Centro Universitario de la Región Este, Universidad de la República, Rocha, Rocha, Uruguay.
Department of Pastures and Animal Production, Facultad de Agronomía, Universidad de la República, Bañado de Medina, Cerro Largo, Uruguay.
J Anim Sci. 2021 Oct 1;99(10). doi: 10.1093/jas/skab279.
The beef sector in Campos grasslands must increase animal productivity without external inputs, while reducing environmental impact. The objective of this study was to estimate herbage intake (g/metabolic body weight [MBW]/d) of straightbred (Hereford/Angus) and crossbred (F1 of Hereford × Angus) beef cows grazing subtropical native grassland with High and Low herbage allowance (HA, 5 vs. 3 kg DM/kg bodyweight [BW]) during gestation and lactation and its relationship with biological efficiency of cow-calf productivity. Herbage intake (estimated via n-alkanes C32:C33 ratio) was measured during early (Ge1, -163 d prior calving) and mid to late [Gm1 (-83) and Gm2 (-90 d prior calving)] gestation and lactation (L0, L1, and L2, 60, 47, and 31d following calving) periods in 24 to 36 cows, selected to create 8 groups (4 per block) of HA × cow genotype treatment. Cows grazed native grassland year-round, under High and Low HA (except in winter). We analyzed the effect of cow genotype (straightbred vs. crossbred cows) and HA (High vs. Low) on herbage mass and height, daily herbage intake rate (DMI), cow body condition score (BCS), calf average daily gain (ADG) and BW at weaning (BWW) and g of calf weaned/kg DMI. High allowance improved DMI during lactation periods (High 115.6 vs. Low 94.1 ± 5.3; P < 0.05 g/MBW/d). Crossbred cows decreased DMI during gestation (Crossbred 81 vs. Straightbred 94 ± 4.3; P = 0.05 g/MBW/d) compared with straightbred cows. Crossbred and High HA improved biological efficiency, 40.0 vs. 26.2 and 36.0 vs. 29.7 g of calf/kg DMI, respectively. High allowance increased herbage mass and sites with greater canopy height that allow greater DMI, positively associated with cow BCS at weaning, calf ADG, BWW, and g of calf/kg DMI. Crossbred cows reduced DMI during gestation showing no greater annual DMI. Animal productivity and biological efficiency can be improved using High HA and crossbred cows, which should decrease the environmental impact of cow-calf systems.
在不依赖外部投入的情况下，坎波斯草原的肉牛产业必须提高动物生产力，同时减少对环境的影响。本研究的目的是估计妊娠和哺乳期（G1 期，产犊前-163 天；Gm1 期和 Gm2 期，产犊前-83 天和-90 天）放牧亚热带本地草地的纯种（海弗 × 安格斯）和杂交（海弗 × 安格斯杂交一代）肉牛的牧草采食量（g/代谢体重[MBW]/d），并研究其与母牛-犊牛生产效率的生物学效率的关系。在 24 到 36 头奶牛中测量了牧草采食量（通过 n-烷烃 C32:C33 比值估计），这些奶牛被选择来创建 8 个组（每组 4 个）高（HA，5 公斤 DM/kg 体重[BW]）和低（HA，3 公斤 DM/kg 体重[BW]）牧草允许量（HA）×母牛基因型处理。奶牛全年在高和低 HA 下（除冬季外）在本地草地上放牧。我们分析了母牛基因型（纯种和杂交牛）和 HA（高和低）对牧草质量和高度、每日牧草采食量（DMI）、母牛体况评分（BCS）、犊牛平均日增重（ADG）和断奶体重（BWW）以及断奶时每公斤 DMI 的犊牛体重的影响。高允许量提高了哺乳期的 DMI（高 115.6 比低 94.1 ± 5.3；P<0.05 g/MBW/d）。与纯种牛相比，杂交牛在妊娠期间减少了 DMI（杂交牛 81 比纯种牛 94 ± 4.3；P=0.05 g/MBW/d）。与低 HA 相比，杂交和高 HA 提高了生物学效率，分别为 40.0 比 26.2 和 36.0 比 29.7 g 的犊牛/kg DMI。高允许量增加了牧草的质量和具有更大冠层高度的部位，这允许更大的 DMI，与母牛断奶时的 BCS、犊牛 ADG、BWW 和断奶时每公斤 DMI 的犊牛体重呈正相关。杂交牛在妊娠期间减少了 DMI，并没有表现出更高的年 DMI。使用高 HA 和杂交牛可以提高动物生产力和生物学效率，这应该会降低母牛-犊牛系统对环境的影响。
