New tools in the fight against salmonella, in ovo nutrition and immune enhancement with onions are some of the ideas that were presented recently at the UK branch meeting of WPSA on the latest in poultry nutrition.
By Dr Naheeda Portocarero
A strain of lactobacillus identified as Lb. Salivarus has been isolated from the chicken gut and selected for its probiotic and fermentation properties. The strain has been tested for use in fermented liquid feed (FLF), which is a moistened feed with high numbers of lactobacilli (>109 cfu/ g), high concentrations of lactic acid (>150mM) and a low pH (<4.5). This type of feed may be a potential tool to reduce the Salmonella carriage in broiler chickens by making chickens less susceptible to colonisation.
Salmonella shedding measured
In work carried out jointly by the University of Plymouth and the Veterinary Laboratories Agency, newly hatched chicks were obtained from a specific pathogen-free white leghorn flock. A total of 68 hatchlings were randomly divided into four groups. One group was provided with a daily dose of 107 cfu/ml of Lb. Salivarus, delivered via drinking water from one day of age. The second group was provided with 109 cfu/g of Lb. Salivarus delivered in FLF. The third group was provided with feed acidified with 30.3 ml lactic acid/kg of wet feed from one day of age, and the last group was the control without any addition. Feed and water were provided ad libitum.
All groups were challenged by oral gavage with 106 cfu of a nalidixic acid - resistant mutant of Salmonella typhimurium (Sal 1344 nal) at two weeks of age. Cloacal swabs were taken for 6 weeks prior to and after challenge to determine the lactobacilli counts and the shedding of Salmonella. The proportion of S. typhimurium-shedding birds decreased significantly in both FLF/Lb. Salivarus and acidified feed treatments. FLF/Lb. Salivarus treatment showed the greatest effect in the control of Salmonella. The results also showed that providing lactic acid bacteria through fermented feed could provide better Salmonella control than providing acid through water. It appears that there is a synergistic effect of both the high numbers of lactobacilli and their production of lactic acid, which reduces the pH in the gastrointestinal tract of the bird.
Humble onions show promise
One of the promising alternatives to antibiotic use in poultry appears to be the common onion. The garden onion, or Allium cepa, is known to have therapeutic properties often attributed to sulphur-containing compounds. In addition, Allium cepa is among the richest dietary flavonoids sources; these flavonoids have shown antimicrobial and anticarcinogenic activities.
Hanieh, Kondo and Abe from Okayama University in Japan studied the immunostimulatory effects of Allium cepa. They distributed day-old White Leghorn male chicks into three groups of eight. After the first week, birds were fed on diets containing powder of Allium cepa at 10 or 30 g/kg of the basal starter diet. On day 14, chickens were immunised intraocularly with Newcastle Disease Vaccine (NDV-clone 30), and intravenously with Brucell Abortus (BA), and repeated 14 days later. Blood samples were drawn weekly for antibody determination.
Average FCR of Allium cepa-fed birds was 2.15 (at 10 g/kg) for low concentration, and 2.17 (at 30 g/kg), which was a significant improvement compared to the control diet with no Allium cepa (2.70; p<0.01, p<0.001, respectively). Feeding a low concentration of Allium cepa (1%) caused a significant increase in anti-NDV antibody production in response to primary immunisation. Anti-BA antibody titre was higher with dietary Allium cepa in response to secondary immunisation. The lower Allium cepa concentration, however, had a stronger and more prolonged stimulatory effect. This work suggests that 1% addition of supplemental Allium cepa to a balanced ration could be used to enhance protective immunity.
Healthy fat without fishy taints
Fatty acid profiles of broiler meat may be modified by adding oils to the diet. A more healthy fat profile would aim to provide increased levels of N-3 fatty acids, which have been proposed to play an important role in the prevention of diseases in humans such as coronary artery disease, hypertension, diabetes, arthritis, other inflammatory and autoimmune disorders, and cancer.
To achieve a raised N-3 profile, marine oils appear to be more effective than vegetable oils. However, attention must be given to avoid the fishy taste that can result from the addition of fish oil.
