Rius A G, Dahl G E
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
J Dairy Sci. 2006 Jun;89(6):2080-3. doi: 10.3168/jds.S0022-0302(06)72277-9.
Exposure to a long-day photoperiod (LDPP) increases mammary and lean growth in heifers relative to a short day (SDPP). Whether these effects influence milk yield, however, is unknown. To test the hypothesis that pre-pubertal long-day exposure would increase milk production, we assigned prepubertal heifers to LDPP (16 h of light:8 h of dark; n = 16) or SDPP (8 h of light:16 h of dark; n = 16) until the onset of puberty. At puberty, heifers were commingled and housed under natural photoperiodic conditions and standard nutritional management for dairy heifers. Heifers were bred according to body weight (BW = 385 kg) and withers height (WH = 132 cm). At parturition, BW, WH, and hip height were evaluated. Analysis of Dairy Herd Improvement Association records was used to evaluate milk yield, milk components, and somatic cell scores. Relative to SDPP (n = 12), heifers on LDPP (n = 10) had greater WH (by 2.4 cm) and BW at calving (by 55 kg). Compared with heifers housed under SDPP, LDPP heifers tended to produce more milk (750 kg of 305-d projected fat-corrected milk) during the first lactation. Relative to SDPP, prepubertal heifers exposed to LDPP during the prepubertal growth phase were taller and heavier at parturition, and tended to produce more milk during their first lactation.
与短日照（SDPP）相比，暴露于长日照光周期（LDPP）会增加小母牛的乳腺和瘦肉生长。然而，这些影响是否会影响产奶量尚不清楚。为了验证青春期前暴露于长日照会增加产奶量这一假设，我们将青春期前的小母牛分为长日照组（光照16小时：黑暗8小时；n = 16）或短日照组（光照8小时：黑暗16小时；n = 16），直至青春期开始。在青春期时，将小母牛混合饲养，并置于自然光照周期条件下，并按照奶牛小母牛的标准营养管理方式进行饲养。根据体重（BW = 385 kg）和鬐甲高度（WH = 132 cm）对小母牛进行配种。在分娩时，评估体重、鬐甲高度和臀高。利用奶牛改良协会的记录分析来评估产奶量、牛奶成分和体细胞评分。与短日照组（n = 12）相比，长日照组（n = 10）的小母牛在产犊时鬐甲高度更高（高2.4 cm），体重更重（重55 kg）。与饲养在短日照条件下的小母牛相比，长日照组小母牛在第一个泌乳期的产奶量往往更高（305天预计脂肪校正奶产量为750 kg）。相对于短日照组，在青春期前生长阶段暴露于长日照的青春期前小母牛在分娩时更高、更重，并且在第一个泌乳期的产奶量往往更高。
