Biomedical subjects

J W Knight

Publications and source records attributed to J W Knight.

71 records · Page 4Linked to original sources

PubMed1985

Supplemental biotin for swine. III. Influence of supplementation to corn- and wheat-based diets on the incidence and severity of toe lesions, hair and skin characteristics and structural soundness of sows housed in confinement during four parities.

The influence of supplementing 0 (NB) or 440 (SB) micrograms biotin/kg to corn- or wheat-based diets on toe lesions, hair characteristics and structural soundness in 116 crossbred female swine was studied from selection (100 kg) until completion of four parities. Gilts that had been previously fed corn-soybean meal diets with 0 or 220 micrograms supplemental biotin/kg diet during growth and development, remained on either the biotin unsupplemented or supplemented diet. Females were housed in buildings containing partially slatted and solid concrete floors. Toe, hair and soundness evaluations were made at a mean age of 240, 521, 732, 916 and 1,090 d. Type of grain fed did not influence (P greater than .10) any response criteria evaluated. Six types of toe lesions were observed across all dietary treatments and varied in severity from minor to very severe. The percentage of females with heel cracks, heel-horn junction cracks and side-wall horn cracks was reduced (P less than .01) when females were fed SB diets. Females fed SB diets had fewer (P less than .001) total lesions, heel cracks, heel-horn junction cracks, side-wall horn cracks and white-line horn cracks (P less than .03) compared with females consuming NB diets. In general, biotin supplementation was more effective in reducing the number and percentage of toe lesions in multiparous sows compared with gilts and primiparous sows. Biotin supplementation increased (P less than .001) the number of hairs/cm2 skin and improved (P less than .001) hair scores. Histological evaluation and soundness scores were not affected (P greater than .10) by level of biotin fed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1983

Effects of exogenous progesterone and estrone on conceptus development in swine.

Administration of progesterone (P4, .55 mg/kg) and estrone (E1, .275 micrograms/kg) during discrete periods in early gestation was found to have beneficial effects on conceptus development in gilts. Three trials were conducted, with each trial examining two hormone treatment groups and one control group. In all trials, P4-E1 supplementation for either one or both of the time periods examined resulted in larger (P less than .05) placentas at d 50 of gestation. Administration of exogenous P4-E1 from either d 20 to 30 (trial 1) or d 25 to 30 (trial 3) of gestation resulted in the greatest augmentation in placental development. In all three trials, exogenous P4-E1 elicited beneficial effects on areolae formation and development. In all nine groups examined (both P4-E1-treated and controls), a positive uterine artery minus uterine vein difference in progesterone concentration was found. This suggests that the conceptus is metabolizing progesterone to metabolites that may have a local effect within the pregnant uterus. It is suggested that augmentation of placental growth, as demonstrated in this study, may reduce secondary fetal death losses in latter gestation (i.e., post-d 70) due to placental insufficiency.

Allantois↗

PubMed1983

Restricted energy and elevated calcium and phosphorus intake for boars during growth. 1. Feedlot performance and bone characteristics.

Eighty crossbred boars were utilized in a 2 X 2 factorial arrangement of two energy levels (ad libitum and 75% ad libitum) and two Ca/P levels (100 and 150% of National Research Council daily requirement) to determine the effect of varying growth rate and Ca/P intake on performance and bone characteristics throughout the growth phase. Boars were fed the diets beginning postweaning at 5 wk of age and continuing until necropsy at 10 +/- 2-d intervals between 80 and 220 d of age, inclusive. Body weight of limit-fed boars was 72% that of ad libitum-fed boars. Daily gain and feed per gain ratio favored boars fed the 150% Ca/P levels. Although limit-feeding enhanced the development of longer, thicker and heavier metacarpals earlier in the growth period (between 80 and 150 d of age), there was little difference between limit-fed and ad libitum-fed boars at 220 d of age when values were corrected for differences in body weight. Mechanical bone characteristics, which were greater for ad libitum-fed than for limit-fed boars at the same age, were not different when values were corrected for body weight. Boars fed 150% Ca/P levels had heavier and thicker walled metacarpals that had greater bone strength than boars fed 100% Ca/P levels, with the magnitude of the difference not as great at 220 d of age and when values were corrected for body weight. Generally, boars fed the ad libitum-150% Ca/P diet had the heaviest and strongest bones. Ether extract, ash and Ca and P content of ash were generally higher for ad libitum-fed vs limit-fed and 150 vs 100% Ca/P diets at 80 and 150 d of age, but were not different at 220 d. Metacarpal weight, size, thickness, strength and ash content increased with age with a small decline in the rate of increase. Ether extract decreased with age. There was a very small increase in the Ca content of ash and a very small decrease in the P content with age, resulting in a slightly wider Ca:P ratio in older boars.

Animals↗

PubMed1983

Restricted energy intake and elevated calcium and phosphorus intake for boars during growth. II. Foot and leg measurements and toe and soundness scores.

