Efficacy of pre-lay diet

Abstract

A biological study was carried out to review the Bureau of Indian Standards (BIS) recommendations for layer pullet feed. Commercial layer chicks were fed till 14 weeks of age as per BIS. At 15 weeks, pullets were randomly assigned to each of the five pre-lay feeding strategies, namely T1 (BIS control), T2 (16/2700), T3 (18/2700) (%CP/kcal ME/kg), T4 (same as T2 + lysine and methionine by 10% higher than BIS) and T5 (same as T4 with 2% oil). At 5% egg production, all groups were fed as per BIS. Pullets fed on high energy and protein pre-lay diets of 2700 kcal and 18% protein-advanced sexual maturity with good body composition. Pre-layers fed 2700/18 feed had the best hen day (85.44±1.52), hen-housed egg production (84.21±1.52), layed heavier eggs, had a higher egg mass output (47.14±0.95g), gave the best feed efficiency, had the lowest pullet production cost and high egg feed price ratio. It was concluded that pre-lay pullets have to be provided with 2700/18 kcal of metabolisable energy and protein level as against the BIS recommendation of 2500/16 dietary energy and protein level.

Keywords:

• pre-lay feed
• sexual maturity
• body composition
• laying performance

1. Introduction

Uniform mature pullet bodyweight and body composition at sexual maturity are much more important considerations than the specific calendar age for a profitable layer for successful egg production as measured by persistency of lay, peak egg production, egg size and feed efficiency. Most breeds and strains of layers have a unique pattern of body weight gain during the pullet development period. A pullet (pre-layer) will increase body weight by about 200–300 g quite dramatically approximately two to three weeks before egg mass production commences. The development of the ovary and oviduct, an increase in liver size and other major physiological changes take place during this stage. This is an extremely important period in the life of a successful layer. During this transition period, the pre-layers nutrient requirement which has plateaued, as she approaches a mature pullet weight will begin to increase and change as well. Furthermore, good body reserve and fat stores are very much essential at the onset of production (Summers 1993). This establishment of an energy reserve occurs during pre-lay phase and has much to do with the bird's composition at the point of lay to sustain good production and egg size throughout the production cycle. Energy and protein are now required in greater quantities for tissue synthesis that takes place during this period of rapid physiological development. An often overlooked, yet critical period nutritionally, is the transition from pullet feeds to layer feeds. The traditional method of feeding layer pullets (Bureau of Indian Standards, BIS) by offering starter diet up to eight weeks and grower diet up to 18/20 weeks needs to be reviewed to increase the length of effective biological egg-laying cycle. Feeding of pre-layers with the traditional low density diets may not support the increased/changed nutritional demand for the present high yielding layers (Rama Rao 2005). Leeson and Caston (1991) suggested that any treatment imposed early in the growing period had little influence on body weight and age at sexual maturity as compared with treatments imposed during the last few weeks prior to lay.

Hence, the present investigation was undertaken to study the efficacy of pre-lay feeding strategy in the BIS during transition period (15 weeks to sexual maturity) on pullet growth, sexual maturity and laying performance.

2. Material and methods

2.1. General management

Day old, Bovans' white commercial strain of white leghorn pullets were raised in conventional floor pens up to 13 weeks. Pullets were vaccinated against Newcastle and infectious bursal disease at 7 and 14 days, respectively. At 13 weeks of age, pullets were transferred from the floor pens to cages with four birds per cage (309.6 cm²) and acclimated to the cage for one week prior to receiving the experimental pre-lay rations. The size of the welded mesh for the sides and the roof of the cage were made of 0.5×1.0 inch. At the age of 5% egg production to 43 weeks of age, each pullet was provided with 412 cm² of cage space. A mild gradient was provided on the floor for gentle and easy rolling of eggs from the cage to the outer extended arm of the welded mesh to facilitate easy collection of the eggs.

During the chick stage (0–2 weeks) 23 hours light with 20 lux intensity and one-hour darkness was provided. After the brooding period, the birds were reared under natural daylight that extended to 11 hours with 10 lux intensity. Thereafter, at 18 weeks (5% egg production) of age the lighting period was increased to half an hour each week to 16 hours with 3 lux of intensity per sq ft.

