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GraphicEffects of dietary minerals on postmolt performance of laying hens
Sohail Hassan Khan*, Abdul Rehman and Jehanzeb Ansari Murree Road, Shamsabad, Rawalpindi, Pakistan * Corresponding author email: email@example.com Received: 15-02-2011, Accepted: 11-03-2011, Published Online: 16-07-2011
Four hundred and fifty Single Comb White Leghorn commercial layers (66-67 weeks-old) were housed 2 birds per cage for the molting procedure. The hens were divided into 5 treatment groups with 90 layers per treatment and 30 layers in each replicate per treatment group following completely randomized design. During molt period (2 Weeks), experimental birds were randomly assigned to five-treatment groups viz., A (15 ppm copper sulphate), B (20 ppm zinc oxide), C (20 ppm aluminium oxide), D (balanced layer diet without added minerals) and E (without induced molting as control). The birds in groups A, B, C and D were offered respective experimental diets at the rate of 30 g/bird except bird's in-group E (ad libitum) and lighting program was followed as 12L: 12D. During rest period (3 Weeks) the birds in groups A, B, C and D were given respective experimental diet at the rate of 50 g/bird for first 2 weeks of the rest period. During 3 week of rest period the birds in groups A, B, C and D were given experimental diets at the rate of 60 g/bird and
were placed on lighting program of 14L:10D. During production phase, the birds of all groups were fed a balanced
layer diet (ad libitum) and birds were placed again on lighting program of 16L:8D. The results showed that the birds
fed diets A, B and C showed greater (p<0.05) percentages of body mass loss than those fed the diet D. The birds fed diet
E (Full feed-non molted group) exhibited the least amount of body mass loss when compared with all other treatments
of molted hens. Un-supplemented mineral group and un-molted hens had higher (p<0.05) ovarian weights than hens on
all other molted treatments. No significant differences (p>0.05) in ovarian weights were found among minerals
supplemented groups A, B and C. The non-molted birds (group E) exhibited the greatest (p<0.05) feed intake over the 2
weeks molt whereas birds on minerals supplemented diets ate the least (p<0.05) feed. On average non-molted hens fed
a balanced layer diet and molted hens fed without minerals diet had lower (p<0.05) egg production when compared
with molted hens fed mineral added diets after 20 weeks post molt. However, molted hens fed without minerals diet had
significantly higher egg production than that of non-molted hens fed a balanced layer diet. Egg shell quality and Haugh
unit score improved (p<0.05) in molted hens compared to non-molted hens. Based on the results of this study, mineral
feeding appears to be the best alternative to without mineral feeding in molting methods and yield comparable results.
Key words: Zinc oxide, copper sulphate, aluminium sulphate, performance.
1983). In addition to increased profit margins, an induced molt rejuvenates hens' reproductive tract to The commercial egg industry commonly uses produce higher quality eggs, which are more induced molt procedures to rejuvenate flocks for a marketable (Keshavarz and Quimby, 2002). second or third laying cycle. According to Holt (2003), There are several programs used for successfully 75 to 80 percent of commercial laying facilities in the molting laying hens such as by feed removal and United States use an induced molt program to photoperiod reduction to obtain a total cessation of egg rejuvenate flocks for increased productivity. The main production (Hussen, 1996). In recent years, there is purpose of molting is to cease egg production in order growing global concern for animal rights and welfare, for the hens to enter a non-reproductive state, which hens during molt has been questioned when feed increase egg production and egg quality postmolt removal is used (Gast and Ricke, 2003). Molting by (Webster, 2003). Body mass loss during molting feed deprivation has also been identified by process has been shown to be directly related to researchers and public health authorities as a significant risk factor for the infection of laying flocks To optimize postmolt performance, a body mass with Salmonella Enteritidis, the most important loss of 25 to 30% should be achieved (Baker et al., pathogen inside eggs and known to be transmitted to Veterinary World, Vol.4 No.9 September 2011 389 Effects of dietary minerals on postmolt performance of laying hens Table-1. Composition of Experimental Diets (g/kg)
Stages of induced molting
1. Provided milligrams per kilogram of diet unless otherwise noted: vitamin A, 8.818 IU; vitamin D, 2.208 IU; vitamin E, 5.86 IU;vitamin K, 2.2 IU; thiamine, 1.1 IU; riboflavin, 4.4IU; niacin, 22 IU; choline, 500 IU; B , 2. Trace mineral premix provided milligrams per kilogram of diet unless otherwise noted: Mn, 68.2; Zn, 55; Cu, 4.4; I, 1.1; Se,0.1. *molting layer diet divided into three treatments; A: 15 ppm copper sulphate; B: 20 ppm zinc oxide; C: 20 ppm aluminium oxide humans (Gast and Ricke, 2003). It seems that mineral raised at Breeding and Incubation Section, Poultry supplementation molting methods would be given Research Institute, Rawalpindi. Birds were housed priority in the coming years. These methods have one per cage and allowed 3 weeks for acclimation. lower mortality rates in the hot climates as compared After acclimation, layers were placed 2 birds per cage to the feed deprivation and feed restriction methods.
