Repeatability of residual feed intake and indices of body composition in growing Columbia ewes fed the same diet

Residual feed intake (RFI), an efficiency measurement based on the difference in expected feed intake for a given weight and growth rate and actual feed intake, is used to improve production efficiency of domestic ruminants. The purpose of this study was to evaluate the repeatability of RFI of sheep...

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Bibliographic Details
Published inJournal of animal science Vol. 94; pp. 373 - 374
Main Authors Perz, K A, Berardinelli, J G, Park, L N, Pollard, R K, Page, C M, Stewart, W C, Thomson, J M
Format Journal Article
LanguageEnglish
Published Champaign Oxford University Press 01.10.2016
Subjects
Alfalfa
Barley
Body composition
Classification
Data analysis
Data processing
Diet
Environmental changes
Environmental conditions
Feeds
Females
Growth rate
Mathematical analysis
Muscles
Proteins
Regression analysis
Reproducibility
Sheep
Studies
Ultrasound
Variance analysis
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Summary:Residual feed intake (RFI), an efficiency measurement based on the difference in expected feed intake for a given weight and growth rate and actual feed intake, is used to improve production efficiency of domestic ruminants. The purpose of this study was to evaluate the repeatability of RFI of sheep measured for two consecutive years and to investigate the relationship between indices of body composition and RFI in yearling ewes. Two trials, using the same Columbia ewe lambs (n = 17 per trial), were conducted in consecutive years. Ewes were individually fed for 47 and 45 d, respectively, beginning in September of each year. The diet, an alfalfa-barley pellet, was the same composition and batch for both years. Residual feed intake was calculated for each ewe in each year. Ewe was the experimental unit. Residual feed intake and performance data were analyzed using ANOVA. Residual feed intake did not differ (P > 0.05) between years, indicating that on the same diet and environmental conditions, RFI does not appear to change with age. Ewes were categorized into 3 RFI classes (efficient, average, and inefficient) based on RFI values 1 SD below and above the yearly average. In 2014, initial and final liveweights, ADG, and DMI did not differ due to RFI classification (P > 0.05). In 2015, DMI was greater for inefficient ewes (P < 0.05), but there was no difference in initial and final liveweights or ADG (P > 0.05). Ultrasound data were analyzed using ANOVA with repeated measures. Rib eye area (REA; cm2) and backfat thickness (BF; cm) were measured by ultrasound on Day 0, 17, and 45 in 2015. These variables were used to calculate estimates of final body composition: whole-body muscle mass, intramuscular fat, empty BW, empty BW DM, empty BW fat, empty BW protein, carcass weight, carcass weight DM, carcass weight fat, and carcass weight protein. Residual feed intake classification did not affect REA or BF (P > 0.05). Regression analysis indicated that both REA and BF increased (P < 0.05) from Day 0 to 17 and BF increased (P < 0.05) again from Day 17 to 45. No body composition estimates were affected by RFI classification (P < 0.05). Results suggest that RFI is repeatable; however, indices of body composition seem to be independent of RFI in Columbia ewes fed the same diet under similar conditions.
ISSN:0021-8812
1525-3163