Hotovy S K, Johnson K A, Johnson D E, Carstens G E, Bourdon R M, Seidel G E
Dept. of Anim. Sci., Colorado State University, Fort Collins 80523.
J Anim Sci. 1991 Mar;69(3):940-6. doi: 10.2527/1991.693940x.
The genetic variation in energy expenditures of cattle at fasting (FHP) and maintenance (MEm) was determined by using 12 pairs of monozygous twins at 20 mo of age. The pairs were of two breed types, eight Angus x Hereford (three steers, five heifers) and four Barzona x Hereford (three steers, one heifer). The heifers were 132 +/- 13 d pregnant at the time of measurement. The pairs were fed at 1.15 x maintenance energy requirements for a minimum of 30 d prior to heat production (HP) measurements in dual indirect respiration calorimetry chambers. The diet fed was cracked corn:alfalfa hay (45:55) with a determined ME of 2.47 +/- .02 Mcal/kg DM. This diet was fed individually for 7 d prior to and during two consecutive 22-h HP measurements. The animals then were fasted for 2 d and fasting heat production measurements (FHP) were made on d 3 and 4 of the fast. Metabolizable energy required for MEm was calculated iteratively by assuming a semi-log relationship between HP and metabolizable energy intake. There were no differences (P greater than .10) in measured energy expenditures due to different breed type. The FHP and efficiency of ME use for MEm (Km) were similar between sexes, although heifers had lower (P less than .025) MEm than steers. Twin pair effects were detected for FHP (P less than .005) and MEm (P less than .05) but not for Km. Broad sense heritability estimates were calculated as the intraclass correlation between members of monozygous twin pairs. Heritability estimates for MEm, FHP, and Km were .52 +/- .22, .75 +/- .13, and .34 +/- .27, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
通过使用12对20月龄的单卵双胞胎牛来测定禁食（FHP）和维持（MEm）时牛能量消耗的遗传变异。这些双胞胎牛有两种品种类型，8对安格斯×赫里福德（3头公牛，5头母牛）和4对巴佐纳×赫里福德（3头公牛，1头母牛）。测量时，母牛已怀孕132±13天。在双间接呼吸测热室进行产热（HP）测量之前，这些双胞胎牛以维持能量需求的1.15倍进食至少30天。所喂日粮为碎玉米：苜蓿干草（45:55），测定的代谢能为2.47±0.02Mcal/kg干物质。在连续两次22小时的HP测量之前和期间，这种日粮单独饲喂7天。然后动物禁食2天，并在禁食的第3天和第4天进行禁食产热测量（FHP）。通过假设HP与代谢能摄入量之间的半对数关系，迭代计算MEm所需的代谢能。由于品种类型不同，实测能量消耗没有差异（P＞0.10）。尽管母牛的MEm低于公牛（P＜0.025），但FHP以及MEm的代谢能利用效率（Km）在性别之间相似。检测到双胞胎对FHP（P＜0.005）和MEm（P＜0.05）有影响，但对Km没有影响。广义遗传力估计值通过单卵双胞胎对成员之间的组内相关性计算得出。MEm、FHP和Km的遗传力估计值分别为0.52±0.22、0.75±0.13和0.34±0.27。（摘要截断于250字）
