Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, Canada.
Department of Large Animal Clinical Sciences, University of Saskatchewan, Saskatoon, SK, Canada.
J Anim Sci. 2019 Jul 2;97(7):3103-3119. doi: 10.1093/jas/skz171.
A 2-yr study was conducted to evaluate the effects of level and source of fat in the diet of gestating beef cows on their prepartum performance and birth weight of progeny. Each year, 75 multiparous (≥3 calving) pregnant Angus cows were stratified by BW (663 ± 21.5 kg) and BCS (2.6 ± 0.12; 1 to 5 scale) and randomly assigned to 1 of 15 outdoor pens. Subsequently, each pen was randomly assigned to 1 of 3 (n = 5) treatments: a low-fat diet (LF; 1.4 ± 0.12% EE) consisting of grass-legume hay, barley straw, and barley grain, or 1 of 2 high-fat diets (HF; 3.3 ± 0.20% EE) that included either a canola seed (CAN) or a flaxseed (FLX) based pelleted feed. Diets were formulated to meet the requirements of pregnant beef cows during the last 2 trimesters of gestation (0.183 ± 4.8 d), adjusted for changes in environmental conditions, and offered such that each pen on average received similar daily amounts of DE (31.2 ± 2.8 Mcal/cow), CP (1.36 ± 0.13 kg/cow), and DM (12.9 ± 1.0 kg/cow). Data were analyzed as a randomized complete block design with contrasts to separate the effects of level (LF vs. HF) and source (CAN vs. FLX) of fat. After 160 d on trial, conceptus corrected-BW (CC-BW) of LF cows (708 kg) and the proportion of overconditioned cows (13.2%) were greater (P ≤ 0.04) than those of HF, with no difference (P ≥ 0.84) between CAN and FLX for CC-BW (697 kg) and proportion of overconditioned cows (3.6% vs. 2.9%). Feeding FLX diet during gestation resulted in cows with a greater (P ≤ 0.01) concentration of conjugated linolenic acid (0.12% vs. 0.05%) and n-3 (0.58% vs. 0.37%) fatty acids, and a tendency (P = 0.09) for conjugated linoleic acid concentration (1.05% vs. 0.88%) to be greater in subcutaneous adipose tissue (SCAT) when compared with cows fed the CAN diet. By the end of gestation, serum NEFA concentration of LF cows (592 µEq/L) was lower (P < 0.01) than that of HF cows, and FLX cows had greater (P < 0.01) serum NEFA concentration than CAN cows (636 vs. 961 µEq/L). Cows receiving the LF diet during gestation gave birth to lighter (P < 0.01) calves compared with those receiving the HF diets (40.2 vs. 42.9 kg), with no difference (P = 0.24) between calves born to CAN (42.4 kg) and FLX (43.3 kg) cows. In conclusion, these results suggest a partitioning of the ME in pregnant beef cows that is dependent on the type of dietary energy, resulting in heavier calves at birth for cows fed high-fat diets. Also, the type of fatty acid in the diet of gestating beef cows affected the fatty acid profile in SCAT and serum NEFA concentration.
一项为期 2 年的研究旨在评估妊娠肉牛日粮中脂肪水平和来源对其产前性能和后代初生重的影响。每年，75 头经产（≥3 胎次）安格斯母牛按 BW（663±21.5kg）和 BCS（2.6±0.12；1 到 5 分制）进行分层，并随机分配到 15 个户外围栏中的 1 个。随后，每个围栏被随机分配到 3 个（n=5）处理之一：低脂肪饮食（LF；1.4±0.12% EE）由草豆科干草、大麦秸秆和大麦谷物组成，或 2 种高脂肪饮食（HF；3.3±0.20% EE）中的 1 种，包括基于油菜籽（CAN）或亚麻籽（FLX）的颗粒饲料。日粮的配制旨在满足妊娠肉牛在妊娠最后 2 个 trimester 的营养需求（0.183±4.8d），并根据环境条件的变化进行调整，以使每个围栏平均获得相似的每日 DE（31.2±2.8Mcals/cow）、CP（1.36±0.13kg/cow）和 DM（12.9±1.0kg/cow）摄入量。数据分析采用随机完全区组设计，进行对比以分离脂肪水平（LF 与 HF）和来源（CAN 与 FLX）的影响。试验进行 160d 后，LF 组母牛的校正胚重（CC-BW；708kg）和超重母牛的比例（13.2%）高于 HF 组（P≤0.04），而 CAN 和 FLX 之间 CC-BW（697kg）和超重母牛的比例（3.6% 与 2.9%）无差异（P≥0.84）。在妊娠期间饲喂 FLX 日粮导致母牛的共轭亚油酸（0.12% 与 0.05%）和 n-3（0.58% 与 0.37%）脂肪酸浓度更高，并且母牛的共轭亚油酸浓度（1.05% 与 0.88%）有增加的趋势（P=0.09），皮下脂肪组织（SCAT）中存在的共轭亚油酸浓度（P=0.09）高于饲喂 CAN 日粮的母牛。在妊娠结束时，LF 组母牛的血清 NEFA 浓度（592µEq/L）低于 HF 组（P<0.01），FLX 组母牛的血清 NEFA 浓度高于 CAN 组（P<0.01；636 与 961µEq/L）。在妊娠期间饲喂 LF 日粮的母牛所生的小牛体重较轻（P<0.01），低于饲喂 HF 日粮的母牛（40.2 与 42.9kg），而饲喂 CAN（42.4kg）和 FLX（43.3kg）日粮的母牛所生的小牛体重无差异（P=0.24）。总之，这些结果表明，妊娠肉牛对 ME 的分配取决于日粮能量的类型，从而导致饲喂高脂肪日粮的母牛所生的小牛初生重更大。此外，妊娠肉牛日粮中的脂肪酸类型影响 SCAT 和血清 NEFA 浓度中的脂肪酸谱。
