Summary

A trial was run with the aim to study the effect of using different vitamin levels in broiler diets (average level used in Spain versus Optimum Vitamin Nutrition levels as recommended by Roche Vitamins - now DSM Nutritional Products) on animal performance, vitamin deposition in meat and meat quality, when broilers were subjected or not to density stress conditions similar to today’s industrial broiler production conditions.

Performance parameters were measured at 20 and 40 days of age. At the end of the experiment, the effect of vitamin levels and stress on meat quality and breast meat yield was studied. Breast meat was also analyzed for vitamin content, drip losses and oxidative stability (TBARS values).

Feeding OVN™ improved performance and slaughterhouse yields as compared with feeding a control diet to broiler chickens from 0 to 40 days of age. High stocking density had a negative impact on most parameters studied. Breast meat of broilers fed OVN™ diets had significantly higher concentration of vitamins E, B1, and pantothenic acid, resulting in meat with a higher nutritional value than their control counterparts. Breast lipid oxidation was also reduced by the OVN™ premix. Therefore, the use of OVN™ premix improves broiler performance and yield, and enhances the nutritional quality of the broiler meat, with a clear benefit for the poultry industry.

Introduction

Poultry vitamin levels in feed have been historically established by NRC (1994) and ARC (1984) to prevent clinical deficiencies and have changed only little over the last 30 years. During the same period of time, broiler feed conversion rates have improved drastically (more than 20%) due especially to a much higher body weight in a shorter production period. On the other hand, modern broiler production systems often place animals under high stress conditions so that an optimum level of vitamins in feed is essential to allow birds to achieve their full genetic potential and enhance health, welfare and therefore productivity.

Poultry meat constitutes a large proportion of the meat consumed today, being an excellent source of essential protein as well as a good source of B-group vitamins. Besides, demand for further processed meat products have increased, as well as the interest of consumers for quality and nutritive meat. This involves continuous product development to create new value added products. Supporting these assumptions, recent consumer surveys (Hernandez and Seehawer, 2001) have shown that consumers consider the nutritive value of meat as one of the most important broiler meat quality factors.

All these facts motivated some research to reevaluate vitamin levels in feed in order to prevent an unbalanced animal nutrition and provide broiler meat to consumers with, at least, the same nutritional value than in the past. Thus, the purpose of the present trial was to study the effect of using different vitamin levels in broiler diets on animal performance, vitamin deposition in meat and meat quality, when broilers were subjected or not to density stress conditions similar to today’s industrial broiler production conditions.

Materials and Minerals

A total of 1,921 day-old male broiler chickens (Ross 308) were used. They were bulk weighed at arrival to the farm and distributed at random in 24 pens, each 5.5 square metres. There were four experimental treatments replicated six times and allocated randomly by blocks in the experimental rooms. The four treatments resulted from the factorial combination of two stocking densities and two feed vitamin levels. For treatments T-1 and T-2, there were 70 animals per pen, which represented a density of 12.7 animals/m². For treatments T-3 and T-4, as stressing factor, there were 90 animals per pen, which represented a density of 16.4 animals/m². Broilers from treatments T-1 and T-3 were fed a vitamin premix (Table 1) formulated according to the usual practice in Spain (Villamide and Fraga, 1999), whereas birds from treatments T-2 and T-4 were fed higher vitamin levels recommended by several worldwide specialists (Barroeta et al, 2002) and described in this paper as Optimum Vitamin Nutrition levels (OVN™).

Table 1 - Composition of experimental vitamin premixes
Vitamins	T1, T3: Control (mg/kg)	T2, T4: OVN (mg/kg)
A: Retinol	13000 IU (26 g)	12500 IU (25 g)
D3: Cholecalciferol	2600 IU (5.2 g)	4000 IU (8 g)
E: alpha-Tocopherol	18.90	225.00
K3: Menadione	2.20	4.00
B1: Thiamin	1.40	3.00
B2: Riboflavin	6.20	9.00
B6: Pyridoxal	3.00	6.00
B12: Cobalamine	21.20	40.00
PP (B3): Niacin	33.00	60.00
B5: Pantothenic acid	10.40	15.00
M: Folic acid	0.68	2.00
H: Biotin	0.07	0.25
C: Ascorbic acid	0	100

