Selection for food conversion in broilers: Body composition of birds selected for increased body‐weight gain,food consumption and food conversion ratio

1. Body composition was determined in 9‐week‐old chickens sampled from four lines selected either for increased body‐weight gain (line W), for increased food consumption (line F), for decreased food conversion ratio (line E), or at random (line C), after three, four and five generations of selection.

2. After five generations of selection the proportions of carcass water (678 g/kg) and protein (187 g/kg) were highest in line E and lowest (636, 180 g/kg respectively) in line F. The proportion of fat was lowest (83 g/kg) in line E and highest (134 g/kg) in line F.

3. Lines W and C were similar and intermediate to lines E and F for all the carcass constituents.

4. There was more fat in females (115 vs 98 g/kg) and less protein (177 vs 190 g/kg) and water (652 vs 665 g/kg) than in males.

5. Line differences in carcass composition were not appreciably altered if birds were killed at equal weight rather than equal age.     

Responses in growth,food intake and food conversion efficiency to different dietary protein concentrations in meat‐type lines of Japanese quail

1. A total of 360 Japanese quail of 4 commercial meat‐type lines and two diet treatments (260 and 216 g/kg or 238 and 195 g/kg of crude protein (CP) in the starter and grower diet, respectively) were used.

2. The positive effect of a high CP diet on body weight was significant only for the first 4 weeks after hatching.

3. The mean age at inflection point of the growth curve (t ⁺) across lines and sexes was 1.4 d (0.6 to 2.8 d within line/sex groups) earlier for quail fed on a high CP diet than in quail receiving a low CP diet. The inflection (y ⁺) and asymptotic (A) weights were similar under both dietary protein concentrations. Nevertheless, the shape of the growth curve, characterised by the ratio y⁺1A and parameter of the maturing rate k, was significantly influenced by diet.

4. A higher food intake and less efficient food conversion were found for quail fed on a high CP diet in the period from 15 to 28 d of age.

5. The fattening traits such as body weight, cumulative food intake and food conversion, were not affected by dietary CP content at the age of 5 weeks.

6. The effects of line on body weight, food intake and food conversion are discussed.     

Informal value chain actors’ knowledge and perceptions about zoonotic diseases and biosecurity in Kenya and the importance for food safety and public health

Zoonotic diseases, transmitted from animals to humans, are a public health challenge in developing countries. Livestock value chain actors have an important role to play as the first line of defence in safeguarding public health. However, although the livelihood and economic impacts of zoonoses are widely known, adoption of biosecurity measures aimed at preventing zoonoses is low, particularly among actors in informal livestock value chains in low and middle-income countries. The main objective of this study was to investigate knowledge of zoonoses and adoption of biosecurity measures by livestock and milk value chain actors in Bura, Tana River County, in Kenya, where cattle, camels, sheep and goats are the main livestock kept. The study utilised a mixed methods approach, with a questionnaire survey administered to 154 value chain actors. Additional information was elicited through key informant interviews and participatory methods with relevant stakeholders outside the value chain. Our results found low levels of knowledge of zoonoses and low levels of adherence to food safety standards, with only 37% of milk traders knowing about brucellosis, in spite of a sero-prevalence of 9% in the small ruminants tested in this study, and no slaughterhouse worker knew about Q fever. Actors had little formal education (between 0 and 10%) and lacked training in food safety and biosecurity measures. Adoption of biosecurity measures by value chain actors was very low or non-existent, with only 11% of butchers wearing gloves. There was a gendered dimension, evidenced by markedly different participation in value chains and lower adoption rates and knowledge levels among female actors. Finally, cultural and religious practices were shown to play an important role in exposure and transmission of diseases, influencing perceptions and attitudes to risks and adoption of biosecurity measures.     

Do we need pathogen-free livestock for food safety?

The reduction of the entry of pathogens in the food chain is an important premise in improving the safety of food of animal origin. Since food animals are the main reservoir for pathogens, the prevalence of pathogens in livestock is of great importance. Unfortunately, classical measures to improve animal health can not exclude the presence of the main food-borne zoonotic agents (Salmonella, Campylobacter, Listeria monocytogenes, verotoxinogene Escherichia coli, Toxoplasma gondii) in "clinically healthy" animals. Absence of pathogens in livestock must be regarded as an unrealistic aim. To achieve an effective improval of product safety through logistical, hygienic or technological measures both farmers and food producers need valid data about the prevalence of pathogens in livestock, in each animal and in raw material of animal origin, respectively. Yet available data are insufficient. New European directives and regulations concerning monitoring and control of zoonosis demand the systematic control of presence of zoonotic agents in livestock and later steps of the food chain.     