2.2. Experimental design

All birds were fed ad libitum feed as per BIS (2007) recommendation from 0 to 14 weeks of age. The birds were provided with 20% CP and 2800 kcal ME/kg chick ration for the first 8 weeks and fed a 16% CP and 2500 kcal ME/kg grower ration from 9 to 14 weeks of age. At 15 weeks of age, pre-lay pullets were randomly assigned to one of five pre-lay dietary treatments in a completely randomised design. Each diet was given to 12 replicates consisting of six birds per replicate. Dietary treatments comprises T1 (BIS control): Diet formulated with crude protein of 16% and metabolisable energy of 2500 kcal/kg; T2 (High energy diet): Dietary treatment with crude protein of 16% and metabolisable energy of 2700 kcal/kg; T3 (High energy + high protein diet): Dietary treatment with crude protein of 18% and metabolisable energy of 2700 kcal/kg; T4 (High energy with 10% extra methionine and lysine): Dietary treatment with crude protein of 16% supplemented with synthetic lysine and dl-methionine by 10% higher than BIS recommendations and metabolisable energy of 2700 kcal/kg; T5 (High energy, 10% extra methionine and lysine with 2% oil): Dietary treatment with crude protein of 16% supplemented with synthetic lysine and dl-methionine by 10% higher than BIS recommendations and metabolisable energy of 2700 kcal/kg with 2% addition of rice bran oil to meet this energy level. Ingredient and nutrient composition of the pre-lay rations are shown in Tables 1 and 2, respectively.

Table 1. Ingredient composition of experimental rations.

		Inclusion level (g/kg)
				Pre-layer feed (15 weeks – 5% egg production)
Sl. no	Ingredients	Chick feed (0–8 weeks)	Grower feed (9–14 weeks)	T1 (BIS control)	T2	T3	T4	T5	Layer feed (5% to 55 weeks)
1	Yellow maize	420	240	240	390	385.0	370.0	280.0	490
2	Broken rice	100	130	130	100	107.5	100.0	120.0	400
3	Cumbu/Bajra	–	220	220	170	127.5	20.00	202.5	500
4	Ragi	55	–	–	–	–	–	–	–
5	Deoiled rice bran	50	125	125	100	107.5	88.7	130.0	450
6	Wheat bran	–	80.0	80.0	20.0	10.0	20.0	35.0	200
7	Sunflower oil cake	50	48	48	40.0	10.0	40.0	25.0	350
8	Soybean oil cake	235	95	95	110.0	182.5	110.0	115.0	195.0
9	Dry fish	70	40	40	50.0	50.0	50.0	50.0	52.0
10	Rice bran oil	–	–	–	–	–	–	20.0	–
11	Mineral mixture^a	20	15.5	15.5	15.5	15.5	15.5	15.5	20.0
12	Dicalcium phosphate	–	5.2	5.2	4.80	4.50	4.50	4.40	2.90
13	Shell grit	–	–	–	–	–	–	–	52.0
14	Lysine	–	–	–	–	–	0.50	0.20	–
15	dl-Methionine	–	0.5	0.5	0.50	–	0.80	0.90	–
16	Salt	–	0.8	0.8	–	–	–	–	–
	Total	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00

Composition of feed supplements: 100 g Ultra Vite-M contains rentinol – 419.22 µmol/L, riboflavin – 0.0001g, cholecalciferol – 43,05,600 nmol/L, cyanocobalamin – 0.0006 mg, tocopherol –6 96.9 µmol/L, phylloquinone – 0.04g, niacinamide – 0.4g, calcium pantothenate – 0.1g, choline chloride–12 g, calcium – 30.4 g, copper – 0.08 g, iodine – 0.08 g, iron – 0.8 g, manganese – 2.2 g, zinc – 2.08 g and cobalt – 0.004 g; 100 g Ultra Sil-TCF contains sodium alumino silicate – 952.5 g/kg, predigested protein – 0.02 g, cobalt and organic acid – 0.02 g.

^a Mineral mixture (TANUVAS) composition (g/kg): calcium – 230, phosphours – 120, magnesium – 65, iron – 5, iodine – 0.26, copper – 0.77, manganese – 1.2, cobalt – 0.12, zinc – 3.8, sulphur – 5, fluorine – 0.0007 (max) and selenium – 0.0003.

2.3. Egg weight and production

At 5% egg production and thereafter individual daily record of egg production and egg weight were taken for the determination of weekly and total egg production. Based on the data, hen day egg production was calculated and expressed in eggs per hen per day for each 28-day period. Individual egg weight was recorded to 0.01g accuracy for all eggs produced each day and this data was used to calculate the mean egg weight of each of the dietary treatment throughout the experimental period. Egg mass was calculated based on hen day egg production and egg weight. The feed consumption was arrived at and feed efficiency for a dozen eggs and kilogram egg mass was calculated for each 28-day period. Every four weeks, 12 eggs were collected randomly from each dietary treatment in the last three days of production and were used to determine egg characteristics such as haugh unit, shell thickness and per cent shell. Livability per cent was worked out based on mortality.

