Effects of energy and lasalocid on productivity of first-calf heifers

One hundred forty-three crossbred, fall-calving first-calf heifers were used to determine the effects of two levels of energy and two levels of lasalocid on cow-calf productivity. Diets fed for approximately 110 d prepartum were calculated to provide a daily intake of 15.3 (LE) or 18.0 (HE) Mcal ME; diets fed for approximately 130 d postpartum were calculated to provide a daily intake of 17.8 (LE) or 21.0 (HE) Mcal ME. Two supplements were fed with each energy level to provide a calculated 0 (C) or 200 mg.hd-1.d-1 lasalocid (L). Heifers fed HE gained .06 kg more (P = .08) per day prepartum than LE heifers. There was an interaction (P less than .05) between treatment and prepartum days on trial for heifer weight approximately 2 wk prepartum and body condition at calving. Energy had no effect on heifer weight at 2 wk prepartum or condition score at calving when estimated and compared at 90 d on trial. However, regression estimates for 130 d on trial showed that HE heifers would have been 19 kg heavier (P less than .001) and would have had .4 unit higher condition score (P less than .01) than LE heifers. Energy and lasalocid had no effect (P greater than .05) on hip height or pelvic area at calving or on calf birth weight, calving ease score or gestation length. Cows fed HE weighed 17 kg more (P less than .05) and had .5 unit higher (P less than .001) condition score than LE cows at approximately 130 d postpartum. Lasalocid had little effect on postpartum changes in weight or body condition. Lasalocid supplementation to the LE diet tended to increase milk production and calf weight, whereas supplementation to the HE diet did not. Feeding the LE diet decreased (P less than .05) cycling activity by 18 percentage points and decreased (P less than .01) overall pregnancy rate by 25 percentage points. Lasalocid had no influence on reproductive performance.     

Effect of energy intake on the postpartum interval in beef cows and the adequacy of the cow's milk production for calf growth

Lactating Hereford and Hereford X Angus cows, 2 to 6 yr old, and their calves were used in two trials to study the effects of energy intake on the postpartum interval (PPI) and the adequacy of the cow's milk production for calf growth. In trial 1, 23 cows were fed either 120 (high energy, HE) or 100% (adequate energy, AE) of National Research Council energy recommendations. Cow weights, calf weights and milk production were determined 1 wk after calving and every 2 wk until 17 wk postcalving . One-half of the calves received creep feed from the start of the study, whereas the other half did not receive creep feed until their average daily gain was below .23 kg/d. In trail 2, 19 cows were fed energy levels of 100 (AE) or 85% (low energy, LE). Estimated percentage body fat ( EPBF ) was estimated twice during the study; other variables were determined as in trial 1. In trial 1, the HE cows gained more weight (P less than .01) and produced more milk (P less than .01). In trial 2, the AE cows gained more weight (P less than .01) and produced calves 17 kg heavier (P less than .01) at the end of the study than did the LE cows. Milk production was not influenced by energy treatment (P greater than .2). It required 7.5 kg of milk and 2.3 kg of creep feed to produce 1 kg of calf gain in trial 1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in pelvic conformation and peripheral estrone concentrations in pre- and post-partum beef cows

An experiment was conducted to investigate the temporal relationship of peripheral estrone (E1) concentration to changes in the size of the pelvic opening preceding and immediately following parturition. Twenty-six multiparous beef cows were observed from approximately 50 d prepartum to 7 d postpartum. Blood samples were collected at 7 d intervals preceding calving and at 1, 3 and 7 d following for E1 quantitation. Estimates of pelvic opening area were made at the time of blood sampling. Peripheral E1 concentrations were elevated beginning at approximately 25 d prepartum. Dams bearing male fetuses had greater (P less than 0.01) concentrations of E1 than did dams with female fetuses. Calf birth weight was correlated (r = 0.44, P less than 0.01) with E1 levels from 10 d prepartum through parturition. Postpartum pelvic area was greater for cows giving birth to male calves, with no significant differences for calf birth weights by sex. Correlations were observed between E1 concentration, and pelvic area measured from 50 d prepartum to 7 d postpartum (r = 0.26, P less than 0.01), 10 d prepartum to calving (r = 0.42, P less than 0.01), and from calving to 7 d postpartum (r = 0.33, P less than 0.01). Percentage increase in E1 concentration from 50 d prepartum to calving was significantly correlated (r = 0.75, P less than 0.01) to percentage pelvic area increase over the same period. A correlation also exists between maternal E1 concentrations and fetal sex and pelvic area. In summary, the increased estrogen concentrations in cows with male calves may facilitate pelvic spread, resulting in a larger pelvic opening.     

