Influence of virginiamycin on growth and efficiency of large white turkeys

The potential post-hatching growth of domestic birds is sufficiently described by the Gompertz function

It has been hypothesised that, for post-hatching domestic birds reared under good conditions, the relative growth rate R = (dW/dt)/W = dlnW/dt is a linear function of lnW; W is body weight. It followed that dW/dt = B.W.ln(A/W), where A is mature weight, and, by integration, that weight by time is described by a Gompertz function: W_t = A.exp.(-exp(-(G₀ - B.t)), where W_t is weight at time t d, B is the rate parameter d^-1, and G₀ = -ln(-ln(W₀/A)).Where growth data published in the literature did not show this relationship, it was likely to be caused by sub-optimal conditions for maximum growth, such as inadequate nutrition or other factors.Published data, which have been diligently examined from both sexes and nine species, over 400-fold range of degree of maturity was seen, collected over nearly a century of data from four continents, which strongly corroborated the hypothesis.The data were not in agreement with other functions using three parameters and made functions with four or more parameters superfluous. The relationship between R and lnW should be carefully examined before subjecting any data set to further analysis.

Maximum levels of cross-contamination for 24 antimicrobial active substances in non-target feed. Part 3: Amprolium

The specific concentrations of amprolium in non-target feed for food-producing animals, below which there would not be an effect on the emergence of, and/or selection for, resistance in bacteria relevant for human and animal health, as well as the specific antimicrobial concentrations in feed which have an effect in terms of growth promotion/increased yield were assessed by EFSA in collaboration with EMA. Details of the methodology used for this assessment, associated data gaps and uncertainties, are presented in a separate document. To address antimicrobial resistance, the Feed Antimicrobial Resistance Selection Concentration (FARSC) model developed specifically for the assessment was applied. However, due to the lack of data on the parameters required to calculate the FARSC for amprolium, it was not possible to conclude the assessment. To address growth promotion, data from scientific publications obtained from an extensive literature review were used. Levels of amprolium in feed that showed to have an effect on growth promotion/increased yield were reported. The lack of antibacterial activity at clinically relevant concentrations for amprolium suggests that further studies relating to bacterial resistance are not a priority.

Effects of virginiamycin and a mannanoligosaccharide-virginiamycin shuttle program on the growth and performance of large white female turkeys

Shuttle programs involving dietary supplementation of mannanoligosaccharides (MOS) and virginiamycin (VM) were evaluated in turkeys by their effects on growth performance, body weight uniformity, and carcass yield characteristics. Diets containing no growth promoter (control), VM (22 mg/kg), or a shuttle program (MOS-VM) of MOS (0 to 6 wk of age at 500 mg/ kg) and VM (6 to 14 wk of age at 22 mg/kg) were fed to Hybrid female turkeys. All diets were formulated to exceed NRC nutrient requirements. Each treatment was assigned to 8 replicate floor pens containing 20 birds that were reared from 1 to 98 d of age. Body weights and feed consumption were recorded at 3-wk intervals, and mortality and culled birds were recorded daily. At the conclusion of the trial, 2 birds per pen were randomly chosen for carcass yield analysis. Feeding VM alone significantly (P < 0.05) increased body weight compared with control fed birds during all periods. The MOS-VM shuttle program resulted in early growth depression for birds less than 3 wk of age, possibly influenced by an unplanned cold stress, but better growth than the nonmedicated control birds after 6 wk of age. Birds fed VM had superior (P < 0.05) feed conversion ratio from 0 to 3 wk, which persisted until 14 wk (P < 0.10). There were no treatment effects on overall feed consumption, uniformity, mortality, or cull rate. Processing yields or weight of various parts were also unaffected by treatment.

The effect of mannanoligosaccharides, bambermycins, and virginiamycin on performance of large white male market turkeys

A study was conducted to evaluate the effects of mannanoligosaccharides (MOS), bambermycins (BAM), and virginiamycin (VIR) on the growth performance of male turkeys. Hybrid Large White male poults were assigned to six dietary treatments: control, MOS, BAM, VIR, MOS+BAM (MB), and MOS+VIR (MV). All diets were formulated to meet NRC (1994) nutrient requirements. There were eight replicate floor pens per treatment with 20 birds per pen reared from 1 to 140 d. Body weight and feed conversion (FC) were collected at 3-wk intervals and at 20 wk of age. Mortality and culled birds were recorded daily. All treatments except MV significantly (P < 0.05) increased 20 wk BW. Body weight was increased at 12 wk by BAM, whereas VIR increased BW at Weeks 12 and 15. All treatments improved FC for Weeks 0 to 3, whereas VIR, MB, and MV improved FC for Weeks 0 to 12 and 0 to 18. There were no treatment effects on cumulative mortality or cull rate. Dietary supplemental MOS, BAM, and VIR resulted in improved growth performance of Large White turkeys. These results indicate that MOS may be utilized as an alternative to antibiotic growth promotants to improve turkey performance.

