Biopsy of the bovine mammary gland.

A technique is described for biopsy of the bovine udder, employing sedation and local anaesthesia. Tissue samples of approximately 5 g were obtained by electrocautery from two quarters of the udder of a cow laterally recumbent. Care was taken to ensure complete haemostasis which was achieved by electrocoagulation and ligation. Postoperative recovery was rapid, and loss of yield was no greater in biopsied glands than in control glands of the same cow. Yield from all quarters returned to preoperative levels within 48 h.     

The measurement and interpretation of genotype-environment interactions

Summary The regression analysis developed by Finlay and Wilkinson to investigate genotype-environment interactions and to assess genotypes for their adaptation to a range of environments is reviewed. Their analysis used the mean yield of many genotypes to provide a measure of the environment; it was not measured in physical terms. To reveal aspects of their analysis it was applied to data of the response of genotypes to variation in a single precisely measured environmental factor. The conclusions were extended to consider variation in several environmental factors.The effects on the regression statistics that occur with different samples of genotypes, sub- and super-optimal environmental conditions, differences in periods of growth, changes in the scale of measurement and the occurrence of several stress factors are outlined.The study byBreese (1969) of genotype-environment interaction inDactylis glomerata is considered against a background of these effects.     

Usefulness of subjective ovine milk scores: II. Genetic parameter estimates

Genetic parameters for a subjective milk score given to ewes within 24 h of parturition were estimated to determine the usefulness of milk score as a selection trait to improve milk production, which influences total litter weight weaned. Heritability of milk score and the genetic correlation of milk score with litter weight weaned were estimated by REML separately for four sheep breeds, Rambouillet (n = 1,731), Targhee (n = 1,638), Columbia (n = 1,731), and Polypay (n = 1,129). Litter weight weaned was the total weight of lambs weaned at approximately 120 d of age under a western range production system. Observed heritability estimates for milk score at first parity were moderate and similar among breeds, ranging from 0.18 to 0.32. Heritability estimates adjusted for a binomial distribution of milk scores at first parity were high (Columbia, 0.43; Polypay, 0.35; Rambouillet, 0.50; Targhee, 0.84). Estimates of observed heritability for second-parity milk score were moderate to high, ranging from 0.23 to 0.46. Milk score at first or second parity was genetically correlated with milk score records at maturity (third parity and greater), with estimates ranging from 0.69 to 1.00. Milk score and litter weight weaned were genetically correlated at first or second parity in Rambouillet (r(g) = 1.00) and Targhee breeds (r(g) = 1.00 and 0.61, respectively), but not in the Columbia and Polypay breeds. Estimates of heritability for lifetime records for milk score ranged from 0.16 to 0.26 across breeds. Estimates of genetic correlations of annual lifetime milk score records with litter weight weaned were high (Columbia, 1.00; Polypay, 0.81; Rambouillet, 1.00; and Targhee, 0.77). Repeatability estimates for milk score were similar across breeds, 0.23 for Columbia, Rambouillet, and Targhee ewes and 0.28 for Polypay ewes. Milk score measured at first or second parity may be a good predictor of future potential milking ability. Further, milk score can be used as a selection trait to improve maternal ability for increasing litter weight weaned. The need for increasing ewe milking performance and lamb growth rate at first parity in commercial range sheep production systems may be addressed by selection for milk score at first parity.     

Usefulness of subjective ovine milk scores: I. Associations with range ewe characteristics and lamb production

Range ewes are commonly evaluated for milking ability by producers to determine the ewe's ability to rear lamb(s). The U.S. Sheep Experiment Station has subjectively scored (low, average, high) a ewe's milking ability within 24 h of lambing for many years. The relationship of subjective milk scores with lamb production was investigated using lambing records of Columbia (n = 1,731), Polypay (n = 1,129), Rambouillet (n = 1,704), and Targhee (n = 1,638) ewes. The incidence of high milk scores increased from less than 10% at first parity to 29 to 40% at second and greater parities. At maturity, Columbia ewes (38%) had the highest percentage of high milk scores. A positive association existed between ewe BW and her milk score at third and later parities. Ewes with high milk scores gave birth to heavier lambs (P < 0.05), whereas ewes with low milk scores were associated with lighter (P < 0.05) lambs at birth. Ewes with low milk scores weaned less (P < 0.05) total weight than ewes with better milk scores across all age groups for all breeds. Lighter weaned litter weights from ewes with low milk scores were linked to lighter birth weights and fewer weaned lambs. Differences for litter weight weaned between ewes with average and high milk scores were generally observed at 2 and 3 yr of age, when litter weights were heavier among ewes with high milk scores (P < 0.05) for all breeds. Between the ages of 1 and 3 yr, Columbia, Polypay, Rambouillet, and Targhee ewes with an average milk score weaned heavier (P < 0.05) litters (average differences of 10, 9, 13, and 12%, respectively) than ewes with low milk scores. For all breeds at all ages, individual lamb weaning weights were heavier (P < 0.05) when they were reared by ewes with high milk scores compared to lambs reared by ewes with low milk scores. Results suggest that milk score is an economically important trait in these four breeds and should be considered in management and breeding objectives; at a minimum, the incidence of low milk scores should be kept as small as possible.     

Bactericidal activity of standard bovine serum against coliform bacteria isolated from udders and the environment of dairy cows.

Coliform organisms were isolated from bedding, udders of cows exhibiting acute or chronic mastitis, and milk of cows tested for udder pathogens. The bactericidal activity of standard bovine serum was tested on 362 isolates, of which 2.4% were killed at a serum dilution of less than 1:5; 2.7% were killed at a dilution of 1.5; 3.0% were killed at a dilution of 1:12.5; and 4.4% were sensitive to a dilution of 1:25. Organisms isolated from mastitic udders were not killed by serum. Sensitivity to agglutination in 1:500 solution of acriflavine was tested on 157 isolates, and only 54 had any degree of agglutination. Of these 54, only 4 organisms had any susceptibility to killing by serum. Results suggest that most organisms in the environment of the cow are resistant to serum, few serum-sensitive coliforms cause mastitis, and agglutination in acriflavine (indicating organisms in the rough phase) does not correlate with sensitibity to serum.     

A serologic method for the detection of Corynebacterium pseudotuberculosis infections in horses

A serologic technique useful for detecting antibodies formed in horses in response to infection with Corynebacterium pseudotuberculosis is described. The test relies on the ability of C. pseudotuberculosis toxin to produce a wide zone of hemolysis when applied to erythrocytes previously treated with a sterile filtrate of Corynebacterium equi broth culture. The synergistic hemolytic activity can be neutralized by anti-C. pseudotuberculosis serum. This test was used to analyze sera from 616 horses for the presence of C. pseudotuberculosis antitoxin. Of 177 animals (see Table 2) found positive, there were 34 horses with bacteriologically confirmed, active infections and 18 with active but unconfirmed infections. In addition, 13 animals had a history of having had the disease and 112 had no history or evidence of having had the infection. The other 439 horses had negative titers. Statistical treatments confirmed the value of the test as an epidemiological tool but precluded using only titers for the diagnosis of active clinical disease.     

Comparative studies of the use of some injectable anaesthetic agents in birds

The effect of three injectable drugs and a combination of two of them was compared in birds. The agents were ketamine hydrochloride, xylazine hydrochloride and the steroid mixture alphaxalone-alphadolone. Ketamine and xylazine were used in combination. One hundred and fifty-four species, all maintained by major zoos in the United Kingdom, were involved in the study. The results indicate that the drugs used produced more widely differing effects in the range of species studied than have previously been reported.