Sources of variation and prospects for improvement of productive efficiency in the dairy cow: a review   总被引：4，自引：0，他引：4  

D E Bauman  S N McCutcheon  W D Steinhour  P J Eppard  S J Sechen 《Journal of animal science》1985,60(2):583-592

In this review, "productive efficiency" in dairy cows is defined as the yield of milk obtained in ratio to the nutritional costs associated with maintenance, milk synthesis and loss of body condition during lactation. Improvements in efficiency could occur as a result of changes in digestion and nutrient absorption, maintenance requirement, utilization of metabolizable energy for production or nutrient partitioning. Digestibility can be greatly enhanced by appropriate dietary manipulation. Likewise, it may be possible to reduce maintenance requirements and improve the efficiency with which metabolizable energy is used for milk synthesis by manipulation of the pattern of nutrients presented to tissues. However, these factors apparently do not respond to selection for increased milk yield, and little variation is observed among cows. In contrast, individual cows differ substantially in feed intake and in the partitioning of nutrients among body tissues. Techniques associated with genetic engineering and the early prediction of genetic merit have the potential to improve productive efficiency by manipulation of these processes. However, changes in nutrient partitioning and feed intake during lactation are coordinated by a complex network of controls that accommodate the nutrient requirements of each tissue while maintaining homeostatic balance. Future improvements in productive efficiency will therefore depend on our ability to understand the manner in which these controls operate.  相似文献   

Behaviour of roaster chickens towards an automatic weighing perch     

Ruth C. Newberry  J. R. Hunt  E. E. Gardiner 《British poultry science》1985,26(2):229-237

1. Automatic weighing equipment was tested on a flock of 752 roaster chickens reared on litter to 10 weeks of age.

2. Mean body weights obtained automatically were lower than those obtained manually, mainly because of birds perching on the automatic weighing perch with part of their body in contact with the floor.

3. Birds observed on the weighing perch on one day of the week were 3–5 times more likely to use the perch again on the following 2 d than expected on the basis of random perch use by flock members. These birds were also more likely to be seen in the area immediately surrounding the perch than in similar areas elsewhere in the pen.  相似文献   

Caprine beta-Mannosidosis in Kids from an Ontario Herd     

Shapiro JL  Rostkowski C  Little PB  Smith-Maxie L  Julian RJ  Van Dreumel AA 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(5):155-158

Caprine β-mannosidosis, a fatal inherited deficiency of the lysosomal enzyme β-mannosidase, was diagnosed in neonatal female Nubian crossbred twin kids from a small herd near Guelph, Ontario. The kids had been tetraplegic since birth, with whole body tremors, abnormal nystagmus and an intention tremor of the head.  相似文献   

Advances in immunoparasitology   总被引：1，自引：0，他引：1  

E J Soulsby 《Veterinary parasitology》1985,18(4):303-319

A selective review of the advances in immunoparasitology is presented. It is selective simply because it is not feasible to embrace the whole field of parasitology within the compass of a single review paper, for if it were attempted, it would suffer undue abbreviation. Emphasis is placed on the advances in helminthology and especially the gastro-intestinal parasites of ruminants, an obvious selection because of the interests of the author. Reviews are always somewhat retrospective in outlook; to write a review at the present time is especially foolhardy since developments in biology are such that totally new concepts can arise almost overnight, as it were. This is a particularly healthy state, and the discipline of parasitology is caught up in the application and interpretation of molecular biological considerations. "Parasitism" is a field of increasing importance and challenge.  相似文献   

Productivity and fruit quality of apple in single-row and full-field planting systems     

S.J. Wertheim 《Scientia Horticulturae》1985,26(3):191-208

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A vesicular dermatitis affecting pig snouts. An important differential diagnosis for infectious vesicular diseases     

Montgomery JF  Oliver RE 《New Zealand veterinary journal》1985,33(6):98

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Diet and control of porcine post-weaning diarrhoea     

Hampson DJ  Beban RL 《New Zealand veterinary journal》1985,33(11):190

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Osmium-187/osmium-186 in manganese nodules and the cretaceous-tertiary boundary     

Luck JM  Turekian KK 《Science (New York, N.Y.)》1983,222(4624):613-615

As a result of the radioactive decay of rhenium-187 (4.6 x 10(10) years) the osmium-187/osmium-186 ratio changes in planetary systems as a function of time and the rhenium-187/osmium-186 ratio. For a value of the rhenium-187/osmium-186 ratio of about 3.2, typical of meteorites and the earth's mantle, the present-day osmium-187/osmium-186 ratio is about 1. The earth's continental crust has an estimated rhenium-187/osmium-186 ratio of about 400, so that for a mean age of the continent of 2 x 10(9) years, a present-day osmium-187/osmium-186 ratio of about 10 is expected. Marine manganese nodules show values (6 to 8.4) compatible with this expectation if allowance for a 25 percent mantle osmium supply to the oceans is allowed. The Cretaceous-Tertiary boundary iridium-rich layer in the marine section at Stevns Klint, Denmark, yields an osmium-187/osmium-186 ratio of 1.65, and the one in a continental section in the Raton Basin, Colorado, is 1.29. The simplest explanation is that these represent osmium imprints of predominantly meteoritic origin.  相似文献   

"Baby Doe" regs thrown out by court     

B J Culliton 《Science (New York, N.Y.)》1983,220(4596):479-480

On April 14, 1983, federal district court judge Gerhard Gesell overturned, as "arbitrary and capricious," a Department of Health and Human Services regulation that required hospitals to post notices concerning the illegality of denying life-saving care to handicapped infants and encouraged anyone with knowledge of such a case to report it to HHS via a telephone hotline. This article reviews the evolution and implementation of the HHS regulation, the legal challenge to it, and the judge's ruling.  相似文献   

FDA assails safety of depo-provera     

Smith RJ 《Science (New York, N.Y.)》1983,219(4583):371

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