Factors affecting dystocia and early calf mortality in Angus cows and heifers.

Calving performance records (965,417) from purebred American Angus herds throughout the United States were used to study dystocia and early calf mortality during the period from 1972 to 1985. A sample of 53 (n = 83,467) herds was used to establish reasonable limits on the expected frequency of dystocia and mortality within and among herds that have good reproductive management programs and to verify the frequencies of scores in all other herds (n = 4,130) reporting calving performance information. The data were analyzed by logistic regression models. Dystocia and perinatal mortality, to a lesser extent, were found to be more frequent in heifers than in cows. The odds of unassisted births vs births with major difficulty were 11.58 times greater in cows than in heifers. In heifers, the odds of an unassisted birth increased with age of dam and decreased with birth weight of calf. At a baseline age of 22 mo the odds of an unassisted birth for calves weighing 30 and 40 kg were .13 and .02 times lower than the odds for calves weighing 20 kg. Alternately, at 29 mo, the odds of an unassisted birth for heifers producing a 20-kg calf were 4.53 times greater than at 22 mo. Survival of calves to 24 h in heifers was primarily affected by birth weight. Heifers producing calves at intermediate weights of 29 kg had higher odds of producing live calves at all ages. Considering all heifers calving at 22 to 29 mo relative to 20-kg calves, the odds for survival to 24 h were 3.83 times greater for 29-kg calves and lower by a factor of .52 for 40-kg calves.     

Factors influencing calving difficulty in beef heifers

Records of 547, 2-yr-old heifers of three breed groups were used to evaluate the relative influence of dam's body and pelvic measurements, calf birth weight, sire birth weight and some relative measures (ratios) of calf birth weight and dam weight at calving on calving difficulty. The data were analyzed by regression and least squares procedures. The full model explained 32.5% of the variation in calving difficulty score. The linear effect of calf birth weight was the most important variable, accounting for 17.8% reduction in the coefficient of determination, and together with dam weight at calving and the quadratic effect of calf birth weight it accounted for 92% for all the variation explained by the full model. Dam weight at calving was negatively related to calving difficulty. Breed, year and sex of calf did not influence calving difficulty score, except when the calf birth weight or dam weight or both were excluded from the model. When calf birth weight was expressed as a ratio of the dam's weight at calving, hip height and pelvic measurements, the total model explained 34.8% of the variation in calving difficulty score. The ratio of calf birth weight to dam weight was the most important variable (R2 = 26.8%). Ratios of calf to dam weight at calving and calf weight to the vertical pelvic diameter (R2 = 29.3%) were the only significant factors when the effects of calf birth weight and dam weight were removed from the model. Pelvic measurements, on their own, did not influence calving difficulty score in this study (P greater than .1), but small pelvic dimensions tended to be associated with higher calving difficulty scores.     

Factors affecting dystocia and offspring vigour in different sheep genotypes

Birth difficulty and poor lamb vigour are significant causes of perinatal lamb mortality. In this study we investigated whether sheep breeds differing in appearance, muscularity and selection history also had differences in dystocia and lamb vigour, and considered some of the factors that may contribute to the variation in these traits. Data were collected at birth from a total of 3252 lambs of two terminal sire breeds selected for lean growth (Suffolk [S], n = 500 and Texel [T], n = 1207), from a Hill breed (Scottish Blackface [B], n = 610), which has been mainly selected for hardiness, and a crossbred (Mule × T [M], n = 935) representing a maternal line. For each lamb the degree of assistance at delivery, lamb presentation, amount of assistance to achieve successful sucking, sex, litter size and birth weight were recorded. T lambs required the most, and B and M lambs the least assistance at birth, S lambs were intermediate (% lambs assisted: T = 55.7, S = 30.7, B = 22.7, M = 24.9, P < 0.001). T and S lambs were equally likely to be malpresented at birth (29% of births) and more likely to be malpresented than B or M lambs (20%; P < 0.001). In T and S breeds lambs requiring veterinary assistance at delivery were mainly heavy and singleton lambs, whereas in B and M breeds these were exclusively low birth weight lambs in multiple litters. Although heavier lambs needed greater birth assistance, T lambs were lighter than S and M lambs, but heavier than B lambs (birth weight (kg): S = 4.66, M = 4.56, T = 4.32, B = 3.67, P < 0.001). S lambs were more likely to require assistance with sucking than other breeds, and T lambs also required more assistance than B or M lambs (% lambs assisted to suck: S = 56.0, T = 31.6, M = 19.8, B = 18.4, P < 0.001). Heavier lambs were more likely to suck unaided than lighter lambs (P < 0.001). The data suggest that the two terminal sire breeds, selected narrowly for greater productivity (muscle growth and conformation), are more likely to experience birth difficulty and poorer lamb vigour than the breed selected for hardiness, or the cross breed. Whether these effects arise as a consequence of genetic selection (e.g. for specific lamb conformation), or as a result of management practices to achieve selection goals (e.g. increased intervention at lambing) is unknown. Specific actions to improve birth difficulty and lamb vigour, such as including these traits in the selection index, would be beneficial in improving the welfare of ewes and lambs of the terminal sire breeds.     