Table 2. Nutrient composition of experimental rations.

				Pre-layer (15 weeks – 5% egg production)
Sl.no.	Nutrients	Starter (0–8 weeks)	Grower (9–14 weeks)	T1 (BIS control)	T2	T3	T4	T5	Layer (5% to 55 weeks)
1	Crude protein^a (g/kg)	204.8	159.4	159.4	160.6	183.3	159.3	162.3	178.5
2	Metabolizable energy^b (MJ/kg)	11.87	2543	2543	2715	2705	2716	2729	2602
3	Calcium^a (g/kg)	9.8	12.3	12.3	10.5	13.3	11.1	10.8	31.2
4	Total phosphorus^a (g/kg)	6.0	6.0	6.0	5.9	5.7	6.0	5.9	5.8
5	Lysine^b (g/kg)	11.0	7.1	7.1	7.3	8.7	7.7	7.7	8.7
6	Methionine^b (g/kg)	3.9	3.5	3.5	3.5	3.7	3.9	3.9	3.5
7	Crude fibre^b (g/kg)	53.0	74.1	74.1	61.5	59.3	59.9	65.5	50.4
8	Salt^b (g/kg)	4.7	4.8	4.8	4.8	4.7	4.8	4.8	4.8

^a Mean of the analysed values.

^b Calculated values.

2.4. Carcass composition

At the onset of sexual maturity, 12 birds from each treatment were sacrificed and the carcasses minus feather, blood, head and shank were ground. The ground samples were subjected to proximate analysis for ether extractable fat and Kjeldahl nitrogen (N×6.25) by using standard procedures of AOAC (2000).

2.5. Economics

Cost of production was calculated for pullets produced for various pre-lay feeding treatments taking into consideration the prevailing market rates of feed ingredient, chick cost and other miscellaneous cost. Egg–feed price ratio was calculated from the receipts from egg and expenditure on feed.

2.6. Statistical analysis

Statistical analysis of data was carried as per Snedecor and Cochran (1994) by using the SPSS 10.0 program package (SPSS 2001). The significance of the difference among the groups was determined by Duncan's multiple range tests (Petrie & Watson 1991).

3. Results and discussion

3.1. Carcass composition

The influence of various pre-lay feeding strategies on carcass composition, the age at sexual maturity and at 50% egg production of pre-lay pullets is presented in Table 3. Pullets fed on higher energy level had approximately 10–11% fat while pullets fed on BIS 2500/16 kcal of energy had only 7.3% fat. Other than the pullets fed BIS standard feed all other pullets had comparable body fat per cent, although, a numerical increase was observed in the fat per cent in pullets fed with added 2% oil in the feed. On the other hand, Other than pullets fed with 2700 kcal dietary energy with 18% protein, all other treatments had comparable body protein per cent. The present study also agreed with findings of Leeson and Summers (1980, 1984) who had observed lower fat and protein per cent in pullets fed with lower dietary protein. Increased pre-layer dietary protein and fat in pre-lay diets conditioned the body to provide the required body composition (Joseph et al. 2000). Brake et al. (1985) attributed the pre-breeder crude protein intake to increased protein stores in the body. Similarly, Kwakkel et al. (1995) stated that the protein content in body initially can vary and later get stabilised and a particular amount of fat-free tissue was critical in pullet development and might be required before sexual maturity. A particular body composition in pre-lay pullets is required to initiate growth of reproductive organ and it has been assumed for some time that the body fat is the major critical determinant. The ratio of protein to fat has also been found as a requirement for body composition along with fat deposition for fast production. As per Yannakopoulos et al. (1995), the carcass fat necessary for sexual maturity in Japanese quails was suggested to be approximately of 10%.

Table 3. Mean (±SE) Effect of varying pre-lay energy and protein diets on body composition and age at sexual maturity.

