Journal of Animal Science

Lewis, R., M.;Shelton,, M.;Sanders, J., O.;Notter, D., R.;Pirie, W., R.

doi: 10.2527/jas1989.6751107xpmid: N/A

Abstract Additive and multiplicative environmental adjustments for effects of dam age, lamb sex and birth-rearing type on 120-d weight were derived using data from 819 Rambouillet range lambs. The relationship between mean and variance within environmental effect classes was one criterion for evaluating suitability of adjustment methods. Among lamb sexes and birth-rearing types, larger means were associated with greater variability (P < .01). Variances became homogeneous (P > .10) when data were expressed on a logarithmic scale, suggesting that multiplicative adjustments for these effects are needed. Because variances were homogeneous with respect to dam age (P > .50), additive adjustment factors are suggested for this effect. Validation of a proposed combined multiplicative and additive adjustment procedure was based on a double cross-validation procedure and suggested difficulty in developing widely applicable sets of factors. Application of established industry adjustment factors failed to eliminate variation associated with lamb sex and birth-rearing type. Concordance between individual lamb rankings for adjusted weights derived from five sets of adjustment factors was observed. Under more (5%) and less (30%) intensive selection of ram and ewe lambs, respectively, similar animals were retained as replacements irrespective of the factors used. These results suggest that the use of autonomous adjustments has greater impact on the calculation of adjusted weights than on selection decisions among lambs within sex based on such weights. This content is only available as a PDF. Author notes 1 The authors gratefully acknowledge the technical advice of the Statistical Consulting Center, Virginia Polytechnic Inst. and State Univ., Blacksburg, and W. H. McElhenny, Cornell Univ., Ithaca, NY. We also thank Angelo State Univ., San Angelo, TX, and the Texas Agric. Exp. Sta., Sonora, for access to production records. 2 Present address: Dept. of Anim. Sci., Virginia Polytechnic Inst. and State Univ., Blacksburg 24061. 3 Anim. Sci. Dept., Texas A&M Univ., College Station 77843. 4 Anim. Sci. Dept., Virginia Polytechnic Inst. and State Univ., Blacksburg 24061. 5 Dept. of Statistics, Virginia Polytechnic Inst. and State Univ., Blacksburg 24061. 6 Texas A&M Univ. System. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Brennan, Robert, W.;Hoffman, M., Peter

doi: 10.2527/jas1989.6751116xpmid: N/A

Abstract An interactive, deterministic linear programming model of a farm feedlot production system was developed to evaluate the effects of type of ration, feeding management practices and marketing alternatives on the relative profitability of producing feedlot cattle under midwestern conditions. Data from a 3-yr series of feeding trials conducted to evaluate six different diets that varied in the proportions of dietary metabolizable energy supplied by corn silage (CS) and a corn grain/alfalfa pellet mixture fed at two levels of intake (restricted vs ad libitum) to yearling steers were the data base for the livestock production coefficients. The farm feedlot model was operated under restrictions that operating capital was limited to $200,000, and feedlot capacity was fixed at 100 head to reflect production conditions that might be encountered in the field. Results from the linear programming model showed distinct differences in relative profitability between the various management systems evaluated, with type of diet being of major importance. Feeding management practices (restricted vs ad libitum feeding) and cattle marketing alternatives had little impact on the relative profitability of the cattle feeding enterprise. This content is only available as a PDF. Author notes 2 Center for Equine Studies, Findlay College, Findlay, OH 45840. Copyright 1989 by American Society of Animal Science American Society of Animal Science

DeRouen, S., M.;Franke, D., E.

