Pelvic Development as Affected by Relaxin in Three Genetically Selected Frame Sizes of Beef Heifers1

Abstract

Purified porcine relaxin was administered into the cervical os on Day 278 of gestation to determine its effects on pelvic development in three genetically selected frame sizes of primiparous beef heifers. Heifers were categorized as small, medium and large frame based upon their genetic composition. Pelvic height, pelvic width and cervical dilatation were determined from Day 270 to 2 days postpartum. On Day 270, heifers were assigned at random to one of three treatments: vehicle control, n = 16; relaxin once (3,000 U), n = 14; and relaxin twice (2 times 3,000 U 12 h apart), n = 17. Each heifer-frame size was represented in each treatment. Relaxin caused marked increases in pelvic height and width, as well as in the rate of linear increase (cm/day) of these parameters (p less than 0.05). These linear increases in pelvic height were 510, 264 and 204%, and pelvic width, were 280, 213 and 204% of the respective pretreatment rates for small, medium and large heifers. The rate of linear increase in pelvic width was greater than pelvic height in all heifers, but maximal in small-frame heifers; relaxin attenuated these intrinsic differences. For small heifers, the rate of linear increase in pelvic width was 121 and 145% of increases for medium and large heifers, respectively, before treatment, and 160 and 200% after treatment. The rate of postpartum involution of pelvic width was -0.03, -0.36 and -0.50 cm/day and, for pelvic height, -0.02, -0.27 and -0.29 cm/day in small, medium and large heifers, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Transmission of Relaxin from Lactating Bitches to their Offspring Via Suckling1

“…This finding is consonant with a relationship between the transmission of milk-borne factor(s) and the expression of hip dysplasia in genetically predisposed pups. By the very nature of its well-known effects on the connective tissues of the pelvic girdle [22][23][24][25][26][27][28], Rlx might be such a factor. Indeed, an early report suggests that treatment of newborn pups with estrogen and an impure porcine Rlx preparation can induce hip dysplasia [291.…”

Relaxin on induction of parturition in cattle: effects on hormonal, pelvic and cervical changes, and postpartum fertility

“…This study indicates that a combined treatment of relaxin with cloprostenol or dexamethasone reduced the incidence and severity of dystocia due to increased cervica^. and pelvic relaxation (Musah et al, 1986b) as well as reduced the incidence of retained placenta as reported earlier (Musah et al, 1986a).…”

“…This study indicates that a combined treatment of relaxin with cloprostenol or dexamethasone reduced the incidence and severity of dystocia due to increased cervica^. and pelvic relaxation (Musah et al, 1986b) as well as reduced the incidence of retained placenta as reported earlier (Musah et al, 1986a).The mechanisms by which relaxin may reduce retained placenta are unknown* The maternal and fetal connective tissue in placentome becomes progressively collagenized up to the time of parturition. At the onset of parturition, the tissue of the placentome becomes loose, a process that is essential for expulsion of the fetal membranes (Grunert, 1980).…”

“…Pelvic canal expansion is due to increase both the rate of linear growth as well as an absolute increase in pelvic height and width (Musah et al, 1986b). The increase in pelvic height and width may be a result of relaxation of sacroiliac ligaments Fields et al, 1981), formation of Interpubic ligaments (Leltch et al, 1959) and modification of the pubic symphysis, by transforming symphyseal cartilage and bone .…”

“…Relaxln was administered IM or OS at 0 h (time of dexasone or cloprostenol) or 24 h later as described in Table 1 These cows were phenotypically divided into size groups* A significant difference (P<0.05) now exists among frame sizes with regard to adjusted yearling body weight, yearling hip height and pelvic canal area of the progeny from this crossbreeding program (Musah et al,, 1986b). Results from the first study were thus analyzed with regard to frame size and treatments.…”