Acceleration of Tegal Duck Molting Period and Re-laying Using Cattle Reticulum Meal in Feed

This research was aimed to evaluate the effect of the level of cattle reticulum meal as cholesterolsource in duck feed to accelerate molting period and post-molting re-laying process of Tegal duck.Experimental method was administered to sixty female Tegal duck aging 68 weeks old. Each treatment,comprised 3 layers with 5 repetitions, were cattle reticulum meal in feed (K), consisting of K0= 0%(control), K1 = 1.43% (equal to 0.37 g cholesterol), K2 = 2.86%, and K3 = 4.29%. The observed variableswere molting period, re-laying period, blood cholesterol level, and progesterone hormone level. Datawere analyzed by analysis of variance based on Completely Randomized Design followed by HonestlySignificant Difference Test. The result demonstrated that level of cattle reticulum meal significantlyaffected (P<0.01) molting period, re-laying period, blood cholesterol and progesterone level. It wasconcluded that 1.43% cattle reticulum meal could accelerate molting period and 2.86% cattle reticulummeal could accelerate re-laying.


INTRODUCTION
Molting of traditionally reared Tegal ducks starts at 17 months old. Ducks in molting condition can cease laying eggs for 3 -4 months (Suswoyo, 1990). Egg production can be increased by accelerating the process of molting period. Ducks lay egg in condition of sufficient Follicle de Graaf in ovary when FSH and LH hormones are secreted.
The extremely low gonadotropin hormones such as FSH and LH lead to the absence of follicle growth since both hormones are required in follicle growth and development and oviposition process (Anwar and Safitri, 2005). Progesterone produced by the ovary will contrarily give negative feedback to hypothalamus and anterior hypophysis that eventually suppress the secretion of gonadotropin produced by anterior hypophysis (Gan et al., 1987).
One of the efforts on sustaining follicle growth and development is stimulating FSH and LH secretion by gonadotropin precursor hormone which can assumed from result of progesterone hormone measurement; in this case, the gonadotropin precursor hormone is cholesterol. Cholesterol is in fact much needed in various metabolic processes namely as cell wall building blocks and bile acid for fat emulsion. All these steroid hormones are synthesized from cholesterol through a common precursor steroid, pregnenolone, which is formed by the enzymatic cleavage of a 6-carbon side-chain of the 27carbon cholesterol molecule, a reaction catalyzed by the cytochrome P450 side-chain cleavage enzyme (P450scc, CYP11A1). Furthermore, cholesterol is needed to synthesize vitamin D and composing sexual hormones and corticosteroid (Tejayadi, 1991).
Cholesterol precursor is obtained from the feed and its biosynthesis occur in body organ such as intestines and liver. Feed consumption essentially contributes to cholesterol synthesis in which high consumption leads to high blood cholesterol. It was supported by Naber (1976) that almost 2/3 of cholesterol is bodily synthesized while 1/3 is obtained from treatment feed.
Cholesterol from feed can be obtained from cattle reticulum meal due to its high cholesterol level. The previous analysis demonstrated that cattle reticulum meal contained higher cholesterol (258.92 mg/g) than rumen (242.88 mg/g), omasum (254.14 mg/g) and abomasum (256.79 mg/g).
Supplementing cattle reticulum meal in feed will meet duck's cholesterol need, serving as gonadotropin hormone precursor to secrete FSH and LH, upon which the follicle will grow and develop so that molting period and relaying are accelerated.
This research was conducted to evaluate the effect of cattle reticulum meal level as the source of cholesterol used in duck feed to accelerate molting period and post-molting re-laying of Tegal duck.

MATERIALS AND METHODS
Materials used in this research were 60 Tegal ducks aging 68 weeks old (17 months), progesterone hormone kit to analyze progesterone level in blood, cattle reticulum meal, corn, rice bran, soybean meal, and "Chicken Mineral B12" to compose treatment rations or feed. Treatment feed was composed based on the calculation of feed composition table according to NRC (1999) and analysis result of Feedstuff Laboratory, Animal Science Faculty, Jenderal Soedirman University. Feed compositions and feed nutrients are presented in Table 1.
Experimental research applied completely randomized design (Steel and Torrie, 1980). Each treatment, comprised 3 female ducks with 5 repetitions, was cattle reticulum meal levels namely K 1 = 1.43% (equal to 0.37 g cholesterol), K 2 = 2.86%, and K 3 = 4.29%.Mathematical model used was Yij = µ + αi + εij Yij = result of observed variables (molting period, re-laying rate, blood cholesterol level, progesterone level) µ = mean of population αi = effect of the-i cattle reticulum εij = experimental error The observed variables were molting period, and laying rate, as well as supporting data namely blood cholesterol and progesterone level from blood serum. Ducks were reared in compartment cages measuring 100 cm x 80 cm x 60 cm, each containing 3 female ducks/layers as experimental unit. Ducks were reared from 68 week old to relaying during 3 months. Feed was measuredly administered as much as 150 g/duck/day and water was given ad libitum.
Blood sample was taken from vena axillaries for four weeks after molting ended. Five mL of blood was extracted using syringe, tilted ± 45 0 for more than 1 hour until blood serum was formed on top layer, then was put into micro tube to analyze the progesterone hormone and to measure the blood cholesterol. Progesterone level was measured using radioimmunoassay (RIA) method in National Atom Power Institute /Badan Tenaga Atom Nasional (Batan) Jakarta. The obtained data were analyzed by Analysis of Variance according to Steel and Torrie (1980) in which significant result (P<0.05) was further analyzed using Honestly Significant Difference Test.

Blood Cholesterol Level of Post-molting Duck
The average of post-molting blood cholesterol level was 159.78± 27.14 mg/dl, within the range of 111.11 mg/dl and 211.11 mg/dl. Level of cattle reticulum meal significantly affected (P<0.01) blood cholesterol (Table 2) The 0% cattle reticulum meal (K 0 ) produced cholesterol level relatively similar to that of K1 and K 2 , but lower (P<0.05) than that of K 3 . Relationship between the level of cattle reticulum meal and blood cholesterol was highly significant (P<0.01), shown in linear equation Y = 137.58 + 10.35 x (Figure 1), with coefficient of determination (R²) = 15.32 %. Figure 1 shows cholesterol role in cattle reticulum meal in producing blood cholesterol. The higher cattle reticulum meal levels, the higher cholesterol produced. Lovita (2005) stated that the response of cholesterol in blood is related to the change of free fatty acid degree in feed, because free fatty acid will be converted into acyl co-A turning into Acetyl co-A which is the main precursor of cholesterol synthesis. Murray et al. (2000) also stated that the influencing factors of blood cholesterol are on the speed of cholesterol synthesis in body and environment. Feed is one of the environmental factors that highly contributes to fat and cholesterol metabolism. Cholesterol precursor was obtained from the feed and its biosynthesis occur in body organ such as intestines and liver. Feed consumption essentially contributes to cholesterol synthesis in which high consumption leads to high blood cholesterol. It was supported by the findings of Naber (1976) that almost 2/3 of cholesterol is bodily synthesized while 1/3 is obtained from treatment feed.
Acceleration Molting Period and Re-laying (Rosidi et al.) 47  (Figure 2), with coefficient of determination (R²) of 54.76%. Figure 2 shows cholesterol role in cattle reticulum meal in the building of progesterone hormone. As reported by Tejayadi (1991), besides body metabolism process, cholesterol is required in the formation of vitamin D, and in building blocks of sexual hormones and corticosteroid. Gonad produces sexual hormones and managed reproductive function. Sexual hormones in female duck produced in ovary are estrogen and progesterone. Since luteinizing hormone (LH) and follicle stimulating hormone (FSH) are produced by two different cell populations in chickens, it is possible that different combinations of GnRHs and GnRHRs differentially mediate the synthesis and release of these gonadotropins (Gregoy, 2006).

