D.N. SINGH2
P. TRAPPET2
T. NAGLE2
1Applied Nutrition Pty. Ltd., Alexandra Hills, Qlds, Australia
2DPI&F, Queensland Poultry Research and Development Centre, Cleveland, Qlds, Australia
A preliminary investigation was conducted to examine the effects on performance of feeding a complete balanced layer diet to laying hens late in lay (70 weeks of age) for 16 weeks where wheat was presented in whole and unground forms and zeolite (insoluble grit) was presented in powdered (<250 µm) and particulate forms (2.0-4.00 mm), a total of 4 treatments. There was no significant effect of grain form on egg production, egg weight, feed intake, egg mass or feed conversion. Zeolite presented in grit form significantly improved egg production, egg mass and feed conversion with whole grain with grit having significantly better egg production, egg mass and feed conversion compared to birds fed the ground grain with zeolite in powdered form. The apparent metabolisable energy (AME) of the diets was determined before and after the same birds were challenged with vaccine strains of coccidia. Before and after the coccidiosis challenge the addition of zeolite in grit form gave a significant improvement in the AME of the diet compared to those diets where zeolite was provided in powdered form. The form of grain had no effect on the AME of the diets either before or after the coccidiosis challenge. Birds fed on whole wheat had a significantly lower (2.5 times) oocyst output than birds fed on ground wheat. The zeolite form had no effect on oocyst output. These experiments demonstrate that balanced diets containing wheat in whole form have economic and health benefits when fed to laying birds. The use of insoluble grit in diets, particularly in diets containing whole wheat have nutritional benefits.
Introduction
The renewed interest in alternative forms of poultry management, such as free range and organic poultry keeping, where the natural social and physical functions of the birds are fundamental, now requires answers on how best to feed, manage and control disease, in particular, coccidiosis, without chemotherapy. The practice of whole grain feeding is encouraged in these alternative management and feeding systems. Feeding whole grain based diets also provides an opportunity to reduce costs through not having to process the grain prior to feeding. Research has shown that whole grain feeding has significant effect on gizzard development (Cumming, 1990) and have unchanged or improved egg production and feed efficiency equal to that of birds fed on all mash diets where the grain has been pre-ground prior to feeding (Blair et al., 1973; Karunajeewa & Tham, 1984; Ouart et al., 1986). In addition, the use of insoluble hard grit may play a major role by improving bird performance and feed efficiency compared with birds fed whole grain without grit (Cumming, 1990). Whole grain feeding in conjunction with grit has been shown to reduce oocysts shedding in crossbred cockerels challenged with coccidiosis (Cumming, 1990).
The purpose of experiment 1 was to investigate the feeding to laying hens late in lay (70 weeks and older) a complete layer diet with the wheat presented in whole and ground form, and with zeolite presented in powder and insoluble grit form (2 to 4 mm) on bird performance. The purpose of experiment 2 was to investigate the effect of a coccidiosis challenge on these same birds on oocyste output and the change in apparent metabolisable energy (AME) of the diets before and after the challenge.
Methods
Two experiments were conducted, the first involved a total of 128 laying birds, 70 weeks of age were divided into 4 treatments with 4 replicates (blocks). Within the treatments there were 2 factors, wheat presented in ground or whole form and zeolite presented in grit or powdered form. Each replicate consisted of 8 birds in 4 cages, 2 birds per cage. Birds were fed the same specification wheat-based diet for layers eating 100 g/head/day and consisted of wheat (whole or ground) 600.0, Soybean meal 167.0, Meat meal 80.0, Tallow 20.0, Sunflower oil 12.0, Sodium bicarbonate 1.1, Choline chloride 1.0, DL-methionine 1.7, Yolk pigment 2.0, Vitamin/Mineral premix 2.0, National Zeolite (powder or grit form). All values are expressed in g/kg.
Since the birds had not been fed whole grain previously, birds on the whole grain treatment had the proportion of whole grain increased by 10% (of the diet) each week until 100% of the grain was in whole form, a period of 6 weeks. Diets were fed ad libitum for 17 weeks. Water was freely available. Egg production was recorded daily and feed intake and egg weight was recorded weekly.
