The role of nucleotides in improving broiler prestarter diets: The Brazilian experience
It is also during these same early days of life that birds face one of their most difficult physiologic transitions: the nutrient sources of lipid and protein in the embryo are replaced by the complex carbohydrates, proteins, and lipids in conventional starter diets. Concomitantly, chick immune systems are immature and chicks are dependent on the antibodies transferred by the breeder (Cutler, 2002).
Prestarter diets
Over the years, broiler body weight gain and feed efficiency have improved, with body weight gain now increasing by a factor of 50 within 40 days of hatch (Noy, 2005).
Nevertheless, although chicks grow quite rapidly in the first few days of life, body weight gain can be further enhanced by use of a prestarter diet (Leeson and Summers, 2005). Based on recent studies on the use of prestarter feeds to enhance weight gain the following recommendations are offered to improve prestarter diet effectiveness:
• Feeding.
Feed diet as soon as possible after hatching to stimulate substrate-dependent enzyme synthesis (Moran, 1990).
• Quantity.
Offer diet in feeders that are nearly full (Miller, 2005).
• Metabolizable energy.
Feed intake is governed by both physical satiety and energy intake. Nevertheless, broiler digestive systems do not reach maturity until up to 14 days of age. This delayed maturation may be related to enzymatic development and nutrient utilization. Therefore, broilers eat to satisfy energy requirements only after two weeks of age (Maiorka et al., 1997).
• Ingredient quality.
Use high quality ingredients in prestarter diets. Corn starch is composed of amylose (25%) and amylopectin (75%). Amylopectin has highly branched chains, with greater potential for gelatinization than amylose. This trait is desirable, because it improves grain digestibility. Collins et al. (1999) showed that corn with high amylopectin content (99%) has 2.5% higher metabolizable energy content. Although corn and soybean meal are considered ideal ingredients for broiler chicks during a prestarter period, Batal and Parsons (2002) observed that diets containing those ingredients had lower metabolizable energy and lower amino acid digestibility than expected in the prestarter period.
• Fat.
Chicks have an immature entero-hepatic circulation of bile salts and low lipase synthesis and secretion. Thus, chicks have a lower capacity for digesting fat compared with mature birds. Attempts to add higher levels of fat to the diet may cause oxidation, resulting in destruction of fat-soluble vitamins and damage to intestinal villi. Furthermore, indigestible fat may serve as a substrate for gut microorganisms. Dietary free fatty acids have an adverse effect on fat digestibility (Wiseman and Salvador, 1991), an effect more pronounced for palm oil and tallow than for soybean oil. An absence of dietary monoglycerides also most likely interferes with fat digestibility.
• Sodium.
Britton (1992) maximized broiler performance by feeding prestarter diets containing 0.39% sodium. Sodium consumption stimulates water consumption and, consequently, feed intake (Viola, 2003). Furthermore, sodium participates in a secondary active transport system of some nutrients in the gut (Widmaier et al., 2004), a system that is most likely not mature at hatching. Increased dietary sodium content does not cause an increase in litter moisture content. Instead water is retained in the carcass (Vieira et al., 2000).
• Feed diameter.
Krabbe (2000) evaluated feed mean geometric diameter (437, 635, 780, 866 and 970 μm) of prestarter diets for broilers and concluded that performance was optimized with diets of mean geometric diameter ranging from 800 to 1000 μm.
• Protein.
Protein requirement declines as broilers age. Schutte et al. (1997) deduced that broiler chicks should not receive a prestarter diet containing less than 21% crude protein, due to a possible sub-optimal level of glycine and serine. According to Penz (1992), high protein content is necessary in a prestarter diet. The high heat increment produced by protein plays a role in maintaining body temperature.
• Additives.
Additives such as enzymes, mannan oligosaccharide, probiotics, and lactic acid (Leeson and Summers, 2005), as well as mycotoxin adsorbents, antioxidants and mold inhibitors are highly recommended in prestarter diets.
• Nucleotides.
