Introduction
Studies in Victoria and Queensland have assessed the welfare and performance of barn systems with hens having with higher mortality (15-30%), lower body weight, better feather condition at 29 weeks old but inferior feather condition and cover at 40 and 64 weeks old. Production and egg weight were lower, with more dirty eggs, with inferior yolk colour and feed intake (FI) 7-10% higher than birds kept in cages. This overall low performance, economics, welfare and high mortality require further research. Protein and dietary amino acids, particularly sulphur amino acids, have been shown to influence cannibalism and feather pecking (Tiller, 2004). Tryptophan, a precursor for serotonin, promotes feelings of wellbeing, calm and relaxation in humans (South, 2004) and suppresses aggression in male broiler breeders (Shea et al., 1990), may be required at higher levels for barn birds to reduce weight loss, stress and to promote calming of birds in a stressed environment. Selenium, an essential constituent of the antioxidant enzyme glutathione peroxidase, has been shown to improve feed conversion, feather growth, egg quality and meat quality in broilers (Edens et al., 2001). The evaluation of selenium in barn systems to improve bird welfare needs further investigation. Another interesting aspect of the complex issue of feather pecking is pullet body weight in which undernourished birds developed pecking and cannibalism behaviour, which may be a response to locate needed nutrients (Parkinson, 2005). The present paper reports preliminary data from a barn production experiment at PRDC in which bird management and nutritional aspects were modified and improved in order to reduce feather peaking, cannibalism and low productivity.
Materials and methods
Four thousand laser beak-trimmed day old chicks (Hy-Line brown) from a Bendigo commercial hatchery were floor-reared to seven weeks of age on pine shavings in a controlled environment shed (pen size 15 x 12 m). Water, temperature, husbandry management and vaccination programme (including coccidia and parasites) were provided in accordance with PRDC management. During the first 48 hours (h) continuous light was provided at 10 lux intensity (LI). From day 2 to seven weeks, light was reduced to 15 h per day to 5 LI. At 18 weeks of age, light stimulation started when the flock reached 1550 grams. Artificial lighting was used throughout to provide a 16-hour constant day-length lighting programme. Following chemical analysis, mash diets were provided following the program suggested in the Hy-Lyne management guide (2005) for adequate body weight and commercially acceptable production. After seven weeks, birds were transferred to a commercial barn system where they remained during the production cycle.
The barn has been built in a naturally-ventilated clean-line poultry shed (L 40.04, W12.2, H 2.550, in meters) with a concrete floor and an opened side (north) and with shutters (south). It is operated as an open-sided barn with a fan-forced ventilation and a fogger system. The internal configuration is 4 pens of approximately 1,000 birds/pen (7 birds/m2) with slatted areas, nest boxes and a deep-litter area. The plastic slatted areas comprise one third to one half of the total floor area. The Jansen roll-away nests are those used commercially. Automatic colony nest belts are provided with Astroturf® floor coverings.
Feed and water are provided ad libitum from an automatic single line of pan feeders and a single line of nipple drinkers suspended over the slats for each pen. Intake in each pen was measured by individually installed silos fitted with 3 x shear beam load cells connected to a digital indicator to access and record feed delivery. Experimental diets were randomly allocated in a randomised block design to 4,000 25-weeks old pullets distributed into 4 pens within a commercial barn house. Two dietary treatments were prepared with Diet 1 (Control diet), formulated as recommended by the breeder management guide. Diet 2 was formulated as Diet 1 but with additional 30% methionine, 30% tryptophan and 0.3 mg of organic selenium added/kg of diet.
The control diet was assigned to pens 1 and 3 and Diet 2 was assigned to pens 2 and 4. Eggs were collected three times daily for egg production. A sample of 10% of eggs was individually weight weekly. Nested and non-nested (floor, slats, corners) eggs were recorded including cracked and soiled eggs. FI was recorded weekly, and monthly body weights to 10% of birds in each dietary treatment. Egg quality including, shell, yolk colour, blood, meat and Haugh units were evaluated on 10 % of all eggs monthly. Temperature and humidity was continuously logged inside and outside the buildings. Litter and feather condition were assessed at intervals. At week 10, 20, 30, 40, and 50, weeks of age random samples of 5% of layer population were individually scored in each treatment (by two observers) for the condition of plumage and skin, as well as for health status of feet and comb (Tauson et al. 1984).
