Effects of consecutive thiouracil exposures in the juvenile and adult single comb White Leghorn chicken on body weight and reproductive performance.

The effects of consecutive exposures to dietary thiouracil (TU) in juvenile and adult Single Comb White Leghorn chickens on plasma thyroxine (T4) concentrations, egg production (EP), egg weight (EW), concentrations eggshell quality were determined. Thiouracil was provided in the feed at levels of 0, 0.1, or 0.2% (PTRT) from 0 to 6 wk of age and at levels of 0 or 0.1% (TRT) from 32 to 38 wk of age. Body weight gain was simulated but T4, EW, EP, and eggshell quality were generally reduced by 0.1% TU TRT. However, TU PTRT alleviated a latent depressing effect of TU TRT on BW after 38 wk of age. Thiouracil PTRT, particularly at the 0.2% level, induced significant decreases in EW but increased EP between 32 and 50 wk. The effects of early thyroid suppression in juveniles with TU PTRT on the subsequent reproduction of adults were primarily in response to a delay in the onset of sexual maturity, and not directly to prolonged responses in T4 or BW that extended into lay.

Effects of added dietary lard on body weight and serum glucose and low density lipoprotein cholesterol in randombred broiler chickens.

The effects of dietary lard on serum glucose (GLU) and lipids were determined in Athens-Canadian randombred broiler chickens. Birds were provided either 0, 3, or 7% added lard in nonisocaloric starter diets through 10 d of age (S1), followed by either 3 or 7% added dietary lard through 21 d of age (S2). A common grower diet was fed to all birds after 21 d. Body and organ weights, feed conversion, and concentrations of various blood constituents, including serum GLU and lipids, were determined weekly from 14 to 42 d of age. Constant levels of added fat in both S1 and S2 diets generally led to higher BW in males at 42 d. Relative testes weight at 14 d was higher in males fed 3% than in those fed 7% S2 diets, whereas 7% added lard in S2 diets preceded by no added fat in S1 diets resulted in higher relative spleen weights in males at 42 d. Serum GLU concentrations were highest in males that received 3% lard rather than no added lard in the S1 diet. Serum low density lipoprotein cholesterol (LDLC) concentrations at 14 d were highest in females fed constant levels of lard at either 3 or 7% in both starter periods. It was concluded that added lard fed to randombred chickens at various times and levels in starter diets elicited responses in organ weight and serum LDLC and GLU concentrations that varied with the sex and age of the bird and were not consistently related to BW.

Effects of added lard fed to broiler chickens during the starter phase. 1. Body and selected organ weights, feed conversion, hematology, and serum glucose.

The effects of added lard in starter diets on BW, selected organ weights, feed conversion, hematological indices, and serum glucose were determined weekly in broiler chickens between 14 and 42 d of age. Nonisocaloric starter diets were formulated to contain either 0, 3, or 7% added lard, where the megacaloric percentages of all major nutrients were held constant. Broiler chickens received either 0, 3, or 7% added lard in starter diets through 10 d of age (S1), followed by either 3 or 7% added dietary lard through 21 d of age (S2). All possible combinations of the three S1 diets and two S2 diets yielded six total dietary treatments. A common grower diet was provided after 21 d. Body weight was not affected by diet and feed conversion did not increase between 21 and 42 d when birds were fed 3 or 7% added lard in the S1 diet. The effects of the S1 and S2 diets on relative liver weight were inconsistent over time and were not influenced by sex. Hematocrits were increased across time in birds fed 3% S1 diets and plasma protein concentrations were increased at 14 d in birds fed 7% S1 diets. It was concluded that the response of broiler chickens between 14 and 42 d to different levels of dietary lard was influenced by age of feeding during the starter period.

Effects of added lard fed to broiler chickens during the starter phase. 2. Serum lipids.

The effects of lard added to starter diets on various serum lipids were determined in broiler chickens between 14 and 42 d of age. Nonisocaloric starter diets were formulated to contain either 0, 3, or 7% added lard, where the megacaloric percentages of all major nutrients were held constant. Birds received either 0, 3, or 7% added lard in starter diets through 10 d of age (S1), followed by either 3 or 7% added dietary lard through 21 d of age (S2). All possible combinations of the three S1 diets and two S2 diets yielded six total dietary treatments. A common grower diet was provided after 21 d. Concentrations of various serum lipids were determined weekly from 14 to 42 d of age. The effects of both the S1 and S2 diets on total cholesterol, low density lipoprotein cholesterol (LDLC), and high density lipoprotein cholesterol (HDLC) were inconsistent and were influenced by sex between 14 and 42 d of age. However, serum triglycerides and very low density lipoprotein cholesterol concentrations showed progressive increases over the 14 to 42 d period in birds that received dietary lard at either level in the S1 diet. These same serum constituents also increased to the greatest extents over the same period when birds were provided 3% added lard in the S2 diet. It was concluded that the response of broiler chickens between 14 and 42 d to different levels of dietary lard were influenced by age of feeding during the starter period. Furthermore, the specific effects of the diets on serum cholesterol, LDLC, and HDLC concentrations between 14 and 42 d varied with the sex and age of the bird.