Molting Period
The average molting period was 55 ± 28.51 days within the range of 27-107 days. Level of cattle reticulum meal significantly affected (P<0.01) molting period (     (Figure 3), with coefficient of determination (R²) of 88.78%. The different molting period between K 0 and K 1 , K 2 and K 3 was due to different progesterone hormone level (Table 2). K 0 produced 7.56 nmol/L, lower than that of K 3 (12.75 nmol/L), K 2 (10.10 nmol/L) and K 1 (9.01 nmol/L). Lower progesterone hormone caused high prolactin hormone level, as reported by Anwar and Safitri (2005) that molting was affected by prolactin hormone either directly induced ovary regression in gonad or indirectly competed with progesterone produced by ovary. With high prolactin, molting took longer period. Progesterone produced in K 1 and K2 was lower than K3; therefore, molting period slightly increased.
Traditionally reared Tegal ducks had molting period of 3-4 months from 17 months old (Suswoyo, 1990). With cattle reticulum meal supplemented in the feed as the source of cholesterol, molting period can be accelerated 60 to 65.2 days. This faster molting period proved that cholesterol can be the precursor of gonadotropin hormone marked by the increased progesterone level in treatment K1, K2 and K3. The higher cattle reticulum meal level, the higher blood cholesterol and progesteron level (Table 2). Progesteron (P4) can determine the status of embryo and hormones of goiter, thyroxine (T4) and triiodothyronine (T3), essential for molting (Pethes et al.,1982;Verheyen et al.,1983). In the first two steps synthesis of all steroid hormones, cholesterol will be converted into progesterone. Cytochrome P450scc inside mitochondria membrane emitted 6 carbons from cholesterol chain, forming pregnenolon which was converted into progesterone, catalyzed by 3b-hydroxysteroid dehydrogenase. The other steroid hormones built from progesterone in reaction involving family member of P450.1. (Rizka, 2010).
This result was in accordance with Beyer and Jensen (1992) and Sim (1998) that chicken egg cholesterol was 195 to 230 mg/egg affected by hen genetic factor, feed and production rate. Elkin (2006) reported two factors responsible to egg cholesterol; the first is related to relative resistance to yolk cholesterol to manipulate genetic selection, and the second is related to the availability of supplement and pharmacology matters to reduce biosynthesis of liver cholesterol and metabolic pathways regardless safety aspect.

Re-laying Rate
The re-laying rate was 97 ± 11.19 days, within the range 71 to 114 days. Level of cattle reticulum meal significantly affected (P<0.01) the re-laying rate ( Table 2). The 0% cattle reticulum meal (K 0 ) resulted in re-laying rate of 108.20 days, relatively similar to that of 1.43% (K1 (100 days) and 2.86% (K 2 ) (94.20 days), but significantly different (P<0.05) from 4.29% (K 3 ), namely 85.40 days. Threatment of K 2 and K 3 resulted in relatively similar re-laying rate (P>0.05). Relationship between level of cattle reticulum meal with the re-laying rate was highly significant (P<0.01) as shown in linear equation Y = 108.08 -5.189 x (Figure 4), with coefficient of determination (R²) = 33.42%.
The re-laying rate gap between K 0 and K 3 was 22.8 days due to different blood cholesterol level (Table 2). K 0 produced 146.67 mg/dl blood cholesterol, that was lower than that of K 3 (184.67 mg/dl). Low blood cholesterol also made progesterone secretion low, because according to Sutton et al. (1984) progesterone was formed from cholesterol) in all steroidogenic tissues in an enzymatic reaction. Low progesterone produced by ovary would give negative feedback to hypothalamus and anterior hypophysis (Gan et al., 1987). PMSG hormone injections on the final phase of laying ducks can increase egg production (quantity) PMSG dose of hormones that influence most effectively to the increasing egg production is a dose of 15 IU (Latifa dan Sarmanu, 2008). Very low gonadotropin hormones like FSH and LH in chicken will cause the absence of follicle growth because both hormones are inquired in follicle growth and development also the oviposition process (Anwar and Safitri, 2005). Prolactin levels did not appear to be influenced by T4 but were mainly dependent on photoperiod and reproductive stage, whereas luteinizing hormone levels remained low throughout. In summary, dietary supplementation with 40 ppm (45.76 mg/kg) T4 was successful in inducing molt in turkey breeder hens. However, dropping the photoperiod was necessary to completely reset the reproductive system (Gulde et al., 2009). According to Pethes et al., (1982) and Verheyen et al. (1983) progesterone (T 4 ) could mark the status of embryo; however, Dickerman and Bahr (1987) reported that supplementing GnRH to hens did not affect the ovary regression.

CONCLUSION
From the result and discussion, it was concluded that 1.43 % cattle reticulum meal could accelerate molting period and at 2.86 % level could accelerate the re-laying of duck. Re-laying Rate (days) ) Level of Cattle Reticulum Meal (%)