	Carcass composition		Age (days) at sexual maturity
Treatments (ME/CP/Ca)	Crude protein (g/kg)*	Fat (g/kg)*	5% egg production	50% egg production
2500/16*	215.4^b (± 0.25)	73.1^b (± 0.09)	133	155
2700/16*	213.4^b (± 0.15)	112.9^a (± 0.35)	128	152
2700/18*	243.8^a (± 0.48)	114.4^a (± 0.14)	126	150
2700/16/ + 10% L + M*,**	213.4^b (± 0.15	112.9^a (± 0.35)	134	152
2700/16/ + 10% L + M** +2% oil*	215.4^b (± 0.31)	133.2^a (± 0.05)	131	151

* Significant (P<0.05), NS, not significant; **L + M – lysine and methionine; values bearing different superscript in a row differ significantly.

3.2. Sexual maturity

The average age at sexual maturity was best in pullets fed with 2700 kcal of energy with 18% and 16% dietary protein. Almost seven to eight days difference was seen in the BIS control group and the added 10% Lysine and Methionine group compared to the other treatments. This is contrary to the finding of Kwakkel et al. (1991) who observed that birds with higher lysine restriction had delayed onset of sexual maturity. Age at 50% egg production was almost similar to the treatment groups provided with 2700 kcal of energy irrespective of protein levels and added Lysine and Methionine or oil, but pullets fed with BIS standard feed of 2500 kcal of energy came to 50% egg production only at 155 days. There are major changes that occur in the pullets metabolism which relate to ovary or oviduct development, pullets that met target body weight influenced these changes and have given the best age at sexual maturity. Although, the age at sexual maturity was almost similar between groups fed 2700 kcal of energy with 16% protein except that with 10% extra lysine and methionine (134 days), at a later stage of 50% egg production, pullets with extra lysine and methinonine and high energy levels had compensated for its lagging behind at 5% egg production and levelled with the other high energy groups at 50% egg production, but pullets fed with BIS standard were not able to compensate and continued to lag behind due to being underweight at the time of sexual maturity. A particular amount of fat-free tissue and body composition was critical in pullet development and might be required before sexual maturity to initiate growth of reproductive organ in pre-lay pullets (Kwakkel et al. 1995). Thus, the ratio of protein to fat obtained in body composition of pre-lay treatment groups might have accelerated fast production. Among the review provided, varying results have been noticed. Keshavarz (1984), Lilburn and Myers-Miller (1990a), Anderson et al.(1995), Keshavarz (1998), Joseph et al. (2000), Oke et al. (2003) and Isika et al. (2006) had observed age at sexual maturity and 50% egg production advanced due to increased dietary protein levels. This agreed with our finding, where the higher pre-lay protein of 18% had advanced age by seven and five days to the BIS control group at sexual maturity and at 50% egg production, respectively. Similarly, Kwakkel et al. (1995) observed a delay in age at 50% egg production due to lysine restriction.

3.3. Egg production

Significantly (P<0.05) the best hen day egg production was observed in the group provided with high energy and protein of 2700 kcal energy and 18% dietary protein (Table 4). Pullets fed with BIS standard had the least per cent hen day egg production of 72.44. As mentioned earlier, body fat and protein played a significant role on sexual maturity and post-production. It may be observed that throughout laying period, pullets with high energy and especially the group with high pre-lay dietary energy and protein had consistently given better body weight and weight gain with advancement in the age at sexual maturity as well. When, looking into body composition, treatments provided with high pre-lay dietary energy and protein had significantly (P<0.05) higher body protein when compared to the other treatments and higher body fat level compared to pullets fed control diet with BIS standard; this gain of pubertal body growth spurt had assured as a prediction for subsequent onset of lay and production. This significant improvement in hen day egg production for high pre-lay dietary energy and protein groups might be due to improved and a large labile mass of energy and protein reservoir sufficient to be withdrawn subsequently to produce additional eggs (Cave 1984; Brake et al. 1985). Lilburn and Myers-Miller (1990a, 1990b). Hawes and Kling (1993), Summers (1993), Summers and Leeson (1993, 1994), Anderson et al. (1995), Hussein et al. (1996), Joseph et al. (2000), Razvani et al. (2000), Oke et al. (2003), Isika et al. (2006) and Babiker et al. (2010) also reported that higher quantity of protein and energy intake and its deposition in body before sexual maturity had significant role in subsequent production. However, Leeson and Summers (1980), Keshavarz (1984, 1998), Leeson et al. (1997) and Anderson and Jenkins (2011) found no significant difference in hen day egg production due to and increase in dietary protein level during pre-lay pullet production.

Table 4. Mean (±SE) hen day egg production of layers as influenced by various pre-lay energy and protein dietary regimens.