Factors associated with shortened estrous cycles after abortion in beef heifers

Forty-six crossbred Hereford heifers were allotted into five experimental groups. Fenprotalene, a prostaglandin analogue, was administered to induce abortion and (or) to regress the corpus luteum (CL) in four groups of heifers about 75 d after conception. The four groups were 1) pregnant heifers, 2) pregnant heifers with the ovary contralateral to the gravid uterine horn removed 24 h after fenprostalene injection, 3) same as Group 2 but with the ipsilateral, rather than the contralateral, ovary removed and 4) heifers with uterus removed (ovaries intact) about 35 d after conception. A fifth group of nonpregnant heifers received implants containing norgestomet from 10 to 76 d after estrus and were given fenprostalene 24 h before removal of the implant. Average length of the first estrous cycle after the fenprostalene injection was 11.2, 8.3, 9.7 and 19.1 for Groups 1, 2, 3 and 5, respectively. Estrous cycles were longer (P less than .05) in norgestomet-treated heifers. Hysterectomized heifers (Group 4) did not exhibit a second estrus by 50 d after fenprostalene treatment; otherwise, all first estrous cycles after the fenprostalene injection were either "short" (7 to 13 d) or "normal" (17 to 23 d). Twenty-two of 24 heifers that aborted had short estrous cycles and two had normal estrous cycles. Short estrous cycles occurred after abortion regardless of whether the ovary ipsilateral or contralateral to the previously gravid uterine horn ovulated. Early regression of the CL (short luteal phase) did not occur in nonpregnant heifers after long-term progestogen stimulation or after hysterectomy, but it did occur in heifers with a previously gravid uterus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nonpuberal estrus in beef heifers

The frequency of occurrence of behavioral estrus without subsequent development of functional luteal tissue (termed nonpuberal estrus, NPE), was determined in 43 Simmental X Hereford-Brahman heifers. Blood samples were collected weekly from the start of the study to first behavioral estrus and then daily from d 1 (d 0 = estrus) through d 14 following first and subsequently observed estrous behaviors. All blood samples were analyzed for serum progesterone (P4) concentrations by radioimmunoassay. More heifers (62.8%) exhibited NPE than had luteal development after their first behavioral estrus (37.2%). There was a tendency for fewer light-weight heifers (less than or equal to 240 kg at the start of the experiment) to exhibit a puberal first estrus compared with the heavy-weight (greater than 240 kg at the start of the experiment) heifers (31.2% vs 68.8%, respectively; P = .12). Heifers that had a puberal first estrus were older (376 +/- 12 d vs 334 +/- 9 d, P less than .05) compared with heifers that had NPE. Weight at first behavioral estrus was similar between heifers that had a puberal first estrus and those that had NPE (298 +/- 8 kg and 289 +/- 6 kg, respectively). More heifers that had a puberal first estrus also had an elevation in serum P4 concentrations before that first estrus (64.3% vs 20.0%, P less than .05), and the serum P4 elevation was greater (2.5 +/- .4 ng vs 1.2 +/- .1 ng, P less than .05) than heifers that had NPE. We have concluded from these results that NPE is a common occurrence in heifers approaching puberty.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors affecting dystocia and birth weight in Grati cattle in Pujon,East Java