Effects of breeder hen age and dietary fat on embryonic and neonatal broiler serum lipids and glucose.

In two experiments, the effects of dietary fat and breeder hen age on relative yolk sac weight (RYSW) and total serum cholesterol (CHOL), high (HDLC) and low (LDLC) density lipoprotein cholesterol, triglycerides (TRI), and glucose (GLU) were monitored in broiler embryos and chicks. In Experiment 1, embryos at 18 d of incubation and chicks at hatch were sampled from eggs laid by breeder hens at 26 (young), 36, and 48 wk of age. No dietary effects were noted in either experiment; however, chicks from young hens exhibited elevated serum CHOL, HDLC, LDLC, and lower GLU when compared with chicks from hens at either 36 or 48 wk of age. Additionally, embryos from young breeders displayed a lower RYSW at 18 d of incubation. Conversely, by hatch there was no difference in RYSW among offspring from different aged hens. In Experiment 2, newly hatched chicks were sampled from breeder hens at 36, 51, and 64 wk of age. Dietary effects were also not evident in this experiment; however, chicks from 51-wk-old breeders displayed the highest and lowest serum HDLC and TRI, respectively, compared to the other two age groups, whereas chicks from either 51- or 64-wk-old breeders exhibited higher levels of CHOL than those at 36 wk. Chicks from 64-wk-old breeders displayed an increase in LDLC when compared with the other two ages. These data suggest that serum concentrations of lipids and GLU, and RYSW in 18 d embryos and newly hatched chicks are influenced by hen age and not by added dietary fat.

Changes in serum lipid, lipoprotein and corticosterone concentrations during neonatal chick development.

Broiler chicks were given a standard commercial starter diet from day 0 (day of hatch) to 9 days of age. Body weight and concentrations of the following serum constituents were measured daily: glucose (GLU), triglycerides (TRI), corticosterone (CORT), cholesterol (CHOL), and high (HDL) and low (LDL) density lipoproteins. Serum GLU and TRI increased at each sampling day to reach a peak on days 3 and 4, respectively, and then decreased thereafter. However, CHOL, HDL, and LDL decreased sharply by day 1 and then gradually decreased to day 5. Conversely, CORT peaked on day 1 and then decreased to day 4. It peaked again on day 5 and remained at that level throughout the remainder of the experiment. In summary, serum concentrations of all constituents measured fluctuated drastically between 1 and 5 days of age, with few changes occurring between days 6 and 9.

Effects of dietary thiouracil on thyroid activity, egg production, and eggshell quality in commercial layers.

The effects of thyroid suppression induced during the rearing period by providing various dietary thiouracil (TU) regimens on plasma thyroxine (T4) concentrations, growth, and subsequent egg production (EP) and eggshell quality were determined in Single Comb White Leghorn chickens. Thiouracil was provided in the feed at levels of 0, .1, and .2% from 0 to 6 wk of age in Experiment 1, and at levels of 0, .05, and .1% from 6 to 16 wk of age in Experiment 2. In both experiments, T4 concentrations were reduced during TU treatment. However, T4 later became elevated at 12 and 20 wk in both dosage level groups in Experiment 1. Additionally, BW and egg weights were suppressed by both TU treatments, and EP was reduced up to Week 23 in the .1% TU-treated birds and through Week 25 in the .2% TU-treated birds. No effects on EP were noted in Experiment 2, but feed consumption (FC) was reduced during Week 6 in birds fed .05% TU and during Weeks 6, 10, and 19 in birds fed .1% TU. Both liver and thyroid weights were increased in .1% TU-treated birds relative to controls at Week 16. Eggshell quality was affected only in Experiment 2, in which birds given .05% TU had a higher relative conductance, or maximum rate of water loss, at Week 38 than 0 and .1% TU dosage levels, and .1% TU-treated birds had a higher breaking strength than 0 and .05% TU-treated birds at Week 22.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of dietary fat on growth performance, carcass composition, and feed efficiency in the broiler chick.

In two experiments broiler chicks were fed nonisocaloric diets with either 0, 3, or 7% added lard. Megacaloric percentages of all major nutrients were the same in all diets. In Experiment 1 (broiler chicks 0 to 5 d of age), added dietary lard did not affect body, heart, spleen, or pancreas weight. Liver weight was suppressed by the inclusion of lard in the diet, yet liver composition changed, becoming higher in protein and lower in fat. Yolk sac weight decreased during the first 5 d posthatch, with the decrease being most pronounced by 3 d of age. There were no differences in feed consumption due to treatment in Experiment 1. In Experiment 2 (broiler chicks 6 to 11 d of age), added dietary fat resulted in differences in liver, body, and fecal excreta composition. Chicks given 7% added lard had lower liver fat throughout the trial than chicks fed no added lard. Additionally, these chicks had a higher body protein content at 6 and 7 d of age. However, body fat only increased in chicks fed 7% added lard by 11 d of age. Furthermore, chicks receiving 7% added lard had elevated fecal fat at Day 6, but did not consume more feed than chicks receiving 0 or 3% added lard. Additionally, chicks fed lard had lower liver weights than those fed 0% added lard.

Ultrasonography as a tool for monitoring in ovo chicken development. 2. Effects of eggshell alteration and ultrasonography on embryonic and posthatch development.

The influence of creating and closing acoustic windows on embryonic and posthatch development for the purpose of chicken embryogenesis monitoring by real-time ultrasonography (US) was evaluated at 2, 6, 9, 14, and 17 days of incubation. Acoustic windows were closed using either a porous dialysis film and tape (FM) or an eggshell allograft attached with collodion (CP). Results from eggs closed in each manner with and without concurrent nonsterile US examination were compared with two control groups. Window creation reduced hatchability. The hatchability reduction was caused primarily by bacterial contamination. Contamination was more common in the FM eggs than in the CP eggs and was greater in eggs that also underwent US. Hatchability increased and contamination decreased when US was performed closer to hatch. Egg weight loss was increased after Day 6 of incubation in FM + US eggs treated on Day 2 and after Day 9 in all eggs with windows except CP eggs treated on Day 9 and CP + US eggs treated on Days 6 and 9. Hatch weight decreased in chicks from eggs that had windows, particularly in FM eggs.

Yolk sac absorption and initiation of growth in broilers.

A series of three experiments was conducted to determine the role of the yolk sac in initiation of growth in broilers. In Experiment 1, absorption of the yolk sac was found to precede initiation of growth in newly hatched broilers by approximately 24 h. Because the yolk sac is essential for early initiation of growth, in Experiments 2 and 3 it was removed and diets with incremental fat levels of 3, 6, and 10% were fed to assess whether fat was essential for optimal growth during the neonatal period. Results suggest that dietary fat has its greatest effect on growth after 10 days of age. Therefore, initiation of growth may be more closely dependent upon other nutrients.

Laying hen performance as affected by diet and caging density.

Two trials were conducted to investigate the effects of caging density and diet on the performance of caged layers. Diets were formulated contain .775, .725, and .675% lysine. The TSAA content was formulated to be 85% of the lysine content of each diet. Pullets were caged in 25.4 cm wide x 40.0 cm deep cages at three, two, or one bird per cage. Production data were collected for 112 days in Trial 1 and 168 days in Trial 2. As dietary protein, lysine, and TSAA increased, hen-day egg production, egg weight, and feed conversion improved (P less than .05) . Feed consumption and feed per dozen eggs were not consistently affected by diet. Caging density had no consistent effects on any of the production parameters. No interactions were detected between dietary treatments and cage density in either trial.

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.

Noted difference in the digestive system in caged and floor-reared commercial egg-type pullets.

Two trials were conducted with Single Comb White Leghorn pullets reared from 0 to 19 weeks of age in cages and on litter at the same environmental temperature. Samples were obtained to determine if digestive system differences existed. Criteria measured were gizzard weight and intestine length. Results showed that floor-reared pullets had heavier gizzards with longer intestines than cage-reared pullets. The difference may be caused by consumption of litter by the floor-reared birds.

Delay of onset of oviposition in pullets promoted by 6-methoxybenzoxazolinone.

Single Comb White Leghorn pullets were used to determine the effects of 6-methoxy-2-benzoxazolinone (6-MBOA) and photoperiod on sexual maturity and egg production. Pullets were maintained on a constant 11L:13D photoperiod until 18 weeks of age and then were divided into two light-controlled chambers. Half the pullets in each chamber received a standard layer mash and the other half received the same diet supplemented with 6-MBOA (MB). Over the ensuing 21 days, the photoperiods were increased to 15L:9D in one chamber and 12L:12D in the other. Consumption of MB resulted in delayed sexual maturity and lower average egg production of those pullets when compared with pullets in the 15L:9D chamber. No significant difference between MB and C pullets was noted in the 12L:12D chamber. These results are similar to those obtained with pinealectomized quail and chickens.