Browsing by Author "Barrett, Nathaniel W."

Now showing 1 - 3 of 3
  • Thumbnail Image
    The Acute and Chronic Effects of a Cyclic Heat Stress on 24 to 28 Week Old Laying Hens on Performance, Egg Quality, Apparent Metabolizable Energy, and Blood Chemistry
    Barrett, Nathaniel W. (Virginia Tech, 2016-11-02)
    Commercial laying hens are heavily selected for increased egg production, but little selection has occurred for resistance to extreme temperatures. The objective of the experiment was to determine the effects of a daily cyclic heat stress (HS) on performance, body temperature, egg quality, nitrogen corrected apparent metabolizable energy, and blood chemistry in laying hens at acute and chronic time points. In total, 407 pure line laying hen pullets (18 wk) were sourced from Hy-Line International and housed individually for the duration of the experiment. Feed intake, egg production, and body weights were significantly decreased while egg weight and feed efficiency increased due to HS exposure. All egg quality parameters except yolk weight were decreased by HS exposure, including Haugh unit, eggshell and albumen weights. Egg yolk weights were increased over the first 2 wk of HS before falling. Blood chemistry was affected by HS resulting in respiratory alkalosis likely caused by increased respiration and evaporative cooling. There was a decrease in the PCO2, an increase in pH and a reduction in iCa in the blood within 4 to 6 hours of HS when compared to pre-HS levels. The data indicate that the hens were negatively affected by HS and the response was different for acute and chronic time points. At the acute time point the changes to the hen's physiology were caused by altered blood chemistry, but after chronic exposure, the low feed intake seemed to influence the responses.
  • Thumbnail Image
    Combination of probiotics and coccidiosis vaccine enhances protection against an Eimeria challenge
    Ritzi, Miranda M.; Abdelrahman, Wael; van-Heerden, Kobus; Mohnl, Michaela; Barrett, Nathaniel W.; Dalloul, Rami A. (BMC, 2016-11-08)
    Coccidiosis is endemic in the commercial broiler industry capable of inflicting devastating economic losses to poultry operations. Vaccines are relatively effective in controlling the disease; their efficacy could potentially be improved with concurrent use of probiotics as evaluated in this study using an Eimeria challenge. Day of hatch 400 Cobb-500 male broilers were assigned to one of four treatment groups including control (CON), vaccine-only gel application (VNC), probiotic-only gel application (NPC), and vaccine-plus-probiotic gel application (VPC). Birds were placed in floor pens (6 replicate pens/treatment, 16–17 birds/pen). NPC and VPC birds received the probiotics in the water on days 2–4, 8, 14–20, 22, 29, and 34–36. On day 15, birds were mildly challenged with 0.5 mL of a mixed oral inoculum of Eimeria sp. prepared with the coccidiosis vaccine at 10× the vaccination dose. Performance measurements were recorded on first day and weekly afterwards, and lesion scores were evaluated 6 days post-challenge. Overall, the probiotics and coccidiosis vaccine resulted in an enhanced protective effect against the challenge, with VPC birds exhibiting lower lesion scores in the duodenum than VNC or NPC birds. Birds in the VPC treatment also demonstrated higher weight gains during days 1–15, days 7–15, and days 21–28 when compared to the VNC birds. These results suggest that the combination of probiotics and coccidiosis vaccines could enhance performance and provide an additional protective effect against a mixed Eimeria challenge.
  • Thumbnail Image
    Effect of various concentration of butyric acid on growth performance, intestinal lesion scores, and body composition of broilers raised on used litter
    Sizmaz, Ozge O.; Barrett, Nathaniel W.; Lewis, James; Yakout, Hathum; Persia, Michael E. (2022-12-01)
    There is still a need for the evaluation of alternative feed additives, including organic acids such as butyric acid, when fed in broiler diets without antibiotic growth promoters. The removal or limitation of growth promoting antibiotics from commercial production changes the opportunities for feed additives in the poultry industry and allows for the evaluation of replacement feed additives that may not have been cost effective when growth promoting antibiotics are available. Therefore, an experiment was conducted to evaluate the effects of various concentrations (200 ppm, 400 ppm, and 800 ppm) of coated butyric acid on growth performance, intestinal lesion score, and body composition of 42-day-old broilers raised on used litter. The addition of the coated butyric acid at 400 ppm and 800 ppm increased BW and 800 ppm improved mortality corrected feed conversion ratio (FCRm) over the 42-d period compared with the negative control (NC) fed broilers. Although performance was improved, the ratio of lean mass to fatty mass in the broilers was unchanged suggesting a generalize growth response. No significant differences were observed in lesion scores in the duodenum and jejunum and overall lesion scores were low. Both 400 and 800 ppm of butyric acid were able to increase 42-d broiler body weight in comparison to the NC fed birds, but 800 ppm of butyric acid was required to also improve the FCRm in comparison to the NC fed birds.