Effect of calf weaning age and cow supplementation on cow productivity

Five years of data were collected on 124 Brangus-type cows to evaluate weaning calves at 8.5 or 10.5 mo of age and winter supplementation of the brood cow with 2.25 kg of molasses daily. Cows with calves weaned at 10.5 mg of age gained 14 kg less weight (P less than .01) during the late nursing period than did cows from which calves were earlier weaned. Age of calf at weaning had no effect on cow reproduction, but calves weaned at 10.5 mo were 2 to 3 d younger (P less than .06) and 5.3 kg lighter (P less than .05) at 8.5 mo of age. During the last 2 mo of nursing, calves weaned at 10.5 mo of age gained 37.2 kg and had a 31.9-kg heavier weaning weight than calves weaned at 8.5 mo of age. Molasses supplementation resulted in differences (P less than .01) in cow weight changes. Cows fed molasses had calving percentages 5 to 7 units higher (P less than .30) than cows not fed molasses. Feeding cows molasses for 145 d throughout the calving and breeding season increased calf weaning weight 7.7 (P less than .02) and 11.2 (P less than .03) kg, respectively, at 8.5 and 10.5 mo of age over the nonsupplemented controls.     

Effects of breeding season length and calving season on range beef cow productivity

A 5-yr study was conducted beginning in 1983 with 460 cows to evaluate the effects of three breeding seasons (30, 45, and 70 d in length) and two times of spring calving, March (early) and April (late), on cattle production under Nebraska Sandhills range conditions. Criteria evaluated included pregnancy and weaning percentages, calving date and distribution, cow weights and body condition at four intervals, calf birth and weaning weights, and cow productivity. The 30-d breeding season included a 10-d estrus synchronization and AI period; in the other breeding seasons only natural breeding was used. The same sires were used over the entire study period. Percentage of cows pregnant and percentage of calves weaned were lower (P less than .01) for cows bred for 30 d than for cows bred for 45 or 70 d. Average calving dates were similar among the breeding groups within the early and late calving herds. Pregnancy rates from AI were higher (P less than .01) for the cows calving in April (64%) than for the cows calving in March (41%). Cows calving in April lost less weight between precalving and prebreeding and were heavier (P less than .05) at prebreeding time than the cows calving in March. Calf weaning weights were not different (P greater than .10) among any of the breeding season groups or between the two calving herds when calves were weaned at a similar age. Cow productivity (calf weaning weight per breeding female) was highest (P less than .05) for the cows bred for 70 d (186 kg), intermediate for the cows bred for 45 d (172 kg), and lowest for cows bred for 30 d (162 kg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Twinning in cattle: III. Effects of twinning on dystocia, reproductive traits, calf survival, calf growth and cow productivity

An evaluation of natural twinning in beef cattle revealed that cows birthing twins had shorter (P less than .01) gestation lengths, more (P less than .01) retained placentas, more (P less than .01) dystocia, more (P less than .01) days to estrus, lower (P less than .01) conception rates and more (P less than .01) days to pregnancy than cows birthing singles. Days to estrus, conception rate and days to pregnancy were not affected by number of calves reared (1 vs 2) in cows birthing twins. Survival at birth was greater (P less than .01) for single- than for twin-born calves, but twins and singles did not differ (P greater than .05) in postnatal survival. When dystocia was experienced, calf survival at birth was 95% vs 73% for singles vs twins compared with 99% vs 92% when no dystocia was experienced. Calves born twins were lighter (P less than .01) at birth, 100 d and 200 d, but twins and singles did not differ in postweaning gains. Total calf weights at 100 d per cow calving were 12% greater (P less than .01) in cows birthing twins vs singles when twin calves reared by foster dams were excluded. The potential increase in cow productivity for total calf weight at 100 d is 40% if calf survival rates of twins with dystocia relative to survival rates of twins without dystocia were comparable to survival rates of singles with and without dystocia, and if cows birthing twins were fed and managed to obtain conception rates equal to those of cows birthing singles. Identification of cows gestating twins to provide for their higher prepartum nutritive requirements and calving assistance at parturition is necessary to make twinning in cattle an economically viable technology.     

Influence of dietary energy on follicular development, serum gonadotropins, and first postpartum ovulation in suckled beef cows

Twenty-eight Hereford x Angus cows (4 yr of age) were used to determine the effects of pre- and postpartum dietary energy on performance and reproductive function in suckled beef cows. The experiment was designed as a 2 x 2 factorial with cows receiving either 70 (L) or 150% (H) of NRC recommended level of dietary energy before and(or) after parturition, resulting in four treatment combinations (L-L, L-H, H-L, H-H). Prepartum diets were fed for approximately 110 d, and postpartum diets were fed until either 10 d after the second postpartum ovulation or 150 d postpartum for those cows that failed to ovulate. Cows receiving low compared with high levels of energy before calving lost more (P less than .01) weight, body condition, subcutaneous fat, and longissimus muscle area before parturition and had calves with lighter (P less than .01) birth weights. Cows receiving low compared with high levels of energy postpartum lost more (P less than .01) weight, body condition, and longissimus muscle area after parturition. Low levels of energy before and after parturition decreased (P less than .01) milk production and calf weight at 70 d of age. Rates of cervical and uterine involution were unaffected by dietary energy treatments. Cows receiving high levels of energy prepartum had increased (P less than .01) mean concentrations and pulse frequency of LH in serum after parturition, and cows receiving high levels of energy postpartum had increased (P less than .05) pulse frequency of LH. Low levels of energy postpartum decreased (P less than .01) appearance rate of small (5.0 to 7.9 mm) and large (greater than or equal to 10 mm) follicles, and low levels of energy prepartum decreased (P less than .02) appearance rate of large follicles based on transrectal ultrasonography. Cows receiving high levels of energy prepartum had shorter (P less than .02) intervals from parturition to ovulation, and a higher (P less than .01) percentage of the cows that received high levels of energy postpartum ovulated by 150 d postpartum. In summary, prepartum level of dietary energy influenced birth weight and weight gain of calves, milk production, concentrations and pulse frequency of LH in serum, appearance rate of large follicles, and the interval to first ovulation. Postpartum level of dietary energy influenced milk production, weight gain of calves, pulse frequency of LH, appearance rate of small and large follicles, and the percentage of cows that ovulated after parturition.     

Effects of body composition, pre- and postpartum energy intake and stage of production of energy utilization by beef cows

Mature Charolais x Angus cows (n = 128) were adjusted to a body condition score (BCS) of 3 (1 = very thin, 3 = moderate, 5 = very fat) between 130 and 190 d of gestation. When cows averaged 190 d of gestation, they were assigned randomly to a maintenance energy diet (ME) or to a diet very low in energy (LE). Cows were allotted within these prepartum (PRP) diets to a high-energy (HE) or LE diet at parturition. At 30 d postpartum (PP), cows were allotted to four treatments: a) slaughter at 0 (n = 32) or b) 48 h after calf removal (n = 32), c) cows whose calves were early weaned at 30 d PP (n = 32) or d) normally weaned at 205 d PP (n = 32). Low energy PRP intake reduced (P less than .01) BCS, cow weight, total empty body lipid (TEBL), body energy (BE) and daily predicted maintenance energy (PME)/W.75 by parturition. Pre- and postpartum energy intake combined to affect (P less than .10) these same factors in a similar manner at 30 d PP. From 30 to 60 d PP, early weaning reduced (P less than .05) PME/W.75. Cow BCS at 190 d of gestation had little effect (P greater than .10) on PME/W.75 or PME/Mcal of BE. Body condition score at parturition, however, affected (P less than .05) delta BCS, delta BE and PME/Mcal of BE by 30 and 60 d PP, with thinner cows losing less condition and requiring more PME/Mcal of BE. Cow BCS had a similar effect from 30 to 60 d PP. Total daily PME was greater for the fat cows during both the PRP and PP periods. Body composition, PRP and PP energy intake and early weaning affect energy requirements and energetic efficiency of beef cows.     

