Effects of a short laying rest on postrest egg production and egg quality Tuomo Kiiskinen and Hilkka Hakatie Kiiskinen, T. & Hakatie, H. 1993. Effects of a short laying rest on postrest egg production and egg quality. Agric. Sci. Finl. 2: 437-445. (Agric. Res. Centre of Finland, Inst. Animal Prod., FIN-31600 Jokioinen, Finland.) Two factorial trials, each including three commercial laying hybrids, were conducted to study the effects of a short laying rest on postrest performance of hens and on egg quality. A total of 1800 hens laying at 65% on an average (70 wks ofage) were subjected to one of the following treatments: no rest (control, C) or feeding only whole-grain barley (WB) or fasting (F, Trial 1 only) until the rate of lay dropped to 0%, after which the birds were returned to the previous all-mash diet. The second laying period was six months. Egg production of the WB and F hens ceased within one week on an average and the birds were out of production for 10 days. Laying intensity during the second production period did not differ significantly between the treatments in each trial, but egg weight and daily egg mass production increased as a result of the rest treatments. The laying rest procedures reduced feed intake, improved feed efficiency and increased live weight significantly. Egg shell and albumen quality traits were significantly better in the laying rest groups than in the controls. Significant differences in performance and egg quality between the hybrids were mainly ascertained in Trial 2. The results suggest that a short laying rest is a feasible means of improving egg quality towards the end of the laying period. It can be accomplished successfully by feeding whole-grain barley. Key words: laying hen, short laying rest, egg production, feed efficiency, egg shell quality, egg albumen quality Introduction Most of the forced molting methods involve the use of extended fasting for 10 days or more and with- drawal of water for a couple of days. Nowadays these kinds of treatments are considered to be too drastic and questionable for animal welfare reas- ons. During a laying period of 14-16 months, egg shell and albumen quality decline rapidly towards the end of the period. Therefore, alternatives for the conventional molting methods have been sought and studied in order to avoid starvation stress while still improving egg quality. The aim of these softer treatments is cessation of lay, after which normal feeding is continued immediately. Cessation of lay is induced by fasting or by using feeding regimens which cause marked and rapid reduction in feed intake. Christmas et al. (1985) obtained good results with a short four-day fasting method, which were comparable to those obtained from a 10-day fasting procedure. These authors proposed the term "rest" instead of the term "molt" when a procedure for cessation of lay is used. How- ever, other results suggest that egg shell quality may further be improved using fasting periods of 10 days or longer (Koelkebeck et al. 1992). One of 437 Agric. Sei. Finl. 2 (1993) https://www.c-info.fi/en/info/?token=o0S5rnt--Styjtk3.M4b_KRcErUreUxZeOngSPA.O3RDuT3_-gxHNedk3X6c1upBUxI42F4-Whf73pBux7eJoXi97fjAsRBJjKtgzNW5eTLkiX9Qdo1TDNA9-46X_KvFQFpMjzIQLcSaY417yYvlQ7ux2oBnUUzitVoqhU1eW3nkuwOpnKqvQTSJR_0m8cJTPm1N850hkrmmydCBiLXe0-wfAoWzEEYOnja114BfEIaRNj-5Bxq0VaZw4a84wuv5n-o0bdDmNEOkAKWXDHcZtZnTcg9Vp1X_0tmHrSzrVuQc0-PyE_Iwqm2FMKJtZrm3EZuOJyd7Yg the most studied feeding procedures is applying diets that are excessively supplemented with a trace mineral like zinc, iodine and copper. Birds fed diets containing 10-20 g/kg zinc (Scott and Creger 1976, Shippee et al. 1979, McCormick and Cun- ningham 1984,Abu-Serewa and Karunajeewa 1985) or 7.5 g/kg iodine (Shirley et al. 1979) were foundto drastically reduce their feed intake, and the rate of lay dropped to zero within one week. Also low-calcium and low-sodium diets have been tested, but these treatments have not proved to be efficient enough to induce a sudden and total drop in egg production (Blair and Gilbert 1973, Whitehead and Shannon 1974, Gilbert and Blair 1975, Nesbeth et al. 1976a,b, Ross and Herrick 1981, Berry and Brake 1985). Al- though many of the above procedures may be use- ful they are not very easy to apply in practice. Additionally, the hen has to excrete or accumulate the extra trace mineral absorbed during the treat- ment. E.g. extensive accumulation of zinc in organs has been reported (McCormick and Cunningham 1984, 1987). Good results have been obtained by giving only whole-grain barley for one week, which is a procedure very easy to accomplish in practice (Abu-Serewa and Karunajeewa 1985). The purpose of the present study was to evaluate the effects of a short laying rest on egg production, feed intake and egg quality during the subsequent laying period, using mainly the whole-grain barley method. Material and methods Two factorial trials were conducted using three commercial laying hybrids in each. The birds in each trial had been used for a previous feeding experiment up to 62 weeks of age, and at the start of the present trials they were 70 weeks old. The hens were housed three to a cage in a 3-tier battery where they remained until 93 weeks of age. Water was given ad libitum and a 16-h daily photoperiod was maintained throughout the experiments. In Trial I, three Finnish White Leghorn laying hybrids (SF 1, LSK 61, MÄ 86) were subjected to the following treatments: 1) no rest (control, C), 2) feeding whole-grain barley (WB) until laying ceased or 3) fasting (F) until laying ceased. Two foreign hybrids Lohmann (LSL) and Isabrown (IB) and one Finnish hybrid (MÄ 86) were subjected to treatments 1 or 2 in Trial 2. Mean rate of lay before the rest procedures was 65.7% (range 64.4-66.4% among the hybrids) in Trial 1 and 64.5% (61.5- 67.3%) in Trial 2. The control groups of each trial were fed a complete layer diet throughout the ex- periments consisting of six 28-day periods. The layer diet in Trial 1 was a commercial all-mash diet containing 15.5% analyzed crude protein (air-dried basis, CP) and 10.5 MJ/kg calculated metabolizable energy (ME). In Trial 2 the all-mash diet was mixed from a commercial concentrate (CP 43%), barley, oats and limestone. The CP content of this mixture was 16.1% and ME content 10.3 MJ/kg. Hens on the laying rest treatments were given the control diet immediately after cessation of lay. In Trial 1, 12 replicates of 30 hens were allocated for each treatment and hybrid. In Trial 2 the treatments had 18 replicates and the hybrids 12 replicates of 20 hens, each. Equal numbers of birds from the treat- ments of the previous feeding experiment were ran- domly assigned to the replicates in both trials. Egg production, feed consumption and mortality were determinedfor each replicate. Egg production (number and weight) was recorded daily and feed intake for every 4-week period during the second laying period. Twelve and six birds per replicate in Trials 1 and 2, respectively, were weighed before and after the rest procedure and at the end of the postrest laying period. Egg quality traits (Haugh Unit=HU, specific gravity, shell strength, number ofblood and meat spots) were determinedwhen the birds were 75 and 93 weeks old. Specific gravity was measured by the saline flotation method (Trial 1) and by the Archimedes’ method (Trial 2). A Wazan compression force meter was used for the determination of shell strength (kg) and an Ames HU micrometer for evaluation of albumen quality (Haugh Unit). Ten eggs from each replicate were randomly collected for each determination. Num- ber of cracked and broken eggs (Trial 2) and total number of shell defects (Trial 2) were recorded for one week during periods 2 and 6. Cracked eggs were detected by candling. The experimental data 438 Agric. Sei. Finl. 2 (1993) Table 1. Effect of the rest procedures on cessation of lay, feed intake and body weight loss'. Trial 1 Trial 2 WB F WB Number of days to zero rate of lay 7 (4-9) 6 (5-7) 6 (4-8) Number of days out of production 10 (7-12) 12 (10-14) 9 (7-12) Barley intake during treatment g/day/bird 39 (31-52) - 19(8-35) Body weight loss during treatment %(±SD) 11.4±4.39 17.6 ±3.78 19.9±6.25 1 Range of replicates in brackets WB = whole-grain barley, F = fast were statistically analyzed by a