S. Leeson

Effects of feeding level and water temperature on growth, nutrient and energy utilization and waste outputs of rainbow trout (Oncorhynchus mykiss)

A study was carried out to determine the effect of feeding level and water temperature on growth and feed efficiency, nutrient and energy utilization and waste outputs of rainbow trout. A practical diet was fed to near-satiation to groups of fish reared at 6, 9, 12 and 15 °C. At each temperature, the feed intake of other groups of fish was restricted to about 85 % or 70 % of the amount of feed consumed in the previous week by the fish fed to near-satiation. Total feed intakes over 12 weeks were, on average, 76 % and 65 % of total feed intake of the near-satiety group for R1 and R2, respectively. Reducing the feed allocation resulted in significantly (P 0.05) effect on feed efficiency, carcass composition or efficiencies of digestible nitrogen and digestible energy retention. Increasing temperature resulted in an increase in the apparent digestibility of dietary dry matter, nitrogen and energy (P < 0.05). The increase in digestibility of dry matter and nitrogen with increasing temperature resulted in higher estimated total solid and solid nitrogen waste outputs per kg fish produced (P < 0.05) at lower water temperatures. Estimated dissolved nitrogen and phosphorus waste outputs (g/kg fish produced) were not affected by the feeding level or water temperature. A highly significant (P < 0.01) linear relationship was observed between metabolizable energy (ME) intake above basal metabolism and recovered energy. The efficiency of ME utilization for growth (Kpf) was 0.61 and this coefficient was not affected by feed intake or water temperature. Protein and lipid were deposited in a constant ratio (1 kJ protein gain: 1.4 kJ lipid gain) regardless of ME intake or water temperature.

Effects of menhaden oil and flaxseed in broiler diets on sensory quality and lipid composition of poultry meat.

1. Three hundred and thirty 1-d-old male broiler chicks from a commercial strain were allocated to 11 dietary treatments comprising combinations of flaxseed at 100 g/kg and menhaden oil (MO) at 7·5 or 15 g/kg. Birds were given the experimental diets 7 or 14 d prior to slaughter. Carcase omega-3 fatty acid profiles and sensory evaluations of different cooked meat portions were carried out. 2. Linolenic acid was preferentially deposited in dark meat and long chain omega-3 fatty acids in white meat. Breast meat sensory quality was not affected in birds given 100 g/kg flaxseed for 14 d (treatment 3), 7·5 g/kg MO for 14 d (treatment 5) or 100 g/kg flaxseed +0·75 g/kg MO for 7 d (treatment 6). In contrast, thigh meat sensory quality decreased in treatments 5 and 6. 3. Feeding flaxseed and MO to birds for just 7 d prior to slaughter resulted in significant omega-3 meat enrichment depending on their dietary concentrations. The linolenic acid and long chain omega-3 fatty acids showed preferential deposition in dark and white meat, respectively, which may affect the sensory quality of various portions differently.

Sorghum tannins: a review

The feeding value of sorghum for poultry has been a subject of study for many years. Of particular interest has been tannin, an antinutritive factor present in some sorghum cultivars, its influence...

Butyric acid glycerides in the diet of broiler chickens: effects on gut histology and carcass composition

Abstract Aim of the study was to verify the effects of butyric acid glycerides, as a supplemental ingredient in the diet, on live performance of broiler chickens and on the morphology of their small intestine, since short chain fatty acids are known as selective protection factors against intestinal microbial parasites, potent growth promoters of the gut wall tissues, also in terms of immune modulation response. An experiment was carried out on 150 Ross 308 female chickens, allotted to 5 treatments, over a 35 d ays period: the control, with soybean oil as the energy supplement, and 4 treatments with increasing amounts (0.2, 0.35, 0.5, 1% mixed feed) of a mixture of butyric acid glycerides (mono-, di- and tri-glycerides). Treated animals showed a higher live weight at slaughtering (P<0.05) with a better feed conversion rate. The carcase characteristics were not influenced, but the small intestine wall resulted slightly modified with shorter villi, longer microvilli (P<0.01) and larger crypts depth in jejunum (P<0.01), only with lowest concentration of the supplement (0.2%). It is concluded that butyric acid glycerides are an efficient supplement to broilers’ diets, deserving particular attention as a possible alternative to antimicrobial drugs, which have been banned in Europe.