Output/input differences among nonpregnant, lactating Bos indicus-Bos taurus and Bos taurus-Bos taurus F1 cross cows

Nonpregnant F1 crossbred cows, progeny of either Hereford (H) or Angus (A) dams and sired by Brahman (Bm), Sahiwal (Sw), Pinzgauer (Pz), H, or A sires, were fed to maintain initial weight while rearing Charolais (C)-sired progeny for a period of 126 d in drylot commencing at about 48 d postpartum. Cow-calf pairs were assigned to equalize cow age, calf sex, and breed of cow's dam among three replicate pens of approximately 12 pairs each. Cows and calves were weighed every 2 wk and feed intake was adjusted to minimize change in cow weight. Metabolizable energy (ME) consumption for zero cow weight change was estimated by regression. Milk production was estimated by weight-suckle-weigh at 58, 85, 125, and 170 d of lactation. Calf gain (GAIN, kg) relative to cow weight (CWT1, kg) was higher (P less than .01) for calves from Bm-X (139.5/585) and Sw-X (132.2/534) than for calves from Pz-X (127.2/552) and HA-X (116.9/547) cows. Estimated mean daily production of milk was 7.40, 7.15, 7.28, and 6.37 kg for the Bm-X, Sw-X, Pz-X, and HA-X, respectively. Total cow ME intake (TMEcow) for breed groups ranked (P less than .05) with cow size and milk production, and calf creep-feed intake (FMEcalf) was inversely related to estimated milk intake. Proportion of total feed ME (TMEcow+calf) consumed by calves was higher (P less than .05) for HA-X cows (18%) than for the others (14%). Total efficiency of calf gain in weight (GAIN/TMEcow+calf) was 11% greater (P less than .05) for crossbred cows of Bos indicus X Bos taurus (Bm-X, Sw-X) than for Bos taurus X Bos taurus (Pz-X, HA-X) cows (35 vs 32 g/Mcal) in the 126-d lactation period.     

Internal parasite levels and response to anthelmintic treatment by beef cows and calves

Albendazole (methyl 5-propylthio-1 H-benzimidazol-2-yl carbamate) was used as an anthelmintic in a 3-yr study involving 578 beef cows and 438 nursing calves. Infection levels for nematodes, coccidia, and tapeworm were relatively low throughout the 3-yr period. Eggs per gram of feces in cows and calves were lower (P less than .01) 2 wk posttreatment but were not different 5 mo later, when calves were weaned. Cow weight gain, rate and time of conception, and adjusted calf weaning weights were not affected significantly by deworming of either cows or calves. Level of nematode infection measured as eggs per gram of feces was higher (P less than .01) in younger cows than in mature cows. Although deworming with Albendazole lowered (P less than .01) nematode infection levels, no responses were observed in cow or calf performance.     

Sire breed effects in matings with Angus cows: I. Fertility, calf survival and performance to 18 months

Over six calf crops, 524 exposures of Angus cows to three sire breeds resulted in 432 weaned calves for an 82.4% calf crop. Least-squares means for weaning rate by sire breed were 81.8, 80.5 and 83.9% for Angus, Charolais and Holsteins, respectively. Sire breed effect was not significant for calving rate, calf mortality or overall weaning rate, but was significant for all growth traits from birth to 18 mo. Angus-sired calves were smallest at birth, grew at a slower rate and were lightest in weight at all ages. Charolais-sired calves were heaviest at all weigh periods and Holstein-sired calves were intermediate. Holstein-sired calves scored significantly lower for both grade and condition than did Angus- and Charolais-sired calves. Charolais-sired calves had the highest grade. Calving rate tended to be influenced by the effect of cow (P less than .10) and sire breed X year (P less than .001). Calving rate was highest for 3-yr-old and for 6- to 10-yr-old cows and was also 1.5 percentage units higher for crossbred matings. Cow productivity (kg of calf weaned/cow exposed) is a combined measure of fertility, calf survival and weaning weight. Although sire breed did not significantly affect cow productivity (P less than .20), actual values favored cows producing crossbred calves by 14 and 9 kg for Charolais and Holstein crosses, respectively. Likewise, weight differences at 18 mo favored these crosses by 50 and 32 kg for heifers and 72 and 62 kg for steers. Among the two crossbred types, Charolais X Angus heifers were 28 kg heavier (P less than .05) than Holstein X Angus heifers at 18 mo but the 10 kg difference in steers was not significant. The fact that the large sire breeds produced calves with heavier weaning weights without demonstrating significant increases in overall productivity points out the importance of high weaning rates.     

