Webb L E, Bokkers E A M, Heutinck L F M, Engel B, Buist W G, Rodenburg T B, Stockhofe-Zurwieden N, van Reenen C G
Animal Production Systems Group, Wageningen University, PO Box 338, 6700 AH, Wageningen, the Netherlands.
J Dairy Sci. 2013;96(12):7765-76. doi: 10.3168/jds.2012-6135. Epub 2013 Oct 4.
The European Union 1997 Directive, stipulating that veal calves should be fed a minimum of 50 to 250 g of fibrous feed from 8 to 20 wk of age, is vague. A fibrous feed ration maximum of 250 g has been implicated in welfare issues, namely the occurrence of abnormal oral behaviors and poor gastrointestinal health. Past research suggests that this amount is insufficient to prevent the development of abnormal oral behaviors and enabling good rumen development. Different sources and particle sizes of roughage could lead to very different welfare outcomes. In a 3×2 × 2 factorial design, 240 group-housed calves (10±1 d; 46.1±0.1 kg) were fed different roughage sources (straw, maize silage, or maize cob silage; the latter 2 were dried and provided no extra moisture compared with straw) in 2 amounts (250 or 500 g of dry matter per day), and 2 particle sizes (chopped or ground). Roughage was supplemented to milk replacer (MR) from 2 wk after arrival. In addition, 60 calves were fed 1 of 3 additional control treatments: MR only (n=20), MR plus an iron supplement (n=20), or MR plus ad libitum hay (n=20). Oral behaviors were recorded using instantaneous scan sampling at 2-min intervals for 2 h in 3 periods per day, at 12 and 22 wk of age. Calves were slaughtered at 24 wk of age and rumen and abomasal health parameters were recorded. Limited provision of straw resulted in behavior comparable with that from unlimited provision of hay, with reduced tongue playing and oral manipulation of the environment, as well as increased chewing compared with diets with no roughage supplement. Straw prevented ruminal hairballs, but impaired rumen development and increased abomasal damage. A higher ration of roughage increased chewing (12 wk), decreased oral manipulation of the trough (12 and 22 wk) and the pen (22 wk), and increased rumen weight. However, more roughage led to increased abomasal damage for certain parameters. Longer feed particles had no obvious benefits for behavior, but decreased hairball prevalence. Overall, unlimited hay had the highest benefit for both behavior and gastrointestinal health. Adding iron to the MR did not alter behavior or gastrointestinal health compared with MR without iron supplement. This study demonstrated that different roughage sources, amounts, and particle sizes have different effects on veal calf behavior and gastrointestinal health, and hence on veal calf welfare.
欧盟1997年指令规定，犊牛在8至20周龄时应至少采食50至250克纤维饲料，但该规定并不明确。纤维饲料定量最高为250克已被认为与福利问题有关，即出现异常口腔行为和胃肠道健康不佳。过去的研究表明，这个量不足以预防异常口腔行为的发展以及促进瘤胃的良好发育。不同来源和粒径的粗饲料可能导致截然不同的福利结果。在一个3×2×2析因设计中，240头群饲犊牛（10±1日龄；46.1±0.1千克）被饲喂不同的粗饲料来源（稻草、玉米青贮饲料或玉米芯青贮饲料；后两者经过干燥处理，与稻草相比不提供额外水分），两种饲喂量（每天250或500克干物质），以及两种粒径（切碎或粉碎）。从犊牛到达后2周开始，在代乳粉（MR）中添加粗饲料。此外，60头犊牛被饲喂3种额外对照处理中的一种：仅喂代乳粉（n = 20）、代乳粉加铁补充剂（n = 20）或代乳粉加随意采食的干草（n = 20）。在12周龄和22周龄时，每天分3个时间段，每隔2分钟使用瞬间扫描取样法记录2小时的口腔行为。犊牛在24周龄时屠宰，并记录瘤胃和皱胃的健康参数。限量提供稻草导致的行为与不限量提供干草时相当，与不添加粗饲料的日粮相比，可以减少舔舌和对环境的口腔操作，同时增加咀嚼次数。稻草可预防瘤胃毛球，但会损害瘤胃发育并增加皱胃损伤。较高的粗饲料定量增加了咀嚼次数（12周龄时），减少了对饲槽（12周龄和22周龄时）和围栏（22周龄时）的口腔操作，并增加了瘤胃重量。然而，更多的粗饲料在某些参数上导致皱胃损伤增加。较长的饲料颗粒对行为没有明显益处，但降低了毛球发生率。总体而言，不限量的干草对行为和胃肠道健康的益处最大。与不添加铁的代乳粉相比，在代乳粉中添加铁对行为或胃肠道健康没有影响。本研究表明，不同的粗饲料来源、数量和粒径对犊牛行为和胃肠道健康有不同影响，因此对犊牛福利也有不同影响。
