Effects of dietary minerals on postmolt performance of laying hens

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. rd 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.


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 postmolt performance.
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 humans (Gast and Ricke, 2003).It seems that mineral raised at Breeding and Incubation Section, Poultry Research Institute, Rawalpindi.Birds were housed supplementation molting methods would be given 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 completely randomized design.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 oxytetrasalt (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 Schedule is given in Table-3.compared to a control group.However, induced Molt period (2 Weeks): During this period, experimolting 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 hens.
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 experimental diets at the rate of 30 g/bird, whereas Comb White Leghorn commercial layers (66-67 weeks-old) were randomly picked up from the flock birds in group E were fed ad libitum feed throughout 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 Newcastle Disease with Lasota.
the nearest 0.01 g.Shell thickness, egg length and rd albumen height were measured with a caliper and During 3 week of rest period the birds in groups recorded to the nearest 0.1 mm.Haugh units were A, B, C and D were given experimental diets at the rate calculated taking into account egg length and albumen of 60 g/bird, however birds in group E were fed ad height as an indicator of interior egg quality libitum.During this week, hens were placed on (Silversides et al., 1993).Egg production and quality lighting program of 14L:10D.The schedule for were measured for 20 weeks after molting.Daily induced molting is illustrated in the Table 3. Molting mortality and etiology of the dead birds, if any, was phase lasted for 35 days in months of June-July.
recorded after conducting the post-mortem Production Phase: During this phase, the birds of all examination.groups were fed a balanced layer diet (Table 1).They Statistical analysis: All data were analyzed using were fed ad libitum and had free access to clean and procedure of SAS software (2001).Differences in fresh drinking water.Hens were placed again on parameters (egg production, feed intake, g of body lighting program of 16L:8D.Production data was weight loss, % of body weight loss, organ weights, recorded for 20 weeks after molting. internal egg quality and external egg quality) among Each diet was analyzed as described methods in treatment groups, when significant, were compared AOAC (2000) for proximate composition, minerals , using Duncan s multiple range test.The level of and aflatoxin at Feed Testing Laboratory, Poultry significance used in all results was p<0.05.Research Institute, Rawalpindi (Table 2).All analyses and determinations were done in triplicate.

Results
Parameter measured: At the end of the molt, 15 Molting phase: The birds fed diets A, B and C birds per treatment were euthanized with CO gas and 2 showed significantly greater (p<0.05)percentages of the ovaries, oviducts, kidneys, hearts, livers and body mass loss (25.89, 25.69 and 25.25%, spleens were excised aseptically and weighed and respectively) than those fed the diet D (20.04%).The expressed as relative weights (%of body weight).
birds fed diet E (Full feed-non molted group) exhibited During molt, bird weights were monitored at d 1, 5, 9 for group E, Table 6).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 respectively).
production and enter a non-reproductive state that Post-molting phase: On average non-molted hens cause body weight losses.fed a balanced layer diet and molted hens fed without Hussein et al., (1988) reported that supplemenminerals 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, attributed to decreases in liver and reproductive organ respectively) after 20 weeks postmolt .
weights (Berry and Brake, 1985).The body weight However, molted hens fed without minerals diet had reduction in the minerals supplemented groups was significantly higher egg production than those of nonshown to be 25.89-25.69%.Therefore, it can be molted hens fed a balanced layer diet.In the present suggested that the termination of fasting should be study, egg weight at the peak of postmolting determined on body weight basis rather than days-ofproduction was not significantly different between the fasting.The weight loss exhibited by non-molted birds molted and non-molted hens (Table 6).could be explained by the reduced photoperiod, In this study, egg shell quality improved because photoperiod and nutrient deprivation have (p<0.05) in molted hens compared to non-molted hens (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 1 non-molt diet on post molt organ weights (as % of body weight)
-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 inducing molting as control. a