Pre-lay treatments	Control-2500/16*	2700/16*	2700/18*	2700/16 (10% L&M)*	2700/16 (10% L&M +2% oil)*
Hen day egg production (eggs/hen/d)
Age in Weeks	Standard layer feed
20–23^NS	0.434^C (± 4.46)	0.465^C (± 4.89)	0.519^B (± 5.37)	0.466^C (± 3.64)	0.469^C (± 4.99)
24–27*	0.725^B, ^c (± 0.99)	0.793^B, ^b (± 1.81)	0.904^A, ^a (± 1.04)	0.789^B, ^b (± 1.86)	0.734^B, ^c (± 1.80)
28–31*	0.788^A, ^c (± 0.50)	0.851^B, C ,b (± 1.76)	0.946^A, ^a (± 1.35)	0.867^A, ^b (± 1.85)	0.841^A, ^b (± 1.71)
32–35*	0.795^A, ^B, b (± 2.83)	0.935^A,a (± 1.43)	0.912^A, ^a (± 1.36)	0.879^A, ^a (± 1.67)	0.877^A, ^a (± 1.81)
36–39*	0.837^A, ^c (± 1.56)	0.942^A, ^a (± 1.81)	0.957^A, ^a (± 0.702)	0.867^A, b, c (± 1.53)	0.888^A, ^b (± 1.84)
40–43*	0.765^B, ^c (± 1.16)	0.869^A, ^B, ^b (± 1.64)	0.886^A, a (± 0.796)	0.747^B, ^b (± 1.51)	0.827^A, ^b (± 1.54)
Overall mean*	0.724^c (± 1.40)	0.809^b (± 1.61)	0.853^a (± 1.52)	0.769^b (± 1.40)	0.773^b (± 1.52)

* Significant (P<0.05), NS, not significant; mean values bearing different lower case superscripts in a same row differ significantly; mean values bearing different uppercase superscripts in a same column differ significantly.

3.4. Egg weight and egg mass

The average egg weight and egg mass was the best in pullets fed with high pre-lay dietary energy and protein (Table 5). With regards to egg weight alone, high energy pre-lay feeds with 16% protein and 2% oil were comparable. However, with regards to egg mass alone, layers fed high pre-lay energy and protein levels had significantly (P < 0.05) better egg mass as compared to all other treatments. Layers fed with a pre-lay feed with control (BIS) standard of 2500 kcal of energy with 16% protein continued to give low weighted eggs (52.34 g) and a very low egg mass (38.47 g). A similar trend was reported in many studies (Kling & Hawes 1990; Summers 1993; Summers & Leeson 1993, 1994; Anderson et al., 1995; Keshavarz & Nakajima, 1995; Leeson et al. 1997; Joseph et al. 2000; Oke et al. 2003; Isika et al. 2006; Babiker et al. 2010; Anderson & Jenkins 2011). Significantly heavy egg weight observed with high pre-lay energy groups might be positively correlated with high body weight of pullets at the time of sexual maturity (Summers & Leeson 1993; Keshavarz & Nakajima 1995). Kling and Hawes (1990) had observed lower egg weight in pullets fed with added methionine. The same trend was noticed in our experiment where the egg weight of bird fed 2700/16 kcal of energy and protein per cent with 10% higher lysine and methionine levels was comparable to the control (BIS) fed pullets suggesting that egg size may respond to lysine and methionine addition only up to certain level. The beneficial effect of diet with 2% added oil with 2700 kcal of energy on egg size may be attributed to its extra calorific effect under a hot tropical climate. It has been suggested that addition of fat under normal climate had no beneficial effect on egg size. Hence, Pullets should be fed in a manner that will give greater chance for full expression of their growth and genetic potential during the growing period to help Leghorn pullet reach the target weight, body composition and possibly age at the onset of laying (Leeson & Caston 1991).

Table 5. Mean (±SE) egg weight and egg mass (g/bird/day) of layers as influenced by various pre-lay energy and protein dietary regimens.

