Masters Theses

Date of Award

8-2000

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

M.O. Smith

Committee Members

J.M. Grizzle, A.G. Mathew

Abstract

Betaine has been studied as an osmolyte and methyl group donor for many species. Recent studies in pigs have found that betaine is able to act as an energy nutrient in the diet. The purpose of this study was to observe its effects in broiler diets, on growth performance, carcass characteristics, blood parameters, pH, hematocrit, plasma Na and K levels of heat-stressed and non-heat stressed broilers, and investigate the possibility that betaine may improve intestinal strength. In the first experiment, thirteen hundred and eighty one day old male broilers (Cobb x Cobb) were obtained. Six replicate pens were assigned to each of five treatments with 46 birds per pen. Diets were supplemented with 0 grams betaine/metric ton, 879 g/ton, 1,209 g/ton, and 1,539 g/ton. Birds and feed were weighed on days 1, 21, 42, and 49. On day 49, eight birds from each pen were selected and slaughtered. At slaughter, carcass weight without giblets (WOG), breast weight, and abdominal fat was recorded. Gut strength was determined using an instron test stand/load cell machine.

In Experiment two, 21 day old broilers (Cobb x Cobb) were moved from floor pens to each of two environmental chambers. Diet treatments were the same as Experiment 1, in addition to a sixth treatment in which the basal diet was supplemented with l,868g betaine/metric ton. There were 20 birds per chamber for each of the six dietary treatments. One chamber was maintained at 23.9°C (thermoneutral), and the other chamber was cycled as follows: 10 hours at 23.9°C, 3 hours to 35°C, 8 hours at 35°C, and 3 hours to 23.9°C (heat stress). Weights of birds and feed were measured on days 21, 28, 35,42, and 49 and water consumption was recorded daily. Blood samples were taken on day 28, 35, and 45, and blood pH, hematocrit, and plasma Na and K were measured. On day 49, all birds from both chambers were slaughtered. Carcass weight WOG, breast weight, abdominal fat, and gut strength were measure.

In Experiment 3, high density and low density diets were compared with and without the addition of betaine. Fourteen hundred and seventy-two straight-run broilers (Ross X Cobb) were obtained at one day of age. Birds were divided into groups of 46 and placed into randomly assigned floor pens. Eight replicates of four treatments were used. Treatment 1 was a high density diet with no betaine added, treatment 2 was a high density diet with 1209 g betaine/metric ton, treatment 3 was a low density diet, and treatment 4 was a low density diet with the addition of 1209 g betaine/metric ton. Birds and feed were weighed on days 1, 21, 42, and 49 of the experiment. On day 49, eight birds (four males and four females) were selected from each pen and slaughtered. The pre-slaughter weight, carcass weight WOG, breast weight, and abdominal fat were measured and recorded. Intestinal strength was also measured.

The addition of betaine to the diet did not improve growth performance of broilers given reduced energy diets, or low density diets. When birds were exposed to heat stress conditions, there was no significant difference between dietary treatments (P > 0.05) on broiler performance, live weight, carcass weight, and breast weight. Adding betaine to the diets of heat stressed broilers did not alleviate the deleterious effects of high ambient temperatures. Heat stressed birds were significantly smaller than their thermoneutral counterparts, and had significantly lower carcass yields. There were no significant differences among dietary treatments for the blood parameters measured, however heat stress altered pH, hematocrit and plasma Na and K levels. Broilers that were fed low density diets had significantly lower feed consumption, gain, and did not utilize feed efficiently, thus birds given low density diets also had significantly smaller carcass values, and the addition of betaine to the diet did not affect growth performance of these birds.

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