Effects of strain and rearing dietary regimens on brown-egg pullet growth and strain, rearing dietary regimens, density, and feeder space effects on subsequent laying performance

Effect of energy level of pullet diet and age on laying performance and expression of hypothalamus-pituitary-gonadal related genes in laying hens

Dietary energy density influences feed intake (FI) and development of layer-type pullets. A total of 384 nine-wk-old Hy-Line Brown pullets were randomly assigned to one of 3 dietary treatments: fed a diet with 2,600, 2,750, and 2,900 Kcal metabolizable energy/kg (ME/kg) from 10 to 21 wk of age. The results showed that the 2,900 and 2,600 ME groups had lower feed and ME intake (P < 0.01) from 10 to 21 wk of age. The 2,600 ME pullets had heavier body weight (BW) and longer shank length (P < 0.05) at 21 wk of age than the 2,750 ME group. The eggshell percentage was increased by the 2,600 and 2,900 kcal/kg treatments (P = 0.002). Serum concentration of 17-β-estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) decreased at 70 wk of age (P < 0.05). Pullet diet and its interaction with age had a significant influence (P < 0.001) on the expression of gonadotropin-releasing hormone 1 (GnRH-1) and gonadotropin-inhibitory hormone (GnIH) in the hypothalamus and of gonadotropin releasing hormone 1 receptor (GnRH-1R) and gonadotropin-inhibitory hormone receptor (GnIHR) in the pituitary. In the hypothalamus, GnRH-1 expression increased from 9 to 40 wk of age and then decreased; however, GnIH expression was highest at 70 wk of age. Follicle-stimulating hormone receptor (FSHR) expression increased (P < 0.001) at wk 40 and decreased at wk 70 compared to wk 21 at various follicular stages. In conclusion, the energy level of pullet diet had no unfavorable influence on feed intake, laying rate, egg mass, and FCR, whereas change egg weight and mortality during the laying period from 21 to 70 wk of age. during the laying period. These results suggest that pullet dietary energy can activate the expression of genes related to reproduction in the hypothalamus, whereas it plays a minor role in the regulation of genes in the pituitary and ovary. Age-induced gene expression in the hypothalamus-pituitary-gonadal (HPG) axis is associated with laying performance in hens.

Jejunal transcriptomic profiling of two layer strains throughout the entire production period

The jejunum plays crucial roles for the digestion and absorption of nutrients and minerals and for barrier functions that are essential for a healthy, productive life cycle of farm animals, including laying hens. Accordingly, knowledge of the molecular pathways that emerge in the intestine during development, and particularly at the beginning of laying activity, will help to derive strategies for improving nutrient efficiency in laying hens. In this study, jejunal samples were obtained from two high-yielding layer strains at five developmental stages (weeks 10, 16, 24, 30 and 60 of life) for RNA-sequencing, alongside the profiling of blood plasma parameters to approximate the dynamics of mineral homeostasis. The results reflected a marked distinction between the pre-laying and laying phase as inferred from levels of parathyroid hormone, triiodothyronine, estradiol, vitamin D, and calcium. Moreover, the expression patterns of the intestinal mucosa responded directly to the changing metabolic and nutritional profiles at the beginning of the laying phase in maturing high-yielding strains of laying hens. These comprise signaling events namely RANK/RANKL signaling and cellular senescence. Taken together, the timing of sexual maturity of laying hens demands closer examination to unravel metabolic requirements and associated endogenous mechanisms.

NÍVEIS DE CÁLCIO E RELAÇÃO CÁLCIO: FÓSFORO EM RAÇÕES PARA POEDEIRAS LEVES DE 24 A 40 SEMANAS DE IDADE

Resumo Objetivou-se determinar a exigência nutricional de cálcio e a melhor relação cálcio:fósforo em rações para poedeiras leves de 24 a 40 semanas de idade. Foram utilizadas 324 aves Hy-Line W-36, distribuídas em delineamento inteiramente casualizado, esquema fatorial 3x3, sendo três níveis de cálcio (3,9; 4,2 e 4,5 %) e três relações cálcio/fósforo (9,3; 10,53 e 12,12/1), totalizando nove tratamentos, seis repetições e seis aves por unidade experimental. Avaliou-se o desempenho produtivo, a qualidade do ovo, as características ósseas, o balanço de cálcio e fósforo e a mortalidade. Não houve interação (P>0,05) entre os níveis de cálcio e as relações cálcio/fósforo para nenhuma das variáveis, porém os níveis de cálcio promoveram efeito (P<0,05) sobre o peso e porcentagem da casca, cálcio na casca, ovos perdidos, consumo de cálcio e fósforo, cálcio e fósforo na excreta, cálcio e fósforo retido. A relação cálcio/fósforo influenciou significativamente (P<0,05) o consumo de ração, ganho de peso, conversão alimentar, consumo de cálcio e fósforo, fósforo na excreta e fósforo retido. Rações contendo 4,5% de cálcio e relação cálcio:fósforo de 12,12:1, correspondendo ao consumo de cálcio de 3,71 g/ave/dia e de fósforo de 306 mg/ave/dia, garantem desempenho satisfatório em rações para poedeiras leves no período de 24 a 40 semanas.