Nucleotides are essential nutrients involved in gut development and repair, skeletal muscle development, heart function and immune response (Grimble and Westwood, 2000). NuPro® (Alltech Inc.) offers a rich source of nucleotides, inositol, glutamate, peptides, minerals and vitamins.
The effect of NuPro® in prestarter diets
The effect of NuPro®, a source of nucleotides derived from yeast cell contents, on chick development and health is the subject of this paper. A general review of how NuPro® stimulates development of broiler gastrointestinal tract, muscle tissue, and the immune system follows. In addition, recent trials conducted in Brazil on broiler response to NuPro® in prestarter diets are summarized.
GASTROINTESTINAL DEVELOPMENT
Feed consumption promotes rapid development of the gastrointestinal tract and associated organs such as liver and pancreas. However, body growth and gastrointestinal tract development do not occur at the same rates. During the posthatch period, the proventriculus, gizzard and small intestine develop faster than overall body weight.
Small intestine development is not uniform, with the duodenum growing faster than the jejunum and ileum. The intestines are fully developed between 3 and 8 days of age (Dror et al., 1977). In contrast, the development of lymphoid tissue associated with the intestine parallels increases in body weight consistent with initial feeding rates.
At hatch, enterocytes and villi are not well developed and few crypts are present.
However, within a few hours posthatch, villi height and area increase rapidly, but not uniformly throughout the intestines. Development is complete at 6 to 8 days in the duodenum and at 10 days in the jejunum and ileum. Crypts increase in number and size, proliferating rapidly during the first days posthatch. Alterations in the enterocytes, villi, and crypts are influenced by diet. For example, delayed feeding of neonatal chicks delays mucosal development (Noy and Sklan, 1997; Uni et al., 1998; Geyra et al., 2001).
The gastrointestinal tract has rapid cell turnover and is unable to produce de novo all necessary nucleotides to satisfy its own requirements (Leleiko et al., 1983). Therefore, intestinal development is highly dependent on the presence of dietary nucleotides.
Nucleotides increase the development of the villi, intestinal wall thickness, protein content, and DNA and RNA contents (Uauy et al., 1990). Likewise, the synthesis of rRNA in the crypts of the jejunum depends on dietary pyrimidines (Udin et al., 1984). Inflammation in the intestines increases the synthesis of rRNA and, consequently, dietary pyrimidine and purine nucleotide requirements (Jain et al., 1997).
Liver weight increases twice as fast as chick body weight during the first week of life (Nir et al., 1993). Endogenous synthesis of nucleotides, mainly in the liver (Mayer et al., 1990), appears to be inadequate to meet nucleotide requirements under conditions of rapid tissue growth and repair or systemic infection. Further, in the case of liver disease, nucleotide requirements increase. The synthesis of hepatic rRNA occurs at a rate of 12 to 25% per day (Grimble and Westwood, 2000). Although the liver is well adapted to supply nucleotides for RNA and DNA synthesis, it is still highly dependent on dietary pyrimidines (Berthold et al., 1995).
Carbohydrates, lipids and proteins are digested and absorbed via an association of pancreatic and brush border enzymes and the presence of intestinal carriers. Posthatch, the activity of intestinal enzymes (i.e., trypsin, amylase and lipase) increases in relation to intestinal weight and body weight (Sklan and Noy, 2000). There is little enzyme secretion between 4 and 14 days posthatch, thus the development of enzymes in the intestinal brush border is highly dependent on the presence of dietary nucleotides (salvage pathway) (Uauy et al., 1990).
MUSCULAR DEVELOPMENT
Posthatch muscular development (weight gain) occurs due to hypertrophy of muscle fiber (Widmaier et al., 2004). During this period, cardiac rRNA is synthesized at a rate of 15% per day (Ray et al., 1973). Availability of nutrients after hatch is critical for satellite cell proliferation and for muscular development, thus maximizing weight gain.
Nucleotides are essential for maintenance and repair of muscle tissue (Grimble and Westwood, 2000).
