Biomedical subjects

T W Knight

Publications and source records attributed to T W Knight.

11 recordsLinked to original sources

PubMed2004

Adding nutritional value to meat and milk from pasture-fed livestock.

Staple meat and milk provide excellent nutrition, but when traditional foods and ingredients are tailored to meet the particular nutritional or lifestyle demands of a population they become even more attractive and valuable. These foods can be considered as delivery systems for health-promoting nutrients. Nutritional improvement of meat and milk can be achieved several ways, preferably by making desirable changes on-farm to directly improve the food without subsequent manipulations. Scope for these changes is limited by animal homeostasis, but alternatives may be less desirable. Methods in vivo that suit typical pastoral farming practice and can complement the solving of animal health and production problems include: selection of traits or phenotypes; specialty diets; long-acting parenteral supplements; and modification of ruminal microflora. Successful techniques to increase the concentration of calcium, selenium, iodine and iron in milk or meat are described. Manipulations to change composition are only one part of bringing tailored foods to market. Commercial realisation of these new products needs the initiative and collaboration of scientists, veterinarians, growers and producers responding to market pull. The uptake of future biotechnologies to capture more value inside the farm gate will also be required if the pastoral industry in New Zealand is to sustain a global competitive advantage.

Journal Article↗

PubMed2001

Calf survival from embryo transfer-induced twinning in dairy-beef cows and the effects of synchronised calving.

In each of 4 years, 94-116 mature cows had two 6-7-day-old embryos, produced by the in vitro fertilisation of oocytes, inserted non-surgically into one uterine horn of each cow. Starting 5 days before the expected date of calving, the cows were continuously observed and assistance at calving was provided when required. In year 1, perinatal calf survival was similar in twin-calving (TC) and single-calving (SC) cows (98.1 versus 100% for calves born to TC and SC, respectively). There was a higher incidence of assistance at birth for TC (52%) than for SC (21%). In years 2 and 3, the calving of 30 SC and 33 TC was synchronised using an injection of Opticortinol (OP) 6-9 days before the injection of Estrumate and Dexol-5 (E+D). A further 34 SC calved naturally. Synchronised calving reduced the spread of calving from 16-25 to 8-9 days without reducing perinatal calf survival and had no significant effect on the incidence of assistance at birth in SC. The TC in years 2 and 3 had a high incidence of retained placenta at 48 h (70%) and a high incidence of assistance at birth (85%). In year 4, calving was synchronised in 16 SC and 21 TC with E+D and no pre-treatment with OP, while 15 SC were treated with both OP and E+D. There were no effects of the hormone treatment on perinatal calf survival and only small effects on the incidence of assisted births for SC. The incidence of retained placenta at 48 h was lower for SC pre-treated with OP (40%) than for SC (88%) and TC (76%) not pre-treated with OP. Continuous supervision over calving produced perinatal calf survival rates for TC that were similar to SC, despite the higher incidence of assistance of TC at parturition. Hormonal synchronisation of calving can halve the time required for continuous supervision of calving, but the hormone treatments exacerbate the already high incidence of retained placenta in TC.

Adrenal Cortex Hormones↗

PubMed2001

Effects of surgical or banding castration on stress responses and behaviour of bulls.