doi: 10.2527/jas1989.6751128xpmid: N/A

Abstract Calving rate and calving date were studied in 859 Angus-, Brahman-, Charolais- or Hereford-sired straightbred or crossbred heifers exposed to calve first at 24, 30 or 36 mo of age. Angus-, Charolais- and Hereford-sired crossbred heifers had calving rates similar to those of contemporary straightbred heifers, whereas Brahman-sired crossbred heifers had higher (P < .01) calving rates than straightbred Brahman heifers (64 ± 4 vs 28 ± 6%). Heifers calving first at 24 and 36 mo had similar calving rates (73 ± 7 and 79 ± 10%), which were slightly higher (P > .10) than for those heifers calving at 30 mo (61 ± 7%). Calving rates for Angus- and Charolais-sired heifers were highest at 24 mo, whereas calving rates for Brahman- and Hereford-sired heifers were highest at 36 mo. Heifers that were older at the start of breeding season had higher calving rates (b = .41 ± .14%; P < .01) at 24 mo, but not at 30 or 36 mo. Breeding season weight adjusted for heifer age influenced (P < .01) calving rate at 30 (b = .32 ± .07%) and 36 mo (b = .23 ± .08%) but not at 24 mo. Brahman-sired heifers calved later (P < .01) during the calving season (63 ± 3 d) than heifers sired by Angus, Hereford or Charolais bulls (45 ± 2, 48 ± 1 and 50 ± 2 d). Heifers that were older and weighed more at the start of the breeding season calved earlier when exposed to calve at 24 mo (b = −.30 ± .08 d for heifer breeding age [P < .01]; b = −.11 ± .05 d for breeding season weight [P < .05]). These data indicate that, under conditions of our study, heifer sire breed and the interaction of sire breed with first calving opportunity influenced calving rate and date. Heifer age influenced calving rate, and heifer age and weight affected calving date when heifers were managed to calve at 24 mo. Heifer breeding season weight influenced calving rate for heifers exposed to calve at 30 and 36 mo. This content is only available as a PDF. Author notes 3 Anim. Sci. Dept., Louisiana Agric. Exp. Sta. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Patterson, D., J.;Corah, L., R.;Kiracofe, G., H.;Stevenson, J., S.;Brethour, J., R.

doi: 10.2527/jas1989.6751138xpmid: 2737973

Abstract Conception rate in heifers after synchronization of estrus with melengestrol acetate (MGA) and fenprostalene (a prostaglandin F2α analogue; PGF) was determined in pubertal Bos taurus and Bos indicus crossbred yearling heifers. Angus × Hereford (AH, n = 137) and Brahman × Hereford (BH, n = 97) heifers were sorted by body weight after weaning into light (LW) and heavy (HW) weight blocks. Heifers were assigned by age to diets to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weight by the start of breeding. Heifers that exhibited estrus and had serum progesterone ≥ 1 ng/ml (0 or 10 d before estrous synchronization treatment) were assigned randomly within breed and nutritional groups to either an estrous synchronization (S) or control (C) group. Heifers in the S group were fed .5 mg of MGA for 7 d and injected s.c. with 2 mg PGF on d 7 of MGA. All heifers were inseminated 12 h after first detected estrus. A greater proportion of AH (P < .01) than of BH heifers were in estrus within 6 d after PGF, and more S heifers than C heifers (P < .01) were in estrus. Conception rate at first service was proportionately higher (P < .001) in AH than in BH heifers and lower (P < .02) in S than in C heifers. There was a breed × energy level interaction (P < .01) for conception rate at first service. Stage of the estrous cycle at the time treatment with MGA was initiated influenced (P < .05) conception rate at first service in the S, AH heifers, with lower conception rates among heifers beginning treatment late in their estrous cycles (≥ d 12). Pregnancy rates after 21 d were higher (P < .01) in AH than in BH heifers and higher (P < .01) in HW than in LW heifers. More HE than LE heifers (P < .02), and more AH than BH heifers were pregnant after 45 d. Pregnancy rates at the end of 21 d were higher among HE, BH heifers than among LE contemporaries. A higher (P < .02) percentage of HE, HW, BH heifers were pregnant at the end of 45 d compared with other BH groups. Results indicated that a 7-d MGA-PGF treatment reduced conception rates at first service in pubertal yearling heifers. Pregnancy rate was affected by prebreeding nutrition in BH yearling heifers at the end of 45 d. This content is only available as a PDF. Author notes 2 Dept. of Anim. Sci. and Industry. 3 Fort Hays Branch Exp. Sta. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Britt, Jack, H.;Day, Billy, N.;Webel, Stephen, K.;Brauer, Michael, A.

doi: 10.2527/jas1989.6751148xpmid: 2737974

Abstract Ten trials involving 678 presumed prepuberal gilts (5.5 to 7.5 mo old) were conducted in North Carolina, Illinois and Missouri to evaluate the reproductive performance of gilts given a combination of 400 IU of pregnant mare's serum gonadotropin and 200 IU of human chorionic gonadotropin (P. G. 600®). Gilts that were presumed to be prepuberal received P. G. 600 or no treatment (control) on the day of movement from finishing facilities to pens for breeding. Detection of estrus, with the aid of mature boars, was conducted daily for 28 d; gilts in estrus were mated naturally. Treatment with P. G. 600 increased the percentage in estrus within 7 (57.5 vs 40.9%) or 28 d (72.9 vs 59.5%); average interval to estrus was reduced (P < .05) from 10.4 to 7.5 d. Farrowing rate (78.5 ± 3.1%), number of pigs born alive (8.6 ± .2) or dead (.26 ± .06) and number of pigs weaned (8.0 ± .2) were unaffected by treatment. Gilts that were heavier than the median for each farm were in heat sooner and more were detected in heat, but no other reproductive traits differed between heavy and light gilts. Overall, the results reveal that P. G. 600 was useful for induction of fertile estrus in prepuberal gilts. This content is only available as a PDF. Author notes 3 Dept. of Anim. Sci., Univ. of Missouri. 4 Dept. of Anim. Sci., Illinois State Univ. 5 Intervet America, Inc. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Sigler, D., H.;Ericson, D., E.;Gibbs, P., G.;Kiracofe, G., H.;Stevenson, J., S.