for the molting procedure. The hens were divided into Inductions of molt through dietary mineral additives 5 treatment groups with 90 layers per treatment and 30 such as Cu, Zn (Stevenson and Jackson, 1984), or Al layers in each replicate per treatment group following (Hussein et al., 1989) have been practiced by various scientists in the past to enhance the post-molt Pre-molt period:The layers were vaccinated against
production. Uses of high levels of either aluminium newcastle disease and were treated with oxytetra- salt (Yousaf and Ahmad, 2006) or dietary zinc (Yousaf cycline (1 ml/liter of drinking water) and vitamins for and Ahmad, 2006) have been successfully used. a period of three weeks during which feed and However, supplementing low levels of dietary zinc drinking water were given ad libitum. During this combined with reduced calcium levels in the diet have period, the birds were fed a complete layer diet (Table also induced molting successfully in laying hens 1) ad libitum and allowed full access to water. Hens (Ricke et al., 2001). Copper is used as an effective were placed on lighting program of 16L:8D. Egg molting agent (Stevenson and Jackson, 1984). production was monitored to ensure that all hens were Supplementation of minerals has resulted in better healthy and actively producing. Induced molting postmolt production performance in laying hens as compared to a control group. However, induced Molt period (2 Weeks): During this period, experi-
molting by high dietary minerals has raised public mental birds were randomly assigned to five treatment health concerns regarding the potential residues of groups' viz., A, B, C, D and E. The experimental birds these minerals in eggs and meat, which may have of groups A, B and C were fed a molted layer diet implications for human health. These risks of high (Table 1) that was contained different minerals added. mineral residues can be minimized by using low The experimental diet “A” contained 15 ppm copper mineral diets and yet induce molting in egg laying sulphate (Yousaf, 2006). The diet “B” contained 20 ppm zinc oxide (North and Bell, 1990). The diet “C” The objective of the current experiment was to contained 20 ppm aluminium oxide (Yousaf and evaluate the effectiveness of different minerals at low Ahmad, 2006). However, diet “D” was balanced layer levels combined with layer ration on the induction of a diet without added minerals. The bird's in-group E molt, postmolt production and postmolt egg quality. (without induced molting as control) was fed balanced layer diet. These diets were prepared at Nutrition Materials and methods
Section, Poultry Research Institute, Rawalpindi. The Experimental birds: Four hundred and fifty Single
birds in groups A, B, C and D were offered respective Comb White Leghorn commercial layers (66-67 experimental diets at the rate of 30 g/bird, whereas weeks-old) were randomly picked up from the flock birds in group E were fed ad libitum feed throughout Veterinary World, Vol.4 No.9 September 2011 390 Effects of dietary minerals on postmolt performance of laying hens Table-2. Nutrient composition of diets offered at various stages of induced molting
Stages of induced molting
the period and kept as control. Water was given ad and 14. Feed intake was measured by weighing each libitum to the birds of all groups. During this phase, diet prior to the start of the molt and after the molt lighting program was followed as 12L: 12D.