Evidence for hepatic glucostatic regulation of food intake in the domestic chicken and its interaction with gastro‐intestinal control

1. Male birds of a laying strain had permanent catheters introduced into the hepatic portal vein via the coccygeo‐mesenteric vein.

2. Infusions of 5 ml of 40, 100 or 150 g glucose/1 solution over 2 min caused a non‐significant depression of food intake compared with a 9 g NaCl/1 control solution.

3. Infusions of a range of isotonic glucose solutions (0 to 60 g glucose/1, 300 mosm) at 1.4 ml/min over 3 h caused food intake depression within the 3‐h period (P<0.01) proportional to the logarithm of the dose.

4. This effect was not observed when 60 g glucose/1 was infused at the above rates into the jugular vein.

5. Starvation of the bird for 21 h accentuated the depressive effect of glucose load on food intake, especially when birds were not given food until after the 3‐h infusion.

6. The infusion of solutions of sodium chloride (1.0 to 13.0 g/1, 33 to 433 mosmoles/kg) at. 1.4 ml/min over 3 h stimulated food intake within the range of 3 to 7 g NaCl/1 (100 to 233 mosm) but suppressed intake outside this range. This can be interpreted as a possible interaction with water intake control.

7. Infusion of 20 ml of glucose solution (0, 18 or 54 g/l) over 5 min into the crop and 0, 3.75 or 60 g glucose/1 at 1.4 ml/min over 3 h into the hepatic portal vein, caused an additive, linear depression of food intake.     

Can goats learn about foods through conditioned food aversions and preferences when multiple food options are simultaneously available?

The objective of this study was to determine the extent to which herbivores are able to use conditioned food aversions and preferences to learn about the nutritional and toxic properties of food plants, when food options are simultaneously available. Conditioned food aversions and preferences have been invoked as important mechanisms by which free-ranging herbivores optimize food selection by learning about the negative and positive consequences of consuming particular plant species through a series of encounters. In most previous tests of this hypothesis, access to individual test foods has been separated in time, giving animals the opportunity to associate particular foods with particular post-ingestive effects. We presented animals with a more complex scenario by offering test feeds simultaneously during the learning phase. Such a test is an important step in assessing the importance of conditioned food responses as mechanisms by which herbivores learn to select an optimal diet. We first assessed the ability of goats to learn about test foods and their post-ingestive effects, when different conifer species were offered on separate days during the learning phase and animals were dosed with compounds eliciting positive, negative, or neutral post-ingestive effects. We then investigated the ability of animals to learn to make appropriate choices when all potential test foods were simultaneously available during the learning phase. The results confirmed that goats can learn to associate particular foods with particular post-ingestive effects and adjust their diet selection accordingly. The success with which animals made such associations was greatly reduced when they were presented with test foods simultaneously during the learning phase. When test foods were simultaneously available, animals tended to select a mixed diet, thereby reducing their opportunity to learn about the post-ingestive effects of particular foods. The results suggest that caution is required in extrapolating results of artificial conditioning experiments to free-ranging herbivores. The results also suggest that reducing the risk of toxicity through selection of mixed diets is an important component of a successful foraging strategy.     

Effects of time‐limited calcium meal upon food and calcium ingestion and egg quality

Food and calcium intake and egg shell strength were measured for 24 d with 40 laying hens fed on a daily ration of either 120 g of an all‐mash diet containing 3.25% Ca or 111 g of a 0.6% Ca diet plus 8.7 g of oyster shell. The additional calcium source was offered for a 3¼‐h period beginning at 09.00, 14.00 or 17.15 h.

Consumption of oyster shell was lowest in the morning. When the calcium meal was offered at this time, the hens slightly increased their calcium ingestion on oviposition days. However, calcium intake was higher on ovulation days when oyster shell was offered after 14 h. In each case, actual requirements seemed to be one of the main factors for determining calcium appetite.