The second experiment had a total of 48 birds, selected from experiment 1, 12 birds were selected from each treatment and allocated to 48 metabolism cages. The birds were allowed to settle into the cages for 2 weeks and the apparent metabolisable energy (AME) was determined according to the conventional total collection method outlined by Fisher (1988). AME was corrected to zero nitrogen balance using the constant 36.5 kJ/g nitrogen retained.
The birds were challenged with a commercially available coccidiosis vaccine (Eimeriavax 4m) sourced from Bioproperties Pty Ltd, Australia. Eimeria species of coccidia in the vaccine were acervulina, brunetti, maxima, necatrix and tenella. Immediately after the challenge clean collection trays were placed under the birds to collect faeces. Faeces were collected for 3 successive days, pooled and a 50 g sample taken for oocyst count determination. Oocyst count was determined according to the method outlined by Work Instruction 33 (Animal Research Institute, Qld). After 1 week the AME of the diets was again determined. The results were subjected to analysis of variance and oocyst count was transformed using the loge(X+1) transformation prior to analysis.
Results and discussion
Table 1 summarises the performance data after 16 weeks into the first experiment. There was no significant effect of the way wheat grain was presented to the birds (ground or whole) on egg production, egg weight, feed intake, egg mass or feed conversion. These results are consistent with those found by other researchers (Blair et al., 1973; Karunajeewa, 1978; Karunajeewa & Tham, 1984; Ouart et al., 1986). This demonstrates there is an opportunity for making a significant economic savings by not having to grind the wheat, the major component of the diet, without any adverse effects on bird performance. Zeolite presented in grit form significantly improved egg production, egg mass and feed conversion but did not influence daily feed intake or egg weight. Hard insoluble grit has not routinely been used in commercial diets for poultry for decades. However, there is evidence from earlier years (Heuser and Norris, 1946; Balloun and Phillips, 1956; Scott and Heuser, 1957) that there is an increase in egg production when insoluble grit was fed in conjunction with whole grain. Our work would support the work of these early researchers. There is less evidence of a need for insoluble grit when all-mash laying diets are fed. Again, earlier researchers (MacIntyre and Jenkins (1952); Fuller (1958)) observed no increase in egg production or feed efficiency from feeding grit with all-mash layer diets. However, our work would support the feeding of grit even when the grain was ground.
Table 2 summarises the AME of the diets before and after a coccidiosis challenge and the back-transformed means of oocyst number output in the faeces in the second experiment. Before and after the coccidiosis challenge the addition of zeolite in grit form gave a significant improvement in the AME of the diet compared to those diets where zeolite was provided in powdered form. The form of grain had no effect on the AME of the diets either before or after the coccidiosis challenge. This is consistent with the findings of McIntosh et al. (1962) who found no consistent effect of the grain form on the ME of the grain. Whole grain fed in conjunction with zeolite in grit form significantly improved the AME of the diet both before and after the coccidiosis challenge. Again, this is consistent with the findings of McIntosh et al. (1962) who found grit feeding consistently increased the ME of cereal grains. They also found the responses due to grit were greater when whole, rather than ground or pelleted grains were fed. There was a significant interaction for the AME of the between grain form and zeolite form after the coccidiosis challenge. This indicated that the diet which contained whole grain had a significantly inferior AME when zeolite was not presented in grit form, but had a superior AME when zeolite was in grit form. Ground grain with and without zeolite in grit form had the same AME and was an inferior AME to the diet with whole grain and zeolite grit but superior to the diet with whole grain and zeolite in powdered form. This AME interaction did not occur prior to the coccidiosis challenge.
Birds fed on whole wheat had a significantly lower (2.5 times) oocyst output than birds fed on ground wheat. This is in agreement with Cumming (1990) who found that when grain was fed in whole form to crossbred cockerels challenged with coccidiosis, oocyst shedding was reduced. The zeolite form had no effect on oocyst output.
Conclusions
These experiments demonstrate that balanced diets containing wheat in whole form have economic and health benefits when fed to laying birds. The use of insoluble grit in diets, particularly in diets containing whole wheat have nutritional benefits.
References
Animal Research Institute, Qld Dept Primary Industries, Yeerongpilly, Work Instruction 33.
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From Proceedings of the "17th Australian Poultry Science Symposium", New South Wales, Australia.