Dietary influence on organ size and in vitro oxygen consumption by visceral organs of growing pigs

Abstract Although visceral organs represent only about 15% of the pig’s body weight, they account for about 45% of whole body oxygen consumption. The effect of diet on organ mass and in vitro oxygen consumption by some visceral organs was investigated in a study using 15 Yorkshire male castrates (18.9±1.5 kg initial body weight). Diets were based on casein-corn starch (CC), barley-canola meal (BCM) or barley-canola meal–alfalfa meal (BCM-ALF) and formulated to contain 0.088 MJ digestible energy (DE) per gram of crude protein. Pigs were fed at 2.6 times maintenance DE requirements twice daily for 3 weeks, then every 3 h for 3 days prior to tissue sampling. One h after feeding, pigs were killed and samples of the liver, jejunum, colon and caecum taken immediately. In vitro oxygen uptake was determined polarographically using an oxygen electrode. Per kg empty body weight (EBW), weight of the small intestine did not differ ( P >0.10) between treatments. Per kg EBW, weights of liver, colon and caecum were higher ( P P >0.10). However, weight-specific oxygen consumption was higher ( P P P >0.10) and lower than those in the BCM–ALF-fed-pigs. In conclusion, changes in diet composition alter energy expenditure in the liver and intestinal tissue. This appears largely mediated via effects on organ size and not via weight-specific oxygen consumption.

Copper metabolism and dietary needs.

It has been about 80 years since Cu was first recognized as being important for maintenance of haemoglobin. Since that time requirement values have been established and signs of deficiency and excess well documented. NRC (1994) provide the most comprehensive list of detailed requirement values for Cu for various classes of poultry, yet these lack extensive detail and are predicated on just five publications, the most recent of which was conducted 30 years ago. Requirement values average 6-8 ppm which traditionally is supplied by inorganic salts and especially copper sulphate. Other inorganic sources vary from 40-115% bioavailability of Cu compared to sulphate. Copper is easily complexed with amino acids or proteins, leading to the development of so-called organic sources of copper which are claimed to have better digestibility and/or less formation of insoluble complexes with other minerals in the digesta. Results on effectiveness of organic vs. inorganic forms of Cu are variable, although this line of research has led to appreciation of the potential to use much lower levels of supplementation. Since at least 80% of dietary copper appears in the excreta, using lower levels of diet supplementation means reduced Cu in the environment. With less supplementation, knowledge about bioavailability of Cu in major feed ingredients becomes important. Copper in cereals is reported to be 80% available to the bird while that in vegetable proteins is closer to 50% available. Availability from animal proteins is very variable, while corn distillers grains now provides the most concentrated source of Cu within the major ingredients. Copper levels greatly in excess of requirement, at around 125 ppm, have been shown to improve performance of meat birds and egg layers. The mode of action is unknown although likely relates to antibacterial properties of Cu. Likewise high levels of diet Cu have been shown to reduce cholesterol content of eggs and poultry meat, although this is often at the expense of loss in performance and contribution of more Cu to the environment.

Effect of dietary flaxseed, flax oil and n-3 fatty acid supplement on hepatic and plasma characteristics relevant to fatty liver haemorrhagic syndrome in laying hens