Effects of body composition, pre- and postpartum energy level and early weaning on reproductive performance of beef cows and preweaning calf gain

Mature Charolais x Angus rotational cross cows were adjusted to moderate body condition by d 190 of gestation then randomly blocked to a maintenance (ME) or low-energy (LE) diet. At parturition, the 128 cows were randomly allotted within prepartum (PRP) diet to a high-energy (HE) or LE diet. At d 30 postpartum (PP), cows were randomly blocked to two treatments in which calves were weaned early (EW) or normally (NW) at 7 mo of age. Cows receiving a LE PRP diet had lighter calves at birth (34.7 vs 39.0 kg) and 105 d (127.9 vs 144.6 kg). Prepartum and PP energy interacted to affect postpartum anestrous interval (PPI, d) and cycling activity (%), respectively (LE-LE = 72.6, 33.3; LE-HE = 54.3, 56.3; ME-LE = 65.7, 52.9; ME-HE = 68.4, 54.3). High PP energy averaged over PRP diet increased (P less than .10) pregnancy rate by 22.7% and 105-d calf weight by 15.1 kg. Early weaning reduced PPI by 24.3 d (P less than .01) and first service conception rate by 21.7% (P less than .10). Cycling activity within 60 d PP was affected (P less than .01) by PRP diet and suckling status (LE-EW = 62.5, LE-NW = 26.7, ME-EW = 88.9, ME-NW = 13.3%). Thin cows had a longer PPI but had a higher first service conception rate than moderate and fleshy cows. Higher pregnancy rates were observed in cows approaching or maintaining average body condition from parturition to conception than for cows moving away from moderate body condition. Results suggest that fleshy and thin cows at parturition should be managed to approach moderate body condition before the breeding season to optimize reproductive performance and preweaning calf gain.     

Cow breeding and calf growth performance as affected by pregnancy status the previous year

A 2-yr study was conducted to compare the subsequent cow breeding and calf performance of cows that were nonpregnant with cows that were pregnant at the time calves were weaned. Cows were Angus (A), Polled Hereford (PH), Santa Gertrudis (SG) straightbreds and crossbreds of these breeds. Nonpregnant cows (G1) were 4- to 9-yr-olds that had a calf the previous year and appeared to be physically sound with no detection (by rectal palpation) of an abnormal reproductive tract due to disease, abnormal growth or calving difficulties. Pregnant cows (G2) were of similar age and breed composition to G1 cows. The 93 G1 and the 193 G2 cows were assigned within age and breed composition to sire breeding groups on pasture in an approximate 1:2 ratio, respectively, per sire. There were six A, three PH and one SG sires. The year prior to G1 cows being nonpregnant, G1 cows calved 11 d later (P less than .01) than G2 cows. Subsequent to their being nonpregnant, G1 cows gained 27 kg more (P less than .001) weight during the breeding period, had 5.4 percentage units more (P less than .29) calves born, had calves 17 d earlier (P less than .001) in the calving period, had calves that gained at a similar rate to weaning and had calves that were 14 kg heavier (P less than .01) at weaning (due to their being 17 d older) compared with G2 cows and calves.     

