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PSXI-13 Effects of stocking density on growth, physiological responses, and puberty attainment of beef heifers reared in drylots.

Year: 2025
Type: conference-abstract
Abstract: This experiment evaluated growth, physiological responses, and puberty attainment in beef heifers reared in drylots with different stocking density. A total of 120 heifers (75% Angus ´ 25% Brahman) were used in this experiment. Heifers were ranked by age (267 ± 2 d) and body weight (BW on d -5; 228 ± 2 kg) on d 0, and assigned to a) 1 of 3 drylot pens (10 × 14 m pens; 10 heifers/pen) with a stocking density of 14 m2/heifer (HDENS), b) 1 of 3 drylot pens (10 × 28 m pens; 10 heifers/pen) with a stocking density of 28 m2/heifer (MDENS), c) 1 of 3 drylot pens (10 × 42 m pens; 10 heifers/pen) with a stocking density of 42 m2/heifer (LDENS), or d) 1 of 3 pastures (1-ha pastures; 10 heifers/pasture) with a stocking density of 1,000 m2/heifer (CON). Negligible forage was available for CON, whereas heifers from all treatments received the same limit-fed diet (~7 kg/heifer daily, dry matter basis). Shrunk BW was recorded after 16 h of feed and water withdrawal on d -5 and 171 to calculate average daily gain (ADG). Blood samples were collected weekly for progesterone analysis (d 0 to 170). Hair samples from the tail switch were collected every 28 d (d 0 to 170). Data were analyzed with pen or pasture as experimental unit, via ANOVA using the MIXED or GLIMMIX procedures of SAS (SAS Inst. Inc., Cary, NC). No treatment effects were detected for heifer ADG during the experiment (0.582, 0.576, 0.548, and 0.567 kg/d for HDENS, MDENS, LDENS, and CON, respectively; SEM = 0.024). Hair cortisol concentrations were less (P < 0.05) for CON compared to all other treatments on d 170 (treatment × day interaction; P = 0.03). Heifers from CON experienced hastened puberty attainment as a greater (P < 0.05) proportion of CON heifers were pubertal beginning on d 120 compared with all other treatments (treatment × day interaction, P < 0.01). Puberty attainment was similar among HDENS, MDENS, and LDENS heifers (P ≥ 0.48). Collectively, results from this experiment demonstrate that heifers reared in drylots, even at lower stocking densities (i.e. 42 m2/heifer) still experience delayed puberty attainment compared with heifers reared on pasture. This work is supported by the USDA National Institute of Food and Agriculture (#2021-67015-34083).
DOI: 10.1093/jas/skaf300.648
Authors: Camila Prado, Reinaldo F Cooke, Izadora de Souza, Shea Mackey, Kelsey M Harvey
Language: English
Open Access status: bronze
OpenAlex ID: W4414831129
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