1. Two experiments were carried out to investigate the effect of dietary flaxseed, flax oil and n-3 fatty acid supplementation (Dry n-3®) on hepatic fat content, plasma triglycerides, hepatic haemorrhage score, egg production, food intake and body weight in an inbred line of Single Comb White Leghorns (UCD-003) predisposed to fatty liver haemorrhagic syndrome (FLHS) and normal SCWL hens. 2. Feeding diets containing 100 g/kg ground flaxseed, 40 g/kg flax oil, or 100 g/kg Dry n-3® reduced body weight and significantly reduced hepatic fat content compared to feeding the control diet with animal and vegetable oil as a fat source. 3. Hepatic malondialdehyde, an indicator of lipid peroxidation within the liver, was not significantly affected by dietary treatment. 4. Normal SCWL hens tended to have higher egg production, greater body weight, greater food intake and higher blood triglyceride concentrations than UCD-003 hens, although the strain effects were not significant. Liver weight as a percent of body weight was significantly lower in normal SCWL hens. Treatments by strain interactions were not found. 5. The result suggested that dietary flaxseed, flax oil and Dry n-3® decrease hepatic fat content and reduce body weight, 2 of the predisposing factors believed to contribute to FLHS onset. However, haemorrhages were still apparent in both strains regardless of treatment, indicating that other unknown underlying mechanisms may also be responsible for FLHS.

Feathering in commercial poultry II. Factors influencing feather growth and feather loss

In commercial production, there is often concern about the quantity and/or quality of feathering in both broilers and layers. For broilers, the concern is adequacy of protective feather cover, while in layers it is usually the necessary degree of feathering needed to optimise feed efficiency. Feather development is under the control of hormones such as thyroxine and oestrogen and indirectly by testosterone. Environmental or nutritional status that influences such hormonal output will indirectly affect feathering. In broilers, rate of feathering is influenced by genetics, since some 20 years ago there was a conscious decision to introduce slow (K) vs. fast (k) feathering as a means of sexing day-old chicks. With the relative “immaturity” of modern broilers, these genes influence feather cover well into the production cycle. In White Leghorn crosses, initial problems with apparent Leukosis susceptibility of the progeny of slow feathering dams had to be overcome by eradication of Leukosis before feather sexing could be generally introduced. Nutrition can influence rate of feathering as well as feather structure, colour and moulting. Amino acid balance and especially deficiencies of TSAA and branched chain amino acids will influence feathering in young birds. Deficiency of vitamins and certain trace minerals also induce characteristic feather abnormalities, as does the presence of dietary mycotoxins. A number of viruses, bacteria and mycoplasma can infect the feather follicle and so influence feather development. Feather pecking and feather licking are behavioural abnormalities, although these conditions can be induced by changes in environmental conditions or nutritional adequacy of the diet.

Feathering in commercial poultry I. Feather growth and composition

Feather growth, structure and patterns of moulting are important characteristics of poultry in commercial environments. As the market age for broilers continues to decline, the “maturity” of feather cover becomes even more important for protection of the skin and underlying tissue. Feather growth begins at around day 5 of incubation while keratinisation is complete 2 – 3 d prior to hatch. Feathers do not grow randomly over the skin surface, but rather in distinct tracts, which cover at most 75% of the skin surface. Broiler chickens will have about 50 g of feathers by market age, although at this early age some feathers will have already been lost by sequential moulting. Although most modern strains of poultry have white or brown feathers, there are various colour schemes that are again dictated during embryo development. In a subsequent paper, we will detail factors affecting feather growth, moulting and the occurrence of various abnormalities.

Voluntary food restriction by laying hens mediated through dietary self‐selection

1. Individually caged Single Comb White Leghorn hens simultaneously received two diets which allowed selection of certain nutrients: these “ split‐diets “, essentially provided concentrated sources of either protein and energy (191 g crude protein, 12.82 MJ ME and 4.7 g Ca/kg diet), or calcium (107 g CP, 7.28 MJ ME and 131 g Ca/kg). 2. During four, 28‐d periods of lay, birds offered these split‐diets consumed some 7% less food in total than did control birds receiving a conventional diet ad libitum. 3. Calculation of nutrient intakes showed that birds on the split‐diets consumed significantly less protein, energy and calcium than the control birds. 4. Giving split‐diets also resulted in superior shell quality; treatment differences were also noted in the timing of oviposition. 5. It is suggested that the voluntary reduction in food intake noted for birds offered split‐diets is associated with an appetite for calcium.