1642
Use of grouped samples of orts does not compromise feed intake data in studies of confined cattle
The orts in the feed bunk are commonly analyzed as composited samples, which are collected within periods of 7 or 28 days for each animal. In this context, the use of only one grouped sample of orts per animal for the entire experimental period may reduce the labor and costs of laboratorial analysis. Therefore, this study aimed to compare samples of orts collected weekly with a grouped sample collected within 12 weeks of feedlot. A total of 24 castrated cattle with average body weight of 397.3 kg were fed diets with 70:30 or 40:60 roughage:concentrate ratio using sugar cane as the only roughage source. Diets were provided, sampled and adjusted daily so the orts remained around 5% of the total offered. Orts were sampled daily and proportionally grouped weekly. Sample of orts were analyzed individually or as grouped samples, formed by grouping 12 weeks samples of the experiment according to the proportion of orts in the feed bunk. Comparisons of nutrient intake were evaluated using the linear regression model of the values observed for the two sampling methods and the simultaneous hypothesis were tested as it follows: Ho: β0=0 e β1=1. Sampling methods were considered similar when the null hypothesis was not rejected. All the statistical analysis was performed by using SAS and differences were considered at α = 0.05. The use of these diets allowed a great variation in the composition of orts where the levels of DM ranged from 25.06 to 82.21 %, CP ranged from 4.01 to 14.11 %, and NDF ranged from 32.52 to 77.06 %. Comparisons of the estimates of nutrient intake are presented in Table 1. In all cases, H0was not rejected (P > 0.05) which indicates that dry matter and nutrient intake does not vary comparing orts collected weekly of a composite sample of 12 weeks. We conclude that the use of a single sample of orts in the period of 12 weeks for each animal is viable and reduces the time and cost of chemical analyzes.
Table 01. Comparisons of estimates of nutrient intake (kg/day). |
||||
Treatment |
Intake |
Average |
max |
min |
Weekly |
DM |
8.85±1.84 |
12.58 |
5.87 |
OM1 |
8.42±1.74 |
11.95 |
5.60 |
|
CP |
1.11±0.23 |
1.57 |
0.73 |
|
NDF |
3.99±0.73 |
5.48 |
2.76 |
|
Grouped Samples |
DM |
8.84±1.84 |
12.46 |
5.85 |
OM |
8.41±1.74 |
11.84 |
5.58 |
|
CP |
1.10±0.22 |
1.56 |
0.73 |
|
NDF |
4.00±0.74 |
5.45 |
2.73 |
|
1Organic Matter
Keywords: Feedlot, Nutrient Intake, Orts