Effects of dietary lactose on incidence and levels of salmonellae on carcasses of broiler chickens grown to market age

Dietary Lactose and its Effect on the Disease Condition of Necrotic Enteritis

Clostridium perfringens is the etiologic agent of necrotic enteritis (NE) and is ubiquitous in nature. The incidence of NE has increased in countries and commercial companies that have stopped using antibiotic growth promoters. The mechanisms of colonization of C. perfringens and the factors involved in onset of NE are not fully understood. Previously, our laboratory has demonstrated that lactose could potentially reduce Salmonella and C. perfringens in ceca of poultry. In the present investigation, we hypothesized that dietary lactose would reduce the clinical signs of NE and could be used as an alternative to antibiotics. In experiment 1, day-of-hatch broilers were fed either a nonlactose control diet, a diet with 2.5% lactose, or a diet with 4.5% lactose throughout the experiment. Birds were administered C. perfringens (10(7) cfu/mL) daily via oral gavage for 3 consecutive days starting on d 17. When evaluating the intestinal lesions associated with NE, birds fed 2.5% lactose had significantly lower (P < 0.05) lesion scores (0.70 +/- 0.52) compared with the control (1.55 +/- 0.52) or the 4.5% lactose (1.60 +/- 0.52). The data from the microbial analysis showed that the addition of lactose did not affect any bacterial populations when compared with the control birds that did not receive dietary lactose over the 21-d evaluation. The overall lesion scores in experiment 2 were significantly (P < 0.05) reduced in birds fed 2.5% lactose compared with the birds fed the control diet with mean lesion scores of 1.10 +/- 0.73 and 1.80 +/- 0.73, respectively. These experiments suggest that lactose could be used as a potential alternative to growth-promoting antibiotics to help control this costly disease.

Transgenic Chickens Expressing β-Galactosidase Hydrolyze Lactose in the Intestine

Chickens do not possess the necessary enzymes to efficiently hydrolyze lactose into glucose and galactose. The bacterial enzyme beta-galactosidase can convert lactose into glucose and galactose. Transgenic chickens that carry the E. coli lacZ gene and express beta-galactosidase could potentially utilize lactose as an energy source. The objective of this study was to determine the ability of the transgenic chicken small intestinal mucosa to hydrolyze lactose into glucose and galactose. Lactase activity was examined in the intestinal muscosa from wild-type chickens and two lines of chickens that carry the lacZ gene and express beta-galactosidase. Lactase activity was significantly higher in both transgenic lines compared with wild-type birds (P < 0.05). The presence of the beta-galactosidase enzyme was revealed by X-gal staining in the intestine of transgenic chickens, whereas it was not present in the wild-type chickens. Overall, it appears that inserting the lacZ gene, which encodes beta-galactosidase, has resulted in a chicken that can utilize lactose as an energy source. This study demonstrates that transgenic technology can be used to modify nutrient utilization in domestic poultry.

Contribution of oligosaccharide and polysaccharide digestion, and excreta losses of lactic acid and short chain fatty acids, to dietary metabolisable energy values in broiler chickens and adult cockerels

1. Two experiments were conducted, using both adult cockerels from a layer strain and 3-week-old broiler chickens. In the first experiment, one of the 2 diets investigated was composed mainly of maize and soyabean meals, the other one containing the latter ingredients diluted with 475 g/kg mature pea seeds. For these 2 diets, the apparent metabolisable energy values corrected to 0 nitrogen retention (AMEn) were derived, together with the apparent digestibilities of nitrogen, amino acids, total lipids, starch, individual oligosaccharides, and non-starch polysaccharides (NSP). Excretions of lactic acid and short chain fatty acids (SCFA) were also determined. 2. In the first experiment, the mean apparent digestibilities of starch, lipids, total amino acids, NSP, sucrose and alpha-galacto-oligosaccharides in adult cockerels were 0.946, 0.785, 0.835, 0.045, 0.99 and 0.99, respectively. In broiler chickens, they were 0.938, 0.675, 0.830, -0.016, 0.988 and 0.867, respectively. The bird type effects were significant (P < 0.05) for the digestibilities of starch, lipids, NSP (for the maize-soyabean meal diet, only) and alpha-galacto-oligosaccharides. Broiler chickens excreted a mean of 11.032 g organic acids/kg diet against 4.190 in adult cockerels (P < 0.001). These digestibility measurements enabled the contribution made by each dietary component to the AMEn value of the diets to be calculated. AMEn values were lower in broiler chickens than in adult cockerels, with on average 0.8 MJ/kg dry matter difference resulting from bird type. This difference was accounted for by differences between bird types in energy supplied by lipids (34.0%), starch (7.5%), alpha-galacto-oligosaccharides (8.7%), NSP (14.2%), and in energy losses from lactic acid excretion (16.4% of the difference in AMEn between bird types). 3. In the second experiment 2 diets were studied, consisting of a basal and the basal diluted with 30 g/kg lactose (a fermentable sugar in chickens) and 12 g/kg of a water-soluble gel-forming component containing 50% polygalacturonic acids. Lactose digestibilities reached 0.928 and 0.712 in adult cockerels and chickens, respectively. The digestibilities of the water-soluble polygalacturonic acids were similar in cockerels and broiler chickens, with a mean value of 0.672. Figures similar to those of the first experiment were found in the comparison between cockerels and broiler chickens, for the AMEn values of diets, the digestibilities of starch and lipids and the excretion of lactic acid. Broiler chickens excreted 4.580 g lactic acid/kg dry food intake, compared with 0.740 g in the adult.(ABSTRACT TRUNCATED AT 400 WORDS)