Effect of dried distillers grains with solubles and dried citrus pulp supplementation on metabolic and reproductive parameters of Charolais beef cows grazing buffelgrass in Northeastern Mexico

Abstract Text: The objective of this study was to evaluate body weight, body condition and reproductive performance of Charolais beef cows (n=32) grazing buffelgrass (Cenchrus ciliaris L., 7.0% crude protein (CP) and 56.6% NDF) supplemented with two isocaloric agroindustrial byproducts. Cows were blocked by age, parity, body condition score (initial BCS was 4.75) and body weight, and randomly assigned to individually receive 1 kg/d of either dried distillers grains with solubles (DDGS; 30.3% CP, 2.65 Mcal ME/kg DM), or a 50:50 mixture of DDGS and dried citrus pulp (DDGS:DCP; 17.45% CP, 2.82 Mcal ME/kg DM) during a 30 d breeding period, applying the standard 9-d synchronization protocol utilizing a controlled internal drug-release (CIDR) device and an additional 8-d CIDR resynchronization beginning on the fifth day after artificial insemination. Body weight (BW), and body condition score (BCS) were registered, and blood samples were collected via coccygeal venipuncture on d 0, 9, 16, 24, and 30, and analyzed to determine Urea Nitrogen (BUN, colorimetrically), and plasma Progesterone (ELISA) using commercial kits. Estrus appearance was registered by visual observation, and pregnancy diagnosis was confirmed using transrectal ultrasonography. Data were analyzed using two-way ANOVA (for BW, BCS, BUN and Progesterone), and Chi-Square test (for reproductive traits). Cows receiving DDGS:DCP were heavier on d 16 (487 vs. 464 kg) and d 24 (500 vs. 485 kg, P < 0.05) than those supplemented with DDGS, whereas BCS (mean =5.0) was not different between treatments (P > 0.05). Cows supplemented with DDGS had increased (P = 0.01) BUN values on d 9 and 24 (12.8 vs. 8.3 and 11.3 vs. 9.4 mg/dL), compared to cows supplemented with DDGS:DCP. No differences were found between treatments in plasma progesterone concentrations (P > 0.05). Cows receiving DDGS:DCP presented 20 estrus, whereas cows receiving DDGS showed 13 estrus (P < 0.05). Differences in pregnancy rate (56.2% for DDGS:DCP; 68.7% for DDGS) were not significant (P > 0.05) between treatments. In summary, supplementing DDGS:DCP to Charolais beef cows grazing buffelgrass increased body weight and estrus appearance, but not BCS and pregnancy rate compared with DDGS supplementation.

Keywords: beef cows, dried citrus pulp, dried distillers grains with solubles