Methods and effect of molting on reproductive performance
Riaz, M. F. 2014
Department of Poultry Production UVAS, Lahore, Pakistan.
Molting:
In avian species molting is the phenomenon in which feathers are replaced and reproductive
organs perform well by going to their earlier condition (Berry, 2003). Generally molting takes four
months in laying hens naturally (North and Bell, 1990).
Induced Molting:
Induced molting is the managemental practice which increases the speed of the molting.
By the help of induced molting all the hens come to rest uniformly and their reproduction
performance increase (McDaniel and Aske, 2000). This is a good method to increase the bird’s
performance but due to feed withdrawal it comes under criticism (Jeong et al., 2013).
Methods of Induced Molting:
There are many ways to induce the forced molting gonadotropin-releasing hormone agonist
(Dickerman and Bahr, 1989; Attia et al., 1994), by not giving water and feed with-drawl (Brake et
al., 1982; Hazan and Yalcin, 1988; Herremans, 1988), or by using diets of low sodium and calcium
or by feed constitutes of high Zinc or Iodine (Wolford, 1984; Decuypere and Verheyen, 1986). In
laying domestic fowls molting is induced by the decrease of feed, water and time of light
(Nakazawa et al., 1968).
Molting with Fasting:
Molting with the help of fasting is of three types i.e. short fasting (4-6 days), medium
fasting (10 days) and long fasting (12-16 days) for the commercial farmers (Ruszler, 1998). But
many researchers said that fasting has many deleterious effects on the health of the bird and
specifically it cause mortality. Many Animal rites agencies raised their voice against the fasting
method of molting as it is against the welfare of the bird.
In induced molting with fasting 30% of the body weight is reduced (Ruszler, 1998) and it
involves fasting of 10 to 15 days. Molting for long time can cause infection of salmonella (Holt,
2003). So feeding a high zinc diet cause molting (Park et al., 2004) while using of alfalfa (Landers
et al., 2005) or whole cotton seed (Davis et al., 2002) effective as feed removal program. Birds
given complete withdrawal of feed result in earlier stop of egg production as compared to chemical
and non-chemical methods (Karimi et al., 2009). However Mejia et al., (2010) conclude that low
energy feeds were alternatives for inducing a molt for good post molt performance. This is for the
well-being of the birds.
Molting with decrease in Photoperiod:
All the molting methods include the reduction of lighting period. Changes in time of light
act as primary environment agent and cause molt in many avian species (Rowan, 1926). Because
as day length decrease it cause regression of gonads and it cause molting (Meier and Farner, 1964;
Pittendrigh and Minis, 1964; Wolfson, 1966; Follett and Sharp, 1969; Meier and MacGregor,
1972; King, 1970). Temperature is also a factor for the induction of molting as it increases the
effect of photoperiod (Follett, 1973).
Molting with Chemicals:
For chemically induced molting desiccated thyroids or thyroxine is given in large doses
(Zavadovsky, 1925; Kobayashi, 1975) and it cause decrease in egg production. In induced molting
changes in many endocrine functions are involved (Sulman and Perek, 1947; Juhn and Harris,
1956; Perek et al., 1957). Zinc also helps for the molting of chickens. As zinc dozes reduce the
egg production (Kienholz et al., 1961). Zinc-induced molting was found to be an improved method
regarding disease resistance along with production performance and the dynamics of pituitaryhormone-producing cells (Sandhu et al., 2010).
Effect of Molting on Egg Production Performance:
As the age of the bird increases the no. of broken shell eggs also increases and the egg
production percentage decreases (Bar, et al., 2001; Bell, 2003). Force molting increase the egg
production from premolt up to 18.6 to 26.1 %in white leg horn hens (Brake et al., 1979). Forced
molting decrease the broken shell, shell less eggs and increase shell quality and production
percentage by decreasing the age dependent rate of decline (Hurwitz et al., 1995). Forced molting
is usually adopted in the industry when there is high rate of feed and low rate of eggs (McDaniel
and Aske, 2000). After molting when the body tissues regenerate the egg production increases
(Bar et al., 2001). According to Swanson and Bell, (1974), the post molt egg production is 7075%. Body weight loss affects the egg weight, as 15% body weight loss results in heavier eggs as
compared to 20-25% body weight loss (Hembree et al., 1980; Buhr and Cunningham, 1994). Peak
of post molt egg production in feed withdrawal method is 82% (Hassanabadi, A. and Kermanshahi,
H. 2007).
Post molt performance of laying hens under different molting methods.
Table no. 1
Molting procedure
Post Molt peak hen Egg weight (g)
day egg production
(%)
Continuous fasting
78.1
63.9
Cottonseed
71.1
65
Zinc
69
67.1
Source: (Karimi et al., 2009).
The post molt hen house egg production increase as the result of molting as compared to
the non-molted flocks of same age. Similarly hen day egg production also increase numerically
compared to their control flock (Thirunavukkarasu, P. et al., 2006).
An experiment was conducted by Ocak, N. (2004) in which eggs yield and egg quality in
the second production cycle was observed. And the result is following.
Table no. 2
Parameters
Pre molting
Post molting
Hen day egg production (%)
45.01
71.53
Crack eggs (%)
26.88
3.51
Unshell eggs (%)
Feed
5.28
consumption/hen/day 87.2
2.29
135.5
(g)
Source: (Ocake, N. 2004).
Effect of Molting on Egg Quality Parameters:
Egg production, fresh egg quality and hatchability decrease as the age of the broiler breeder
increases. To increase the egg quality and egg production of breeder induced molting is a good
practice (Decuypere and Verheyen, 1986; Buhr and Cunningham, 1994). Induced molting cause
improvement in the specific gravity, shell thickness, shell percent and smoothness of shell in layers
and broiler breeders (Berg and Bearse, 1947; Thomas and Bray, 1976; Roland and Bushong, 1979;
Roland and Brake, 1982).