Variations of food intake in relation to laying cycle were evident with the control diet but disappeared when oyster shell was offered separately in the afternoon. Consumption of low Ca diet was greater than that of control diet only when oyster shell was given in the late afternoon of days without ovulation.

The best egg shell quality was obtained by offering oyster shell between 14.00 h and 17.15 h but the difference with control was rarely significant. Practically it is recommended that oyster shell is given at least 3 h before light extinction.     

Diurnal‐nocturnal changes in food intake,gut storage of ingesta,food transit time and metabolism in growing broiler chickens: A model for temporal control of energy balance

1. Diurnal—nocturnal changes in food intake, gut storage of ingesta, food transit time and heat production were studied in male broiler chickens reared under a 14L:10D lighting schedule (lights on from 06.00 to 20.00 h).

2. Food consumption during the scotophase was negligible. Peak food consumption during the photoperiod occurred at the beginning of the photoperiod and in the late afternoon.

3. During the photoperiod, the crop and proventriculus/gizzard contained only small quantities of ingesta. However, at the beginning of the scotoperiod, dried ingesta content of crop and proventriculus/gizzard increased by 10.5‐ and 2.76‐fold respectively. This increase was followed by a gradual decrease towards the end of the scotoperiod.

4. Food transit time during the scotoperiod was significantly longer than that during the photoperiod.

5. The daily pattern of heat production closely followed the 14L:10D lighting schedule. Total heat production during darkness averaged 53% of total heat production during the photoperiod.

6. It was estimated that the storage of energy (as ingesta) in the crop and proventriculus/gizzard, followed by its gradual release and the increased food transit time during the night, contributed 75.5% of nocturnal energy needs. It must be recognised that these mechanisms play a major role in the energy balance of the growing chicken during periods without food intake.     

Acrylamide, antiparasitic agents, dioxins and more: how dangerous are contaminants and residues in food?

Within the European Union, food safety and consumer protection are topics of highest priority. The evaluation of the safety of contaminants and residues in food is usually based on the determination of the acceptable daily intake (ADI), which in turn is the basis for maximum residue levels (MRLs). As this procedure depends on animal testing, a safety factor of 100 is usually applied to provide a margin of safety. This paper discusses the occurrence of relevant contaminants (e.g. dioxins, acrylamide) and residues (e.g. antibiotics, antiparasitic agents) in food and provides a brief assessment of the risks resulting from the consumption of food containing these substances.     

Growth and laying performance of light‐hybrid pullets subjected to quantitative food restriction

1. Three degrees of quantitative food restriction producing body weights 88, 76 or 64% of controls at 20 weeks and three times of starting restriction 3, 6 or 9 weeks of age were compared with ad libitum‐fed pullets in a factorial experiment with 1800 light‐hybrid hens. Restrictions were applied such that the target weights were produced irrespective of time of starting.

2. Food intake was least when restrictions were started at 3 weeks.

3. Sexual maturity was delayed in proportion to the severity of restriction and resulted in lower percentages of small eggs.

4. Egg numbers decreased as restriction increased.

5. Mortality in restricted groups during rearing and laying was higher.

6. Optimal restriction was apparently intermediate between treatments producing 88 or 76% of ad libitum‐fed body weight. Body weight was so excessively affected by the most severe restriction that total production was adversely affected.

7. Restriction from 3 weeks was more profitable than restriction from 6 or 9 weeks, resulting in lower food cost during rearing and higher total egg production.     

Divergent selection for residual food intake in Rhode Island Red egg‐laying lines: Gross carcase composition,carcase adiposity and lipid contents of tissues

1. A sample of 48 hens and cockerels from generation 17 of a divergent selection experiment on residual food intake was examined to determine whether the large food intake differences between those lines were associated with differences of body composition.

2. Adiposity and lipid contents of various parts of the carcase were higher in the low residual food intake line than in the high residual food intake line, both in males and females, with the cockerels of the high residual food intake line markedly lean.

3. On an equal weight basis obtained by linear correction for body weight differences, males had heavier thigh, drumstick and bones, but less adipose tissue and smaller amounts of lipids in the liver, meat, skin and abdominal adipose tissue than females.     

Effect of diets containing raw and extrusion‐cooked rice bran on growth and efficiency of food utilization of broilers

1. Meat strain chicks were fed on diets containing 600 g rice bran/kg for the 7 to 8 week period required to reach broiler weight.

