Masters Theses

Date of Award

8-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

M. O. Smith

Committee Members

A. G. Matthew, J. K. Miller

Abstract

A study was conducted to investigate the effects of supplemental Chromium-Lmethionine (CrMet) on plasma and serum metabolites, growth performance, and meat yield of market parts of heat-stressed and non-heat-stressed broilers. In a completely randomized design, broilers reared under heat stress or thermoneutral condition consumed diets supplemented with 0, 200,400, and 800 µg/kg of chromium as chromium-L-methionine (CrMet). Initially, three hundred commercial broiler chicks (male) were randomly assigned to one of four CrMet treatments, with 75 birds per treatment. Broilers were reared in floor pens and fed a common starter diet (day 1-21) supplemented with four levels of CrMet. At 3 weeks, 160 broilers were randomly selected and transferred to individual, wire cages, within two environmental chambers. One chamber cycled between 18.3 and 23.9° C (Thermoneutral, TN), while the other chamber cycled between 23.9 and 35° C (Heat Stress, HS). Within the two environmental chambers, broilers consumed a grower diet (day 22-45) and a finisher diet (day 45-49); both supplemented with the four levels of CrMet. Gain, as well as feed and water consumption, were measured weekly. Blood samples were collected prior to (3 weeks) and during (7 weeks) heat stress. At 7 weeks, ten birds per treatment, per chamber, were weighed, slaughtered, and cut into market parts for determination of carcass yield and composition.

In three-week-old broilers, there was a dose-dependent response to CrMet supplementation with 800 µg Cr/kg resulting in a 67.6 % increase (P < 0.0001) in serum TG concentration. Supplementation of 400 and 800 µg Cr/kg decreased (P < 0.0001) plasma glucagon concentrations by 60.93 % and 44.54 % respectively. Serum NEFA and plasma insulin concentrations were not affected by CrMet supplementation. In 7-week old broilers, CrMet supplementation had no effect on serum NEFA or plasma glucagon concentrations. Serum TG levels of CrMet treated birds tended (P < 0.1643) to be lower than for birds receiving no supplementation. Additionally, CrMet treated birds tended (P < 0.17) to have increased insulin concentrations (25.5 %). Heat stress increased (P < 0.0001) serum TG and NEFA and plasma glucagon concentrations, but decreased plasma insulin levels. In 3-week-old broilers, CrMet supplementation had no impact on feed efficiency or feed consumption, however 800 µg Cr/kg decreased (P < 0.03) average total gain by 8.5 %. In 7-week-old broilers, CrMet supplementation did not affect average total gain or feed efficiency, however 200 pg Cr/kg reduced feed (P < 0.0351) intake by 14.5 % under heat stress conditions. Additionally, heat stress reduced (P < 0.05) average total gain, feed efficiency, and feed consumption by 26.7, 24.7, and 15.9 % respectively. Furthermore, CrMet supplementation did not affect dressing percentage or percent yield of breast, thigh, and leg quarter. Supplementation of 800 µg Cr/kg increased (P < 0.0151) percentage of leg under thermoneutral conditions. While temperature had no effect on leg and thigh percentages, heat stress reduced (P < 0.0008) percentage of breast by 4.8 % and increased (P < 0.0211) percentage of leg quarter and dressing percent (P < 0.0098). Supplementation with CrMet had no impact on percent abdominal fat nor breast or leg quarter visible (subcutaneous plus intermuscular) fat. Percent ether extract of breast and thigh, as well as crude protein of breast, leg, and thigh were unaffected by CrMet supplementation. However, supplementation with 400 pg Cr/kg decreased (P < 0.0148) percent ether extract of the leg by 10 %. Heat stress increased (P < 0.05) percent abdominal fat and visible breast fat by 16 and 34.2 % respectively, as well as percent crude protein of leg by 3 %. In addition, percent ether extract of the breast and leg were reduced (P < 0.01) by 11.3 and 7.1 % respectively. Results indicate that heat stress alters serum and plasma metabolite concentrations, growth performance, as well as carcass yield and composition of broilers while dietary supplementation of CrMet was ineffective in negating the ill-effects of heat stress.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS