Reproductive Development and Response of White Leghorn Pullets Subjected to Increasing Day-Lengths at Different Ages

Harrison, Paul C.; Schumaier, George; McGinnis, James

doi:10.3382/ps.0481021

Cited by 20 publications

(9 citation statements)

References 6 publications

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“…In comparison to the RBC3 line hens, the Egg line hens had a decrease in intrasequence LH surge intervals, a decrease in the incidence of blind LH surges, and a decrease in the incidence of LH surge intervals of Ͼ33 h (intersequence intervals), resulting in a higher rate of egg production in the Egg line hens. Several factors may contribute to poorer egg production of laying hens late in the reproductive period, including 1) an increase in intrasequence LH surge intervals, resulting in longer intervals between intrasequence ovipositions [20]; 2) an increase in the incidence of intersequence intervals of Ͼ33 h between clutches of eggs [2], resulting in a decrease in clutch size [21]; 3) an increase in follicular atresia, resulting in a lower rate of follicular maturation and number of follicles available for ovulation [22,23]; 4) a loss of synchronization of ovulation and oviposition [24][25][26], resulting in an increase in the number of defective eggs late in the reproductive period, and 5) abnormal secretion of P 4 , associated with a blockage of LH surge secretion and ovipositions [12].…”

Section: Introductionmentioning

confidence: 99%

Interval Between Preovulatory Surges of Luteinizing Hormone Increases Late in the Reproductive Period in Turkey Hens1

Liu¹,

Long²,

Bacon³

2002

Biology of Reproduction

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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.

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Section: Introductionmentioning

confidence: 99%

Interval Between Preovulatory Surges of Luteinizing Hormone Increases Late in the Reproductive Period in Turkey Hens1

Liu¹,

Long²,

Bacon³

2002

Biology of Reproduction

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“…Clearly absolute photoperiod is therefore not an important factor in the timing of sexual maturation in this species. Nevertheless, at 17 weeks of age the immature hen responds rapidly to an abrupt increase in photoperiod from 8 to 16 h light per day by a two-to threefold increase in the concentration of luteinizing hormone (LH) in the plasma (Wilson & Cunningham, 1980) and the transfer of birds from a short to a long photoperiod can advance the onset of lay by as many as 7 weeks, depending on the age at which the transfer takes place (Morris, 1962;Harrison, Schumaier & McGinnis, 1969).…”

Section: Introductionmentioning

confidence: 99%

Evidence of a photoinducible phase for the release of luteinizing hormone in the domestic hen

Wilson¹

1982

Journal of Endocrinology

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Hens raised on a schedule of 8 h light : 16 h darkness (8L : 16D) were exposed to changes in photoperiod at 17 or 18 weeks of age. These involved exposure to either an abrupt increase in photoperiod to 16 h per day or to skeleton photoperiods comprising a main period of 7\m=.\75or 4 h light together with a pulse of 15 min or 4 h light provided at different times during the period of darkness.An increase in photoperiod to 16 h per day stimulated a two-to threefold increase in the plasma concentration of LH within 1\ p=n-\ 3 days. Interruption of a 7\m=.\75L :16D schedule by 15 min light between 13\m=.\75and 19\m=.\75h after the beginning of the main photoperiod stimulated LH secretion in the immature and adult hen and a higher rate of lay than that of the 8L : 16D control group. There was a significant (P < 0\ m=. \ 01) correlation between the concentration of LH in the plasma and the rate of lay. The photostimulated rise in the plasma concentration of LH in the immature hen was not associated with any increase in the responsiveness of the pituitary gland to LH releasing hormone. Of the treatments in which a 15-min pulse of light was provided, the schedules of 7\m=.

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“…Harrison et al (1969) reported a consistent positive association between age at stimulation and early egg weight. Early-stimulated pullets persisted in smaller egg size throughout the entire egg production cycle.…”

Section: Introductionmentioning

confidence: 76%

“…Earlier studies dealing with decreased age at sexual maturity (Bray et al, 1965;Harrison et al, 1969;Leeson and Summers, 1980;Bell, 1982 involved housing of underweight pullets. The reduced egg size in early maturing pullets may be associated with the smaller body size of the pullet at stimulation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Early Maturation of Brown Egg-Type Pullets, Flock Uniformity, Layer Protein Level, and Cage Design on Egg Production, Egg Size, and Egg Quality

et al. 1985

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Eight-week-old Harco Sex-Link pullets were assigned to four growing regimens. Feed was restricted to Group 1. The birds reached an average weight of 1.52 kg at 20 weeks of age and were then light stimulated. Group 2 received the same ration ad lib and reached an average weight of 1.64 kg at 16 weeks. At this age they were light stimulated. Birds in Groups 3 and 4 were separated into two weight classes at 8 weeks of age. Those below the median weight received an 18% protein grower ration and those above the median weight a 16% ration. Group 3 birds were grown similarly to Group 1; Group 4 birds were grown similarly to Group 2. At housing, each group was equally divided and given either a 17 or 19% protein layer ration. Two cage designs (standard and reverse) were used and each treatment combination was equally represented. Ad lib-fed, early-housed pullets reached 1.64 kg at 16 weeks of age, but they did not come into production until 19.4 weeks of age. Hen-day percent production (HDP) was significantly less than for the late-housed pullets. Feed per dozen eggs was not affected by the early housing, but early-housed pullets laid significantly smaller eggs and feed per gram egg was significantly increased. Hens in reverse cages on a 19% protein layer ration laid the largest eggs in weight and size. Although early housing had a detrimental effect on average egg weight, it appeared possible to manipulate egg weight and size distribution through a combination of cage design and layer protein. Birds grouped by body weight at 8 weeks had higher uniformity, but this trait was not correlated with egg numbers or size. Moreover, housing body weights were not significantly correlated with egg size, suggesting factors other than body weight were responsible for the smaller eggs from early-housed pullets.

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Reproductive Development and Response of White Leghorn Pullets Subjected to Increasing Day-Lengths at Different Ages

Cited by 20 publications

References 6 publications

Interval Between Preovulatory Surges of Luteinizing Hormone Increases Late in the Reproductive Period in Turkey Hens1

Interval Between Preovulatory Surges of Luteinizing Hormone Increases Late in the Reproductive Period in Turkey Hens1

Evidence of a photoinducible phase for the release of luteinizing hormone in the domestic hen

Effects of Early Maturation of Brown Egg-Type Pullets, Flock Uniformity, Layer Protein Level, and Cage Design on Egg Production, Egg Size, and Egg Quality

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