period. Feed efficiency was calculated on the basis of Rest period (3 Weeks): The birds in groups A, B, C
feed intake/dozen eggs during production period. Egg and D were given respective experimental diet at the production was measured daily (%of hen-day rate of 50 g/bird for first 2 weeks of the rest period. assuming 1 egg per day = 100%), whereas egg quality Water was offered ad libitum to the birds of all groups. parameters were measured once per week. Egg weight The birds of all groups were vaccinated against was measured with electronic balance and recorded to the nearest 0.01 g. Shell thickness, egg length and During 3 week of rest period the birds in groups albumen height were measured with a caliper and A, B, C and D were given experimental diets at the rate recorded to the nearest 0.1 mm. Haugh units were of 60 g/bird, however birds in group E were fed ad calculated taking into account egg length and albumen libitum. During this week, hens were placed on height as an indicator of interior egg quality lighting program of 14L:10D. The schedule for (Silversides et al., 1993). Egg production and quality induced molting is illustrated in the Table 3. Molting were measured for 20 weeks after molting. Daily phase lasted for 35 days in months of June-July. mortality and etiology of the dead birds, if any, was Production Phase: During this phase, the birds of all
recorded after conducting the post-mortem groups were fed a balanced layer diet (Table 1). They were fed ad libitum and had free access to clean and Statistical analysis: All data were analyzed using
fresh drinking water. Hens were placed again on procedure of SAS software (2001). Differences in lighting program of 16L:8D. Production data was parameters (egg production, feed intake, g of body weight loss, % of body weight loss, organ weights, Each diet was analyzed as described methods in internal egg quality and external egg quality) among AOAC (2000) for proximate composition, minerals treatment groups, when significant, were compared and aflatoxin at Feed Testing Laboratory, Poultry using Duncan s multiple range test. The level of Research Institute, Rawalpindi (Table 2). All analyses significance used in all results was p<0.05. and determinations were done in triplicate. Parameter measured: At the end of the molt, 15
birds per treatment were euthanized with CO gas and
Molting phase: The birds fed diets A, B and C
the ovaries, oviducts, kidneys, hearts, livers and showed significantly greater (p<0.05) percentages of spleens were excised aseptically and weighed and body mass loss (25.89, 25.69 and 25.25%, expressed as relative weights (%of body weight). respectively) than those fed the diet D (20.04%). The During molt, bird weights were monitored at d 1, 5, 9 birds fed diet E (Full feed-non molted group) exhibited Table-3. Induced Molting Schedule
Deworming, Antibiotic Course IB+ND Vaccination IB=Infectious bronchitis; ND= Newcastle disease Veterinary World, Vol.4 No.9 September 2011 391 Effects of dietary minerals on postmolt performance of laying hens Table-4. Effects of copper sulphate, zinc oxide, aluminium oxide, without mineral molt diets and a
non-molt diet on feed intake, body weight loss and percentage of body weight loss during molting
Feed Intake (g/bird)
Body weight loss (g/bird)
Body weight loss (%)
a-d means with the different superscript within columns are significantly different (P< 0.05).
*A: 15 ppm copper sulphate; B: 20 ppm zinc oxide; C: 20 ppm aluminium oxide; D: without minerals; E: without inducing molting as control.