generalized multi- variate analysis of variance and covariance (MA- NOVA) using a SPSS-programme. The compari- son between the treatments was performed using Tukey’s test (STEEL and TORRIE 1960). Results and discussion Hens of the rest treatments in both trials showed a complete interruption of egg production within one week (Table 1). The birds of the WB groups were out of production for 9-10 days and those of the fasted group for 12 days. Daily intake of barley was 39 g and 19 g in Trials 1 and 2, respectively. Birds lost 11% (WB, Trial 1), 18% (F, Trial 1) and 20% (WB, Trial 2) of their weight during the treatments. This is markedly less than the 27-31% recom- mended by BAKER et al. (1983) for hens moltedby a conventional fasting method. Laying rate of the rest groups recovered quickly after the treatments and reached the level of the control group in period 2 and the highest peak (72-73%) in period 3 (Figures 1 and 2). The rested hens were still laying at a higher rate (60-63%) than the controls (51 %) in the last period. In neither trial did the rest procedures signific- antly affect the average laying intensity (Tables 2 and 3). In Trial 1, the mean rates of hen-day egg production were 57.4% (C), 57.7% (WB) and 60.1% (F). Rate of lay of the treatment groups in Trial 2 was very similar on an average (57.0/57.1%). Increased egg weight (P<0.05) is to be seen as a result of the laying rest in Trial 1 and the response in Trial 2 was even more prominent (P<0.05). Thus the daily egg mass of the rested groups was 1-2 g higher than that of the controls, and the difference between the F and C groups was found to be significant (P<0.05, Trial 1). Egg pro- duction per housed hen was also slightly higher in the rested goups compared with the controls. In Fig. I. Percentage egg production during the postrest laying period (Trial I). Fig. 2. Percentage egg production during the postrest laying period (Trial 2), 439 Agric. Sei. Fint. 2 (1993) Table 2. Performance of hens in the second laying period (70-93 wks, Trial 1). Treat- Hybrid Rate Egg Egg output Feed intake Final Weight Mortality aT (H) lay *% W6 g ht g/ .hen/ kg/ ,hOUSed g/ ,hen/ kg/kg weight kg Tday hen day eggs C SF 1 54.9 66.9 36.7 6.1! 120.3 3.28 1.84 -2.9 15.9 LSK 61 59.7 65.5 37.9 6.31 116.4 3.08 1.85 0.8 12.5 MÄ 86 57.8 65.7 39.1 6.54 119.6 3.06 1.96 1.9 7.5 Mean 57.4 66.1 37.9» 6.32» 118.7» 3.14» 1.88» 0.02» 11.9» WB SF 1 57.8 67.0 38.9 6.51 112.6 2.92 1.93 6.0 10.0 LSK 61 59.0 66.4 39.4 6.60 112.9 2.91 2.08 7.6 4.2 MÄ 86 56.4 66.7 37.8 6.34 112.7 2.87 2.11 7.3 5.0 Mean 57.7 66.7 38.7=" 6.48"" 112.7h 2.92» 2.04 b 7.0 h 6.4h F SF 1 59.7 66.6 40.0 6.70 110.6 2.77 1.95 6.0 6.7 LSK 61 58.8 66.0 39.1 6.56 113.9 2.92 2.20 10.2 5.0 MÄ 86 61.8 66.4 41.2 6.91 112.7 2.74 2.11 10.6 8.3 Mean 60.1 66.3 40.1 b 6.72b 112.4b 2.81b 2.09b 9.0b 6.7b SEM 0.54 0.16 0.35 0.060 0.62 0.033 0.014 0.51 0.98 Significance of F-value -r Njc * * * *** *** *** *** H NS NS NS NS NS NS *** ** T x H NS NS NS NS * * * NS a b Treatment means with no common superscript letter are significantly different (P < 0.05). If no letters are used the differences are non-significant. SEM = standard error of mean. Significances; NS = non significant, * = P < 0.05, ** = P < 0.01, *** = P < 0.001 C = control, WB = whole-grain barley, F = fast Trial 1 this was partly due to reduced (P<0.05) mortality among the rested hens. In Trial 2 mortal- ity was not affected by the laying rest. No signific- ant differences between the rest procedures were found in the production parameters (Trial 1). The results of earlier studies obtained either with a short fast (Christmas et al. 1985, Koelkebeck et al. 1992) orby feeding whole-grain barley (Abu- Serewa and Karunajeewa 1985) show that these methods have a tendency to improve egg yield during the second laying period. These observa- tions are confirmed by the results of the present study. Birds subjected to the rest procedures, with the rest period included, consumed significantly (P<0,001) less feed and utilized feed more effi- ciently than the control birds in each trial (Tables 2 and 3). The decreases in feed conversion ratio (FCR) were 7-10% (P