放养密度对旱地肉牛生长、生理反应和青春期发育的影响

IF 2.9 2区农林科学 Q1 AGRICULTURE, DAIRY & ANIMAL SCIENCE

Journal of animal science Pub Date : 2025-06-27 DOI:10.1093/jas/skaf170.125

Izadora de Souza, Reinaldo F Cooke, Camila Prado, Shea Mackey, Kelsey M Harvey

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引用次数: 0

摘要

本试验评估了在不同放养密度的旱地饲养的肉牛的生长、生理反应和青春期发育情况。试验选用120头小母牛（安格斯75%，婆罗门25%）。按年龄（267±2 d）和体重(d -5 BW；228±2 kg)，分配给a) 3个旱地栏（10 × 14 m栏）中的1个；10头母牛/栏)，放养密度为14 m2/头母牛（HDENS）； b) 3个旱地栏（10 × 28 m栏）中的1个；10头母牛/栏)，放养密度为28 m2/头母牛（MDENS）； c) 3个旱地栏（10 × 42 m栏）中的1个；10头小母牛/栏)，放养密度为42平方米/头小母牛（LDENS），或d) 3个牧场中的1个(1公顷牧场；10头母牛/牧场)，放养密度为1,000 m2/头母牛（CON）。CON的饲料可忽略不计，而所有处理的小母牛均饲喂相同的限饲饲粮（~7 kg/头，干物质基础）。在第5天和第171天分别取料取水16 h后，记录萎缩体重，计算平均日增重（ADG）。每周采集血样进行孕酮分析（d 0 ~ d 170）。每28 d （d 0 ~ 170）采集尾开关毛发样本。数据采用SAS （SAS institute . Inc., Cary， NC）的mix或GLIMMIX程序，以围栏或牧场为实验单元，通过方差分析进行分析。试验期间，HDENS、MDENS、LDENS和CON的平均日增重分别为0.582、0.576、0.548和0.567 kg/d，对犊牛日增重无显著影响（P = 0.53）；Sem = 0.024)。毛发皮质醇浓度较低(P <；与所有其他处理相比，CON在第170天(治疗×日相互作用；P = 0.03)。来自CON的小母牛作为一个更大的(P <；0.05)与其他各处理(处理×日互作，P <；0.01)。HDENS、MDENS和LDENS母牛的青春期发育程度相似（P≥0.48）。总的来说，该试验的结果表明，即使在较低的放养密度（即42平方米/头母牛）下，在旱地饲养的母牛与在牧场饲养的母牛相比，青春期发育仍然延迟。这项工作得到了美国农业部国家粮食和农业研究所（#2021-67015-34083）的支持。

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24 Effects of stocking density on growth, physiological responses, and puberty attainment of beef heifers reared in drylots

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 (P = 0.53) 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).

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来源期刊

Journal of animal science 农林科学-奶制品与动物科学

CiteScore

4.80

自引率

12.10%

发文量

1589

审稿时长

3 months

期刊介绍： The Journal of Animal Science (JAS) is the premier journal for animal science and serves as the leading source of new knowledge and perspective in this area. JAS publishes more than 500 fully reviewed research articles, invited reviews, technical notes, and letters to the editor each year. Articles published in JAS encompass a broad range of research topics in animal production and fundamental aspects of genetics, nutrition, physiology, and preparation and utilization of animal products. Articles typically report research with beef cattle, companion animals, goats, horses, pigs, and sheep; however, studies involving other farm animals, aquatic and wildlife species, and laboratory animal species that address fundamental questions related to livestock and companion animal biology will be considered for publication.