain tended (P < .10) to increase quadratically, whereas gain:feed was not affected by DEB. Carcass marbling score increased quadratically (P < .05), but other carcass measurements were not affected by DEB. On d 42, arterial blood pH was increased quadratically (P < .10) and HCO3 responded cubically (P < .10) to DEB, whereas ionized Ca, pCO2, and pO2 were not affected by treatment. On d 84, pCO2 (P < .10) and HCO3 (P < .05) decreased linearly as DEB increased. On d 42, plasma concentrations of Na, K (P < .10), and Mg (P < .05) decreased quadratically with increasing DEB. Plasma CV concentrations decreased linearly (P < .05) with increasing DEB on d 42. On d 84, total plasma Ca increased linearly (P < .10) with increasing DEB.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1994

Dietary electrolyte balance effects on performance and metabolic characteristics in growing steers.

The effects of dietary electrolyte balance (DEB; mEq of Na + K - Cl/100 g of DM) on performance and acid-base status of growing cattle consuming a corn silage-based diet were established using 120 Angus (n = 60) and Angus crossbred (n = 60) steers (247 +/- 2.4 kg). Treatments consisting of 0, 15, 30, or 45 mEq of DEB/100 g of DM were obtained by varying NH4Cl and NaHCO3. Average daily gain showed a linear increase (P < .05) with increased DEB for the first 28 d and a quadratic response (P < .05) for the remainder of the 84-d study. Average daily feed intake was not affected by DEB the first 28 d. However, feed intake over the entire feeding period showed a linear increase with increasing DEB (P < .01). On d 28, plasma Na, K, and Mg were not affected by DEB, whereas Ca followed a quadratic pattern (P < .10). On d 84, plasma Na and Mg decreased linearly with increasing DEB. Plasma Cl concentrations decreased linearly (P < .01) with increased DEB on d 28 and 84. On d 28 arterial blood pH and HCO3 increased linearly (P < .05) with increased DEB, whereas ionized Ca, pCO2, and pO2 were unchanged. On d 84, arterial blood pH (P < .10), HCO3 (P < .05), and ionized Ca (P < .10) increased quadratically, whereas pO2 and pCO2 were not affected by treatment. Ruminal pH increased linearly (P < .05) with increased DEB on d 28 but showed no differences on d 84. These data indicate that DEB affects performance and systemic values in growing feedlot cattle. A DEB in the range of 15 to 30 mEq seemed to provide normal homeostasis of growing steers fed a corn silage-based diet.

Acid-Base Equilibrium↗
PubMed1994

Duodenal calcium uptake, femur ash, and eggshell quality decline with age and increase following molt.

An experiment was conducted to test the hypothesis that the decline in eggshell quality over time during egg production, and its improvement after molting, paralleled the rate of calcium uptake by the duodenum of the laying hen. In vitro duodenal calcium uptake rate and femur ash (percentage of femur weight) were determined at 37, 45, 51, 58, 68, and 72 wk of age. Percentage shell and shell thickness (millimeters) were determined at 22, 29, 36, 44, 50, 57, and 71 wk of age. Molt was induced at 63 wk of age. Three commercial strains DeKalb XL-Link, ISA/Babcock B-300V, and Hy-Line W-36 were compared. There were no differences in duodenal calcium uptake rate among strains. There was a significant decline (P < .01) in duodenal calcium uptake from 408 pmol/mg tissue per min at 37 wk of age to 329 pmol/mg per min at 58 wk of age. Femur ash decreased (P < .01) from 50.8% at 37 wk of age to 47.6% at 58 wk of age. Percentage shell and shell thickness declined (P < .01) from 9.79% and .403 mm at 22 wk of age to 8.88% and .373 mm at 57 wk of age, respectively. After the induced molt, duodenal calcium uptake increased (P < .01) to 402 pmol/mg tissue per min, and percentage shell and shell thickness increased (P < .01) to 10.23% and .389 mm, respectively. Duodenal calcium uptake increased immediately postmolt, whereas femur ash did not increase until 72 wk of age (P < .01).

Age Factors↗
PubMed1993

Calcium deficiency and food deprivation improve the response of chickens to acute heat stress.

