Lake S L, Weston T R, Scholljegerdes E J, Murrieta C M, Alexander B M, Rule D C, Moss G E, Hess B W
Department of Animal Science, University of Wyoming, Laramie, WY 82071-3684, USA.
J Anim Sci. 2007 Mar;85(3):717-30. doi: 10.2527/jas.2006-353. Epub 2006 Oct 23.
Two experiments were conducted with lactating Angus x Gelbvieh beef cows to determine the effects of postpartum lipid supplementation, BCS at parturition, and day of lactation on fatty acid profiles in plasma, adipose tissue, and milk. In Exp. 1, 36 pri-miparous cows (488 +/- 10 kg of initial BW; 5.5 +/- 0.02 initial BCS) were given ad libitum access to hay and assigned randomly to a low-fat (control) supplement or supplements with cracked, high-linoleate safflower seeds (linoleate) or cracked, high-oleate safflower seeds (oleate) from d 3 to 90 of lactation. Diets were formulated to be isonitrogenous and isocaloric; safflower seed diets provided 5% of DMI as fat. Plasma and milk samples were collected on d 30, 60, and 90 of lactation. Adipose tissue biopsies were collected near the tail-head region of cows on d 45 and 90 of lactation. In Exp. 2, 3-yr-old cows achieving a BCS of 4 +/- 0.07 (479 +/- 36 kg of BW) or 6 +/- 0.07 (580 +/- 53 kg of BW) at parturition were used in a 2-yr experiment (n = 36/yr). Beginning 3 d postpartum through d 61 of lactation, cows were fed diets similar to those of Exp. 1. Adipose tissue and milk samples were collected on d 30 and 60, and plasma was collected on d 31 and 61 of lactation. Responses to postpartum dietary treatment were comparable in both experiments. Cows fed linoleate and oleate had greater (P < 0.001) total fatty acid concentrations in plasma than cows fed control. Except for 15:1, milk fatty acids with <18 carbons were greatest (P < or = 0.01) for cows fed control, whereas milk from cows fed linoleate had the greatest (P < or = 0.02) 18:1trans-11, 18:2n-6, and cis-9, trans-11 CLA. Milk from cows fed oleate had the greatest (P < 0.001) 18:1cis-9. In Exp. 1, total fatty acid concentrations in adipose tissue samples decreased at d 90 compared with d 45 of lactation, but the fatty acid profile of cow adipose tissue was not affected (P = 0.14 to 0.80) by dietary treatment. In Exp. 2, the percentage of cis-9, trans-11 CLA in adipose tissue of cows with a BCS of 6 decreased (P = 0.001) from d 30 to 60 of lactation. Plasma and milk fatty acid composition reflected alterations in postpartum diet. Less medium-chain fatty acids and more 18-carbon fatty acids in milk were indicative of reduced de novo fatty acid synthesis in the mammary gland of beef cows fed lipid supplements; however, the metabolic demands of lactation prevented the deposition of exogenously derived fatty acids in adipose tissue through d 90 of lactation.
进行了两项试验，以确定产后补充脂肪、分娩时的体况评分（BCS）以及泌乳天数对泌乳期安格斯×吉尔维肉牛血浆、脂肪组织和乳中脂肪酸组成的影响。在试验1中，36头初产母牛（初始体重488±10 kg；初始BCS 5.5±0.02）自由采食干草，并随机分为低脂（对照）补充料组，或从泌乳第3天至第90天分别补饲破碎的高亚油酸红花籽（亚油酸组）或破碎的高油酸红花籽（油酸组）的补充料组。日粮配制为等氮等热；红花籽日粮提供占干物质采食量5%的脂肪。在泌乳第30天、60天和90天采集血浆和乳样。在泌乳第45天和90天，在母牛尾根区域附近采集脂肪组织活检样本。在试验2中，使用分娩时BCS为4±0.07（体重479±36 kg）或6±0.07（体重580±53 kg）的3岁母牛进行一项为期2年的试验（每年n = 36）。从产后第3天开始至泌乳第61天，给母牛饲喂与试验1相似的日粮。在泌乳第30天和60天采集脂肪组织和乳样，在泌乳第31天和61天采集血浆。两项试验中对产后日粮处理的反应具有可比性。与饲喂对照日粮的母牛相比，饲喂亚油酸和油酸的母牛血浆中总脂肪酸浓度更高（P < 0.001）。除了15:1外，饲喂对照日粮的母牛乳中碳链长度小于18的脂肪酸含量最高（P≤0.01），而饲喂亚油酸的母牛乳中18:1反-11、18:2n-6和顺-9，反-11共轭亚油酸（CLA）含量最高（P≤0.02）。饲喂油酸的母牛乳中18:1顺-9含量最高（P < 0.001）。在试验1中，与泌乳第45天相比，泌乳第90天脂肪组织样本中的总脂肪酸浓度下降，但日粮处理对母牛脂肪组织的脂肪酸组成没有影响（P = 0.14至0.80）。在试验2中，BCS为6的母牛脂肪组织中顺-9，反-11 CLA的百分比从泌乳第30天至第60天下降（P = 0.001）。血浆和乳脂肪酸组成反映了产后日粮的变化。乳中中链脂肪酸减少、18碳脂肪酸增多表明，饲喂脂肪补充料的肉牛乳腺中脂肪酸从头合成减少；然而，泌乳的代谢需求使得外源脂肪酸在泌乳第90天前无法在脂肪组织中沉积。