Comparison of crossbred cows containing various proportions of Brahman in spring or fall calving systems: III. Productivity as three-, four-, and five-year olds

Productivity of 3-, 4-, and 5-yr-old crossbred cows containing various proportions (0, 1/4, or 1/2) of Brahman breeding out of Angus or Hereford dams was evaluated using 489 spring-calving and 427 fall-calving records collected over a 4-yr period. Cows were bred to Limousin sires for the first 3 yr and to Limousin and Salers sires the 4th yr. Interactions between crossbred cow group and season of calving were not significant. Percentage of cows exposed to breeding that weaned a calf increased (P less than .01) as proportion Brahman breeding increased, was higher (P less than .01) for cows out of Angus dams than for cows out of Hereford dams, and was higher (P less than .01) for spring-calving cows. As the proportion Brahman increased, the percentage requiring assistance at birth decreased, and cows out of Angus dams required less (P less than .05) assistance than those out of Hereford dams. Preweaning ADG, adjusted weaning weight, weaning conformation, weaning condition, and adjusted weaning hip height increased a proportion Brahman breeding increased. Spring-born calves gained .12 kg/d faster (P less than .01) than fall-born calves. However, weight at weaning was similar for the two groups; spring-born calves were weaned at an average age of 205 d, and fall-born calves were weaned at an average age of 240 d. Fall-calving cows were heavier (P less than .05) than spring-calving cows, and 0 and 1/2 Brahman cows were heavier (P less than .01) than 1/4 Brahman cows. These data indicate that Brahman-cross dams can be used to improve reproductive rate and increase preweaning growth rate, and thus weaning weight.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductive performance of Gyr cows: the effect of weaning age of calves and postpartum energy intake

Two nutritional levels following parturition and five weaning ages for the calf were evaluated to study their effect of reproduction in Gyr cows in the savannas of West Central Brazil (Campos Cerrados). Early weaning of calves reduced postpartum weight losses and shortened the postpartum interval to conception. Energy level did not affect cow weight at weaning or conception, the number of days from parturition to first estrus or the number of matings/conception; however, the postpartum period to conception was reduced (116 vs 160 d; P less than .05) for cows on the higher energy diet. Weaning age significantly affected postpartum weight loss in cows. Six months after calving, cows that nursed calves for 1 mo were 89 kg heavier than those that nursed calves for 6 mo (384 vs 295 kg; P less than .05). Cows that were nursed for 1 mo returned to estrus at an average of 40 d postpartum, which was 23 d earlier (P less than .05) than the average of the other groups nursed for longer periods of time. There was no significant difference in the postpartum period to conception among cows that had their calves weaned at 1 mo, 3 mo and cows which were nursed twice daily beginning 30 d after parturition (57, 94 and 97 d, respectively), but was less (P less than .05) for cows nursed for 5 or 6 mo (212 and 231 d, respectively). The results show that Gyr cattle are genetically capable of responding reproductively to improve nutrition and reduced lactation stress achieved through early weaning or controlled nursing.     

Effects of pre- and postpartum nutrition on reproduction in spring calving cows and calf feedlot performance

Crossbred, spring-calving cows (yr 1, n = 136; yr 2, n = 113; yr 3, n = 113) were used in a 3-yr experiment to evaluate the influence of supplemental protein prepartum and grazing subirrigated meadow postpartum on pregnancy rates and calf feedlot performance. A 2 x 2 factorial arrangement of treatments was used in a switchback design. From December 1 to February 28, cows grazed dormant upland range in 8 pastures (32 +/- 2 ha each). The equivalent of 0.45 kg of supplement/cow per d (42% CP) was provided to half of the cows on a pasture basis 3 d/wk. For 30 d before the beginning of breeding (May 1 to May 31), half of the cows grazed a common subirrigated meadow (58 ha), and the remainder was fed grass hay in a drylot. Cow BW and BCS were monitored throughout the year, and steer calf performance was determined until slaughter. Feeding supplement prepartum improved (P = 0.01 to P < 0.001) BCS precalving (5.1 vs. 4.7) and prebreeding (5.1 vs. 4.9) and increased (P = 0.02) the percentage of live calves at weaning (98.5 vs. 93.6%) but did not affect (P = 0.46) pregnancy rate (93 vs. 90%). Calves born to dams fed supplement prepartum had similar (P = 0.29) birth weight (37 vs. 36 kg) but greater (P = 0.02) weaning weight (218 vs. 211 kg). However, steer feedlot DMI (8.53 vs. 8.48 kg), ADG (1.6 vs. 1.6 kg), and carcass weight (369 vs. 363 kg) were not affected (P = 0.23 to P = 0.89) by prepartum supplementation. Allowing cows to graze subirrigated meadow postpartum improved (P < 0.001) BCS prebreeding (5.2 vs. 4.9) but did not affect (P = 0.88) pregnancy rate (92 vs. 91%). Allowing cows to graze subirrigated meadow increased (P = 0.01) calf weaning weight (218 vs. 211 kg) but not (P = 0.62 to P = 0.91) feedlot DMI (8.4 vs. 8.3 kg), ADG (1.6 vs. 1.6 kg), or carcass weight (363 vs. 362 kg) of their steer calves. Increased percentage of live calves at weaning as a result of feeding supplemental protein increased net returns at weaning and after finishing in the feedlot. Net returns were increased by allowing cows to graze subirrigated meadow postpartum regardless of whether calves were marketed at weaning or after finishing in the feedlot.     

