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Relationship of frame size and body measurements with feed efficiency traits in heifers
The objective was to examine the relationship between heifer size and feed efficiency. This project is a part of a multi-year study examining the effects of frame size on feed efficiency and longevity in cattle fed forage-based diets. Eighty-nine crossbred heifers (BW=342±3.4 kg) were sorted into groups based on frame score (small to moderate <5.5, average frame size =4.27±0.132, average BW=317±6.1 kg, n=49; moderate to large ≥5.5, average frame score=6.45±0.191, average BW=371±11.8, n=40). The heifers contained Angus, Red Angus, Gelbvieh, Hereford, Lowline, Shorthorn, and Simmental breeding. Heifers were fed over a 106-d feeding period. Feed intake was measured using the Insentec feeding system, which allows for the measurement of individual feed intake and feeding behavior in a group-fed situation. Body length, hip height, hip width, and heart, mid-, and flank girth were measured on the first and last d of the experiment. Body weight was measured on two consecutive days at the beginning and end and every 14 d of the experiment. Average daily gain, DMI, G:F, and residual feed intake (RFI) were analyzed using the Mixed procedure of SAS with fixed effects of frame score group (n=2), sire breed group (n=8), and age (350-406 days of age). Pearson correlation analysis was used to examine relationships between body measurements and growth performance traits. Average daily gain, G:F, and RFI were not influenced by frame score group (P= 0.28, 0.71 , and 0.85, respectively). Dry matter intake (% of BW) was greater (P<0.001) in small to moderate heifers vs. moderate to large heifers (2.29 vs. 1.92%, respectively). Average daily gain was negatively correlated (P=0.01; r=-0.26) with final hip height. Dry matter intake (% of BW) was negatively correlated (P≤0.007) with initial frame score (r = -0.65), and initial and final BW (r=-0.74 and -0.74),body length (r=-0.33 and-0.29) hip height (r=-0.65 and -0.61), hip width (r=-0.52 and -0.52), and heart (r=-0.69 and -0.65), mid- (r=-0.68 and -0.51), and flank girth (r=-0.58 and -0.46). Gain:feed and RFI were not correlated with body measurements. These data indicate that for this group of growing heifers fed a forage-based diet, heifers in the small to moderate frame size group had greater feed intake relative to BW which agreed with the correlation analysis suggesting a negative relationship between body size and relative DMI with less of an effect on ADG, G:F, and RFI. These findings will be validated in heifers from future years of the project.
Keywords:
body size, feed efficiency, heifer