The rates of development of 2 tissues in mammary glands, parenchyma (PAR) and the mammary fat pad (MFP), in response to nutrition in early life might have a major bearing on lifetime milk production. Historical studies reported that feeding greater amounts of dietary nutrients from postweaning to puberty increased growth rates of heifers and stimulated the growth of MFP at the expense of PAR, which might suggest compromised mammary development and future milk production. The current study sought to determine if a higher volume of whole milk (8 vs. 4 L/d) offered to calves would increase rates of growth and development of PAR in mammary glands at weaning (1 to 12 wk). To measure these tissues, we developed 2 simple methods to assess the size of PAR and MFP at the time of screening using ultrasound. We report that calves offered 8 L/d of whole milk had greater rates of growth until weaning (0.86 ± 0.06 vs. 0.81 ± 0.09 kg/d), compared with calves offered 4 L/d. Ultrasonography showed that despite the faster rates of growth in calves offered 8 L/d of milk/d, the ratio of PAR:MFP depth was 40% less at weaning in the front glands (34%) compared with calves offered 4 L of milk/d. Rear glands were less impaired. The ultrasound methods developed here might be useful to monitor the development of mammary glands in response to different nutritional regimens during the preweaning period.

中文翻译：

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全脂奶摄入量对断奶后奶牛乳腺活体增重，薄壁组织和脂肪垫生长的影响。

乳腺中的2种组织，薄壁组织（PAR）和乳腺脂肪垫（MFP）的生长速率，是对早年营养的响应，可能对终生乳汁产生重要影响。历史研究报道，从断奶到青春期喂养更多的饮食营养素会增加小母牛的生长速度，并以PAR为代价刺激MFP的生长，这可能表明乳腺发育和未来的牛奶产量受到损害。当前的研究试图确定提供给犊牛的全脂牛奶量（8对4 L / d）是否会增加断奶（1至12周）时乳腺中PAR的生长发育速度。为了测量这些组织，我们开发了2种简单的方法来评估使用超声筛查时PAR和MFP的大小。我们报告说，与提供4 L / d的犊牛相比，提供8 L / d的全脂牛奶的犊牛在断奶前的生长率更高（0.86±0.06 vs. 0.81±0.09 kg / d）。超声检查显示，尽管犊牛提供8升/天的牛奶/天的生长速度更快，但与小牛提供4升牛奶的情况相比，前腺断奶时PAR：MFP的深度比（34％）少40％ / d。后腺受损较少。此处开发的超声方法可能有助于监测断奶前期对不同营养方案的乳腺发育情况。与犊牛每天提供4升牛奶相比，前腺断奶时的MFP深度降低了40％（34％）。后腺受损较少。此处开发的超声方法可能有助于监测断奶前对不同营养方案的乳腺发育情况。与犊牛每天提供4升牛奶相比，前腺断奶时的MFP深度降低了40％（34％）。后腺受损较少。此处开发的超声方法可能有助于监测断奶前对不同营养方案的乳腺发育情况。