the least amount of body mass loss (5.25%) when or without mineral added diets. The molted birds compared with all other treatments of molted hens showed higher (p<0.05) Haugh unit score values (Table 4). No significant differences in ovarian (85.08, 86.11, 85.08 and 84.27 for groups A, B, C and weights were found among minerals supplemented D, respectively) compared to non-molted birds (82.00 groups A (0.75% BW), B (0.55% BW) and C (0.65% BW; Table 5). All treatments exhibited differences Discussion
(p<0.05) in feed intake during the molt. The non- Molt induction to rejuvenate the egg laying molted birds (group E) exhibited the greatest feed performance of commercial laying hen flocks is an intake (739.5 g/bird over the 2 weeks molt), whereas important practice in many parts of the world, often birds on group D ingested 450.6 g/bird (Table 5). Birds being necessary to make a flock profitable under on minerals supplemented diets ate the least feed certain market scenarios. The first objective of an (280.5, 257.8 and 274.3 g/bird for groups A, B and C, induced molt program is to cause hens to cease egg production and enter a non-reproductive state that Post-molting phase: On average non-molted hens
fed a balanced layer diet and molted hens fed without Hussein et al., (1988) reported that supplemen- minerals diet had significantly lower (p<0.05) egg tation of aluminium sulphate in molted diet led to a production (60.16 and 65%, respectively) when significant reduction in body weight and feed intake of compared with molted hens fed mineral added diets birds. Approximately 25% of the body mass loss was (71.80, 74.50 and 72.15% for groups A, B and C, respectively) after 20 weeks postmolt (Table-6). attributed to decreases in liver and reproductive organ However, molted hens fed without minerals diet had weights (Berry and Brake, 1985). The body weight significantly higher egg production than those of non- reduction in the minerals supplemented groups was molted hens fed a balanced layer diet. In the present shown to be 25.89-25.69%. Therefore, it can be study, egg weight at the peak of postmolting suggested that the termination of fasting should be production was not significantly different between the determined on body weight basis rather than days-of- fasting. The weight loss exhibited by non-molted birds In this study, egg shell quality improved could be explained by the reduced photoperiod, (p<0.05) in molted hens compared to non-molted hens because photoperiod and nutrient deprivation have (Table-6). However, there was non-significant similar modes of action on the hypothalamic (p>0.05) difference found among the molted hens with hypophyseal axis causing an inhibition of circulating Table-5. Effects of copper sulphate, zinc oxide, aluminium oxide, without mineral molt diets and a
non-molt diet on post molt organ weights (as % of body weight)
a-c. means with the different superscript within columns are significantly different (P < 0.05).
1. Relative organ weight (%) = (organ weight/100 g of body weight) x 100.
*A: 15 ppm copper sulphate; B: 20 ppm zinc oxide; C: 20 ppm aluminium oxide; D: without minerals; E: without inducingmolting as control.
Veterinary World, Vol.4 No.9 September 2011 392 Effects of dietary minerals on postmolt performance of laying hens Table-6. Effects of Minerals Supplementation on performance of molted Commercial layers in
second production cycle
reproductive hormone concentrations with subsequent No differences (p<0.05) were found among treatments ovary regression and weight loss (Berry, 2003). The when comparing heart and spleen weights. Un- reduced photoperiod also provides fewer day light supplemented mineral group and un-molted birds had hours for feeding, which decreases feed intake and significantly higher liver weights when compared causes weight loss as exhibited by all birds (Andew et with all other treatments (1.80 and 2.26% BW, al., 1987). Birds on A, B and C lost more body weight respectively), whereas mineral-treated birds had than birds on groups D and E due to a decreased feed significantly lower liver weights (1.55, 1.49 and intake, which could be attributed to several factors 1.60% BW for groups A, B and C, respectively) than including supplementation of minerals in the diet.
those of control groups. Liver weight loss indicates a loss of liver energy sources, such as glycogen and Ovarian weight loss occurs simultaneously with body mass loss due to the regression of the ovaries that lipids, which are metabolized in the liver (Berry and is directly associated with the rejuvenation process. Brake, 1985). Weight loss from the liver is also Maximum involution of the reproductive organs is indicative of the loss of estrogen-dependent egg essential for optimum postmolt performance (Baker et component synthesis, which is dependent on stimulation from ovarian steroids (Berry and Brake, Un-supplemented mineral group and un-molted 1985). The most common ovarian steroids are the hens had higher (p<0.05) ovarian weights than hens on estrogens whose target organ is the liver where yolk all other molted treatments (1.25 and 2.16 % BW, phospholipoprotein synthesis occurs and is dependent respectively). Similar results were published by primarily on estrogens (Berry and Brake, 1985).