Animals were weighed at the beginning of the experiment, at 20 days and at the end of the trial (40 days), and body weight gain, feed intake and feed to gain ratio was evaluated in each period and for the overall experiment. At the end of the experiment, five numerically identified chickens (using tags) from each pen were weighed and slaughtered. In order to evaluate the effect of vitamin levels and stress on meat quality, breast yield was studied. Both breasts of each identified chick were separated and weighed. Left breasts were used to determine drip losses (at day 0, 4 and 7 after 4°C storage) and one sample of the right breast was sent frozen to Roche Vitamins (now DSM Nutritional Products) laboratory to determine vitamin content. Another aliquot of these right breasts was used to determine the TBARS (Thiobarbituric Acid Reactive Substances) values.

Data were analyzed according to the GLM procedure of SAS, to determine main effects of vitamin premix, stocking density, and the interaction between these factors. Storage time was used as a factor and its effect on TBARS values and drip losses was also determined.

Results and Discussion

Treatments significantly affected all production parameters. Chickens fed OVN diets were heavier (P<0.01), ate more feed (P<0.01), and presented better average daily gain (P<0.04) than those fed control diets. Instead, high-density stress conditions statistically reduced average daily intake (P<0.001) and thus, lower growth rate of these animals was found (P<0.0001). Also, high stocking density negatively affected slaughterhouse results, and the birds reared under stress conditions had lower breast meat yield (P<0.01) than the controls.

A summary of these results is shown in Table 2; more detailed information on performance improvements was presented by the authors at the 11th European Poultry Conference in Bremen (Hernández et al, 2002).

Table 2 - Performance parameters and breast meat yield
	BWT 40dg	DWTG g/b/d	FI g/b/d	FCR g/g	Breast Yield % bw
T1	2268	55.7	96.60	1.746	16.33
T2	2341	57.5	100.70	1.746	16.59
T3	2069	50.5	91.70	1.818	15.61
T4	2122	52.0	92.70	1.801	15.84
P
(vit. level)	0.0433	0.0434	0.0111	ns	ns
(density)	0.0001	0.0001	0.0001	0.0026	0.0097
(vit. level *dens.)	ns	ns	ns	ns	ns

Higher levels (P<0.0006) of vitamin E, vitamin B1 in breast meat were achieved by feeding chicks the OVN premix (but not enough to be considered as vitamin enriched meat), thus improving the nutritive value compared to control broiler meat (Figures 1 and 2). Feeding the OVN premix also increased breast meat panthotenic acid (P<0.0013); however, the effect was observed only in high stocking density conditions, thus leading to a premix×density interaction that was significant at P<0.0005. Levels of the rest of vitamins were not modified by the OVN premix (results not shown). Stocking density had no effect on vitamin content in breast meat (results not shown).

Lipid oxidation (TBARS) of breasts was statistically affected by type of vitamin-premix (P<0.001), density stress conditions (P<0.021) and also storage (P<0.001). Breast meat of birds fed OVN premix showed lower TBARS values (0.27 vs 0.42 nmol/g) than animals fed control diets (Table 3). Breasts of chickens reared at high density presented slightly lower TBARS values, what could be related to their lower weight of abdominal fat and thus with their lower level of intramuscular fat.

Drip losses obtained in breast of chickens fed enriched-vitamin diets were numerically lower than those from birds fed control feeds, but this difference failed to reach significance.

References

Barroeta, A., Calsamiglia, S., Cepero, C., López-Bote, C. and Hernandez, J.M., 2002, Óptima nutrición vitamínica de los animales para la producción de alimentos de calidad. Ed. Pulso Ediciones S.L.

Hernández, J.M. and Seehawer, J., 2001. Consumer attitude towards meat quality in Germany in the year 2000. XVth European Symposium on the Quality of Poultry Products, Turkey.

Hernández, J.M., Pérez-Vendrell, A.M. and Brufau, J., 2002. Effect of vitamin level in broiler diets on the productive parameters and meat deposition. 11th European Poultry Conference, Bremen, Germany.

Villlamide, M.J. and Fraga, M.J., 1999. Composition of vitamin supplements in Spanish poultry diets. British Poultry Science, 40: 644-652.

From Proceedings of the XVI European Symposium on the Quality of Poultry Meat, Saint-Brieuc, Ploufragan, France.

March 2010