Summary

This paper discusses factors affecting dystocia and birth weight in Grati cattle in three villages in the Pujon district, East Java. Records of birth weight, dystocia score, village, season, parity, sex, artificial versus natural service, and age and weight of dam, were obtained from 268 parturitions. Village and weight of the dam had a significant effect on birth weight but not on dystocia. Parity had a significant effect on dystocia score. More abnormal births occurred with Al using exotic bulls. Calves from an abnormal birth were on average more than three kg heavier. First parity births combined with A1 with exotic bulls had a particularly high incidence of dystocia. It is concluded that farmers in Pujon can reduce the incidence of dystocia in heifers by using local bulls only.     

Factors affecting dystocia and birth weight in Grati cattle in Pujon, East Java

This paper discusses factors affecting dystocia and birth weight in Grati cattle in three villages in the Pujon district, East Java. Records of birth weight, dystocia score, village, season, parity, sex, artificial versus natural service, and age and weight of dam, were obtained from 268 parturitions. Village and weight of the dam had a significant effect on birth weight but not on dystocia. Parity had a significant effect on dystocia score. More abnormal births occurred with AI using exotic bulls. Calves from an abnormal birth were on average more than three kg heavier. First parity births combined with Al with exotic bulls had a particularly high incidence of dystocia. It is concluded that farmers in Pujon can reduce the incidence of dystocia in heifers by using local bulls only.     

Energy metabolism in lactating beef heifers

To obtain measurements of energy balance in lactating beef cows, respiration calorimetry and digestion trials were conducted using seven lactating (613 kg BW) and three nonlactating (598 kg BW) Hereford x Angus heifers fed a pelleted 75% alfalfa:25% concentrate diet. Five measurements of energy balance were obtained at 6- to 7-wk intervals beginning 6 to 10 wk postpartum in lactating heifers and at 6-wk intervals in nonlactating heifers. Milk yield was measured using a combination of weigh-suckle-weigh and machine milking to adapt heifers to milking by machine without the use of oxytocin. Heifers were milked only by machine during measurements of energy balance. Weekly milk yield averages ranged from 8.2 kg/d at wk 5 postpartum to 3.2 kg/d at wk 32 postpartum. When scaled to BW(.75), the regression of NE1 on ME intake and the regression of ME intake on NE1 were remarkably similar to previously published regressions for measurements obtained from lactating Holstein-Friesian cows. The average daily maintenance energy requirement from these regressions was 503 kJ ME/kg BW(.75), a value similar to the average value reported previously for lactating Holstein-Friesian cows (488 kJ/kg (BW.75)). This is in contrast to numerous published comparisons of the maintenance requirements of cattle breed types in the nonlactating state and current NRC standards for estimating maintenance energy requirements of beef and dairy cattle. The results of the present study suggest that when expressed on the basis of BW(.75) the efficiency of utilization of incremental ME above maintenance for milk and tissue energy (i.e., NE1) is similar among lactating Hereford x Angus heifers and lactating Holstein-Friesian cows. The breeds differ in terms of their propensity for milk yield and the resulting partition of ME between milk synthesis and tissue energy retention.     

Induced Tritrichomonas foetus infection in beef heifers

Four virgin beef heifers were inoculated intravaginally with 7 x 10(6) Tritrichomonas foetus organisms. Protozoal colonization of the vagina, cervix, and uterus developed within the first week after inoculation. Protozoa were no longer detected in secretions from these regions at approximately the same time in each heifer. Trichomonads were detected in reproductive tract secretions for 13 to 28 weeks. Eight weeks after clearance of trichomonads from the reproductive tract, a second infection was established in 2 of the 4 heifers by intravaginal inoculation of T foetus. The second infections were maintained for up to 4 weeks. The diagnostic sensitivity of wet-mount examination of the reproductive tract secretions was 30%, compared with 78% for culture of trichomonads in secretions. Collection and culturing of specimens of cervical and vaginal mucus provided the most reliable method for diagnosis of trichomoniasis during induced infection of heifers.     