IMMUNE SYSTEM DEVELOPMENT
Immune system development starts in the embryo and continues post-hatch. During the first week of life, there is a rapid increase in the number of leukocytes, as well as an increase in lymphoid organs (Jull-Madsen et al., 2004). These increases are important for acquired immunity development.
Although the yolk sac is important because it transfers passive immunity in the form of immunoglobulins (IgA, IgG) from the yolk and albumen to the neonatal chick (Cutler, 2002), an early excess or deficiency of nutrients can still harm the development of immune response (Klasing et al., 1998).
The synthesis of immune cells is a metabolically expensive process, highly dependent on the presence of dietary nucleotides (Grimble and Westwood, 2000). Macrophage activation and lymphocyte production also depend on nucleotides. Feeding birds NuPro® results in rapid immune system response, as evidenced by increases in lymphocytes and macrophage activity after challenge (Qureshi, 2002).
Brazilian trials
PERFORMANCE AND CARCASS TRAITS
A study was conducted at the Federal University of Pelotas to test the effect of dietary NuPro® on broiler performance. A total of 810 day-old male broiler chicks (Ross), housed in floor pens on litter, were assigned to one of nine replicate groups of 30 chicks, three replicates per treatment: (T1) a corn-soybean meal control diet; (T2) control diet plus 20 g/kg NuPro®, 1 to 7 days of age; or (T3) control diet plus 20 g/kg NuPro®, 1 to 7 days of age and 38 to 42 days of age. Body weight, feed consumption and feed conversion were evaluated.
At trial end, one bird per treatment was euthanized; carcasses were weighed and scored. Birds fed NuPro® from 1 to 7 days of age had higher feed intake and body weight gain than control birds indicating that NuPro® improved performance of broiler chicks when included in a prestarter diet (Table 1).
At trial end, birds fed T3 had body weight gain significantly higher than controls and numerically higher than birds fed T2 from 1 to 7 days of age only. These findings are consistent with those of Leeson and Summers (2005) who found that, in general, each 1 g increase in 7- day-old body weight improves 49-day-old body weight by 5 g. Birds fed diets containing NuPro® also showed numerically higher carcass yield and yields of drumstick, thigh, wing, and breast weights (not shown).
Table 1. Performance of broilers fed diets containing yeast extract (NuPro®).
abMeans differ P<0.05.
Zauk et al. (2006) evaluated the performance and carcass traits of broiler chicks fed prestarter diets (1 to 7 days of age) containing graded levels (0, 1, 2, 3 or 4%) of NuPro®. No significant differences were observed in feed intake, weight gain, or carcass traits.
Contrary to results from other studies, these data may indicate differences in the environmental challenge to which birds are exposed under commercial versus university poultry facility conditions.
In contrast, a similar study (0, 1.5, 3.0, 4.5, 6.0 and 7.5% NuPro®) conducted at the Catholic University of Ecuador (Torrealba, personal communication) indicated that weight gain and feed efficiency of both Cobb and Ross strains were significantly increased by inclusion of 1.5% NuPro® in prestarter diets.
IMMUNE RESPONSE
Qureshi (2002) evaluated the production of leukocytes and macrophage activity in chicks fed diets containing (0, 2.5, 5.0 and 10%) NuPro® and observed improved production of leukocytes and macrophage activity when NuPro® was included up to 5% of the diet.
This result is consistent with studies in several species in which the effects of nucleotides on the immune system are well documented (Grimble and Westwood, 2000).
| Conclusion NuPro® offers a rich source of dietary nucleotides. When NuPro® is included in broiler prestarter diets, chick intestinal maturation and health, brain function, erythrocyte multiplication, hepatic regeneration, skeletal muscle growth and repair, cardiac development, and immune system response are enhanced. |
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Authors:
Universidade Federal de Pelotas, Pelotas, RS, Brazil
1. What is the percentages of ATGC in nupro or this dietary nickel tide mix contains?
2. What is the difference between dietary and GE no mic nickel tide?
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