Pre-lay treatments	Control-2500/16*	2700/16*	2700/18*	2700/16 (10% L&M)*	2700/16 (10% L&M +2% oil)*
Egg weight (g)
Age in weeks	Standard layer feed
20–23^NS	44.86^D (± 0.52)	45.55^C (± 0.67)	46.20^D (± 0.74)	45.86^C (± 0.81)	46.50^D (± 0.79)
24–27*	50.42^C, ^c (± 0.23)	51.25^B, ^a, ^b (± 0.21)	51.34^C, ^a, ^b (± 0.24)	50.59^B, ^b, ^c (± 0.36)	51.50^C, ^a (± 0.24)
28–31*	54.11^B, ^c (± 0.22)	55.23^A, ^a, ^b (± 0.20)	56.12^B, ^a (± 0.41)	54.86 ^A, ^b, ^c (± 0.38)	55.41 ^B, ^a, ^b (± 0.28)
32–35*	55.50^A, ^b (± 0.23)	56.99^A, ^a, ^b (± 1.09)	57.58^A, ^a (± 0.39)	55.72^A, ^b (± 0.29)	56.94 ^A, ^a, ^b (± 0.31)
36–39*	55.12^A, ^c (± 0.19)	56.58^A, ^b (± 0.31)	57.50^A, ^a (± 0.35)	55.17^A, ^c (± 0.18)	56.20^A, ^B, ^b (± 0.21)
40–43*	54.03^B, ^b (± 0.12)	56.43^A, ^a (± 0.49)	57.22^A, ^B, ^a (± 0.44)	55.01^A, ^b (± 0.37)	56.17^A, ^B, ^a (± 0.25)
Overall mean*	52.34^c (± 0.31)	53.67^a, ^b (± 0.39)	54.33^a (± 0.37)	52.87^b, ^c (± 0.32)	53.79^a, ^b (± 0 .33)
Egg mass (g/hen/day)
20–23^NS	19.97^D (± 2.16)	21.97^D (± 2.52)	24.97^D (± 2.80)	22.11^C (± 1.97)	22.79^C (± 2.61)
24–27*	36.59^C, ^d (± 0.56)	40.70^C, ^b (± 0.95)	46.45^C, ^a (± 0.64)	39.91^B, ^b, ^c (± 0.91)	37.77^B, ^c, ^d (± 0.91)
28–31*	42.66^A, ^B, ^c (± 0.33)	47.07^B, ^b (± 1.05)	53.15^A, ^B, ^a (± 0.94)	47.7^A, ^b (± 1.21)	46.68^A, ^b (± 1.06)
32–35*	44.14^A, ^B, ^c (± 1.57)	53.27^A, ^a (± 1.24)	52.58^A, ^B, ^a (± 0.99)	49.04^A, ^b (± 1.01)	49.98^A, ^a, ^b (± 1.08)
36–39*	46.16^A, ^c (± 0.84)	53.36^A, ^a (± 1.05)	55.02^A, ^a (± 0.47)	47.81^A, ^a, ^b (± 0.82)	49.96^A, ^b (± 1.07)
40–43*	41.31^B, ^c (± 0.59)	49.99^A, ^a (± 0.82)	50.69^B, ^a (± 0.46)	41.12^B, ^c (± 0.87)	46.50^A, ^b (± 0.88)
Overall mean*	38.47^d (± 0.83)	44.39^b (± 1.01)	47.14^a (± 0.95)	41.28^c (± 0.86)	42.28^b, ^c (± 0.93)

* Significant (P<0.05), NS, not significant; mean values bearing different lower case superscripts in a same row differ significantly; mean values bearing different uppercase superscripts in a same column differ significantly.

3.5. Feed consumption and feed efficiency

The mean feed consumption (g) per day of layer as influenced by pre-lay feeding strategies is furnished in Table 6. Varying pre-lay dietary treatments differed significantly (P < 0.05) in the overall cumulative feed consumption during laying period, the control BIS feed recorded significantly (P < 0.05) highest feed intake. This agreed with findings of Summers (1993), Summers and Leeson (1994), Hussein et al. (1996), Leeson et al. (1997), Keshavarz (1998), Razvani et al. (2000) and Anderson and Jenkins (2011) who had observed lower feed intake in layers fed with higher protein or energy levels during rearing. In accordance to our finding, Isika et al. (2006) have also recorded lower feed intake during lay with oil addition in pre-lay pullet feed. However, Summers and Leeson (1993), Joseph et al. (2000), Oke et al. (2003) and Babiker et al. (2010) observed no significant difference in feed consumption due to either higher dietary protein or energy levels.

Table 6. Mean (±SE) feed consumption (g) per bird per day of layers as influenced by various pre-lay energy and protein dietary regimens.

