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Responses of adult broiler breeders to feeding time
- D. Backhouse, R.M. Gous
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- Journal:
- World's Poultry Science Journal / Volume 62 / Issue 2 / June 2006
- Published online by Cambridge University Press:
- 18 September 2007, pp. 269-281
- Print publication:
- June 2006
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Feeding time has the potential to influence the performance of adult broilerbreeder flocks and is thus of great importance. Aliterature review is presented concerning the responses of adult broilerbreeders to feeding time. It appears that there is no benefit in feeding broiler breeders later in the day with regard to egg numbers oregg weight.
There is a potential improvement in shell quality that results from feeding laterin the day or from splitting the daily feed allocation across more frequent feeding periods throughout the day. However, anticipated improvements in shell quality due to delayed feeding times may not be realised, particularly when birds are housed on litter floors. Furthermore, improvements in shell quality may not be translated into improvements in hatchability due to increases in shell thickness adversely affecting the watervapourconductance of the eggshell.
Broiler hatching egg producers should be aware that later feeding times may delay the time of oviposition, which may demand changes in farm procedures. Furthermore, delayed feeding times may result in feeding activity coinciding with other important periods of activity, such as mating and oviposition, resulting in a reduction in fertility and an increase in the production of eggs with abnormal shells. The current commercial practice of feeding adult broiler breeders early in the day, at, ornear, lights-on, is justified, as feeding at this time has positive consequences for other aspects of hatching egg production. However, afternoon feeding is not necessarily detrimental and may be an option to consider in cases where improvements in shell quality are required, although this may not be the solution for hatchability problems. If a change in feeding time is under consideration, environmental conditions, particularly the photoperiod and ambient temperature, must be taken into account, and any changes should be made gradually, as broiler breeders may be sensitive to abrupt changes in feeding time. Furthermore, changes in the feeding schedule should be accompanied by close monitoring of performance parameters, including the number of settable, abnormal and floor eggs, percentage of fertile eggs, and hatch of fertiles.
Effect of constant photoperiods on the laying performance of broiler breeders allowed conventional or accelerated growth
- P. D. LEWIS, D. BACKHOUSE, R. M. GOUS
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- Journal:
- The Journal of Agricultural Science / Volume 143 / Issue 1 / February 2005
- Published online by Cambridge University Press:
- 28 June 2005, pp. 97-108
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An experiment was conducted at the University of KwaZulu–Natal to assess the effect of constant photoperiods on sexual maturity and egg-laying performance in broiler breeders given two levels of control-feeding during the rearing phase. Cobb broiler breeder females were grown to reach 2·1 kg body weight at 17 or 21 weeks, and maintained on 10, 11, 12, 13, 14 or 16-h photoperiods from 2 days to 68 weeks of age. There were no significant interactions between photoperiod and growth rate for any production parameter. The time required reaching 2·1 kg increased proportionally with photoperiod but, because of delayed sexual development, birds on longer photoperiods consumed more feed to, and were heavier at, sexual maturity than shorter daylengths. The longer-photoperiod birds also had inferior rates of lay in the first half of the cycle, but superior in the second, which, together with the photoperiodic effects on maturity, resulted in birds on 11, 13 or 14 h producing most eggs to 68 weeks, and those on 16 h fewest. It is possible that the pattern of egg production was due to some of the birds on [ges ]13-h photoperiods becoming photorefractory, having a mid-cycle pause, and then spontaneously resuming egg production in the latter half of the cycle. However, a hinge-analysis of current and other data to the more usual depletion age of 60 weeks showed that the combined effects of photoperiod on sexual maturity and egg production resulted in constant 10-h birds producing the highest number of eggs, with numbers decreasing by 3·6 eggs/h of photoperiod above the hinge and 7·8 eggs/h of photoperiod below it. Mean egg weight increased by 0·4 g/h of photoperiod, but the proportion of abnormally large and floor eggs and the incidence of mortality were unaffected by daylength. For each photoperiod, accelerated growth resulted in body weights being heavier than controls at sexual maturity, despite the mean age at maturity being 10 days earlier for the faster-growing birds. Body weights for the two growth groups were not significantly different at 68 weeks. Faster-growth birds consumed 1 kg less feed to 2·1 kg body weight, but 1·3 kg more feed to sexual maturity and 2·7 kg more to 68 weeks, and produced 6 more eggs than, but had similar patterns of egg production to, the conventionally managed controls. Mean egg weight, the proportion of floor eggs and the incidence of mortality were similar for both groups. Notwithstanding that the overall production of abnormally large eggs was low (1·1 eggs per bird); the faster-growing birds produced significantly more than the controls. Egg weight was positively influenced by age at sexual maturity, body weight at sexual maturity and photoperiod, but was unaffected by rate of growth to 2·1 kg per se.
These findings show that there are differences between broiler breeders and egg-type pullets in their response to constant photoperiods. It is likely that the factors responsible for these differences, particularly in terms of sexual development, are the exhibition of photorefractoriness by, and the retardational effects of controlled feeding on, broiler breeders.
Roundtable: The Progress of Heterodox Economics
- A. W. Bob Coats, Roger E. Backhouse, Sheila C. Dow, Daniel R. Fusfeld, Craufurd D. Goodwin, Malcolm Rutherford
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- Journal:
- Journal of the History of Economic Thought / Volume 22 / Issue 2 / June 2000
- Published online by Cambridge University Press:
- 11 June 2009, pp. 145-148
- Print publication:
- June 2000
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The central theme of this session is the changing relationship between “orthodox” (i.e., mainstream, neoclassical) and “heterodox” economics, especially in the USA, during the past two or three decades. Economics is such a large and heterogeneous discipline that it cannot be characterized both briefly and accurately. Alongside the growth of formalization and mathematization, and the high degree of uniformity in the undergraduate and graduate curricula and in the leading textbooks, there are also within the subject a number of dissenting or deviant doctrinal schools, rival methodological approaches, and innovative developments designed to remedy its defects and/or overcome its limitations. Moreover, many of the outspoken criticisms of the status quo, proposed remedies, and innovations, originate with or are endorsed by prominent economists with impeccable professional credentials. Indeed, in some cases their contributions threaten the discipline's foundations and can, therefore, be considered a species of “orthodox subversion.”