Maughan B, Provenza F D, Tansawat R, Maughan C, Martini S, Ward R, Clemensen A, Song X, Cornforth D, Villalba J J
Department of Wildland Resources, Utah State University, Logan 84322-5230.
J Anim Sci. 2014 May;92(5):2309-24. doi: 10.2527/jas.2013-7297. Epub 2014 Mar 26.
We determined if tall fescue in a mixture with either tannin-containing sainfoin or saponin-containing alfalfa affected cattle foraging behavior, performance, meat quality, and consumer acceptance of meat. Foraging behavior, BW, and pasture biomass before and after grazing were monitored when cattle strip-grazed 3 replications of 2 treatments from May through September 2010 (12 calves/replication) and from June through September 2012 (8 calves/replication). Animals were allowed a choice between tall fescue and sainfoin (SAN) or tall fescue and alfalfa (ALF) growing in strips (fescue, legume, and fescue-legume mixture). Incidence of use (scan samples) of legumes increased from the beginning to the end of the trials (P < 0.05), suggesting that cattle learned to mix legumes with tall fescue. Scan samples and assessments of pasture biomass removal revealed greater use of sainfoin than alfalfa when both legumes were abundant in the spring (P < 0.05); that pattern reversed toward the end of the growing season (P < 0.05) as the abundance of sainfoin declined more than that of alfalfa. Intake of forage per kilogram of gain was greater for SAN than for ALF in 2010 (P = 0.0003) and showed a tendency to be greater for SAN than ALF in 2012 (P = 0.19). There were no differences in ADG between SAN and ALF in either year (1 kg/d; P > 0.05). No incidences of bloat were detected. When cattle (3 calves/treatment in 2010 and 8 calves/treatment in 2012) were slaughtered in September to assess meat quality and consumer acceptance, carcasses were lean (4% to 6% fat content of the longissimus muscle), but compared with ALF, SAN had higher marbling scores, quality grades (Select versus Standard), and back fat thicknesses (P < 0.05) in 2012. Steaks from cattle finished on SAN were redder in color than steaks from cattle finished on ALF (P < 0.05; 2012). Meat samples from SAN and ALF showed some differences in unsaturated fatty acid profiles and volatiles concentrations (P < 0.05), but consumer acceptance did not differ between SAN and ALF (P > 0.05). Thus, cattle incorporated a lower-quality grass into their diets even when legumes were available ad libitum during most grazing trials. Choices between tall fescue and legumes differing in the type of secondary compound (tannins vs. saponins) and bloating potential influenced patterns of forage use by cattle and led to differences in meat quality.
我们研究了与含单宁的红豆草或含皂苷的苜蓿混播的高羊茅是否会影响牛的采食行为、生产性能、肉质以及消费者对肉的接受度。2010年5月至9月（每组12头犊牛）以及2012年6月至9月（每组8头犊牛），当牛进行条带放牧两种处理的3次重复时，监测了放牧前后的采食行为、体重和牧场生物量。动物可以在条带状生长的高羊茅与红豆草（SAN）或高羊茅与苜蓿（ALF）之间进行选择（高羊茅、豆科植物以及高羊茅 - 豆科植物混合物）。从试验开始到结束，豆科植物的采食发生率（扫描取样）有所增加（P < 0.05），这表明牛学会了将豆科植物与高羊茅混合采食。扫描取样和对牧场生物量去除情况的评估显示，在春季两种豆科植物都充足时，牛对红豆草的采食多于苜蓿（P < 0.05）；随着生长季节临近结束，这种模式发生了逆转（P < 0.05），因为红豆草的丰度下降幅度大于苜蓿。2010年，每千克增重的采食量SAN组高于ALF组（P = 0.0003），2012年也表现出SAN组高于ALF组的趋势（P = 0.19）。两年中SAN组和ALF组的平均日增重均无差异（1千克/天；P > 0.05）。未检测到胀气病例。2010年每组3头犊牛、2012年每组8头犊牛于9月屠宰以评估肉质和消费者接受度，胴体较瘦（背最长肌脂肪含量为4%至6%），但与ALF相比，2012年SAN组的大理石花纹评分、质量等级（精选级与标准级）和背部脂肪厚度更高（P < 0.05）。在SAN组育肥的牛所产牛排的颜色比在ALF组育肥的牛所产牛排更红（P < 0.05；2012）。来自SAN组和ALF组的肉样在不饱和脂肪酸谱和挥发性物质浓度方面存在一些差异（P < 0.05），但消费者对两者的接受度没有差异（P > 0.05）。因此，即使在大多数放牧试验中豆科植物可随意采食，牛仍会在日粮中摄入较低质量的草。高羊茅与含有不同次生化合物类型（单宁与皂苷）且胀气潜力不同的豆科植物之间的选择，影响了牛的采食模式，并导致肉质产生差异。