2. Extrusion cooking of rice bran resulted, in improved chick weight gain and food efficiency for the first two weeks of feeding, but this advantage was lost by the end of the feeding period.

3. Addition of 10 g calcium/kg to the stabilised rice bran diet prevented the decline in performance after two weeks of age, and birds fed on this diet continued to gain at an increasing rate until the end of the experiment.

4. Calcium supplementation of stabilised rice bran diets produced significantly greater gains and superior food utilisation compared to stabilised rice bran diets without added calcium.

5. Calcium supplementation did not affect weight gain of chicks fed on diets containing raw rice bran.

6. Taste panel evaluation of meat from birds fed on diets containing raw rice bran, stabilised rice bran, or no rice bran indicated a significant preference in only one combination tested. Any ‘off flavour could not be related to dietary treatment.     

Bioethics Symposium: The ethical food movement: What does it mean for the role of science and scientists in current debates about animal agriculture?

Contemporary animal agriculture is increasingly criticized on ethical grounds. Consequently, current policy and legislative discussions have become highly controversial as decision makers attempt to reconcile concerns about the impacts of animal production on animal welfare, the environment, and on the efficacy of antibiotics required to ensure human health with demands for abundant, affordable, safe food. Clearly, the broad implications for US animal agriculture of what appears to be a burgeoning movement relative to ethical food production must be understood by animal agriculture stakeholders. The potential effects of such developments on animal agricultural practices, corporate marketing strategies, and public perceptions of the ethics of animal production must also be clarified. To that end, it is essential to acknowledge that people's beliefs about which food production practices are appropriate are tied to diverse, latent value systems. Thus, relying solely on scientific information as a means to resolve current debates about animal agriculture is unlikely to be effective. The problem is compounded when scientific information is used inappropriately or strategically to advance a political agenda. Examples of the interface between science and ethics in regards to addressing currently contentious aspects of food animal production (animal welfare, antimicrobial use, and impacts of animal production practices on the environment) are reviewed. The roles of scientists and science in public debates about animal agricultural practices are also examined. It is suggested that scientists have a duty to contribute to the development of sound policy by providing clear and objectively presented information, by clarifying misinterpretations of science, and by recognizing the differences between presenting data vs. promoting their own value judgments in regard to how and which data should be used to establish policy. Finally, the role of the media in shaping public opinions on key issues pertaining to animal agriculture is also discussed.     

Effects associated with the pea‐comb gene on chick weight,and body weight and food efficiency of adult hens

1. Growth rate, laying traits, food intake and food conversion efficiency of laying hens were compared in several experiments on pairs of full or half sibs one of which was a pea‐comb bird (Pp), the other single‐comb (pp).

2. There was a slight but significant depressing effect associated with the Pp genotype on 8‐week weight of chicks and body weight of laying hens in some populations.

3. Pea‐comb hens showed a reduction of about 2% in food consumption, independent of the effects on body weight and egg production, and we suggest that with the smaller size of comb and wattles for Pp hens, heat losses and hence energy requirements are less.

4. Appetite seemed to be more depressed at high ambient temperature in birds of the Pp genotype.     

Do methods for predicting paleohabitats apply for mountain and insular fossil bovids?

A variety of methods have been developed to use bovid postcranial elements in the functional morphology approach to paleohabitat prediction. This study represents a first attempt at testing morphometric methods based on astragalus and phalanges on extant mountain‐dwelling bovids and insular fossil bovids from Sardinia assigned to the so‐called ‘Nesogoral group’, already regarded as close to the Caprini tribe. We intended to answer the questions whether a classic four‐habitats model could be successfully applied to extant mountain‐dwelling bovids, and whether results obtained could support the hypothesis of a radiative evolution for the Sardinian bovids. Results obtained, on the one hand, highlighted some inadequacies of the method if not applied to African bovids; on the other hand, they stressed the difficulties of discriminating habitat preferences of Sardinian taxa only based on biometry of astragalus and phalanges. Nonetheless, statistical habitat predictions suggest the contemporaneous presence in Sardinia of bovids having about the same size, but inhabiting different environments, giving support to the hypothesis that Sardinian representatives of the genus Nesogoral originated from a still unknown ancestor by an adaptive radiation evolutionary process.