This special report is based on the proceedings of a workshop organised by the Federal Ministry of Consumer Protection, Food and Agriculture, the Institute for Animal Science, Mariensee and the Federal Agricultural Research Centre (FAL), on ‘Management of newly hatched male chicks from layers.’

The background was the fact that in Europe each year, about 280 million male chicks from layers are culled immediately after hatching. In Germany and in other countries, this has resulted in some public concern and political discussion. The objective of the workshop was to summarise and exchange current knowledge on sex determination and sex diagnosis in chicken with special emphasis on potential alternatives to culling male layer chicks.

The major polyunsaturate in phospholipids of chicken spermatozoa is docosatetraenoic acid, 22:4n-6, which is positively correlatable with sperm motility and fertility. The potential for dietary manipulation of sperm fatty acid in order to improve male fertility has been extensively studied in the chicken. The effects of diets enriched in n-3 and n-6 long chain polyunsaturates have been investigated in different trials using different oil sources and levels of oil inclusion.

The 22:6n-3 and 22:5n-3 content of avian spermatozoa is increased by supplementing the feed with fish oil (rich in 22:6n-3) and linseed oil (rich in 18:3n-3) respectively. The 22:4n-6 content is also increased by supplementing the feed with evening primrose oil (rich in 18:3n-6) in association with high level of vitamin E (200 mg/kg) and with arasco oil (rich in 20:4n-6). The effects of these fatty acid manipulations on sperm quality and/or fertility are reviewed. Both n-3 and n-6 rich diets showed a positive effect on sperm movement during the reproductive period and an age-dependent positive effect on fertility. Reported effects of n-6 rich diets on semen production have been variable with 20:4n-6 rich diet having a positive effect on semen volume and thus on total sperm number and 18:3n-6 rich diets having a negative effect on semen concentration. Spermatozoa enriched in 22:5n-3, or 22:6n-3 or 22:4n-6 result in significantly higher fertility values following artificial insemination compared to control spermatozoa; however, such a positive effect is age dependent and observed at 37 to 42 weeks, but not in older birds.

The n-6 fatty acid composition of chicken spermatozoa is recognised as a specie-specific characteristic. The fundamental relation between dietary lipid, spermatozoa fatty acid composition and thus sperm quality and fertility can be seen as having a potential commercial application.

Proper estimation of the nitrogen (N) content of poultry manure and proper manure handling are necessary to ensure that application rates minimize emissions from the manure and nitrate leaching into the cropland. Uric acid and undigested proteins are the two main N components in poultry manure that cause ammonia emissions and nitrate leaching in the ground water. The ammonia that is applied to cropland may be 50 to 90% of total N, depending upon the way the manure has been stored or treated. Ammonia and hydrogen sulphide contents have been proven to be useful alternative measures of odour reduction. The order of importance in influencing ammonia formation is : litter pH > temperature > moisture content. Total fixation of ammonia was achieved below pH 4 and temperatures down 10°C are necessary to have a negative effect on degradation and volatilisation. Adsorbants such as sawdust and straw enable the capture some of the readily available N and enable the microbial population to start immobilizing N. The organic fraction of poultry manure had a C/N ratio that varied from 1 to 27:1. Most of the N (approximately 60 – 70%) excreted in poultry manure is in the form of uric acid and urea. Total N, total Kjeldahl N (TKN), organic N, ammonium, nitrate and nitrite are significantly correlated with the amount of N mineralised as well as the fraction of organic N mineralised during incubation. Some useful equations are: Inorganic N (IN) = ammonium + nitrate + nitrite; Total N (TN) = TKN + nitrate + nitrite; Organic N = TKN – ammonium or TN – (ammonium + uric acid) or TN – IN; Available N (AN) = Inorganic N + 0.4 × organic N; Predicted available N (PAN) = 80% Inorganic N + 60% Organic N.

Chickens, unlike red meat species, do not show grand ma1 epilepsy in the brain following electrical stunning. The underpinning causes of this and the brain mechanisms associated with the induction and maintenance of electrical stunning induced unconsciousness in chickens have not been elucidated. However, the changes occurring in the electroencephalogram (EEG), abolition of somatosensory evoked potentials (SEPs), induction of seizure and loss of muscle tone or physical reflexes following electrical stunning have been used in the past to ascertain the effectiveness of waterbath electrical stunning in chickens.

The purpose of this appraisal is to evaluate scientifically the relative merits of some of the criteria that have been used for ascertaining the effectiveness of electrical stunning in chickens. Scientific literature suggests that, unlike red meat species, the electrical stunning-induced release of monoamines and inhibitory amino acid neurotransmitter(s) in the chicken brain may play prominent roles in the induction and maintenance of unconsciousness following electrical stunning. These mechanisms would also appear to be relevant to the manifestation of a profoundly suppressed EEG and abolition of SEPs following electrical stunning, which are suggested to be meaningful indicators of an effective electrical stunning in chickens.

This report will cover studies of the metabolism of a supplemental source of L-methionine (L-met), Alimet® feed supplement. The goal of these studies was to gain an understanding of how this methionine precursor is converted to L-methionine and how it is used by the chick, in order to optimise the conditions for its use. The methionine precursor in Alimet is 2-hydroxy-4- (methylthio) butanoic acid (HMB). HMB differs from methionine by having a hydroxyl group on the alpha carbon rather than an amino group. Like synthetic DL-met, HMB has one asymmetrical carbon atom and therefore occurs as a mixture of 50% L-isomer and 50% D-isomer. Because HMB bears a hydroxyl group instead of an amino group, it is an organic acid. Until it is converted to L-met antimicrobial properties of HMB resemble those of organic acids such as lactic acid. Once inside the tissue of the animal, however, HMB is rapidly converted to L-met. Following conversion to L-met, HMB will have the same availability for methyl group transfer or cysteine synthesis as L-met from any other source. This report will cover the bioavailability of HMB polymers, the conversion of HMB to L-met and the role of HMB in normal L-met intermediary metabolism. It will also include a discussion of HMB absorption and incorporation into protein.

Fungi may develop in stored grains following field inoculation. In the course oftheir development fungi utilize plant nutrients, contributing to a reduction in their content. This reduction is obviously related to the degree of fungi development, but may become relevant in extreme cases. During the process of host colonization fungi may also produce toxins that are harmful for humans and animals. This occurs mainly under specific conditions of plant stress, such as those produced by adverse weather conditions, for instance drought has been shown to prompt aflatoxin production in peanuts. Differences in mycotoxin production are also related to plant genotype. Aflatoxin B1 produced by Aspergillus flavus is the most carcinogenic natural substance known. It is frequently charged with the reduction in performance of domestic birds, even when its concentration in the feed is very low. Approaches to eliminate mycotoxins from contaminated grains are not always worthwhile in practical and economical terms. Strategies used to reduce mycotoxin levels in cereal grains include the dilution of infected with healthier grains or the addition of adsorbents to the feeds. Several compounds such as activated charcoal, aluminosilicates and processed cell wall of Saccharomyces sp. (esterified glucomannan) have shown to be effective as mycotoxin adsorbents in poultry feeds. Adsorbent effectiveness has been reported with in vitro and in vivo techniques; however, it is still very difficult to quantify their benefits in commercial operations.