Assessment of flesh colour in Atlantic salmon, Salmo salar L.

The degree of pigmentation in muscle of Atlantic salmon, Salmo salar L., fillets of fish that were fed eight diets fortified with 10, 20, 40, 60, 80.100, 150 and 200 mg astaxanthin kg^?1 and a non-supplemented control diet from 3 to 21 months was assessed using different methods. A tristimulus colorimeter (Minolta Chroma Meter) was used to measure the colour composition of the fillets instrumentally. The colour was also determined using the Roche Colour Card for Salmonids. The concentration of astaxanthin in the muscle was measured by chemical analyses. All measurements for colour were done directly on the epaxial muscle anterior to the dorsal fin. The lightness factor (L *). the red/green chromaticity (a*), the yellow/blue chromaticity (b*) and the saturation C* of the colorimetric readings and the Colour Card scores were compared with the chemical analyses. The astaxanthin concentration in the flesh varied from 1 to 10 mg kg^?1 and the visual appearance of the fillets varied from yellowish-white to red. The relationship between the a*, b* and C* values and the astaxanthin concentration in the muscle was non-linear. Non-linear regression lines were found between the a* value and the astaxanthin concentration in the flesh (r²= 0.974) and the b* value and the astaxanthin concentration in the flesh (r²= 0.984). The instrument was not able to detect differences in astaxanthin concentration at astaxanthin levels above 3-4 mg kg^?1 using the presented method directly on the fillet. The instrument might be useful for rejecting groups of salmon with poor pigmentation. A good linear regression was found between the Colour Card score and the mean astaxanthin concentration in the flesh (r² - 0.992). The Colour Card provided a better prediction of the astaxanthin concentration at higher astaxanthin levels than the Chroma Meter. None of the methods provided a satisfactory prediction of the astaxanthin concentration in the muscle of individual fish using the presented methods.     

Does sward height grazed by ewes in mid- to late-pregnancy affect indices of colostrum intake by twin and triplet lambs?

AIMS: To determine if sward height grazed by ewes in mid- to late-pregnancy affects subsequent indices of colostrum intake by twin and triplet lambs, and the extent of the variation in colostrum intake between twin and triplet litter-mates.

METHODS: Blood samples were collected from 75 twin and 46 triplet litters, respectively, 24–36 h after birth. Samples were not collected from lambs that died before this age. Lambs were born to ewes which had grazed one of four sward heights (2, 4, 6 and 8 cm) during mid- to late-pregnancy. Serum samples were analysed for gamma-glutamyl transferase (GGT) activities and glucose concentrations. The number of lambs present at weaning was used to determine lamb survival rate.

RESULTS: GGT activities of lambs born to ewes that grazed swards 2 cm high were lower than those born to ewes that grazed swards 4 and 6 cm high (p=0.053 and p=0.037, respectively). Glucose concentrations were higher in twin than triplet lambs (p=0.003) and in lambs born to ewes grazed on swards 6 cm high than those born to ewes grazed on swards 2 cm high (p=0.033). These differences were not evident after correction for differences in birthweight. There was significant (p<0.001) variation within litter-mates for GGT activities and glucose concentrations in both twins and triplets. The blood constituent status of lambs that died before the 24–36 h collection period is not known. However, lambs which died after this period had significantly lower GGT activities (p=0.009) and glucose (p=0.010) concentrations at the time of sampling than those which survived.

CONCLUSIONS: Farmers should ensure twin- and tripletbearing ewes in mid- to late-pregnancy are grazing at least 4 cm of herbage to ensure colostrum intake of lambs in the postpartum period is not adversely affected.     

Associations between lamb growth to weaning and dam udder and teat scores

ABSTRACT

Aims: To investigate associations between lamb growth to weaning and dam udder and teat scores measured at pre-mating, pre-lambing, docking and weaning.

Methods: Mature Romney ewes (n?=?1,009) were enrolled from a commercial sheep flock located near Masterton, in the Wellington region of New Zealand in 2017. A range of udder and teat traits were scored in all ewes, using visual assessment and palpation, at pre-mating, pre-lambing, docking and weaning. During the lambing period, each newborn lamb was matched to its dam and lamb sex, birthweight and birth-rank were recorded. A rearing rank was allocated to each live-lamb at weaning, when all lambs were weighed (n?=?1,570), allowing calculation of daily growth rates (g/day). Associations between udder and teat scores and lamb growth rates to weaning were examined using multivariable models for each udder-scoring time.

Results: Growth rates of lambs whose dams had udder palpation scores of hard, or both teats recorded as abnormal, pre-mating were lower than lambs whose dams had normal scores (229.9 (95% CI?=?213.2–246.6) vs. 254.5 (95% CI?=?245.6–263.5) g/day; p?=?0.011) and (227.4 (95% CI?=?208.3–246.6) vs. 247.9 (95% CI?=?235.7–260.2) g/day; p?=?0.024), respectively. Growth rates of lambs whose dams had clinical mastitis at docking or weaning were lower than those without mastitis (215.8 (95% CI?=?199.9–231.7) vs. 235.4 (95% CI?=?225.4–255.0) g/day; p?=?0.007) and (220.0 (95% CI?=?205.2–234.8) vs. 254.7 (95% CI?=?248.9–260.5) g/day; p?<?0.001), respectively. Growth rates of lambs whose dams had asymmetrical udders at docking or weaning were lower than lambs whose dams had symmetrical udders (204.6 (95% CI?=?189.7–219.5) vs. 240.2 (95% CI?=?225.4–255.0) g/day; p?<?0.001) and (223.3 (95% CI?=?213.9–232.7) vs. 242.2 (95% CI?=?229.4–255.0) g/day; p?=?0.014), respectively.