OBJECTIVE: To compare the effects of surgical and latex banding methods of castration in 14- and 9-month-old bulls. DESIGN: Two randomised, controlled experiments. PROCEDURE: In Experiment 1, following administration of local anaesthetic, 14-month-old bulls were castrated by either surgical or banding methods, or left entire. Behavioural, plasma cortisol, plasma haptoglobin and bodyweight responses were recorded. A group of steers from the same mob was used as an additional comparison for bodyweight data. In Experiment 2, following administration of local anaesthetic, 9-month-old bulls were castrated by either surgical or banding methods and cortisol, haptoglobin and bodyweight responses were recorded. Entire bulls from the same group were used as an additional comparison for bodyweight data. RESULTS: In Experiment 1, surgical castrates exhibited more leg stamping and tail swishing than banded or entire animals in the hours after castration. Surgical castrates in both experiments also showed an increase in plasma haptoglobin, which resolved after 4 days. Plasma cortisol was generally not affected by castration. Surgical castrates grew more slowly than entire bulls, but faster than banded animals, in the 56 days after treatment. In Experiment 1, after 56 days, the bodyweights of surgical and banded castrates were not different from the bodyweights of the steers. Fourteen-month-old banded cattle developed persistent wounds above the latex band which remained for several weeks after scrotal dehiscence, but this did not occur in the 9-month-old animals. CONCLUSION: The banding procedure produced fewer acute effects, but a greater suppression of growth than surgical castration and induced prolonged wound formation in the older age group, suggesting that this procedure may not be as suitable for yearling cattle.

Age Factors↗

PubMed1981

Corpus luteum function in ewes stimulated by rams.

In late February Dorset rams were introduced (day = 0) to 40 mature Romney ewes that were observed by laparoscopy to be anovular. The ovaries of 20 of these ewes were examined by laparoscopy every second day while the remaining 20 ewes served as unoperated controls. Jugular blood samples were taken daily and plasma progesterone concentrations assayed to provide information on the functional status of any corpora lutea (CL) arising from ovulations stimulated by introduction of the rams. Eighty-five percent (17/20) of the ewes that were repeatedly laparoscoped had ovulated within 4 days of ram introduction and premature regression of the CL had occurred between days 4 and 8 in 8 ewes and days 6 to 10 in 2 ewes. A second ovulation was observed after or during the premature regression of the first CL and this subsequent CL was maintained for the normal duration. The prematurely regressing CL produced a small peak in progesterone concentration on days 4 to 5 but the concentrations declined on days 6 to 7. In the unoperated ewes 50% (10/20) appeared, from the progesterone profiles, to have ovulated by day 4 and half of these appeared to have premature CL regression. The interval from introduction of the ram to first oestrus was 23 days in ewes with premature regression of the CL and 19 days in ewes ovulating within 4 days but having no premature regression. From the results it was concluded that the premature regression of the CL is the cause of the delayed interval from ram introduction to first oestrus in Romney ewes and is a major factor contributing to the two peaks of oestrous activity observed after ram introduction.

Journal Article↗

PubMed1979

Relationship between plasma progesterone in late gestation and the incidence of dystocia in romney ewes.

Thirty-eight percent (6 16 ) of the ewes with a previous history of dystocia and 15% (2 13 ) of the ewes with no dystocia in 4 lambings, had difficult births in 1976. Despite large variations in plasma progesterone concentrations among ewes at the same stage of gestation there were no differences in the progesterone concentration during the last 30 days of gestation for both single- and twin-bearing ewes with or without a history of dystocia, nor for single-bearing ewes with or without a dystocia. The progesterone concentrations declined during the last 10 days before parturition in ewes with and without dystocia. The lambs from single-bearing ewes with a dystocia did not have heavier birth weights than the lambs from single-bearing ewes without a dystocia.

Journal Article↗

PubMed1979

Intervals between multiple ovulations in PMSG-treated and untreated ewes and the relationship between ovulation and oestrus.

The timing of ovulations in 42 PMSG-treated ewes was determined by repeated endoscopy. The first ovulation occurred at a median time of 23 . 6 +/- 0 . 5 (s.e.m.) h after the onset of oestrus. The median interval between first and second ovulations was less than 1 h, and that between first and last ovulations was approximately 6 h. In 59 untreated ewes, probit regression analysis was applied to the number of ovulations which were found by endoscopy to have occurred by 23, 25 and 27 h after the onset of oestrus. The median time of first ovulation was 25 . 5 +/- 0 . 5 h after the onset of oestrus, this interval being similar in single- and twin-ovulating ewes. The median interval between twin ovulations was 1 . 2 +/- 0 . 6 h. Ovulation occurred after the end of oestrus in at least 75% of ewes.

Animals↗

PubMed1975