Search Results

You are looking at 1 - 10 of 19 items for

  • Author: N. L. FIRST x
Clear All Modify Search
Free access

N. L. FIRST

Two experiments were conducted to determine if methallibure (ICI 33828), a hypothalamus-inhibiting dithiocarbamoylhydrazine (Malven, 1971) would prevent parturition.

In Exp. 1, thirteen pregnant Yorkshire, Poland China and Yorkshire × Poland China gilts were divided into three groups. Three gilts were assigned to be controls, four were fed 150 mg ICI 33828/gilt/day from the 100th to the 116th day of gestation and the six remaining gilts received ICI 33828 from the 100th day of gestation until parturition. Piglet numbers and weights were determined on the day of parturition.

In Exp. 2, fourteen pregnant Yorkshire or Poland China sows were randomly assigned to be untreated controls or fed 200 mg ICI 33828/sow/day from Day 100 of gestation until parturition. Piglet numbers and weights were obtained at birth and at 1 week of

Free access

D. L. GARBERS and N. L. FIRST

It is the purpose of this study to determine the effect of relative centrifugal force (RCF) × g on various semen characteristics of the bull and boar.

Entire ejaculates of mature Yorkshire boars were collected and separated from the gel fraction by allowing the semen to run through three layers of cheesecloth into a warm thermos. The ejaculate was then placed in 50-ml centrifuge tubes and centrifuged at 1000g for 10 or 15 min to remove the spermatozoa. Part of the first supernatant was kept for further analyses, while the remaining semen was centrifuged at forces and times given in Tables 1, 2 and 3. Bull epididymal fluid was collected by flushing through the vas deferens with a 154 mm-KCl, 10 mm-tris buffer at pH 7·2 according

Free access

D. L. GARBERS and N. L. FIRST

Summary.

Two experiments using twenty-four sows and forty-eight gilts were designed to study ovarian and pituitary functions after treatment with oestradiol-17β (3 mg/day), progesterone (150 mg/day) or ICI 33828 (50 or 100 mg/day). The dose levels were chosen so that oestrus and ovulation would be inhibited.

None of the treatments blocked total synthesis of fsh or lh within the 10-day treatment period. ICI 33828 at 100 mg blocked fsh release early in the cycle but 50 mg did not. Oestrogen also blocked fsh release early in the cycle. All follicle growth greater than 4 mm diameter was effectively inhibited by oestrogen and the corpora lutea were maintained. Both progesterone and ICI 33828 reduced the number of follicles growing larger than 5 mm as compared to the control gilts. All treatments blocked fsh release late in the cycle.

There were increased levels of pituitary lh in ICI 33828-treated gilts compared to progesterone-treated gilts early in the cycle, but none of the treatments caused differences in lh levels from those found in the control gilts early in the cycle. All treatments blocked pituitary lh release late in the oestrous cycle.

The pituitary content of prolactin did not differ significantly between treatments.

Free access

D. L. GARBERS and N. L. FIRST

Summary.

Thirty-five sexually mature gilts were fed either the compound ICI 33828 (100 mg/day) or a control ration on Day 18 of the oestrous cycle (Day 1 = oestrus). At 2, 4 or 6 days after oestrus, gilts were killed and ovarian and pituitary data collected. Treated gilts not showing an oestrus were killed 10 days after treatment was started. Sixty-seven per cent of the treated gilts showed the forthcoming oestrus. A high percentage (75%) of the treated gilts which exhibited oestrus failed to ovulate. The number of follicles was less than would normally be present before ovulation, and pituitary fsh and lh levels were greater in the ICI 33828-treated (non-ovulating) gilts than in controls. Gilts killed 10 days after initiation of treatment had high levels of pituitary fsh and lh, which may explain the occurrence of superovulation in one gilt (> 100 corpora lutea). These gilts, which did not ovulate except for one pig, also had no follicles greater than 6 mm in diameter, indicating that fsh release was blocked by the drug. The lower ovulation rate in the three ICI 33828-treated gilts which ovulated, compared to the controls, was thought to be the result of decreased follicular growth in the treated gilts.

Free access

D. L. GARBERS and N. L. FIRST

Exogenous oestrogens maintain the corpora lutea (cl) in the cycling gilt (Gardner, First & Casida, 1963). The pituitary is required, since oestrogen will not maintain cl in the gilt in which the pituitary stalk has been transected (Anderson, Dyck, Mori, Henricks & Melampy, 1967). Oestrogen blocks pituitary lh and fsh release, and Rothchild (1966) has therefore suggested that increased prolactin release due to oestrogen may maintain the corpora lutea in the intact gilt. Prolactin, however, will not delay cl regression in the hypo-physectomized pig (Du Buisson, Leglise, Anderson & Rombauts, 1964). Since a single oestrogen injection was found to maintain cl in the sow (Nishikawa, 1959), oestrogen may stimulate a single release of a pituitary luteotrophin, induce a constant pituitary release of a luteotrophin, or act directly at the ovarian or uterine levels to effect
Free access