Conclusions and Clinical Relevance: Pre-mating udder palpation and teat palpation scores can be used to identify ewes whose lambs are predicted to have lower growth to weaning. Assuming a mean lamb age at weaning of 84.4 days, lambs born to ewes with a pre-mating score of hard would be expected to have a mean weaning weight that was 2.1?kg less than those whose dams had normal scores. Udder palpation, udder symmetry and clinical mastitis scores during lactation were also associated with lamb growth rates.

Abbreviation: CALW: Conceptus-adjusted liveweight     

Components of electroencephalographic responses to slaughter in halothane-anaesthetised calves: Effects of cutting neck tissues compared with major blood vessels

AIM: To identify whether cutting neck tissues or cutting major blood vessels initiates the mechanisms responsible for electroencephalographic (EEG) responses to slaughter by ventral-neck incision without prior stunning in halothane-anaesthetised calves.

METHODS: Calves were assigned to two groups, viz transection of neck tissues with intact blood circulation through the brain (n=10), or transection of the major blood vessels of the neck but not most other neck tissues (n=7). They were minimally anaesthetised with halothane, using an established anaesthesia protocol. The animals in the neck-tissue transection group had their carotid arteries and jugular veins exposed and cannulated proximal and distal to the proposed site of subsequent ventral-neck incision; this diverted blood fl ow through these vessels so that cerebral perfusion and drainage were preserved. In animals in the blood-vessel transection group, the carotid arteries and jugular veins were exposed bilaterally by surgical dissection. They were then transected without further damage to the remaining structures of the neck. Changes in the median frequency (F50), 95% spectral edge frequency (F95), total power of the EEG (Ptot), and arterial blood pressure were compared within each group before and after neck-tissue or blood-vessel transection, and between groups following treatments.

RESULTS: Neck-tissue transection resulted in little overall change in the F50, an increase in the F95, and an initial increase in Ptot followed by a transient decrease and eventual return to pre-treatment values. There was between-animal variation in these EEG parameters. Transection of the major blood vessels of the neck resulted in a decrease in F50 in most animals; changes in F95 were highly variable, and there was a decrease in Ptot.

CONCLUSIONS: The EEG responses seen following necktissue and blood-vessel transection were qualitatively distinct, and suggested that cutting neck tissues caused greater noxious sensory input than transection of only the major blood vessels of the neck. These observations support the conclusion that the EEG responses seen after ventral-neck incision in intact animals are primarily due to noxious stimulation as a result of incision of ventral-neck tissues and not mainly as a result of loss of blood flow through the brain.     

Blood metabolites and body temperature of single calves between 1 and 4 days of age in a dairy herd in New Zealand

AIM: Using specified indices, to determine the nutritional and thermal status of calves between 1 and 4 days of age.

METHODS: After birth, calves (n=106) were collected daily, according to farm practice. Over the following 4 days a jugular blood sample and rectal temperature were taken twice daily before feeding. Plasma concentrations of glucose, beta-hydroxybutyrate and urea, and gamma-glutamyl transferase (GGT) activities were determined. The significance of differences in plasma composition and rectal temperature between calves whose birth had been assisted or unassisted, and between calves with low and high plasma GGT activities 24 h after birth, was determined using repeated measures analysis of varianc

RESULTS: There were no marked differences in plasma metabolite levels or body temperature of assisted and unassisted calves. Calves that had high plasma GGT activities 24 h after birth had higher plasma glucose concentrations over the 4 days than calves that had low plasma GGT activities (p<0.001). Overall, compared to published data on poorly-fed and hypothermic calves, calves in this study were normoglycaemic, their plasma beta-hydroxybutyrate and urea concentrations were low and their rectal temperatures were normal, indicating that they were well fed and did not become hypothermic.

CONCLUSIONS: The nutritional and thermal status of at least 90% of the calves was compatible with good health and survival during the first 4 days after birth.     

Investigation of abortions in brucellosis tested herds

The mandatory reporting and investigation of bovine abortions provides a system for the surveillance of the progress of the Brucellosis Eradication Scheme and a warning of resurgence of brucellosis in tested herds. Before the scheme was introduced in 1971, about a quarter of all abortions were caused by Brucella abortus. By 1976, the percentage of abortions due to Brucella in herds under test for brucellosis had been reduced to 3.4%. Most Brucella abortions occurred during the seventh and eighth months of gestation. Cows in the 4- to 6-year-old age group were at greater risk of aborting from Brucella infection than heifers. Approximately 94% of all aborting cows were in herds which experienced three or fewer abortions. Less than 4% of herds experienced four or more abortions annually. In most cases of abortion due to brucellosis, more than one diagnostic test yielded positive results. However, 13.3% of cases were recognised by positive bacteriological results alone.     

Coexistence of diploid and triploid hybrid water frogs: population differences persist in the apparent absence of differential survival

Background  

The role of differential selection in determining the geographic distribution of genotypes in hybrid systems has long been discussed, but not settled. The present study aims to asses the importance of selection in structuring all-hybrid Pelophylax esculentus populations. These populations, in which the parental species (P. lessonae with genotype LL and P. ridibundus with genotype RR) are absent, have pond-specific proportions of diploid (LR) and triploid (LLR and LRR) genotypes.