Boars were assigned at 5 wk of age in a 2 X 2 factorial arrangement to two energy (ad libitum and 75% of ad libitum) and two Ca and P levels (100 and 150% of the National Research Council daily recommended amounts) to determine the effect of reduced growth rate and elevated Ca and P intake on foot and leg measurements, pad and horn incidence and severity of lesions, and structural soundness. There were 20 boars/treatment; 15 boars from each treatment were necropsied at 10 +/- 2-d intervals from 80 to 220 d of age (45 to 185 d on test), with the remaining five boars in each treatment being necropsied at 220 d of age. Feet and leg measurements were taken and toe pads and horns were scored initially and after 78 and 131 d on when necropsied. Boars remaining after 130 d on test were scored for overall structural soundness. Toe size and circumference and length of limbs increased as boars grew, with larger values for ad libitum-fed compared with limit-fed boars when observed at a constant age. However, when these values were corrected for body weight, the effect of energy was generally removed and, in some cases, reversed. Limit-fed boars appeared to have fewer pad and horn lesions, but the effects were inconsistent. In general, Ca and P levels had little or no effect on toe and limb sizes and pad and horn lesion scores, whether or not the values were expressed on a constant age or corrected body weight basis. A comparison of inside and outside toes on the front and hind feet revealed that outside toes were larger than inside toes, with the magnitude of the difference much larger for the hind foot than for the front foot. The hind inside toes had fewer pad and horn lesions. Structural soundness scores were more desirable in ad libitum-fed compared with limit-fed boars; but, elevated Ca and P levels had no effect. Thus, these data do not support a hypothesis that structural soundness can be improved by reducing the growth rate of developing boars or by feeding an elevated level of Ca and P.

Animals↗

PubMed1982

Peripheral testosterone in boars after administration of hCG, ACTH and testosterone at three ages.

Forty-four purebred Yorkshire boars, reared outdoors on concrete, were randomly assigned to one of three age groups (150 +/- 7, 200 +/- or 250 +/- 7 days of age) for the purpose of examining endogenous testosterone concentration in response to one of four exogenously administered treatments. Four boars from each age group were administered either human chorionic gonadotrophin (hCG; 1000 U.S.P. units intravenous), adrenocorticotrophin (ACTH; 100 IU intravenous), or testosterone proprionate (TP; 25 mg intramuscular). The remaining boars served as controls and were given saline (S; 5 ml IV). Blood samples were collected from each boar at -120, -90, -60, -30, and 0 min pre-treatment and at 15, 30, 45, 60, 75, 90, 105, 120, 150, 180, 210, 240, 270, 300, 330, and 360 min post-treatment via an indwelling anterior vena cava catheter. Plasma testosterone was quantified by radioimmunoassay. Within treatment, boars receiving hCG, ACTH or S responded similarly (P>.10) across the three age groups for measured testosterone. Plasma testosterone was elevated (P<.05) by 30 min (4.7 +/- .5 ng/ml; X +/- SEM) and 15 min (5.5 +/- 1.1 ng/ml) post-treatment in boars administered hCG and ACTH, respectively, when compared with the S (1.0 +/- .3 ng/ml) group. Testosterone in hCG treated boars peaked by 90 min (21.8 +/- 1.8 ng/ml) post-treatment, declined slightly until 210 min (18.8 +/- 1.8 ng/ml) post-treatment and increased thereafter. Hormone levels in ACTH treated boars plateaued by 45 min (7.5 +/- 1.4 ng/ml) post-treatment and began to decline by 90 min post-treatment. Plasma testosterone for TP treated boars differed (P<.05) over time among the three age groups. Boars 150 +/- 7 and 200 +/- 7 days of age had an increase in plasma testosterone at 150 and 240 min post-treatment with TP, respectively. Results suggest that the testosterone biosynthetic and secretory capabilities of the boar testes are fully operational by 150 days of age.

Journal Article↗

PubMed1982

Daily alterations in plasma testosterone in boars at different ages.

Eighteen purebred Yorkshire boars, reared outdoors on concrete, were randomly assigned in equal numbers to three age groups (150+/-7, 200+/-7 and 250+/-7 days of age) for the purpose of examining endogenous testosterone concentrations over a 24-hr period. Blood was obtained at 30-min intervals for 24 hr, and plasma testosterone concentrations were quantitated by radioimmunoassay. For each set of 24-hr samples, mean concentration (C), frequency (F) and magnitude (M) of secretory spikes of testosterone were determined. There was no difference (P>.10) in C, F and M across the three age groups. When averaged over ages, testosterone mean (+/-SEM) for C, F and M was 1.4+/-.1 ng/ml, 2.9+/-.5 and 3.0+/-.3 ng/ml, respectively. The results suggest that testosterone secretory patterns are established in boars by five months of age and that these patterns may be influenced by degree of daylight.

Journal Article↗

PubMed1982

Restricted energy intake and elevated calcium and phosphorus intake for gilts during growth. I. Feedlot performance and foot and leg measurements and scores during growth.

