Meeting Abstract

P3.147  Wednesday, Jan. 6  Intraspecific scaling of chewing cycle length and jaw-muscle activity in goats, alpacas and horses. STOVER, KK*; WILLIAMS, SH; College of Charleston; Ohio University kkstover@edisto.cofc.edu

Chewing cycle length (CCL) and frequency influence the rate of food processing and an animal’s ability to meet its metabolic requirements. Interspecific studies on the scaling of CCL in mammals have demonstrated an inverse relationship with body size. However, scaling exponents relating CCL to body mass (BM) or jaw length (JL) differ depending on the phylogeny, morphology and diet of the sample. Intraspecific studies controlling many of these variables are rare given the limited size range within a species. Here, we conduct an intraspecific study on the scaling of CCL and jaw-muscle activity in goats, alpacas and horses. Goats and alpacas comprised independent ontogenetic samples of pre-weaned infants to adults, while horses include only adults ranging from 140 to 794kg. CCL and jaw-muscle activity durations were determined from kinematic data or electromyographic recordings from the jaw adductors during rhythmic chewing. Reduced major axis regressions of log-transformed data revealed significant correlations between CCL and both BM and JL in goats and alpacas but not in horses. Slope estimates for the scaling of CCL with BM in goats and alpacas and horses are 0.35, 0.37, and 0.23, respectively. Slope estimates for the scaling of CCL with JL are higher, ranging from 0.79 (horses) to 1.61 (alpacas). In goats, but not alpacas or horses, jaw-muscle activity duration was also significantly and positively correlated with both BM (0.41) and JL (1.06). Within species, CCLs and jaw-muscle activity durations are influenced by changes in the biomechanics, function or neuromuscular control of the masticatory system. However, the lack of a correlation between CCL and size in the adult horses suggests that selective breeding may not result in concomitant changes in feeding mechanics.