Dairy cattle exposed to high ambient temperatures and humidity suffer heat stress, which may result in lower DM digestibility. Our objective was to evaluate the content of neutral detergent fiber (aNDFom), nitrogen (N), phosphorus (P), potassium (K), lignin and starch in the feces of slick-hair (SL) and wild-type (WT) lactating dairy cows under heat stress. SL (n = 8) and WT (n = 8) lactating cows with an average of 140 DIM, were in a feeding trial for 60 d during April and May of 2018 in a commercial dairy farm in southwestern Puerto Rico (18.027435, −67.094955). Average temperature-humidity index (THI) during the feeding trial was 75.8 ± 0.03. Animals were fed a totally mixed ration (TMR) based on Brachiaria spp. forage, soybean meal, steam flaked corn grain, brewer’s grains, and minerals. The DMI was recorded daily with Calan Feeding System and no differences in DMI in were documented between the genotypes (P = 0.72). For the fecal analysis TMR samples were collected from a.m. feedings on d 58 and 59. Fecal samples were collected from each cow intra-rectum at 0900 h and 1700 h on d 59 and 60. Fecal and TMR samples were analyzed by wet chemistry. On average the TMR contained 15% CP, 1.39 Mcal NE_L/kg, 18.7% starch, 4.8% lignin, 0.32% P, 1.17% K, and 36.7% aNDFom. All fecal components were similar between genotypes. Average fecal aNDFom % in SL cows was 42.7 ± 1.1 while WT cows average was 40.9 ± 1.1 (P = 0.235). Average fecal lignin % in SL cows was 4.29 ± 0.2, and 4.11 ± 0.2 in WT (P = 0.591). Average fecal K % was 0.723 ± 0.045 while WT cows average was 0.718 ± 0.042 (P = 0.93). Average fecal N was 2.12 ± 0.04 while WT cows average was 2.13 ± 0.036 (P = 0.8262). When evaluating P fecal concentration, SL cows had an average P of 0.66 ± 0.032 while WT cows average 0.597 ± 0.022 (P = 0.098). Average fecal starch % in SL cows was 9.09 ± 1.05, and 8.67 ± 0.98 in WT (P = 0.776). In this experiment, where SL and WT dairy cows were exposed to heat stress, we found no differences in their fecal content of aNDFom, N, P, K, lignin and starch.