Researchers Mirghelenj and co-workers from Ferdowsi University in Iran have looked at levels of fish oil from 0-50 g/kg in diets for broilers from 28-42 days of age. While weight gain and FCR were similar for all treatments, significant linear relationships were found between the levels of fish oil and Eicosapentaenoic acid (EPA) in the breast and thigh, and between the fish oil and Docosahexaenoic acid (DHA) in the breast and thigh. There were no significant treatment effects on linoleic acid and alpha linoleic acid ALA.
Sensory evaluation showed that panellists did not identify the fishy smell of cooked thigh or breast meat of birds fed up to 20 g/kg fish oil. However, already at this level of fish oil inclusion, the concentration of DHA in breast and thigh meat increased from 0.046 mg/g and 0.086 mg/g to 0.166 mg/g and 0.27 mg/g, respectively. Thus a level of 20 g/kg fish oil appears to be sufficient to enhance fatty acid profile of the meat, without negatively influencing taste.
Palm olein aids yolk fat profile
Work into fatty acid profiles has also been carried out in Iran by Hosseini and co-workers from the University of Mashhad and Birjand University. This work focused on eggs, or more specifically, looking at palm oil olein as a means to improve the yolk fatty acid content. While palm oil itself is very high in saturated fatty acids, other more beneficial fatty acids are present in low concentrations and can be extracted during processing. Palm olein is produced in this way; it contains high amounts of oleic acid (the major fatty acid in the omega-9 family) with some other unsaturated fatty acids.
Increasing the level of palm oil olein in the diet from 0 to 4.5% resulted in an increased oleic acid content of the egg yolk, an increase in the ratio of omega 6 / omega 3 fatty acids and an increased blood cholesterol of the birds (p<0.05). It was concluded that the dietary palm olein could be used to beneficially modify the egg fatty acid content.
Feeding the egg to aid hatching
The few days before and after hatch are critical for the development and survival of broilers. Injecting solutions of supplemental nutrients directly into the amniotic fluid (in ovo feeding) may be a means to overcome the constraints of limited egg nutrients. To test the value of in ovo feeding with carbohydrates and threonine, alone or in combination, an experiment was carried out by Mousavi and colleagues from Azad University, Iran, and the University of Tehran. On day 16 of incubation, 480 fertile eggs were distributed into 4 treatments. On day 17, 1 ml of solution was injected into the amniotic fluid. The solutions were: 1) carbohydrate solution: 25 g of maltose/L, 25 g of sucrose/L, 200 g of dextrin/L in 0.5% saline; 2) Threonine solution: 1% threonine in 0.5% saline; 3) Threonine plus carbohydrate solution in 0.5% saline. The controls were not injected.
Hatchability of fertile eggs was not affected by treatments, but hatching body weight of chicks and the ratio of chick body weight:initial egg weight of in ovo fed hatchlings was higher than in controls. Chicks from eggs injected with 1% threonine and 1% of threonine plus carbohydrate had greater body weight at 42 days compared with the chicks from eggs injected with carbohydrates or control chicks. Chicks from eggs injected with 1% threonine had the best feed conversion ratio (Table 1). Researchers proposed that the injected nutrients may provide the fuel for hatch and subsequent development and growth.
Lysine gives a good start
After hatch and throughout the starter period are also critical times for broilers. A good supply of nutrients aids gut development and could result in long-term benefits. The effects of different lysine levels on growth and immune response have been investigated by Alemi and co-workers from various research institutes in Iran. They used 240 Arbor Acres broiler chicks (1-18 days) that were fed various levels of digestible lysine (0.68, 0.8, 0.92, 1.04, 1.16 and 1.28%). Diets were formulated on a digestible amino acid basis with maintained ratios of essential amino acids to lysine levels, and to meet NRC requirements.
Increased immunity, N-retention
Increasing the dietary digestible lysine levels - from 0.68 to 1.28% of the NRC recommended requirement – significantly increased immune response and nitrogen retention (Table 2). It has previously been suggested that the influence of lysine is probably mediated by IGF-1. High immune response is possibly due to increased protein availability for liver protein synthesis associated with immune response or antibody production. The researchers concluded that optimising digestible lysine level can be used to enhance protein utilisation in broilers.
By having a good understanding of the nuances of nutrition and immunity is important for optimising bird health and productivity. Least-cost diets are not usually optimal for immunity because they deliver too much energy and are marginal in some nutrients. More attention to nutrient levels, especially in the early stages of growth, can boost long-term health and productivity.