J.W. Bolte

Effects of prepartum and postpartum bolus injections of trace minerals on performance of beef cows and calves grazing native range12

ABSTRACT Our objective was to evaluate the effects of pre- and postpartum bolus injections of a trace mineral solution on reproductive performance, BW change, and BCS change of beef cows and on growth of suckling calves. Mature beef cows (n = 460; initial BW = 497 ± 89 kg, initial BCS = 5.4 ± 0.74) managed in 2 locations were stratified by BCS, age, parity, and predicted calving date and assigned randomly to 1 of 2 treatments: 1) supplemental s.c. trace-mineral (TM) injection containing 15 mg/mL Cu, 5 mg/mL Se, 10 mg/mL Mn, and 60 mg/mL Zn or 2) s.c. injection of physiological saline (SA). Injections were administered to cows (1 mL/90 kg of BW) 105 d before the first projected calving date and again 30 d before fixed-time AI. Calves received the same treatment as their dams and were injected (1 mL/45 kg of BW) at birth and again at 71 ± 21 d of age. Cows grazed native pastures for the duration of the study; trace-mineral supplements and white salt were available to all cattle ad libitum before and during the study. Ovulation was synchronized using a 5-d CO-Synch + CIDR protocol, and cows were inseminated 72 h after CIDR removal. Cows were exposed to fertile bulls for natural-service breeding 10 d after AI for 50 d. Conception to AI and final pregnancy rate were assessed 36 d after AI via ultrasound and 120 d after AI via rectal palpation, respectively. Change in BW and BCS from initiation of the study to calving and from AI to weaning did not differ (P ≥ 0.15) between TM and SA cows. Conversely, TM cows had greater (P = 0.04) BCS increase than did SA cows between calving and AI. Calf BW at birth, ADG, and age-adjusted weaning BW did not differ (P ≥ 0.36) between treatments. Proportion of cows with estrous cycles 17 and 8 d before fixed-time AI was similar (P ≥ 0.51) between treatments. In contrast, conception to fixed-time AI was greater (P = 0.05) for cows receiving TM (60.2%) than for cows receiving SA (51.2%). Final pregnancy rate did not differ (P = 0.24) between treatments and averaged 92%; however, calving distribution by TM-treated cows was more favorable (P = 0.01; i.e., calving was generally earlier) than calving distribution of SA-treated cows. Under the conditions of this study, pre- and postpartum trace-mineral injections improved conception to fixed-time AI and subsequent calving distribution of beef cows.

Growth and reproductive performance of beef replacement heifers fed development diets containing soybean meal or wet distillers grains 1

ABSTRACT Our objective was to evaluate the effects of replacing soybean meal with wet distillers grains plus solubles (WDG) in beef heifer development diets on growth and reproductive performance. Weaned heifers (n = 172; initial BW 319 ± 2 kg; age 282 ± 1 d) were stratified by BW and age and assigned randomly to be fed development diets using soybean meal (CON) or WDG as the primary source of CP in the diet. Heifers were allotted equally to 8 pens, adapted to diets for 14 d, and fed for ad libitum intake for 94 d. Heifer BW was measured on d 28, 56, and 84 relative to the beginning of the experiment and at breeding; paired serum samples were collected at these times to define puberty status. After 94 d, treatments were combined in a native short- grass rangeland pasture. Heifers from each treatment were exposed to ovulation synchronization and fixed-time AI 23 or 51 d after diets ended. Total DM delivered was 4,695 kg less (P 0.10). Conception to fixed-time AI and overall pregnancy rates were not different (P > 0.60) between treatments. Under the conditions of our study, developing replacement heifer diets using WDG as the primary source of CP had negative temporal effects on growth performance and age at puberty; however, these effects were nullified when heifers were allowed to graze native range for at least 23 d before breeding.

Effects of mineral-supplement delivery system on frequency, duration, and timing of supplement use by beef cows grazing topographically rugged, native rangeland in the Kansas Flint Hills.