doi: 10.2527/jas1989.6751154xpmid: 2737975

Abstract Lactating mares were assigned as controls or fed altrenogest (.044 mg·kg body wt−1·d−1) for 15 d after foaling. Mares (n=6) fed altrenogest were inseminated during the first estrus after treatment and mares (n=6) in the control group were inseminated during the second postpartum estrus. Ovulation during the estrus in which mares were inseminated occurred 26 ± 1 d postpartum for treated mares and 36 ± 1 d postpartum for control mares. The percentage of mares conceiving was not different for control (67%) and altrenogest-treated (100%) mares. No differences were observed in tone and size of the uterus or size of the ovulatory follicle between treated and control groups. Uterine cultures and biopsies collected on d 7 and 15 postpartum were similar between treatment and control groups in bacterial populations or endometrial epithelial cell height. Blood was collected on d 7, 11, 15, 19 and 23 postpartum, and concentrations of estradiol-17β in serum were determined by radioimmunoassay. Mean concentrations of estradiol-17β across days were 10 ± .8 and 12 ± .6 pg/ml for control and treated mares, respectively. Concentrations of serum estradiol-17β were higher (P < .05) in treated mares on d 23 postpartum. Daily milk yields, determined by the weigh-suckle-weigh method, and milk composition were similar between treatment groups on each collection day. Altrenogest can be used to predictably delay estrus in the postpartum mare without altering fertility, yield and composition of milk, or foal growth. This content is only available as a PDF. Author notes 2 Dept. of Anim. Sci. and Industry. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Lewis, R., D.;Meyer, H., H.;Gradin, J., L.;Smith, A., W.

doi: 10.2527/jas1989.6751160xpmid: 2737976

Abstract Efficacy of reducing footrot by use of a commercial vaccine was evaluated over 2 yr with 223 ewes from five crossbred genotypes. Ewes were assigned randomly within genotype, age and initial footrot status to a 2 × 3 factorial array of vaccination in the 1st yr and fall vaccination, winter vaccination or control in the 2nd yr. The flock contained a single Bacteroides nodosus serotype (XV) known to be highly cross-reactive with one of the vaccine serotypes (British serotype H). Vaccination reduced footrot incidence by 61% (P < .01) in the 1st yr and by 45% (P < .01) in the 2nd yr. Vaccination of previously uninfected ewes did not significantly reduce the rate of new infection, but vaccination of infected ewes reduced re-infection by 92% (P < .01). Vaccination in the 1st yr failed to produce any carryover or additive protection in the 2nd yr. Genotypes differed in both footrot incidence (P < .05) and footrot reduction following vaccination (P < .05), but the effect was inconsistent between years. Vaccination increased serum antibody titers in both years (P < .01). Among vaccinates in the 1st yr, infected ewes had lower titer levels than uninfected ewes (P < .01), but no correlation between titer level and incidence was observed in the 2nd yr. This content is only available as a PDF. Author notes 1 The authors wish to acknowledge the financial support of the Oregon Sheep Commission for this research project. Technical Paper No. 8539, Oregon Agric. Exp. Sta. 2 Dept. of Anim. Sci. 3 College of Vet. Med. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Pope, W., F.;McClure, K., E.;Hogue, D., E.;Day, M., L.