Effect of genetic selection on growth parameters and tonic immobility in Leghorn pullets

Four genetic stocks of Leghorn pullets were used to evaluate the effects of genetic selection on growth and fearfulness behavior. Three of the stocks were the Ottawa randombred control stocks from 1950 (CS5), 1959 (CS7), and 1972 (CS10). The fourth stock was a 1993 commercial laying stock (CCS) whose ancestors were involved in the formation of the randombred control stocks. Pullets were reared in a brood and grow poultry house with flat deck cages. Each stock was comprised of 840 birds with 21 replicates per strain. Body weight and feed consumption were monitored biweekly. At 16 wk of age, a 20-hen sample from each strain was analyzed for BW, body composition, and tonic immobility. There were significant (P < 0.05) differences among the stocks for BW of 1,403; 1,333; 1,332; and 1,428 g for the CS5, CS7, CS10, and CCS stocks, respectively. Furthermore, significant differences occurred with regard to feed consumption, livability, and frame size. There were no differences among the stocks in tonic immobility. Measurement of circulating corticosterone levels were shown to be significantly (P < 0.05) higher in the CCS stock (7.64 ng/mL) than for both the CS5 (4.50 ng/mL) and CS7 (4.61 ng/mL) stocks, whereas the CS10 stock was intermediate with 6.45 ng/mL. Genetic selection has affected growth parameters, although there appears to be no change in fearfulness behavior but an increase in corticosterone levels in stocks from later years.

Effects of dietary energy content on the performance of laying hens in furnished and conventional cages

This study examined the effects of dietary energy content on the egg production and egg quality of hens kept in 3-hen conventional cages or 8-hen furnished cages. A total of 1,088 Lohmann Selected Leghorn hens were housed in either furnished or conventional cages and offered low- or high-energy diets (from 2,342 to 2,414 kcal/kg or from 2,581 to 2,629 kcal/kg) during 3 consecutive feeding phases of 20, 16, and 16 wk, respectively. The same dietary energy effects were observed in both cage systems. The hens that received the low-energy diet consumed more feed (P < 0.01) and produced fewer eggs per day (P < 0.05) than the birds fed the high-energy diet. Over the entire experiment, housing had no significant effects on production parameters, but during the third feeding phase, the production rate was smaller in furnished cages than in conventional cages (P < 0.01). Because of the greater live weight of the hens in furnished cages at the beginning of the experiment, these hens consumed more feed during the first feeding phase than the hens in conventional cages. During the third feeding phase, the hens in furnished cages consumed less feed than those in conventional cages (P < 0.01), probably because of their better feather cover. No differences in feed conversion ratio were found between the cage types. The results of this study confirm the results of previous studies providing evidence of equal production rates and feed conversion ratios in furnished and conventional cages.

Effect of bird cage space and dietary metabolizable energy level on production parameters in laying hens

A study was conducted to assess the effects of varying cage spaces on a commercial laying hen strain fed differing levels of dietary metabolizable energy (ME) for 15 wk. Four cage space allowances (342, 413, 516, and 690 cm2/hen) were combined with 3 levels of dietary ME (2,800, 2,850, and 2,900 kcal of ME/kg) in a 4 x 3 factorial arrangement. Each treatment was assigned to 6 replicate cages for a total of 72 cages in randomized complete block design. Feed intake and metabolizable energy intake were significantly (P < 0.01) greater for hens housed at 690 cm2/hen compared with those housed at 413 and 342 cm2/hen, but not those housed at 516 cm2/hen, across all dietary ME levels. Egg production and egg mass were significantly (P < 0.001) improved for hens housed at 690 cm2/ hen in contrast to other cage spaces and across all energy levels. There were no interaction effects of ME levels on laying hen performance at varying cage space except for body weight change. Hens housed at 516 cm2/ hen and fed 2,800 kcal of ME/kg exhibited the greatest weight change, which was significantly (P < 0.05) greater than those fed other levels of ME at the same cage space. Hens housed at 690 cm2/hen had significantly (P < 0.05) greater ME efficiency of egg production than hens housed at other cage spaces. Hens fed the diet with 2,900 kcal of ME/kg had significantly (P < 0.001) greater ME digestibility compared with those fed 2,800 or 2,580 kcal of ME/ kg with differences of 107 and 118 kcal of ME/kg, respectively. There were no significant effects of ME levels observed except ME digestibility, and no significant effects of cage space allowance on egg weight, hen weight, bone ash, or maintenance energy intake. It is evident that decreasing the number of birds per cage and increasing cage space allowance per hen had an overall positive effect on performance.