Pre-lay treatments	Control-2500/16*	2700/16*	2700/18*	2700/16(10% L&M)*	2700/16 (10% L&M +2% oil)*
Feed consumption (g) per bird per day
Age in weeks	Standard layer feed
20–23^NS	94.07^B (± 1.00)	90.36^B (± 2.17)	91.07^B (± 1.71)	91.31^B (± 0.60)	90.17^B (± 1.68)
24–27^NS	112.0^B (± 1.87)	110.1^B (± 0.71)	110.2^B (± 1.71)	110.9^B (± 1.75)	110.2^B (± 1.83)
28–31^NS	113.8^B (± 1.58)	113.1^B (± 1.09)	112.8^B (± 0.38)	113.0^B (± 2.00)	114.8^B (± 0.92)
32–35^NS	130.8^A (± 0.24)	117.7^A (± 0.22)	118.5^A (± 0.21)	118.3^A (± 1.43)	119.1^A (± 1.26)
36–39*	131.1^A, ^b (± 1.12)	120.1^A, ^a (± 0.46)	120.1^A, ^a (± 0.08)	120.1^A, ^a (± 0.91)	120.9^A, ^a (± 1.19)
40–43*	129.1^A, ^c (± 1.60)	117.5^A, ^a, ^b (± 0.44)	117.1^A, ^a (± 0.48)	117.9^A, ^a, ^b (± 2.29)	119.3^A, ^b (± 1.08)
Overall mean	118.5^b (± 0.99)	111.5^a (± 0.76)	111.6^a (± 0.75)	111.9^a (± 0.79)	112.4^a (± 1.27)

* Significant (P<0.05), NS, not significant; mean values bearing different lower case superscripts in a same row differ significantly; mean values bearing different uppercase superscripts in a same column differ significantly.

Feed efficiency per dozen eggs and feed efficiency per kg egg mass was consistently the best in the high dense pre-lay feed of 2700 kcal of energy and 18% protein (Table 7). Again, pullets fed with the control (BIS) feed of 2500 kcal energy and 16% protein had a poor feed efficiency for both per dozen and kg egg mass. This result agreed with the findings of Cave (1984), Kling and Hawes (1990), Hawes and Kling (1993), Oke et al. (2003), Babiker et al. (2010) and Anderson and Jenkins (2011) who observed better feed efficiency either in per dozen or egg mass in birds reared on high dietary protein or energy during growing period; while Summers (1993), Keshavarz (1998) and Isika et al. (2006) who observed no significant difference in feed efficiency in layers due to varying rearing dietary energy and protein levels. A better feed efficiency in birds fed a high dense diet could be attributed to the number of eggs laid and the egg mass as they have played a more significant role in these results.

Table 7. Mean (± SE) feed efficiency per dozen, and kilogram egg mass of layers as influenced by various pre-lay energy and protein dietary regimens.

Pre-lay treatments	Control-2500/16*	2700/16*	2700/18*	2700/16 (10% L&M**)*	2700/16 (10% L&M +2% oil)*
Feed efficiency per dozen table eggs
Age in weeks	Standard layer feed
20–23^NS	3.10^B (± 1.23)	2.80^B (± 0.34)	2.61^B (± 0.45)	2.53^B (± 0.36)	2.97^B (± 0.58)
24–27*	1.86^A, ^b (± 0.04)	1.71^A, ^b (± 0.05)	1.71^A, ^a (± 0.02)	1.72^A, ^b (± 0.05)	1.84^A, ^b (± 0.07)
28–31*	1.73^A, ^c (± 0.02)	1.61^A, ^b (± 0.02)	1.44^A, ^a (± 0.01)	1.58^A, ^b (± 0.04)	1.65^A, ^b, ^c (± 0.04)
32–35*	2.52^A, ^b (± 0.56)	1.52^A, ^a (± 0.02)	1.57^A, ^a (± 0.01)	1.63^A, ^a (± 0.04)	1.65^A, ^a (± 0.05)
36–39*	1.90^A, ^d (± 0.03)	1.54^A, ^a (± 0.02)	1.51^A, ^a (± 0.01)	1.68^A, ^c (± 0.03)	1.65^A, ^b (± 0.04)
40–43*	2.03^A, ^d (± 0.03)	1.64^A, ^a (± 0.02)	1.59^A, ^a (± 0.01)	1.92^A, ^c (± 0.06)	1.74^A, ^b (± 0.03)
Overall mean*	2.10^c (± 0.24)	1.80^a, ^b (± 0.07)	1.67^a (± 0.08)	1.84^a, ^b (± 0.08)	1.92^b (± 0.11)
Feed efficiency per kg egg mass
20–23^NS	5.87^B (± 2.38)	5.23^B (± 0.73)	4.86^B (± 0.94)	4.71^B (± 0.80)	5.55^B (± 1.22)
24–27*	3.08^A, ^c (± 0.07)	2.77^A, ^b (± 0.09)	2.37^A, ^a (± 0.04)	2.83^A, ^b (± 0.08)	2.97^A, ^b, ^c (± 0.11)
28–31*	2.67^A, ^c (± 0.04)	2.43^A, ^b (± 0.04)	2.14^A, ^a (± 0.03)	2.40^A, ^b (± 0.06)	2.51^A, ^b (± 0.06)
32–35*	3.79^A, ^b (± 0.85)	2.24^A, ^a (± 0.04)	2.27^A, ^a (± 0.03)	2.44^A, ^a (± 0.06)	2.42^A, ^a (± 0.06)
36–39*	2.87^A, ^c (± 0.04)	2.27^A, ^a (± 0.04)	2.12^A, ^a (± 0.02)	2.53^A, ^b (± 0.05)	2.45^A, ^b (± 0.05)
40–43*	3.14^A, ^d (± 0.05)	2.37^A, ^a (± 0.03)	2.31^A, ^a (± 0.02)	2.90^A, ^c (± 0.08)	2.59^A, ^b (± 0.04)
Overall mean*	3.57^c (± 0.46)	2.89^a, ^b (± 0.15)	2.69^a (± 0.19)	2.97^b (± 0.17)	3.08^b (± 0.23)