Feed Additives: Do They Add to Animal Welfare? An Evaluation

The welfare of farm animals is strongly influenced by the man-made environment. Welfare problems also arise from reduced homeostatic capacities in animals. Feed additives, used to promote growth or to prevent diseases can alter the animals' self-regulating capacities thus affecting their welfare. The EU regulates the use of these additives within specified groups of Directive 70/524/EEC. Although these feed additives can be regarded as prescription-free veterinary drugs, critical remarks on their desired and adverse effects have received little attention.

A survey of the available literature shows that about one-third of licensed feed additives alter adrenal function in vitro. Reports of the adverse effects of anticoccidial additives in vivo suggest they can be classified under three headings: (i) substances with a very narrow safety margin (the difference between the permitted dose and the dose with adverse effects) and often irreversible effects on growth and feed conversion; (ii) substances with a narrow safety margin and largely reversible effects; (iii) substances with an adequate safety margin. The growth promoters (including antibiotic growth promoters) can - on the basis of their adverse effects - be classified into two groups: (i) substances with a very narrow safety margin; and (ii) substances with an adequate safety margin.

On the one hand, animal welfare considerations require use of disease-preventing additives, but on the other hand, they also demand discontinuation of current practices. Judicious use of additives can add to animal welfare. However, their unlimited use to obscure defects in husbandry is detrimental to animal welfare. A major obstacle to the judicious use of feed additives, is the lack of published, unbiased information on their efficacy and safety for farm animals.

Influence of a hydrated sodium calcium aluminosilicate and virginiamycin on aflatoxicosis in broiler chicks

Male broiler chicks were fed diets containing 0 or 3.5 mg aflatoxin (AF)/kg from 1 to 28 d of age. The diets were amended with either .5% hydrated sodium calcium aluminosilicate (HSCAS), 16.5 mg virginiamycin (VM)/kg of diet, or .5% HSCAS + 16.5 mg VM/kg of diet to determine the effects of these compounds during aflatoxicosis. When compared with controls (814 g), BW gains were significantly lower for broilers fed the AF (731 g) or AF+VM (716 g) diets. No differences were found between the BW gains of chicks fed diets without aflatoxin (814 g) and those of chicks fed AF+HSCAS (793 g) or AF+HSCAS+VM (803 g), indicating approximately 75% protection against decreased BW gain by HSCAS and 87% protection by the HSCAS+VM combination. Relative weights of the liver and kidney and creatine kinase activity were significantly increased and albumin, total protein, cholesterol, uric acid, and inorganic phosphorus concentrations were decreased in chicks fed the diet containing AF alone. With the exception of albumin, HSCAS was effective in restoring these values to control values. The findings of this research suggest that HSCAS and HSCAS+VM can counteract some of the toxic effects of AF in growing broiler chicks.

Responses of turkey poults to virginiamycin as influenced by litter condition and experimentally induced stunting syndrome

Two experiments were conducted to evaluate the effect of virginiamycin (VM, 22 mg/kg of diet) on performance of uninfected (CON) turkey poults and those infected (INO) with stunting syndrome and reared on used woodshavings (Experiment 1) or on clean or used woodshavings (Experiment 2). Virginiamycin improved BW (P less than .001) and feed efficiency (FE) (P less than .05) from 1 to 29 days of age, irrespective of type of litter or disease condition. The increase in BW induced by VM, however, was greatest when poults were kept on used litter, resulting in significant (P less than .05) VM by litter interaction. Induced stunting syndrome depressed BW (P less than .01) to 29 days of age and impaired FE from 1 to 9 days of age (P less than .05) and from 5 to 9 days of age (P less than .01) in Experiments 1 and 2, respectively. Virginiamycin did not prevent early adverse effects of INO on BW and FE, but facilitated notable recovery of INO poults relative to INO poults not fed VM. Virginiamycin increased specific activities of maltase and sucrase of the jejunum of CON poults in Experiments 1 and 2; in Experiment 2, this VM effect was evident irrespective of type of litter. Maltase-specific activity and sucrase were reduced by INO (P less than or equal to .05 and P less than or equal to .01 in Experiments 1 and 2, respectively) and VM did not modify this effect. The maltase and sucrase data suggest that VM improved BW and FE of CON poults, in part, by helping to maintain digestive and absorptive functions of the small intestine during the early growth period, but, in the instance of INO poults, VM was not effective in this regard.