Department of Agriculture and Fisheries, Charters Towers, Queensland, Australia.
Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Gatton, Queensland, Australia.
Reprod Domest Anim. 2022 Oct;57(10):1176-1186. doi: 10.1111/rda.14188. Epub 2022 Aug 2.
Beef-calf mortality rates across tropical and subtropical Australia are high, with sub-optimal nutrition in pregnant cows being the primary risk. The nutritional deficiencies associated with calf mortality are the same as those associated with reduced milk yields. Although the highest mortality risk occurs during neonatal life, the role of inadequate milk delivery to beef neonates is not well established. This study investigated the frequency of low milk delivery in tropically adapted neonatal calves and the time for their dams to initiate full lactation in five management groups of Brahman and Droughtmaster calving cows in the dry tropics of northern Queensland, Australia. Change in calf weight in the days following birth was the primary measure of milk uptake. Plasma globulin concentration was used to indicate colostrum uptake. Across management groups, data were available on 250 calves for regression analysis of average daily gain vs. globulin and on 78 for plotting calf growth profiles. Calves had one of two growth profiles, either with immediate high growth from birth (day one) or with high growth delayed until day three. The frequency of delayed growth calves (with inadequate milk intake to gain at least 0.5 kg by day three after birth) was on average 30% across management groups, with management groups ranging 25%-50%. The frequency of calves growing ≤0.2 kg/day to day three was 15%-37%, depending on management group. The frequency of calves growing ≤0.2 kg/day to day five was 7%-20%, depending on management group. Calf globulin explained only 25% of the variation in calf average daily gain. Our study shows that a third of tropically adapted calves may experience a three-day delay to initiation of full lactation by their dams. Although study conditions were relatively benign, any additional risks with milk delivery, such as those that occur widely in tropical and subtropical northern Australia, would place such calves at risk of dehydration and mortality. Calf plasma globulin should not be used as a standalone measure of adequacy of neonatal milk delivery, especially when comparing across herds. This study demonstrates a fundamental problem of high frequency in northern Australia. The underlying risks for delayed milk delivery should be considered in the quest for practical solutions to reduce tropically adapted beef-calf mortalities.
澳大利亚热带和亚热带的肉牛犊死亡率很高，怀孕母牛的营养状况不佳是主要风险。与产奶量减少相关的营养缺乏与降低牛奶产量相关的营养缺乏相同。尽管最高的死亡风险发生在新生儿期，但向肉牛新生儿提供不足的牛奶量的作用尚未得到充分确立。本研究调查了澳大利亚北部热带干旱地区五个婆罗门牛和抗旱牛分娩牛群管理组中热带适应型新生牛犊牛奶供应量不足的频率，以及它们的母牛开始完全泌乳的时间。出生后几天内犊牛体重的变化是牛奶吸收的主要衡量标准。血浆球蛋白浓度用于表示初乳吸收情况。在管理组中，有 250 头小牛的数据可用于回归分析平均日增重与球蛋白的关系，有 78 头小牛的数据可用于绘制小牛生长曲线。小牛有两种生长曲线之一，要么出生后立即高生长（第 1 天），要么高生长延迟到第 3 天。在所有管理组中，生长迟缓小牛（出生后第 3 天至少摄入不足 0.5 公斤牛奶）的比例平均为 30%，管理组的比例范围为 25%-50%。出生后第 3 天生长速度小于等于 0.2 公斤/天的小牛比例为 15%-37%，具体取决于管理组。出生后第 5 天生长速度小于等于 0.2 公斤/天的小牛比例为 7%-20%，具体取决于管理组。小牛球蛋白仅解释了小牛平均日增重变化的 25%。我们的研究表明，三分之一的热带适应型小牛可能会经历其母牛完全泌乳的三天延迟。尽管研究条件相对温和，但任何与牛奶供应相关的额外风险，例如在澳大利亚热带和亚热带北部广泛存在的风险，都会使这些小牛面临脱水和死亡的风险。小牛血浆球蛋白不应单独用作衡量新生儿牛奶供应充足性的指标，特别是在比较不同牛群时。本研究证明了在澳大利亚北部普遍存在的一个高频率的基本问题。在寻求减少热带适应型肉牛犊死亡率的实用解决方案时，应考虑延迟牛奶供应的潜在风险。