Effects of inorganic and organic copper supplemented to first-calf cows on cow reproduction and calf health and performance

Two experiments were conducted to determine whether the supplementation of Cu in the organic or inorganic form to 2-yr-old cows, before and after calving, affects reproduction rate, calf health and performance, passive transfer of immunoglobulin, or liver and serum Cu concentrations compared with unsupplemented controls. Cows (n = 75 in 1997; n = 120 in 1998) were randomly assigned by estimated calving date and body condition score to one of three treatments: 1) Control, control; 2) Inorganic, inorganic Cu supplement (200 mg Cu from CuSO4); 3) Organic, organic Cu supplement (100 mg Cu from AvailaCu). In 1998, a fourth treatment was added; 4) CU-ZN, organic Cu and Zn (400 mg Zn from AvailaZn in the Organic diet). Cows were fed a hay-based diet and individually fed supplements for approximately 45 d before and 60 d after calving (approximately January 15 to May 15 each year). Liver biopsies were obtained from cows before supplementation began, and from cows and calves at 10 and 30 d after calving. Blood samples were obtained from both cows and calves at calving, and colostrum samples were collected for IgG and mineral content. Cow liver Cu concentrations before supplementation began were 58 mg/kg in 1997 and 40 mg/kg (DM basis) in 1998. By 10 d after calving, liver Cu concentrations of Control cows had decreased (P < 0.05) to 24 mg/kg (Cu deficient) in both years, whereas liver Cu concentrations of Cu-supplemented cows increased (P < 0.05) in both years. Calf liver Cu concentrations at 10 d of age were similar (P > 0.10) for all treatment groups. No differences (P > 0.10) were found in colostrum Cu concentrations, or in calf health among treatments. No differences (P > 0.10) were found in cow BW change, calf serum Cu concentrations, calf weaning weights, or in cow 60-d pregnancy rates among treatments in either year. In 1998, cows in the Organic group had higher (P < 0.05) 30-d pregnancy rate than Control cows. Neither serum samples nor placental tissue were reliable indicators of Cu status in cows. Feeding supplemental Cu (either inorganic, organic, or organic with extra Zn) to cows with liver Cu concentrations of approximately 50 mg/kg before calving did not improve cow 60-d pregnancy rates or the health and performance of their calves when compared with unsupplemented cows.     

Influence of Prepartum Fat Supplementation on Subsequent Beef Cow Reproduction and Calf Performance

High fat range supplement (HFRS) and HFRS with lipid from soybean soapstock (HFRS-SPH; Consolidated Nutrition, Omaha, NE) were compared with a corn-soybean meal supplement (control). In Exp. 1, primiparous cows were individually fed the control supplement (n = 12), HFRS (n = 12), or HFRS-SPH (n = 10) for 62 ± 2 d prepartum. Heifer body condition score pre- and postpartum did not differ (P=0.78) among groups. Milk production was not influenced (P=0.15) by source of supplement. Somatic cell counts, however, tended to be less (P=0.07) in HFRS-supplemented heifers than in heifers fed the control supplement. At birth, calf body temperature (P=0.8), vigor (P=0.7), and BW (P=0.6), as well as BW gain through 90 d postpartum (P=0.6), did not differ among prepartum supplementation treatments. Plasma concentrations of linoleic acid were greater (P=0.02) in fat-supplemented heifers at 30 d prepartum and at calving compared with heifers on the control treatment; however, concentrations of plasma linoleic acid returned to levels comparable with those in control heifers by 30 d postpartum. Neither number of cows cycling by 90 d postpartum (P=0.15) nor length of the postpartum interval (P=0.25) differed among treatment groups. In Exp. 2, multiparous cows were pen-fed the control supplement (n = 49), HFRS (n = 47), or HFRS-SPH (n = 49) for 59 ± 2 d prepartum. Prior to parturition, cows fed the control supplement had better body condition scores (5.8 ± 0.1; P=0.004) than cows fed either commercial supplement (5.4 ± 0.1). Calf performance (P=0.7) and conception rates (P= 0.5) did not differ among treatments. Productivity of cows and calves was not improved with provision of supplemental fat prepartum.     

