Evaluation of a cow-calf system without perennial grass
Utilizing confinement, cover crop and corn residue compared to traditional, pasture-based
By Zac Carlson, Galen Erickson, Mary Drewnoski and Jim MacDonald
Traditional pasture has been converted to corn and soybean production in the northern plains region which has limited pasture availability for grazing. Limited grazing areas, and overall feed prices have steadily increased pasture rental rates. The reduction in perennial grasslands and increase in land values created a need for use of alternative forages and intensive cow-calf systems. Research has demonstrated that limit-feeding cows in a drylot setting is a comparable alternative to traditional pasture cow-calf systems. Additionally, winter grazing corn residue is an economical alternative to harvested forage or limit-feeding in confinement for non-lactating cows.
The use of double-crop annual forages (DCAF), commonly referred to as cover crops, has increased in popularity. Cover crops provide several advantages, including soil conservation, weed control, and an alternative forage source for livestock producers. Grazing late-summer planted cover crops provides economic incentives for livestock owners by adding weight to cattle, as well as economic incentives for crop producers with grazing rent and no impact on subsequent crop yields.
The objective of this study was to evaluate an alternative cow-calf system without access to perennial grass by utilizing drylot feeding, fall forage oat and corn residue grazing compared to a traditional cow-calf system which utilized perennial pasture and corn residue grazing. We evaluated reproductive performance and calf growth performance, and subsequent post-weaning calf performance in a growing/finishing system.
Experimental proceduresMultiparous, cross-bred beef cows (n = 160; average age = 6.2 ± 2.8 years-old) were utilized in a general randomized block design with two treatments. In year 1, cows were blocked by cow age, stratified by age and origin source (two sources), and assigned randomly within strata to one of two production systems treatments with four replicates, each consisting of 20 cows. Once allocated, cows remained in assigned treatment for both years of the experiment.
Treatments were (1) alternative fall-calving system utilizing confinement, summer-planted oats, and corn residue grazing (ALT) with calves born in the fall (August/September) or (2) traditional extensive spring calving (March/April) system utilizing perennial pasture and corn residue grazing (TRAD). To maintain herd size, cows culled between years were replaced with open, multiparous cows sourced from the same herd of the original cows. An additional replicate was maintained for each system so that replacement cows entered the experiment after being maintained in that system.
Each year, after the conclusion of weaning, calves were maintained in their respective dam’s experimental unit to measure animal growth performance in a grower phase, finisher phase and carcass characteristics. The post-weaning experiments utilized the same generalized randomized block design maintaining the same treatment and replication as the calf’s dam.
Cow breeding, cow-calf health processingCows from both treatments were exposed to the same set of Simmental × Angus bulls that had passed an annual breeding soundness exam 30 days prior to breeding. The bull:cow ratio was 1:10 and the breeding season was 63 d (year 1) and 61 d (year 2). Two bulls were allocated to each replication of cows to prevent reproductive failure due to inadequate bull performance.
All cows were given 5 ml of prostaglandin F2α (5 mg/ml dinoprost tromethamine, Lutalyse, Zoetis Animal Health) following five days of bull exposure. Approximately one month before breeding, cows were vaccinated Bovi-Shield Gold FP 5 VL5 (Zoetis). Pregnancy was diagnosed via pregnancy detection blood test 31 d (TRAD; year 1), 29 d (ALT; year 1), 52 d (TRAD; year 2), and 50 d (ALT; year 2) after bulls were removed. Cows were treated annually with 1% doramectin (Dectomax, Zoetis) for control of internal and external parasites. Approximately one month before calving, cows were vaccinated Scourguard 4KC (Zoetis).
Calves were vaccinated at birth with Inforce 3 (Zoetis), given a clostridial vaccine (Ultrabac 7; Zoetis), navels treated with iodine, and received a panel tag in the right ear with individual identification number, and birth weight recorded. If a cow gave birth to twins, one calf was selected randomly and removed from the experiment.