Results and discussion
The data in the present experiment is yet to be statistically evaluated. However, bird performance at 50 weeks of age (Table 1) indicates that production parameters of layer hens were satisfactory with not marked influence of dietary treatment. Egg production in both treatments was acceptable when compared with the 85-87% reported under cage systems (Hy-Line Guide 2005). In the present study, egg weight at 50 weeks of age was 61.4g and 61.2g for diets 1 and 2 respectively (Table 1). The expected egg weight should be higher, at around 65.3 and 63.4 g for cage and barn system respectively (Hy-Line Guide, 2005; Thomas et al., 2000). Other barn studies have also found lower egg weight (Barnet, 1999).
In the present study Diet 2, which was supplemented with methionine, did not appear to influence egg weight. Linoleic acid, another dietary component influencing egg weight, was provided at 1.24% (25-32 weeks of age) and 1.18% (33-44 weeks of age), but influence egg weight. If the birds body weight, FI and production in the present study are shown to be adequate, additional levels of linoleic acid may be needed to increase egg weight. However, by increasing egg weight there is a possibility of inducing other negative aspects such as cloacal haemorrhage, an important precursor to vent trauma and cannibalism (Parkinson, et al 2005). Thus, the relatively low egg weight in the present study may be seen as a beneficial rather than a negative aspect, but more consideration and comparative studies with different levels of linoleic acid are needed.
In the current study, the mean bird feed intake at 50 weeks of age was 122 g/b/d for both dietary treatments. This barn data is similar to the 124 g/d reported for barn systems (Thomas et al., 2000) but slightly higher when compared with the 111 g/d/b in cage systems (Hy-line Guide, 2005).
The main problem with regard to egg quality in the present study is the number of floor eggs, particularly in Diet 1. Reports indicated that between 15-50% of eggs were laid on the litter under barn systems (Barnett, 1999; Lu and Dingle, 1999; Nagle et al., 2004). In order to reduce floor eggs in the present study, pullets were reared in one large group in floor pens, then transferred to the barn at a young age (7 weeks), and had limited access to the nest box by closing nests at night (Barnett 1999; Lu and Dingle, 1999, Industry staff advice). However, the number of floor eggs in our study is evident and needs further investigation particularly as it has been reported that floor eggs usually have poorer microbial quality on the shell surface with higher coliform, E. coli bacteria counts (Barnett, 1999). In previous barn studies at PRDC, blood stained eggs increased gradually from 0.5 to 2.5-5.9% (at 25, 41-45 weeks of age respectively). Further analysis indicated a positive correlation between egg weight and blood stained eggs (Nagle et al, 2004). However, in the present study the proportion of cracked, dirty or blood stained eggs were relatively low suggesting that the lower egg weight may contribute to reducing the risk for blood stained eggs. Although nearly 14% of eggs were laid on the litter, the proportion of dirty eggs contaminated with either soil or excreta was relatively low (Table 2) when compared with 8.89% from extensive systems (Glatz and Ru 2004).
In general, mortality was low but the total bird feather score was reduced from 3.75 and 3.70 at week 40 to 2.96 and 3.0 for 50 weeks of age for dietary treatments 1 and 2 respectively. Damage to the back plumage is the main aspect influencing the score. These obtained values are similar to those reported elsewhere (Nagle et al, 2004; Barnet, 1999). Although, in our experiment birds were beak-trimmed at day old, it would appear that changes in nutrient requirements for a lower specification formula which occurred after 40 weeks of age may have negatively influenced feather cover.
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From Proceedings of the “18th Australian Poultry Science Symposium”, New South Wales, Australia.
R.A. PEREZ-MALDONADO1,
S. ROBERTSON,
P. TRAPPETT,
K. BARRAM,
T. NAGLE
1 Department of Primary Industries and Fisheries,
Queensland, PRDC, Cleveland
Australia