Production characters of first-generation cows of a five-breed diallel: reproduction of young cows and preweaning performance of inter se calves

Data from cows of a five-breed diallel involving Angus, Brahman, Hereford, Holstein and Jersey were analyzed. Females were used in inter se matings to produce three second-generation parturitions per cow. Crossbred (CB) cows were 43 d younger (P less than .05), 14 kg heavier (P less than .05) and 2 cm taller (P less than .05) at first calving than straightbred (SB) cows; however, no differences were detected (P greater than .10) between the two groups for pelvic measurements. Although large differences among breed types existed for gestation length, crossbreds generally did not differ from straightbreds for this character. Crossbred cows exhibited a 7.5 d shorter (P less than .05) interval from parturition to first service, but did not exhibit a shorter interval from parturition to conception (P greater than .10). The dairy breeds (Holstein and Jersey) and their crosses exhibited similar postpartum and calving intervals as Angus, while Brahman and their crosses had longer intervals. Crossbred calves were 1.3 kg heavier (P less than .01) and had greater (P less than .01) shoulder and hip dimensions at birth than SB calves, but no difference in the amount of calving difficulty was detected (P greater than .10) between the two groups. Higher (P less than .01) rates of survival to 24 h (3.7%) and to weaning (8.7%) were observed for CB calves compared with SB calves. Heterotic effects for weaning weight (15.2 kg), weaning height (2 cm) and preweaning average daily gain (68 g) were large and illustrate the importance of individual and maternal heterosis for these characters. These results suggest that substantial amounts of heterosis may be retained for survival and weaning characters of calves in early generations of inter se mating of CB.     

Calving system and weaning age effects on cow and preweaning calf performance in the Northern Great Plains

A 3-yr study evaluated late winter (Feb), early spring (Apr), and late spring (Jun) calving systems in conjunction with varied weaning strategies on beef cow and calf performance from Northern Great Plains rangelands. Crossbred cows were randomly assigned to one of three calving systems (on average n= 168.calving system(-1).yr(-1)) and one of two weaning times (Wean 1, 2) within each calving system. The Feb and Apr calves were weaned at 190 and 240 d of age, whereas Jun calves were weaned at 140 and 190 d of age. Breeding by natural service occurred in a 32-d period that included estrous synchronization. Cows were managed throughout the year as appropriate for their calving season. Quantity and quality of hay and supplements were provided based on forage and weather conditions, physiological state of the cows, and available harvested feed resources within a year. After weaning, two-thirds of the early weaned steers were fed in confinement in Montana, and one-third were shipped to Oklahoma and were grazed or fed forage. One-half of the early weaned heifers grazed seeded pastures, and the other half was fed in confinement. Early weaned calves were weighed on approximately the same day as late-weaned calves. Birth weight and overall rate of gain from birth to weaning did not differ for calves from the three calving systems. Calf weaning weight differed by weaning age within calving system (P = 0.001), and calves from the Jun calving system that were weaned at 190 d of age tended (P = 0.06) to be lighter than calves of the same age from the Feb or Apr calving systems. Cow BW change and BCS dynamics were affected by calving system, but the proportion of cows pregnant in the fall was not. Cows suckled until later dates gained less or lost more BW during the 50 d between the first and second weaning than dry cows during this period. The previous year's weaning assignment did not affect production in the following year. Estimated harvested feed inputs were less for the Jun cows than for the Feb and Apr cows. We conclude that season of calving and weaning age affect outputs from rangeland-based beef cattle operations.