Stevenson and Jackson (1984); ovarian weights of The reduction in feed intake could have been due hens fed diet supplemented with copper sulphate were to some factors, including appetite suppression with significantly reduced from ovarian weights of hens fed minerals supplementation, decreased feeding non-supplemented mineral diet. Loss of gonadotropin stimulation with reduced daylight hours (Andews et support during induces molting causes involution of al., 1987). Dietary aluminium has been tried as a the ovary. Follicles in the maturational hierarchy molting agent (Hussein et al., 1989). They reported become atretic and the yolk material is resorbed. that dietary aluminium causes reduced feed intake by Ovary weight declines as follicles become atretic. hens. Pearce et al., (1983) reported that supplementing Reduction in ovary weight is initially dependent on the copper sulphate (2000 mg Cu/kg) reduced feed intake duration of fasting and rate of body weight loss. of bird's upto 30%. Increasing levels of dietary zinc Beyond 25% body weight loss, the ovary is fully caused progressive declined in feed consumption regressed (Heryanto et al., 1997). In the present study, (Breeding et al., 1992) such that hens given 20,000 hens lost more than 25% body weight in mineral ppm zinc oxide in an otherwise typical layer ration supplemented groups showing more declined in ovary virtually begin fasting. Whether there is a specific weight compared to other groups. Involution of the metabolic function of zinc in inducing a forced rest is oviduct follows the loss of ovarian steroidal support. Regression of the oviduct is a true re-modeling of the The goal of a viable molting program is to tissue rather than a decline in the size of cells or increase post molt egg production and quality. Hussein shrinkage of the tissue. Apoptosis removes cells of the et al., (1989) and Hussein, (1996) reported that egg glandular epithelium during regression (Heryanto et production of hens was increased in postmolting al., 1997). Zinc has an inhibitory effect on ovarian performance by supplementing of aluminium acetate function; it causes oviposition to cease without greatly in the diets of molted birds. After the molting period, depressing feed consumption (Breeding et al., 1992). hens improve their egg production due to the all as 1% Veterinary World, Vol.4 No.9 September 2011 393 Effects of dietary minerals on postmolt performance of laying hens rejuvenation of the reproductive organs and overall performance was achieved when body weight loss was body weight loss (Ocak et al., 2004). Hens that lost the greater than 25%. They reported that uterine lipid was greatest amount of weight exhibited the greatest not lost until body weight decreased to that point improvement in highest egg production after molting which coincided with maximum oviductal regression. (Baker et al., 1981). One of the major reasons for Duodinal weight decreased during fasting and returns increased postmolt egg production was decreased to original size upon refeeding (Donalson et al., 2005). postmolt production of shell less eggs. Increased egg Following the molt, intestinal calcium binding protein production can relate to profits for the industry concentration increases compared to unmolted hens. depending on bird prices, feed prices and egg demand Intestinal uptake of calcium also improves following (McDaniel and Aske, 2000). A change in supply as molt (Al-Batshan et al., 1994). Higher eggshells small as 1% can result in a 6% opposite change in egg thickness of molted birds is a desirable characteristic prices, which can cost or make a producer with a for the egg industry (Keshvarz and Quimby, 2002).
typical operation $1.46 million annually (McDaniel The Haugh unit is a measure of the internal and Aske, 2000). Yousaf, (2006) reported that molted quality of an egg. Haugh unit score were improved by hens treated by aluminium oxide in the second forced molt. Karunajeewa et al., (1989) reported production cycle produced maximum number of eggs higher (p<0.05) Haugh units of eggs from hens molted followed by copper sulphate treatment. Similar by fasting than from hens fed 10 ppm ZnO. However, in the present experiment, higher Haugh units of eggs findings have been reported by Hussein et al. (1989), from hens molted by feeding ZnO than from hens who reported that the birds induced to molt by molted by non-mineral diets. This difference is due to minerals supplementation performed better than feed use of high level of ZnO (20 ppm) than above study.
deprivation method. North et al. (1990) and Yousaf In conclusion, this study shows that mineral (2006) who reported that different induced molting feeding appears to be the best alternative to without programs did not significantly affect egg weight when mineral feeding in molting methods and yield Hens that lost more weight exhibited the best improvement in highest egg shell quality after molting Acknowledgement
(Baker et al., 1981). Improved shell gland function We would like to thank a lot Dr. Muhammad following induced molting may be due to remodeling Yousaf, Department Poultry Sciences, Faculty of at the cellular level. Cellular proliferation in the Animal Husbandry, University of Agriculture, oviduct replaces cells lost during the regression, as Faisalabad, Pakistan for his help and directions to evidenced by increased staining of the proliferating cells for proliferating cells nuclear antigen, a marker of cell proliferation (Heryanto et al., 1997). References
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