Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX 79409, USA.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad358.
Beef genetics are used with increasing frequency on commercial dairies. Although use of beef genetics improves calf value, variability has been reported in beef × dairy calf phenotype for traits related to muscularity and carcass composition. The objective of this study was to characterize morphometric and compositional differences between beef, beef × dairy, and dairy-fed cattle. Tested treatment groups included Angus-sired straightbred beef steers and heifers (A × B; n = 45), Angus × Holstein crossbreds (A × H; n = 15), Angus × Jersey crossbreds (A × J; n = 16), and straightbred Holsteins (H, n = 16). Cattle were started on trial at mean BW of 302 ± 29.9 kg and then fed at 196 ± 3.4 d. Morphometric measures were recorded every 28 d during the finishing period, ultrasound measures were recorded every 56 d, and morphometric carcass measures were recorded upon slaughter. Muscle biopsies were collected from the longissimus thoracis of a subset of steers (n = 43) every 56 d. Strip loins were collected from carcasses (n = 78) for further evaluation. Frame size measured as hip height, hip width, and body length was greatest for H cattle (P < 0.05), and A × H cattle had greater hip height than A × J cattle (P < 0.05). Relative to BW as a percentage of mature size, ribeye area of all cattle increased at a decreasing rate (negative quadratic term: P < 0.01), and all ultrasound measures of fat depots increased at an increasing rate (positive quadratic term: P < 0.01). Although no difference was observed in muscle fiber area across the finishing period from the longissimus thoracis (P = 0.80), H cattle had a more oxidative muscle phenotype than A × B cattle (P < 0.05). Additionally, H cattle had the smallest area of longissimus lumborum in the posterior strip loin, greatest length-to-width ratio of longissimus lumborum in the posterior strip loin, and least round circumference relative to round length (P < 0.05). Beef genetics improved muscularity in portions of the carcass distal to the longissimus thoracis.
商业奶牛场越来越频繁地使用牛肉基因。尽管使用牛肉基因可以提高小牛的价值，但已经有报道称，在与肌肉和体组成相关的性状方面，牛肉×奶牛小牛的表型存在变异性。本研究的目的是描述牛肉、牛肉×奶牛和奶牛饲养牛之间的形态和组成差异。测试的处理组包括安格斯种公牛纯牛肉阉牛和小母牛（A×B；n=45）、安格斯×荷斯坦杂交牛（A×H；n=15）、安格斯×泽西杂交牛（A×J；n=16）和纯荷斯坦牛（H，n=16）。牛在平均体重为 302±29.9kg 时开始试验，然后在 196±3.4d 时进行喂养。在育肥期的每 28d 记录形态测量值，每 56d 记录超声测量值，屠宰时记录形态学体腔测量值。每隔 56d 从一部分阉牛（n=43）的胸最长肌采集肌肉活检。从胴体（n=78）中收集里脊条进行进一步评估。髋高、髋宽和体长的框架大小以 H 牛最大（P<0.05），A×H 牛的髋高大于 A×J 牛（P<0.05）。与成熟大小的 BW 百分比相比，所有牛的眼肌面积都以递减的速度增加（负二次项：P<0.01），所有脂肪沉积的超声测量值都以递增的速度增加（正二次项：P<0.01）。虽然在胸最长肌的育肥期内没有观察到肌肉纤维面积的差异（P=0.80），但 H 牛的肌肉表型比 A×B 牛更具氧化性（P<0.05）。此外，H 牛在后里脊条中具有最小的腰最长肌面积、后里脊条中最长的腰最长肌长度与宽度比，以及相对于圆形长度的最小圆形周长（P<0.05）。牛肉基因改善了胸最长肌远端胴体部分的肌肉发达度。