Note: NS, not significant; mean values bearing different lower case superscripts in a same row differ significantly; mean values bearing different uppercase superscripts in a same column differ significantly.

* Significant (P<0.05)

3.6. Egg quality parameters

Egg quality parameters such as Haugh unit, egg shell weight and shell thickness did not differ significantly. Pre-lay diets with varying energy, protein, lysine methionine levels or 2% oil in the feed did not seem to have an immediate or extended effect on albumen quality or the shell.

3.7. Livability

During the transitional period of 15 weeks to 5% egg production, there was no mortality. Later during period of lay the per cent mortality was 6.3%. This falls well within the allowed standard mortality per cent during lay.

3.8. Cost of pullet production

The influence of various pre-layer diets on cost of pullet production and egg feed price ratio is presented in Table 8. Compared to high dense pre-lay diets, production cost per pullet in birds fed with the control (BIS) feed was comparatively higher. This could be attributed to high feed consumption and feed cost in these birds; while for the birds fed with 2% oil, higher production cost per pullet could be attributed to high feed cost and it may be noted that oil fed bird consumed more feed as oil feed is more palatable. However, when calculating the cost of production per 100 g of body weight in pullets, birds fed with control (BIS) feed produced costlier pullets. This could be attributed to higher feed cost and lower body weight in these birds.

Table 8. Cost of pullet production and egg feed price ratio in layers as influenced by various pre-lay energy and protein dietary regimens.

Economic traits	Control-2500/16^a	2700/16^a	2700/18^a	2700/16 (10% L&M^b)^a	2700/16 (10% L&M +2% oil)^a
Standard layer feed
Cost per bird (day old)	18.60	18.60	18.60	18.60	18.60
Cost of feed per bird from first week – 5% egg production	97.0	92.00	91.10	92.10	107.60
Cost of medicine and vaccine per bird	15.00	15.00	15.00	15.00	15.00
labour cost per bird	23.75	23.75	23.75	23.75	23.75
Electricity charges per bird	8.00	8.00	8.00	8.00	8.00
Miscellaneous charges	4.00	4.00	4.00	4.00	4.00
Production cost per pullet	166.3	161.3	160.4	161.4	176.9
Egg feed price ratio^a (HDEP^b basis)	1.10	1.30	1.40	1.20	1.20

^a Feed price: average cost of layer and pullet feed.

^b Hen day egg production.

A good egg feed price ratio (EFPR) will be 1.4 and above. In EFPR on hen housed egg production basis (Table 8), all groups had an excellent EFPR, but when compared on hen day egg production basis, birds provided with pre-lay diet of 2700 kcal energy and 18 protein gave the best EFPR; while all the others were below par. This could be attributed to a higher HDEP with lower feed consumption in this group.

4. Conclusion

It could be concluded that a pre-layer diet is required for better egg production and it would be ideal to provide a diet with a 200 kcal above that recommended by BIS and with 2% higher crude protein levels from 15 weeks to 5% egg production for birds reared under a tropical maritime climate.