The effects of mineral-supplement delivery system on patterns of supplement use by grazing beef cows were measured in 2 studies. Study 1 was conducted on 4 pastures grazed by pregnant, mature beef cows (BW = 562 ± 38 kg) from February to May. Study 2 was conducted on 4 pastures grazed by lactating beef cows (BW = 579 ± 54 kg) and their calves from May to September. Treatments were mineral delivered in salt-based, granular form (salty) or mineral provided in a low-protein, cooked, molasses-based block (sweet); both were fed ad libitum. The salty supplement was supplied to cattle via a covered mineral feeder; the sweet supplement was supplied via an open-topped barrel. Both salty and sweet supplements were deployed in each pasture. No additional salt was supplied to cattle. Forage use in the vicinity of each supplement-deployment site and the frequency and duration of herd visits to each supplement-deployment site were measured during four 14-d periods during study 1 and seven 14-d periods during study 2. Supplements were moved to new locations within pastures at the beginning of each period. Consumption of the sweet supplement was greater than salty during each data-collection period in study 1; however, relative differences in consumption diminished over time (treatment × time, P = 0.03). In study 2, sweet consumption was greater than salty in periods 1, 6, and 7 but was not different from salty during periods 2, 3, 4, and 5 (treatment × time, P < 0.01). Increased consumption of the sweet supplement in study 1 translated to greater frequency of herd visits to supplement-deployment sites compared with the salty sites (2.82 vs. 2.47 herd visits/d; P = 0.02) and longer herd visits to supplement-deployment sites compared with the salty sites (125.7 vs. 54.9 min/herd visit; P < 0.01). The frequency of herd visits to mineral feeding sites in study 2 was similar (P > 0.10) between treatments for periods 1 through 6; however, herds visited the sweet sites more often than salty during period 7 (P < 0.01). Herd visits to the sweet sites were longer than those to the salty sites in study 2 (83.8 vs. 51.4 min/herd visit; P < 0.01). Forage disappearance within 100 m of supplement-deployment sites was not influenced (P ≥ 0.54) by treatment in either study. Results were interpreted to suggest that the sweet supplement influenced the location of grazing cattle more strongly than the salty supplement and may be more effective for luring cattle into specific areas of pasture during the winter, spring, and early fall but not during summer.

Length of the weaning period affects postweaning growth, health, and carcass merit of ranch-direct beef calves weaned during the fall

Introduction Bovine respiratory disease (BRD) is the most economically devastating feedlot disease. Risk factors associated with incidence of BRD include (1) stress associated with maternal separation, (2) stress associated with introduction to an unfamiliar environment, (3) poor intake associated with introduction of novel feedstuffs into the animal’s diet, (4) exposure to novel pathogens upon transport to a feeding facility and commingling with unfamiliar cattle, (5) inappropriately administered respiratory disease vaccination programs, and (6) poor response to respiratory disease vaccination programs. Management practices that are collectively referred to as preconditioning are thought to minimize damage to the beef carcass from the BRD complex.

Effects of Prepartum Whole Fuzzy Cottonseed or Whole Raw Soybean Supplementation on Response to Timed Artificial Insemination by Suckled Mature Beef Cows Following Ovulation Synchronization1

Cows (n = 188; average initial BW = 579±54 kg) were stratified by BCS and BW and assigned to 3 supplementation treatments: whole raw soybeans (21.6% fat), whole fuzzy cottonseed (21.7% fat), or a 50:50 mixture of ground corn and soybean meal (2.6% fat; i.e., the control supplement). Supplements were fed daily at 1.8 kg/cow for 45 d before the first projected calving date. Supplementation was continued until calving. Ovulation was synchronized using the Cosynch + controlled internal drug release (CIDR) protocol (injection of GnRH 7 d before and 64 h after a 7-d intravaginal CIDR insert containing 1.38 g of progesterone) and a 25-mg injection of PGF2α. Cows were inseminated artificially at 60 to 64 h after CIDR removal. Eleven days after AI, cows were exposed to fertile bulls for natural-service breeding for 50 d. Conception to AI was assessed 33 d after AI; overall pregnancy rate was assessed 126 d after AI. Body weight of cows fed control or oilseed supplements was similar (P > 0.3) at calving, at initiation of ovulation synchronization, and at the end of the breeding season. Cottonseed-supplemented cows lost more BW and more BCS (P < 0.03) from the onset of supplementation until calving than those fed soybeans. Proportion of cows with estrus cycles was similar (P = 0.57) among treatments. Pregnancies per fixed-time AI and final pregnancy rate were similar (P ≥0.75) between control and oilseed-supplemented cows. Conversely, supplementation with cottonseed tended (P = 0.08) to increase pregnancies per timed AI (54 and 39% for cottonseed and soybeans, respectively) and increased (P = 0.03) final pregnancy rate compared with soybean-fed cows (100 and 93% for cottonseed and soybeans, respectively). In conclusion, cows supplemented with whole, fuzzy cottonseed tended to have a greater timed AI pregnancy rate and had a greater final pregnancy rate than cows supplemented with whole, raw soybeans. Effects of cottonseed and soybean supplementation on response to ovulation synchronization and fixed-time AI by beef cows warrant further study.

