Silva Tiago A C C, Quigley Simon P, Kidd Lisa J, Anderson Stephen T, McLennan Stuart R, Schatz Timothy J, McCosker Kieren D, Poppi Dennis P
School of Agriculture and Food Sciences, The University of Queensland, Gatton, Australia.
School of Veterinary Science, The University of Queensland, Gatton, Australia.
PLoS One. 2022 Feb 10;17(2):e0263786. doi: 10.1371/journal.pone.0263786. eCollection 2022.
This study investigated the effect of five post-weaning supplementation strategies and two weaning weight groups on long-term growth, puberty and pregnancy percentage of Brahman crossbred heifers. Early-weaned (118 ± 6 kg liveweight) and normally-weaned (183 ± 6 kg liveweight) heifers were allocated to group pens (n = 4 and n = 5/pen for early- and normally-weaned respectively) and offered one of five levels of post-weaning protein supplementation: 0, 1, 2.5, 5 and 10 g of supplement/kg liveweight.day with ad libitum access to a low quality sabi grass (Urochloa mosambicensis) hay during the first dry season (169 days) after weaning. After the post-weaning supplementation period, all heifers grazed the same pastures as a single mob until the end of the experiment and were exposed to fertile bulls from January to May 2016. During the first dry season, supplement intake had a positive linear effect on liveweight gain and hip width gain with no difference in the response between weaning groups. Overall, heifers with higher supplement intakes (i.e. 5 and 10 g/kg) had higher hip height gain (P < 0.005), hip width gain (P < 0.001), body condition score (P < 0.001), and concentration of insulin-like growth factor-1 (P = 0.001), triiodothyronine (P = 0.04) and insulin (P = 0.05) in plasma compared to unsupplemented heifers. These changes resulted in thicker proliferative and hypertrophic zones (both P = 0.03) of the tuber coxae growth plate, larger diameter of terminal hypertrophic chondrocytes (both P = 0.004) at the end of the post-weaning supplementation period when comparing the highest level of supplementation with unsupplemented group. Unsupplemented heifers from both weaning weight groups demonstrated compensatory liveweight gain over the first wet season while evidence of catch-up growth in skeletal dimensions was observed in the second wet season. The main determining factor for pregnancy status of two-year-old Brahman crossbred heifers was pre-mating liveweight (P < 0.001), the pre-mating liveweight was in turn affected by post-weaning supplementation (P = 0.02) or weaning weight group (P < 0.001). This study further demonstrated the positive relationship between premating weight and the occurrence of pregnancy, with an approximate 300 kg pre-mating liveweight required to achieve approximately 80% (67.1-90.3% for a 95% confidence interval) probability of pregnancy in two-year-old Brahman crossbred heifers mated for 4 months.
本研究调查了五种断奶后补饲策略和两个断奶体重组对婆罗门杂交小母牛长期生长、青春期及妊娠率的影响。将早期断奶（体重118±6千克）和正常断奶（体重183±6千克）的小母牛分配到组栏中（早期断奶和正常断奶的小母牛每组分别为4头和5头/栏），并给予五种断奶后蛋白质补饲水平之一：0、1、2.5、5和10克补饲物/千克体重·天，在断奶后的第一个旱季（169天）自由采食低质量的萨比草（莫桑比克罗非草）干草。断奶后补饲期结束后，所有小母牛作为一个群体在相同牧场放牧直至试验结束，并在2016年1月至5月期间与可育公牛接触。在第一个旱季，补饲摄入量对体重增加和髋宽增加有正线性影响，断奶组之间的反应无差异。总体而言，补饲摄入量较高（即5和10克/千克）的小母牛与未补饲的小母牛相比，髋高增加更多（P<0.005）、髋宽增加更多（P<0.001）、体况评分更高（P<0.001），血浆中胰岛素样生长因子-1（P=0.001）、三碘甲状腺原氨酸（P=0.04）和胰岛素（P=0.05）浓度更高。与未补饲组相比，在断奶后补饲期结束时，将最高补饲水平与之比较，这些变化导致髋结节生长板的增殖区和肥大区更厚（均P=0.03），终末肥大软骨细胞直径更大（均P=0.004）。两个断奶体重组中未补饲的小母牛在第一个雨季均表现出补偿性体重增加，而在第二个雨季观察到骨骼尺寸有追赶生长的迹象。两岁婆罗门杂交小母牛妊娠状态的主要决定因素是配种前体重（P<0.001），配种前体重又受断奶后补饲（P=0.02）或断奶体重组（P<0.001）的影响。本研究进一步证明了配种前体重与妊娠发生之间的正相关关系，对于两岁婆罗门杂交小母牛配种4个月，要达到约80%（95%置信区间为67.1-90.3%）的妊娠概率，配种前体重约需300千克。