D. L. GARBERS and N. L. FIRST

It has been shown that a dithiocarbamoylhydrazine, ICI 33828, inhibits the milk-ejection reflex in lactating rats without significantly altering milk formation (Benson & Zagni, 1965), and that oxytocin treatment can overcome the milk ejection inhibition caused by ICI 33828 in the sow (Gerrits, Johnson & Kraeling, 1965). Because the site of action of the ICI 33828 compound is believed to be at the pituitary or hypothalamic level, we have directed research effort to establishing the effect of this compound on various pituitary hormones. This brief communication is presented to demonstrate further, using a larger number of sows, that exogenous oxytocin can overcome the inhibitory action of ICI 33828 on milk ejection.

Ten crossbred sows were assigned to this study as pairs dependent on the time of farrowing. One sow in each pair was then assigned

Free access

R. B. STAIGMILLER and N. L. FIRST

Studies by Robertson, Casida, Grummer & Chapman (1951) demonstrated that ovulation rate in swine could be influenced by the level of feed intake. Most studies showing this `flushing effect' utilized 6- to 21-day intervals of high energy feeding. Recently, however, attempts have been made to obtain a flushing effect by feeding a single high energy feed during oestrus in the pig. Feeding the increased energy levels on the 1st day of oestrus has been reported to result in a significant flushing response (Lodge & Hardy, 1968; Brooks, Cooper, Lamming & Cole, 1972) while other reports have not shown this effect (Naber & Zimmerman, 1971; Moore, Dutt, Hays & Cromwell, 1971; Cooper, Brooks, Cole & Haynes, 1973). Flushing on the 2nd day of oestrus was reported as not leading to an increase in ovulation rate (Brooks et al., 1972).

The study reported here was conducted to determine if an increase in

Free access

W. H. Eyestone and N. L. First

Summary. In Exp. 1, 5–8-cell embryos from superovulated cattle were co-cultured with oviducal tissue suspended in Ham's FIO + 10% fetal calf serum (F10FCS) or in F10FCS alone. After 4 days, the proportion of embryos developing into compact morulae or blastocysts was greater (P < 0·005) in co-culture (38/82; 46%) than in F10FCS (1/27; 4%). In Exp. 2, a solution of collagenase, trypsin, DNAse and EDTA was used to disperse oviducal tissue, which was then cultured in TCM199 + 10% fetal calf serum (M199FCS) to obtain monolayers. Embryos (1–8 cells) were then co-cultured with monolayers or in M199FCS alone. The proportion of embryos developing into compact morulae and blastocysts after 4–5 days was higher (P < 0·005) in co-culture (15/34; 43%) than in M199FCS (1/37; 3%); mean numbers of cells/embryo were also higher (P < 0·001) (27·70; range 2–82 in co-culture; 8·83; range 2–18 in M199FCS). In Exp. 3, embryos obtained from in-vitro maturation and fertilization were used to compare development between co-culture and medium conditioned by oviducal tissue. Initial cleavage rate (no. embryos > 1 cell/total) was 76% (611/807) and did not differ among treatments. After 5 days, the proportion cleaving to > 16 cells was higher (P < 0·005) in co-culture (71/203; 35%) and conditioned medium (48/205; 23%) compared to M199FCS (14/203; 7%). Similarly, the proportion developing into compact morulae and blastocysts was greater (P < 0·005) in co-culture (44/203; 22%) and conditioned medium (46/205; 22%) than in M199FCS (7/203; 3%). Developmental potential was tested in Exp. 4 by transferring embryos to 11 recipients, of which 6 (55%) became pregnant.

Keywords: embryo; co-culture; cattle; in vitro; oviduct

Free access

R. B. STAIGMILLER, D. L. GARBERS and N. L. FIRST

Increasing the level of energy intake of gilts has been shown to increase ovulation rate, but the exact hormonal mechanism by which this phenomenon occurs is unknown. Different quantitative changes in the pituitary content of lh and fsh of gilts on high and low energy intakes were reported, however, by Kirkpatrick, Howland, First & Casida (1967). They also noted a higher progesterone content of the corpora lutea from gilts on high energy than from those on low energy intake.

Methallibure (ICI 33828) inhibits the release of pituitary lh and fsh in swine (Garbers & First, 1969). Gilts receiving the compound showed a lower level of luteal progesterone than control gilts on Day 8 but a higher level on Day 16 (Stormshak, Leverage, Kelley & Gerrits, 1970).

The present study was conducted to determine

Free access

L. R. French, J. J. Rutledge and N. L. First

Summary. Litter size increased (P < 0·01) as the age of the dam at farrowing increased. However, previous reproductive experience (parity) had no direct effect on litter size of dams of the same age.