doi: 10.2527/jas1989.6751167xpmid: 2737977

Abstract The objective of this study was to compare rebreeding activities of spring- vs fall-lambing Polypay, Dorset, St. Croix and Targhee ewes that either suckled their lambs for 40 d or had lambs weaned at birth. Seasonal effects of male fertility were reduced by utilizing an excess number of fertile rams in the spring. Plasma concentrations of progesterone were monitored to assess days to the first normal ovulation, days to conception and estrous vs anestrous activity. Breed, season and lactation affected the rebreeding performance. Dorset ewes had similar conception rates between spring and fall but a shorter interval from lambing to first ovulation in the fall. Polypay and Targhee ewes were the opposite; they had higher conception rates in fall than in spring matings with no seasonal influence on postpartum interval. Postpartum ewes in the fall had higher conception rates, and fewer of these ewes became anestrous or had estrous cycles of abnormal duration than of those ewes lambing in the spring. Ewes that suckled for 40 d in the spring had delayed estrous activity, but when these ewes became estrual they had higher conception rates than ewes whose lambs were weaned at birth. Lactation had no inhibitory affect on the postpartum interval of fall lambing ewes. These data suggest that the response of different breeds to various components of postpartum fertility varies with season and management of the flock. This content is only available as a PDF. Author notes 3 The authors gratefully acknowledge Michael Bishop, Donna Broermann, Gary Lowe, Brian Magee and Michael Wright for their technical assistance. 5 Dept. of Anim. Sci., Ohio State Univ. 6 Dept. of Anim. Sci., Cornell Univ. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Greer, R., C.;Urick, J., J.;Frank, M., D.;Carroll, L., G.

doi: 10.2527/jas1989.6751175xpmid: N/A

Abstract Fort Keogh Livestock and Range Research Laboratory, Miles City, single-sire breeding herd records provided 1,728 observations on the breeding performance of yearling and 2-yr-old novice Line 1 Hereford bulls. Breeding results from the joint performance of the male and female, with the female as the elementary unit of observation, formed a Bernoulli experiment, in which the female either was pregnant or was not pregnant. Thus, the measure of performance is the probability of pregnancy, the probability being conditional on certain factors (e.g., female traits, bull traits and herd characteristics). The Logit model, not subject to the shortcomings of a linear probability model, was utilized to compare the breeding performance of the yearling with the 2-yr-old novice bulls. The observed difference in herd pregnancy rate between yearling and 2-yr-old bulls was explained largely by a lower probability of pregnancy when the female was a yearling heifer in a predominately heifer herd exposed to a good gain ratio yearling bull, or the female was of any age in a mixed-age herd exposed to a medium gain ratio yearling bull. The breeding performance of 2-yr-old novice and good or excellent gain ratio yearling bulls assigned to mixed-age female breeding herds was not statistically different. Decreased breeding performance was found for 2-yr-old cows nursing a calf. However, this result was attributed to the cow, because no discernible difference in performance due to bull age or other traits was found. This content is only available as a PDF. Author notes 2 Dept. of Agric. Econ. and Econ. 3 Fort Keogh Livest. and Range Res. Lab., USDA, SEAAR. Copyright 1989 by American Society of Animal Science American Society of Animal Science

Brumm, M., C.;Jesse, G., W.;Mayes, H., F.;Clemens, E., T.

doi: 10.2527/jas1989.6751183xpmid: 2737978

Abstract An experiment was conducted to determine the effects of 1) long-acting oxytetracycline injection at market arrival, 2) feed or water access at the auction market and 3) receiving diet management on commingled feeder pig performance. A total of 288 commingled feeder pigs transported over 1,000 km after market management treatments were used in two trials. Pigs given access to feed and water (FW) at the market weighed more (P < .001) following marketing and transport than pigs given water only (W). Pigs given neither feed nor water (N) were intermediate in arrival weight (19.7, 18.7 and 18.9 kg). There was no effect (P > .1) of feed and water offering at the market on final weight (96.6, 95.9 and 96.6 kg), overall average daily gain (.70, .69 and .70 kg/d), overall gain/feed (.31, .31, .32) or percentage death loss (1.0, 2.1 and 4.2%). Injection of long-acting oxytetracycline upon arrival at auction market had no effect (P > .1) on pig weight following marketing and transport (19.0 vs 19.2 kg), final weight (96.1 vs 97.0 kg), percentage death loss (3.4 vs 1.4%) or percentage of pigs treated (3.4 vs 4.9%). Compared to providing ad libitum access to feed, restricting feed intake by floor feeding for the first 7 d post-arrival reduced (P < .01) rate of gain for the first 9 d (−.04 vs .08 kg/d), but overall there was no effect (P > .1) on daily gain (.70 vs .69 kg/d) or gain/feed (.31 vs .31). This content is only available as a PDF. Author notes 4 Dept. of Anim. Sci., Univ. of Nebraska. 5 Dept. of Anim. Sci., Univ. of Missouri. 6 Agric. Engineer, USDA-ARS, Bioeng. Res. Unit, Univ. of Missouri. 7 Northeast Res. & Ext. Center. Copyright 1989 by American Society of Animal Science American Society of Animal Science