Haugh Unit of albumen increases with the induced molting (Attia, et al., 1994Molting
affects the eggshell quality, albumen quality, and hatchability characteristics of the eggs (Decupere
and Verheyen, 1986; Verheyen et al., 1990; Attia et al., 1994). The increase in HU scores just after
molting is similar to the observations of Attia et al., (1994). The improvement of HU after molting
may be due to rejuvenation of laying hen reproductive organs, as well as in broiler breeders (Brake
and Thaxton, 1979; Wolford, 1984; Berry and Brake, 1985; Verheyen et al., 1987; S. H. Khan et
al., 2011).
Table no. 3
Parameters
Premolt
Post molt
Shape index
73.86 ± 0.51
74.92 ± 0.27
Egg shell weight (g)
5.05 ± 0.11
5.43 ± 0.07
Egg shell thickness (mm)
0.35 ± 0.03
0.36 ± 0.03
Albumen length (mm)
97.51 ± 2.21
92.95
Albumen width (mm)
75.41 ± 1.75
70.06 ± 0.80
Albumen height (mm)
5.34 ± 0.19
5.95 ± 0.12
Albumen index (%)
Yolk weight (g)
6.25 ± 0.30
18.82 ± 0.32
7.38 ± 0.18
19.63 ± 0.26
Yolk width (mm)
42.02 ± 0.39
42.00 ± 0.21
Yolk height (mm)
17.69 ± 0.24
18.44 ± 0.11
Yolk index (%)
42.18 ± 0.70
43.98 ± 0.32
Yolk color
13.02 ± 0.71
13.89 ± 0.08
Hough unit
72.81 ± 1.52
76.44 ± 0.95
External egg quality traits
Internal egg quality traits
Source: Deger, H. et al., (2013)
According to Y. Cufadarc et al., (2011) if molted hens given different concentration of
Calcium i.e. 30g/kg, 36g/kg and 42g/kg, it does not show significant result on the egg shell
thickness and egg shell weight. But if we take the interaction of Calcium concentration and particle
size it has significant effect on the breaking strength of the egg shell (Y. Cufadarc et al., 2011).
Abdullah (2007) observed higher egg shell weight and thickness in eggs from hens molted
with Zn. Because in Zn induced molting, extra Zn deposit in the egg shell and it enhance the effect
of Calcium and cause better egg shell weight and thickness (Abdullah, 2007; Klecker et al., 2002;
Innocenti et al., 2004).
Effect of Molting on Hatching Traits:
Egg quality and the hatchability of broiler breeder hens decrease with the age (Lapaˆo et
al., 1999).As molting cause histophysiological changes in ovary and oviduct (Decupere and
Verheyen, 1986), so it also affects the hatchability and chick quality. Baker et al. (1981) conclude
that maximum involution of reproductive organs is essential for maximum post molt performance.
Hall (1946) concludes that molting through feed restriction cause high fertility and hatchability in
White Leg Horn hens. Molting is the method for the improvement of the hatchability (Tona, K. et
al., 1994). The higher hatchability after long storage time for molted hens, compared to nonmolted, can partly be explained by the higher HU values after molt (Hurnik et al. 1978).
The increase of eggshell weight, percentage shell, and shell thickness following the
induced molt (Baker et al., 1983; Al-Batshan et al., 1994; Attia et al., 1994) might also have
positively affected hatchability of eggs from molted hens, even after long storage. Molting
increased incubating egg quality by increasing the albumen HU. So it can be concluded that
molting broiler breeders can improve hatchability and juvenile growth performance.
Effect of Molting on Progeny Growth Performance:
Progeny performance of the chickens is largely depending on the genetic potential of their
parents. In chickens difference in body weight in next generation is due to the genetics make up of
different flocks (Hafez, 1963; Marks, 1971; Sefton and Siegel, 1974; Shamma, 1981; Darden and
Marks, 1988). As genetic make 85% of the bird’s performance. However many researchers work
on that how molting of parent affect the different traits of chicken. And according to it hatchability
of the eggs increase after the induced molting, but the 1 day old chick of non-molted hen is heavier
than the molted. But at the age of 7 days chick hatched from molted hen gain higher body weight
than the non-molt (Tona, K. et al., 1994). As for as body weight gain, FCR concerned, these
depends on the genetic potential and then on the managmental practices. As body weight of the
chicken reduced up to 30% due to molting (Ruszler, 1998) so the eggs from the molted hen having
low weight. And the weight of DOC’s depend on the egg weight, so the chick weight is also low.
And it affects its finale body weight.
The percentages of chicks of good quality were 89.38 and 89.87, respectively, before molt
and after molt (Tona, K. et al., 1994). The slightly greater body weight of the chicks from the eggs
laid BM was probably due to the greater weight of the eggs from which they were hatched. Merritt
and Gowe (1965) and Moran (1990) have reported a linear relation-ship between the egg weight
and 1-d-old chick weight.
The 1-d-old chick weight/egg weight ratio after molting was higher than before molting,
indicating that chicks hatching from eggs of similar weights were heavier after molting than before
molting. There is less egg weight loss during incubation of eggs from molted hens because
incubating egg weight losses are a function of egg characteristics such as shell structure and
membrane structure (Christensen and McCorkle, 1982). Chick weight at Day 7 was greater for
chicks produced after molting of the breeders, although the 1-d-old chick weight was lower, this
may indicate that quality and vigor of the hatched chicks of molted breeders are higher than those
from non-molted hens.
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faisal riaz