Feed efficiency differences and reranking in beef steers fed grower and finisher diets1

Abstract

This 3-yr study used 490 steers to determine whether feedlot steers changed their feed efficiency (FE) ranking when fed a grower diet, then a finisher diet. The steers were crossbreds and were between 5 to 7 mo of age. There were 2 feeding periods each year. Within each year, approximately 90 steers had their diet switched from a grower to a finisher diet (feed-swap group), whereas another 90 steers were fed either the grower (grower-fed group) or the finisher (finisher-fed group) diet throughout the feeding trial. Each feeding test lasted for a minimum of 10 wk, and all steers were fed ad libitum. Individual animal feed intakes were collected using the GrowSafe feeding system, and BW were measured every 2 wk. Residual feed intake (RFI), G:F, and Kleiber ratio (KR) were computed at the end of each feeding period. For each measure of efficiency, animals were classified as low, medium, or high based on 0.5 SD from the mean. The majority of steers did not maintain the previous efficiency class in the second period. Approximately 58, 51, and 51% of steers in the feed-swap group, finisher-fed group, and the grower-fed group, respectively, changed their RFI measure by 0.5 SD. A low rank correlation occurred in all test groups but was less in the feed-swap group. Spearman rank correlations between the 2 feeding periods in the feed-swap group were 0.33, 0.20, and 0.31 for RFI, G:F, and KR, respectively. Classifications based on G:F and KR showed that a greater number of steers (P < 0.05) in the feed-swap group did not maintain their FE class from 1 feeding regimen to the other, whereas classification based on RFI did not show any difference (P> 0.05) between the proportions of individuals that changed or maintained their FE class. In the groups without a feed-swap, there was no difference (P > 0.05) in the proportion of steers that changed or maintained the same FE class for all FE measures. Our results suggest that diet type and feeding period affect the FE ranking in beef steers. A feedlot diet is ideal for evaluating the FE potential of steers for feedlot profitability; however, we suggest that tests involving less dense diets should be examined in an effort to understand the relationships between FE and feeder profitability.

Effect of post-weaning residual feed intake classification on grazed grass intake and performance in pregnant beef heifers

“…However, a higher correlation was observed in 2012 (r p 00.55, P 00.02) than 2013 (r p 00.13, P 0 0.51) indicating re-ranking for the trait when growing heifers were fed a high-forage diet under drylot conditions compared with pregnant heifers during summer grazing. Similar re-ranking has been observed by Kelly et al (2010a,b) and Durunna et al (2011) for heifers and steers on high-forage grower diets and higher-grain finishing diets. Few studies have reported the effect of post-weaning RFI classification in heifers on grazed forage intake in first-and higher parity cows.…”

Residual Feed Intake, Digestibility of Nutrients and Efficiency of Water Utilizations in Murrah Buffalo Heifers

“…It is important to realize that RFI value of a given livestock is not as such a fixed value, and could vary depending upon models used and precision of data collection. Supporting evidence have been reported earlier [12] where more than half steers tested changed their RFI estimate by more than 0.5 standard deviations or 0.20 kg DM/d when measured on grower and finisher diets sequentially.…”

Grazed grass herbage intake and performance of beef heifers with predetermined phenotypic residual feed intake classification

“…of RFI (range of 0.71 to 0.97 v. 0.61 to 0.88) compared with those using high-energy grain-based diets (Nkrumah et al, 2007;Lancaster et al, 2008 and2009b). However, Durunna et al (2011) found that the s.d. of RFI measured in the same cohort of steers fed a low-energy diet during the growing phase was lower than when RFI was measured using a high-energy diet during the finishing phase.…”

“…In beef heifers, Kelly et al (2010b) estimated a moderate to high repeatability for RFI (r 5 0.62), calculated during growing and finishing periods when fed the same diet, indoors. Second, differences in the diets employed between the two measurement periods, that is, ensiled grass herbage plus supplementary concentrates v. grazed grass herbage, may be a factor as feed efficiency ranking can be affected by diet type (Durunna et al, 2011). In steers, Clarke et al (2009) reported a correlation of 0.30 between intake of grazed herbage determined using n-alkanes and subsequent individual intake of grass silage (weighed in and out) following housing 3 months later.…”