The tolerance of chickens to acute heat stress may be modified by diet. Broiler chickens fed calcium-adequate (0.90% Ca) or -deficient (0.45% or 0.15% Ca) diets were either fed or not fed for 24 h and exposed to increasing temperatures (from 24 to 41 degrees C). Diets were fed for 7 d before heat stress in Experiment 1 and for 14 d before heat stress in Experiment 2. Body temperature, blood ionized Ca, pH, pCO2, plasma inorganic phosphate and total Ca were determined. During heat stress, Ca+2 and inorganic phosphate were depressed in all treatments. Feeding the 0.45% Ca diet for 7 d reduced hyperthermic body temperature of fed chickens but had no effect on body temperature of unfed chickens relative to the groups fed 0.90% Ca. No further improvement in body temperature response to heat stress was obtained by lowering the dietary Ca level to 0.15% or extending the feeding period to 14 d. Food deprivation was more effective in counteracting the heat-induced rise in body temperature than a dietary Ca deficiency. Heat-induced changes in body temperature, Ca+2, inorganic phosphate and blood pH were highly correlated (P < 0.001). The change in Ca+2 followed a pattern similar to that of changes in body temperature, but changes in inorganic phosphate seemed to be more indicative of changes in pH. Control birds fed 0.90% Ca exhibited the highest changes in Ca+2 and body temperature values. Feeding Ca-deficient diets reduced changes in both Ca+2 and body temperature. Unfed birds, regardless of dietary Ca level, showed the lowest changes in Ca+2 and body temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1992

Molt induced by dietary zinc in a low-calcium diet.

Three experiments were designed to test the hypothesis that zinc has a specific effect independent of anorexia during induction of molt. In Experiment 1, hens were fed a low-calcium (.08%) basal molt diet to which was added 0, 110, 620, or 1,120 mg/kg (ppm) zinc as zinc sulfate heptahydrate (ZnSO4.7H2O) for 7 days and 0, 1, 400, 2,800, or 4,200 ppm zinc, respectively, for the following 14 days. In Experiment 2, hens were provided ad libitum access to the low-calcium basal molt diet with 2,800 ppm added zinc for 14 days during which a paired control hen received a similar amount of the low-calcium basal molt diet. In Experiment 3, hens were fed the low-calcium basal molt diet on a restricted basis amended with either 0 or 2,800 ppm zinc on a restricted basis for 10 days. In Experiment 1, all hens that consumed zinc had significantly fewer days to last oviposition as compared with control hens, and this occurred without significant differences in body weight or feed consumption for the lowest zinc group. When compared with the control group, higher levels of zinc did decrease body weight and feed consumption. In Experiment 2, the hens consuming the diet with 2,800 ppm zinc (Zn2800) reached last oviposition significantly sooner than control hens, although the Zn2800 hens actually consumed more feed. In Experiment 3, the Zn2800 hens lost more body weight than control hens due partially to earlier reproductive tract regression. Serum luteinizing hormone was increased in the Zn2800 hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of overcooked soybean meal on chicken performance and amino acid availability.

Studies were conducted to evaluate the effect of overcooked soybean meals (SBM) on chick growth and amino acid availability. The SBM were custom-prepared at a commercial processing plant by changing the conditions of a desolventizer-toaster (DT) unit. Six progressively overcooked meals (designated SBM1 to 6 with SBM1 as normal, and SBM6 overcooked) were produced by increasing temperature by up to 50% and extending retention time by up to 75% above normal. The meals measured .05, .03, .01, .09, .00, and .00 delta pH of urease activity; 6.10, 5.01, 4.62, 4.83, 2.32, and 1.78 mg/g SBM of trypsin inhibitor activity; 92, 89, 91, 88, 81, and 81% of protein solubility in .2% KOH; and 46, 43, 41, 40, 23, and 19% of protein solubility in .1 M borate at 40 C, respectively. Glucose content in the hydrolysate of the soluble carbohydrate extract did not differ among the meals, indicating no differences in the degradation of sucrose, raffinose, and stachyose with increasing heat treatment. In a chick growth experiment with a methionine-adequate, low-protein diet, chicks fed SBM1 showed significantly greater weight gain than chicks fed SBM3, 5, or 6. The SBM1, 2, 5, and 6 were chosen for a study of amino acid availability. No differences were observed in amino acid content. There were significant differences in apparent amino acid availability to growing chicks, but not in true amino acid availability by adult roosters among the four meals. The results suggest that the temperature or the retention time of a DT unit may be increased by 50% over the usual operating conditions without reducing amino acid availability from SBM.

Amino Acids↗
PubMed1991

Nutritional, physiological, genetic, sex, and age effects on fat-free dry matter composition of the body in avian, fish, and mammalian species: a review.

The purpose of this review is to outline and interpret the effects of nutrition, physiological state, sex, genetics, and age on composition of the fat-free dry matter of birds, mammals, and fishes in order to test the hypothesis that the protein:ash ratio in the body is constant. Calculations from a broad array of published data revealed that nutritional factors, including mineral, protein and amino acid nutriture, frequency and level of feeding, and energy intake and nonnutritional factors, including physiological state, sex, genetic background, and age of animal, may each alter the ratio of protein:ash in the body. All or part of the response may be associated with changes in accretion of body protein and(or) skeletal development and mineralization imposed by these nutritional and nonnutritional factors. In most cases of amino acid or protein deficiency, the protein:ash ratio was decreased relative to the control because the deposition of protein in muscle and viscera was reduced more than the growth and mineralization of the skeleton. In other cases, the protein:ash ratio was increased relative to a control because the dietary Ca or P intake or absorption limited skeletal mineralization. More knowledge is needed of how skeletal development and protein:ash ratio in the body is regulated, especially under the influence of nutritional, ontogenetic, and physiological variables among different genotypes of mammals, birds, and fishes. Documentation that the protein:ash ratio in the whole body of representative mammals, birds, and fishes is not constant, but is subject to manipulation, has important physiological and economic implications for developing food animals for the efficient production of lean meat.

Age Factors↗
PubMed1991

Effect of overcooked soybean meal on turkey performance.

Three turkey growth experiments were conducted to evaluate the effect of overcooked soybean meal (SBM) on BW gain and gain:feed ratio (FE). On two occasions soybean meals were custom prepared by changing the temperature and the retention time (RT) of the desolventizer-toaster unit at a commercial soybean processing plant. Three different meals were produced for each occasion mainly by altering RT from normal to approximately 1.35 and 2.43 times normal operating conditions (designated SBM1 to 3 on the first occasion and SBM4 to 6 on the second occasion). For SBM1 to 6, urease activities were .06, .00, .20, .01 and .00 delta pH, protein solubilities in .1 M borate at 40 C were 44, 45, 16, 44, 32, and 24%, and protein solubilities in .2% KOH were 86, 84, 76, 90, 85, and 85%, respectively. In two sequential long-term experiments, SBM1 to 3 were fed to turkeys from 0 to 8 wk, then a control (normal processing conditions, SBMF), was fed to the all treatment groups from 8 to 12 wk of age. The SBM4 to 6 were fed from 12 to 18 wk of age after rerandomizing treatment allocation of replicate pens. In the first trial, poults fed SBM3 showed significantly reduced BW gain from 3 wk on and a lower FE shown at 9 wk. No difference in BW gain and FE was observed in the trial from 12 to 18 wk. In a 15-day, short-term experiment starting with 3-day-old poults and feeding diets containing SBM2 to 6, BW gain and FE did not differ among treatment groups. It is concluded that SBM did not show a detrimental effect on turkey growth until it was overcooked by 2.4 times the normal conditions. The usual operating conditions in a commercial processing plant are well within the range for producing adequate SBM for poultry feed.

Animal Feed↗
PubMed1989

Effect of fasting and acute heat stress on body temperature, blood acid-base and electrolyte status in chickens.

1. The tolerance of chickens to acute heat stress, evaluated by the time required to reach the critical body temperature (Tr) of 44.5 degrees C, was markedly enhanced as the period of fasting was extended. 2. Fasting reduced the rates of heat-induced changes in blood acid-base and electrolyte status. 3. Changes in Tr were correlated with changes in blood pH, pCO2, [Cl-] and [Pi] but not with changes in [Na+] or [K+]. 4. Blood acid-base and electrolyte status were related to Tr rather than time of exposure to heat stress.

Acid-Base Equilibrium↗
PubMed1989

Effects of lighting program during the growing period and dietary fat during the laying period on broiler breeder performance.

In two experiments, broiler breeders were grown in either of two lighting regimens, fed diets without added fat, and then fed diets with or without 5% added poultry fat during the subsequent laying period. In Experiment 1 half the birds were subjected to decreasing daylength using daylight (800 lx) and half were subjected to 9 h of incandescent light (20 lx) to 20 wk of age. In Experiment 2 the lighting regimen was either an 8-h photoperiod supplied by daylight (800 lx) or an 8-h photoperiod supplied by incandescent light (20 lx) to 20 wk of age. Added dietary fat produced significantly higher egg weight (Experiments 1 and 2), egg production (Experiment 2), and significantly lower fertility and hatchability of fertile eggs (Experiments 1 and 2). Short photoperiods (8 or 9 h) provided by incandescent light produced significantly higher fertility (Experiments 1 and 2) and hatchability of fertile eggs (Experiment 2), and significantly lower egg specific gravity, shell percentage (Experiment 1), egg weight, and eggshell weight (Experiment 2). Effects on fertility may be related to higher female body weight during lay due to daylight rearing or added fat, or relative changes in light intensity at photostimulation.

Analysis of Variance↗