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Reproductive senescence in domestic fowl: Effects on egg production, sequence length and inter‐sequence pause length a

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F. E. Robinson , R. T. Hardin & A. R. Robblee

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Department of Animal Science , University of Alberta , Edmonton, Alberta, T6G 2P5, Canada Published online: 08 Nov 2007.

To cite this article: F. E. Robinson , R. T. Hardin & A. R. Robblee (1990) Reproductive senescence in domestic fowl: Effects on egg production, sequence length and inter‐sequence pause length, British Poultry Science, 31:4, 871-879, DOI: 10.1080/00071669008417318 To link to this article: http://dx.doi.org/10.1080/00071669008417318

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British Poultry Science (1990) 31: 871-879

REPRODUCTIVE SENESCENCE IN DOMESTIC FOWL: EFFECTS ON EGG PRODUCTION, SEQUENCE LENGTH AND INTER-SEQUENCE PAUSE LENGTH F. E. ROBINSON, R. T. HARDIN AND A. R. ROBBLEE Department of Animal Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5 Downloaded by [New York University] at 08:52 15 May 2015

Received for publication 25th January 1990

Abstract 1. Age-related changes in egg production, oviposition sequence length and inter-sequence pause length were studied by analysis of oviposition records of 50 individually-caged broiler breeders from 24 to 62 weeks of age. 2. The 44 surviving hens exhibited a production profile characteristic of broiler breeders (184 eggs per hen), with a peak mean sequence length of 19 eggs at 32 weeks of age. Inter-sequence pause length was maximum (1.6 d) at 54 weeks of age. Overall, the hens averaged 48 sequences, with a mean sequence length of 4.1 d. 3. Most hens had a single characteristically long sequence about the time of peak egg production (average: 24.3 d). The term 'prime' is suggested to denote this sequence. 4. Sorting the hens into groups on the basis of total egg output (upper and lower 50% and upper and lower 25%) indicated that high producing hens (upper 50% and 25%) had a very long prime sequence early in lay, and had few inter-sequence pauses of greater than 1 d duration. The converse was true for low producers (lower 50% and 25%). 5. The length of the prime sequence may be a good indicator of reproductive efficiency of hens later in life.

INTRODUCTION

Relatively little is known about the factors contributing to reproductive senescence in female domestic fowl. Egg production reaches peak values at about 8-12 weeks after the onset of lay and then declines at variable rates depending upon strain, nutrition and environmental conditions. Theoretically, a loss of potential egg production should be able to be traced back to one or more of the following phenomena: losses prior to ovulation (altered rate of follicular maturation, follicular atresia and/or increased incidence of intersequence pauses of greater than 1 d duration), losses at ovulation (altered 871

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F. E. ROBINSON, R. T. HARDIN AND A. R. ROBBLEE

incidence of internal laying) or losses post-ovulation (retrograde transport in oviduct or shell deposition impairment). Ovulation rate in the hen is dependent upon the asynchronous relationship between rate of follicular maturation and the duration of the 'open period' for luteinizing hormone (LH) release as proposed by Fraps (1955) and as mathematically demonstrated by Etches and Schoch (1984). Hence, ovulation rate (and oviposition rate) may be reduced as a consequence of a decreased rate of follicular maturation or recruitment (Williams and Sharp, 1978a; Joyner et al., 1987), by a shortening of the duration of the 'open period', or both. Wood-Gush and Gilbert (1970) reported that 11-17% of ovulations could be lost through internal laying. The effects of ageing on this loss is not clear. Reductions in egg laying towards the end of a laying year have been associated with the incidence of follicular atresia (Williams and Sharp, 1978a; Waddington et al., 1985). A further decrease in egg output could be due to a condition known as erratic oviposition and defective egg syndrome (EODES) (van Middlekoop, 1972). The work reported here was undertaken to characterize age-related changes in egg production, oviposition sequence length and inter- sequence pause length in broiler breeder hens to 62 weeks of age. A second objective was to compare the degree to which ageing influences the above variables in hens which differed in total egg output. MATERIALS AND METHODS

A flock of 500 Indian River broiler breeder pullets were reared to 21 weeks of age following typical Canadian commercial practice. Food intake was restricted using skip-a-day feeding to maintain body weight of the pullets to that weight recommended by Indian River International. At 21 weeks of age, the 50 hens closest to this recommended weight were selected and individually housed in laying cages in a windowless poultry house. A photoperiod of 14L:10D was imposed. All hens were fed on the same breeder laying ration (165 g CP and 11-93 MJ ME/kg) in quantities which maintained recommended body weight. Egg production was recorded for each hen at the same time each day for a continuous 271-d period. The incidence of soft-shelled and shell-less eggs was recorded. Egg sequence length and the number of egg sequences were determined from oviposition records following the procedure reported by Blake and Ringer (1987). Briefly, a sequence was considered to be a period of consecutive ovipositions which was terminated by a pause of one or more days. From 24 to 62 weeks of age, the oviposition records were subdivided into nineteen 14-d periods. For each hen, the length of the current laying sequence was determined on the third last day of each period (day 12). If for a particular hen, for a particular period, an oviposition did not occur on day 12, the length of the current sequence on day 11 was used for that period. If neither day 11 nor day 12 were egg laying days, day 13 was used. In some instances, day 10 or day 14 were used. If a hen failed to lay during days 10 to 14, no sequence

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length value was recorded for her for that period. It should be noted that it was possible for hens which laid sequences of greater than 14 d, to have the same value for sequence length extend into one or more periods. For example, a hen laying a 38 egg sequence, could have a value of 38 d recorded for three consecutive periods. The length of the inter-sequence pause was also determined for each hen for each 14-d period. If a hen had only one pause during the period, the length of that pause was recorded. If a hen had two or more pauses during that period, the average pause length was calculated and recorded. If a hen did not experience a pause during that period, no value was recorded. At the completion of the laying period, the total egg output was calculated for each individual hen. Hens were sorted into groups based on egg output to determine if these groups of hens experienced similar age-related changes in sequence length and inter-sequence pause length. Hence a second data set was formed based on hens sorted into the upper 50% and the lower 50% based on egg output. A third data set was formed of hens that were in the upper 25% and the lower 25% of the flock in terms of egg output. Statistical analysis

The upper 50% were compared with the lower 50% and the upper 25% with the lower 25%. All quantitative data were subjected to a one-way analysis of variance using SAS method (Joyner et al., 1985). Statistical significance was set at P

Reproductive senescence in domestic fowl: effects on egg production, sequence length and inter-sequence pause length.

1. Age-related changes in egg production, oviposition sequence length and inter-sequence pause length were studied by analysis of oviposition records ...
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