鸡摄取养分的动力何在

究竟是什么推动着鸡摄食小量或大量的饲料？鸡体内是否存在能够自动对环境变化作出反应从而使采食量发生相应改变的机制呢？确实是存在的。     

Serological survey of the incidence of Hypoderma bovis in cattle in 1988

Sera from 74,502 cattle from 3087 farms in England and Wales were tested for the presence of antibodies against Hypoderma bovis in the spring of 1988. Twenty-nine positive sera were identified on 18 premises and these animals were treated; an examination of 6030 sera taken from 108 neighbouring herds identified another 17 seropositive animals on 10 farms in Devon, Cornwall, Lancashire, Shropshire and Powys, indicating that these counties still harbour populations of warble fly.     

猪轮状病毒2型(PCV2)是潜在的“定时炸弹”吗?

对猪轮状病毒2型(PCV2)的研究,为全球探讨断奶后多系统消瘦综合征(PMWS)的特殊问题,提供了许多答案。但是本文提出了一些还需要特别注意的地方 ,用以避免其可能导致的“恶果”出现。过去几年里 ,在关于断奶后多系统消瘦综合征(PMWS)、猪轮状病毒病(PCVD )全球性的探讨中 ,已经对许多关于疾病流行特点的来源和特征进行了广泛的研究。猪血清中猪轮状病毒2型 (PCV2)抗体以及猪的组织样本的检测表明 ,至少从1969年起 ,猪轮状病毒2型 (PCV2)的抗体就已经存在于猪的群体中了。现在已经确定 ,从1986年起在西班牙和英国就发现了传统的PMWS…     

Performance,milk fatty acid composition and behaviour of high-yielding Holstein dairy cows given a limited grazing period

The effects of a limited grazing period on the performance, behaviour and milk composition of high-yielding dairy cows were examined. A total of 56 Holstein cows yielding 44.7 ± 0.42 kg/day were allocated to one of four treatments in one of two, 4-week periods. Treatments were as follows: control (C)—cows housed and offered TMR ad libitum; early grazing (EG)—cows grazed for 6 hr after morning milking then housed; delayed grazing (DG)—cows returned to housing for 1 hr after morning milking followed by grazing for 6 hr, then housed; restricted TMR (RT)—cows grazed for 6 hr after morning milking, then housed and fed TMR at 75% of ad libitum. Intake of TMR was highest in cows receiving C, intermediate in EG and DG, and lowest in RT at 26.9, 23.6, 24.7 and 20.3 kg DM/day respectively. Pasture intake was similar in cows receiving EG or DG, but was higher in RT at 2.4, 2.0 and 3.5 kg DM/day respectively. Milk yield was similar between cows receiving C, EG or DG, but lowest in RT at 45.7, 44.2, 44.9 and 41.7 kg/cow, respectively, while milk fat content of C18:3 n-3 was increased by grazing. Cows in C spent more than 55 min/day longer lying and had three additional lying bouts/day, while lying bouts were shorter than for cows receiving EG, RT or DG. It is concluded that high-yielding cows can be grazed for 6 hr/day with little impact on performance, provided TMR is available ad libitum when housed.