## Abstract

The appreciation of adipose tissue complexity has initiated a new era of multifaceted investigations that continue to provide findings in adipocyte biology, but quantitative descriptions of adipocyte distribution are lacking. The first objective was to develop a finite mixture model to model adipocyte bimodal distribution and to correlate these estimates with carcass and meat characteristics. A secondary objective was to demonstrate within-animal observed variability in adipocyte cellularity. Steers were finished on a high-grain diet (n = 14) or grass (n = 16). One 12-cm thick LM steak from each steer was collected during harvest. A probability density function was developed that partitioned the cell diameter population into small and large populations and described the relative proportions of cells for each animal in these 2 distinct populations. Five parameters were estimated through the finite mixture model: the means (μ_{1} and μ_{2}) and SD (σ_{1} and σ_{2}) for the small and large adipocyte populations, respectively, and a proportion parameter (p) describing the proportion of the distribution of the smaller adipocyte populations. The proportion parameter for all animals tended to be different (P = 0.07) between groups with the grain presenting a p of 22.5 ± 12.5% and grass 16.2 ± 4.7%. The μ_{2} was correlated with yield grade (YG, P = 0.04), and σ_{2} with final BW, HCW, dressing percentage, YG, and quality grade score (P = 0.01). When correlating these parameters with the sensory data, μ_{2} and σ_{2} were correlated with tenderness (P ≤ 0.05), σ_{1} and p with juiciness (P ≤ 0.05), and p with overall palatability (P = 0.01). Adipocyte cellularity variability was measured by examining the results from 5 randomly chosen steers from each group (grain and grass). In this subset, the μ_{1} and p ranged from 32.1 to 46.1 μm and 1 to 27% for grass-finished steers, and ranged from 33.7 to 41.0 μm and 10 to 48% for grain-finished steers. The μ_{2} and (1 p) ranged from 75.0 to 105.1 μm and 73 to 99% for grass-finished steers, respectively, and ranged from 84.8 to 124.0 μm and 52 to 90% for grain-finished steers, respectively. The finite mixture model provides a quantitative description of the distribution of adipocytes and contributes to explaining adipocyte biology. Adipocyte cellularity variability among samples within an animal is a topic that should be further evaluated, as well as its correlation with other factors, such as gene expression and hormone secretion.

Original language | English (US) |
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Pages (from-to) | 2995-3002 |

Number of pages | 8 |

Journal | Journal of Animal Science |

Volume | 90 |

Issue number | 9 |

DOIs | |

State | Published - Sep 2012 |

## Keywords

- Adipocyte cellularity
- Adipocyte distribution
- Beef cattle
- Finite mixture model

## ASJC Scopus subject areas

- Animal Science and Zoology
- Food Science
- Genetics