Effects of prepartum and postpartum bolus injections of trace minerals on performance of beef cows and calves grazing native range

The most widely used means of trace-mineral supplementation for grazing cattle is selffed, salt-based, loose mineral supplements. Although cattle do not balance their mineral needs when consuming a self-fed mineral supplement, usually no other practical way of supplying mineral needs exists under grazing conditions. The greatest limitation to using self-fed mineral supplements is variation in animal intake. More direct methods of mineral supplementation include adding minerals to drinking water or feed, oral drenching, ruminal boluses, and injection. Variation in mineral intake is reduced relative to self-fed supplementation, and the additional labor requirement and expense are relatively small.

Effects of prepartum ruminally protected choline supplementation on performance of beef cows and calves

Choline is classified generally as a B vitamin and is an essential nutrient. Phosphatidylcholine and other choline-containing lipids maintain the structural integrity of cellular membranes and play a vital role in metabolism of dietary fat. Choline-containing phospholipids are also important precursors for intracellular-messenger molecules and cell-signaling molecules critical to the reproductive process.

Long-term CIDR program for synchronizationof estrus in beef heifers produces acceptable AIpregnancy rates

Introduction Routinely achieving pregnancy rates greater than 50% with fixed-time artificial insemination (AI) in heifers has been difficult. The Beef Reproduction Task Force recently added the intravaginal progesterone-releasing device (CIDR)-Select to its list of recommended fixed-time AI protocols. Research and field trials in Missouri have achieved AI pregnancy rates in the range of 55% to 60%. Another relatively new protocol is the 5-day CO-Synch, a timed AI protocol + CIDR that has produced pregnancy rates similar to or higher than those obtained with the standard 7-day CO-Synch + CIDR protocol. It is not known whether these two systems differ in terms of estrous response. The objective of the current study was to compare effects of a long-term, 14-day CIDRSelect protocol and a 5-day CO-Synch + CIDR protocol on estrous distribution and AI pregnancy rate in yearling beef heifers.

Length of the ranch-of-origin weaning periodDoes not affect post-receiving growth or carcass merit of ranch-direct, early-weaned beef calves

Study Description: Angus crossbred calves (n = 400) were stratified by age and assigned randomly to one of five weaning periods that corresponded to the length of time between separation from dam and shipping to market: 60, 45, 30, 15, or 0 days. Calves were vaccinated against common diseases 14 days before and again on the day of maternal separation. On a common shipping date (day 0; August 24), calves were transported 3 hours to a commercial auction market and held for 14 hours. Calves were then transported for less than 1 hour to a feedlot. All calves were fed the same diet ad libitum throughout the trial. Upon slaughter, livers and lungs were evaluated and carcass measurements were collected.

Behavior of beef cows grazing topographically rugged native range is influenced by mineral delivery system

Poor grazing distribution is a major problem on rangelands of the western United States. Grazing animals tend to congregate in areas near water, shade, and level terrain. These areas typically become overgrazed, while less preferred areas of pasture remain under-grazed. Solutions to localized overgrazing include cross-fencing and water development; however, most land managers are unwilling to bear the expense associated with these strategies.