Three groups of 96 crossbred gilts each were weaned at 4 to 5 wk of age (avg wt, 7.2 kg) and assigned to four treatments in a 2 X 2 factorial arrangement (ad libitum vs 75% of ad libitum energy intake and 100 vs 150% of NRC-recommended daily Ca and P). The effects on feedlot performance and on foot and leg scores and measurements were examined at approximately 50 and 100 kg body weight. Also, pigs were subjectively scored for overall structural soundness at the same weights. Limit-fed gilts consumed 78.1% as much feed as gilts fed ad libitum. Average daily gain of the limit-fed gilts was 86.7% that of the gilts fed ad libitum (P less than .01), and feed/gain was nonsignificantly improved by 8.4% for limit-fed gilts. The feeding of 150% of NRC-recommended levels of Ca and P resulted in a 5% increase (P less than .05) in daily gain, but daily feed intake and feed/unit of gain were not significantly affected. At the same age, almost all foot and leg measurements were larger for gilts fed ad libitum than for limit-fed gilts. However, when the values were adjusted for body weight, there was little or no measureable effect of energy intake. Elevated Ca and P levels had minimal effects, with only a trend toward larger measurements for gilts fed 150% of NRC-recommended daily Ca and P levels. Foot and leg measurements increased from 50 to 100 kg and were larger for the outside toes than for the inside toes for both front and hind feet. Energy intake and elevated Ca and P levels had little effect on the incidence and severity of toe lesions. The incidence of pad and horn lesions increased over time and was much greater on the outside toes on the front and hind feet. Restricted feeding and increased Ca and P levels did not improve overall structural soundness.

Animals↗

PubMed1982

Restricted energy intake and elevated calcium and phosphorus intake for gilts during growth. II. Gait characteristics analyzed from 16-mm motion picture photography.

Three groups of 96 crossbred gilts were weaned at 4 to 5 wk of age (average initial weight, 7.2 kg) and assigned to four dietary treatments in a 2 X 2 factorial arrangement of treatments (ad libitum vs 75% ad libitum and 100 vs 150% of NRC daily Ca and P). The effects of dietary treatments on the gait characteristics of gilts were analyzed by 16-mm motion picture photography. At approximately 50 and 100 kg body weight (periods 1 and 2, respectively), pigs were photographed walking on a treadmill, and gait characteristics were measured from the motion picture film. Ad libitum-fed gilts were longer, taller, wider and deeper when compared with restricted-fed gilts on an equal age basis, but not when compared on an equal weight basis. Other side view and rear view measurements were inconsistently affected by energy level (ad libitum vs restricted) at the two time periods, and all measurements were unaffected by Ca and P level. Analysis of the side and rear view characteristics over time generally revealed undesirable changes (P less than .01) from 59 to 100 kg. Both left and right hock-joint deviation increased (P less than .01) from period 1 to period 2, when expressed on an equal weight basis, suggesting the development of joint weakness. The hind pastern angle and the angle at the hock-joint also increased with time (P less than .01), suggesting development of post-leggedness as pigs increased in age and weight. Correlation coefficients among the various photographic characteristics and structural soundness scores were generally very low. Long-term effects of the dietary treatments on structural development are under study.

Animals↗

PubMed1980

Glucocorticoid concentrations, corticosteroid binding protein characteristics and reproduction performance of sows and gilts subjected to applied stress during mid-gestation.

Two experiments were conducted to evaluate the effects of applied heat (greater than or equal to 28 C) and crowding (less than or equal to .9 m2 floor space/animal) stress for 50 days during mid-gestation on glucocorticoid concentrations, corticosteroid binding globulin (CBG) characteristics and reproductive performance of 20 sows (Exp. 1) and 23 gilts (Exp. 2). Blood as collected via puncture of the anterior vena cava on days -1 and 0 before initiation of treatment and on days 1, 2, 12, 13, 48, 29 and 1, 5, 9 +/- l, 19 +/- 1, 50, 63 +/- 3, 90 +/- 1 after initiation of treatment for sows and gilts. respectively. Plasma glucocorticoids and CBG characteristics were determined by competitive protein binding techniques. Overall mean glucocorticoid concentrations for eight sows and 12 gilts subjected to stress were lower (P less than .05) than those of control animals, CBG binding capacities (CBC) were lower (P less than .05) in treated sows and gilts bled on days 12 and 9 +/- 1 after initiation of stress, respectively. Overall mean CBC and affinity (Ka) of cortisol to bind to the CBG molecule were lowered (P less than .05) in stressed gilts. Other than a reduction (P less than .05) in gestation length observed in stressed crossbred sows, reproductive performance was not affected by stress. When infrequent blood samplings are employed, measurement of CBC may serve as a more precise indicator of a physiological stress response than glucocorticoid concentration.

Animals↗

PubMed1979

Control of estrus in gilts with a progestogen.

Two trials were conducted to evaluate the effectiveness of a synthetic progestogen, allyl trenbolone, for control of estrus and ovulation in gilts. Estrus was effectively synchronized with 33 of 38 gilts exhibiting estrus 2 to 7 days after last progestogen feeding. There was no effect on fertilization rate in gilts free of ovarian abnormalities. Ovulation rate was higher in gilts fed the progestogen in both Trial 1 (P less than .01) and Trial 2 (P less than .10). Progestogen treatment caused an increase (P less than .01) in the incidence of cystic follicles which resulted in a decrease (P less than .01) in conception rate in Trial 1.

Animals↗

PubMed1977