Effect of antiparasitic treatment in beef replacement heifers

Two studies were conducted in western Canada to evaluate the impact of antiparasitic treatment on weight gain and reproductive performance in beef replacement heifers from weaning to first breeding. Treatment of heifers at weaning with ivermectin increased the rate of weight gain in comparison to treatment with fenthion. The feed efficiency of ivermectin-treated animals was also significantly better than those treated with fenthion. Increased weight was associated with an increased number of animals in estrus at the end of the feeding period for heifers receiving ivermectin. We concluded that treatment with ivermectin improved feed efficiency and weight gain in heifers from weaning to breeding. In turn, this weight gain appeared to be associated with an increased number of heifers in estrus.     

Serum copper concentrations in beef cows and heifers

OBJECTIVE: To characterize serum copper status of cows and heifers in beef cow-calf herds throughout the United States and to evaluate use of copper supplements in those herds. DESIGN: Cross-sectional survey. ANIMALS: 2,007 cows and heifers from 256 herds in 18 states. PROCEDURES: Producers participating in a health and management survey conducted as part of the National Animal Health Monitoring System voluntarily allowed serum samples to be obtained from cows and heifers for determination of copper concentration. Results were categorized as deficient, marginally deficient, or adequate. The proportion of cattle and herds (on the basis of mean value of the tested cattle) in each category was determined. Copper concentrations were compared between herds that reportedly used copper supplements and those that did not. RESULTS: Overall, 34 of 2,007 (1.7%) cows and heifers were deficient in copper, and 781 (38.9%) were marginally deficient. In each region, at least a third of the cattle were deficient or marginally deficient. For herds, 92 of 256 (35.9%) were marginally deficient, and 22 (0.8%) were deficient. Approximately half of the producers reported use of copper supplements, but a sizeable proportion of those producers' cattle and herds were classified as marginally deficient or deficient. CONCLUSIONS AND CLINICAL RELEVANCE: Copper deficiency is not restricted to a single geographic region of the United States. Copper deficiency can persist despite reported use of supplements by producers. Veterinarians dealing with beef cow-calf herds that have problems consistent with copper deficiency should not rule out copper deficiency solely on the basis of geographic region or reported use of copper supplements for the herd.     

Effects of long-term estrogen implants in beef heifers

Crossbred beef heifers (n = 78) were assigned randomly to one of three treatments. Heifers received either no implant, one estradiol-releasing implant (Compudose), or two estradiol-releasing implants. Heifers were implanted at birth and then reimplanted every 150 d. Calves were maintained with the cows until weaning at approximately 200 d of age. Heifers were placed in the feedlot as one group and fed a growing diet for 56 d. Following the growing phase, heifers were segregated into their respective treatment groups and fed until selected by industry buyers for harvest. Beginning at 1 yr of age and continuing every 14 d until puberty or harvest, heifers were palpated per rectum, and blood samples were collected for determination of ovarian activity and attainment of puberty. Serum progesterone of > or =1 ng/mL and(or) palpation of a detectable corpus luteum were criteria of puberty. At weaning and again at harvest, an x-ray was taken of the left front leg of six heifers selected randomly from each group. Metacarpal bones III and IV from the same animals were collected at harvest and transected for determination of epiphyseal plate closure. The x-ray scores and the actual measurements had a correlation of .94. Epiphyseal plate closure occurred in a dose-related manner, with heifers on the higher dose of estrogen having earlier plate closure than heifers on the lower dose. At harvest, reproductive tissues and carcass data were collected for all heifers. Eighteen of 25 untreated control heifers (P < .05), 6 of 26 heifers treated with one implant, and 2 of 26 heifers treated with two implants attained puberty by the end of the experiment. No differences (P > .10) were detected among treatment groups for carcass traits. These data suggest that early and continuous treatment of heifers with estradiol implants can retard reproductive function.