Alternative cow-calf system breedingEach year of the experiment began at breeding, which occurred from Oct. 11 to Dec. 12 of 2017 (63 d; year 1) and Oct. 18 to Dec. 17 of 2018 (61 d; year 2). In year 1, cows were non-lactating at the time of breeding. Part of the ALT treatment design was to use fall forage oats to meet the nutrient requirements of the cows during lactation and breeding. Fall oat grazing began for the ALT treatment on Oct. 11 and 23 (years 1 and 2, respectively). Stocking rates for the fall oat fields were approximately 2.5 to 3.0 acres/pair. Each replicate of cow-calf pairs had full access to their assigned oat field.
On March 14 and 16 (years 1 and 2, respectively) cows in the ALT treatment were housed in open feedlot pens with approximately 30 in. of bunk space and 850 ft2 of pen space per cow. Cows were limit-fed to meet requirements based on physiological stage during both gestation and lactation periods (NASEM, 2016; Table 1). Breeding body condition scores for the ALT treatment indicate that energy intakes were adequate for maintenance and lactation during the confinement period, which occurred directly prior to breeding.
Cows were fed once daily between 0900 to 1200 h with ad libitum access to fresh water. The limit-fed diet, for year 1, consisted of 55.0% modified distillers grains plus solubles (MDGS), 40.0% wheat straw, and 5.0% supplement (DM basis). In year 2, the limit-fed diet consisted of 54.5% MDGS, 40.5% wheat straw, and 5.0% supplement (DM basis). In both years, the limit-fed diet was formulated to provide 200 mg/cow daily of monensin (Rumensin 90; Elanco Animal Health, Greenfield, Indiana). Diets were mixed and delivered using a truck-mounted feed mixer and delivery unit with scale measurements to the nearest 0.5 kg (Roto-Mix model 420, Roto-Mix, Dodge City, Kansas). All scales used for the study were calibrated twice annually.
Cows in the ALT treatment were managed as a fall calving herd with calving occurring in feedlot pens from July 16 to Sept. 12 of 2018 and July 20 to Sept. 28 of 2019 (years 1 and 2, respectively). Cow-calf pairs remained in the feedlot until Oct. 23 (years 1 and 2) for a total of 222 and 224 d (years 1 and 2, respectively). At which time, cows would be moved to oat fields, as previously discussed.
Alternative cow-calf system weaningCow-calf pairs grazed fall oats from Oct. 23 to Jan. 13 of 2019 and Oct. 23 to approximately Jan. 8 of 2020 (years 1 and 2, respectively). Grazing days were variable between years, with 82 d (year 1) and an average of 77 d (58 to 92 d; year 2). Cow-calf pairs were moved off oat fields when it was visually estimated that forage height was 5.1 cm. I
n the event this occurred prior to weaning, cows-calf pairs returned to the feedlot and were provided the same limit-fed diet at the same intake amount they received prior to oat grazing. After weaning, cows were moved to corn residue fields on Jan. 10, 2019 and Jan. 29, 2020 (years 1 and 2, respectively). Stocking rates were approximately 3 acres/cow and grazing days were 64 and 52 d (year 1 and 2, respectively) for corn residue fields.
Traditional cow-calf system breedingCows were exposed to bulls from July 12 to Sept. 12 of 2017 (63 d; year 1) and July 6 to Sept. 4 of 2018 (61 d; year 2). In year one, TRAD cows were lactating and had the previous, non-experimental calf, with them.
Traditional cow-calf system calvingOn approximately March 17, 2018 and March 12, 2019 (years 1 and 2, respectively), cows from the TRAD treatment were comingled prior to calving and fed ground grass hay provided at 30 lbs. for 31 d (year 1) and 20 lbs. for approximately 81 d (year 2) on dormant smooth bromegrass pastures. Calving began on April 10 to June 16 of 2018 and April 5 to June 6 of 2019 (year 1 and 2, respectively). On May 7, 2018 and May 2, 2019 (year 1 and 2, respectively), cows in the TRAD treatment were moved to smooth bromegrass pastures. Stocking rate was 1.2 ha/cow (years 1 and 2) and grazing days were 186 and 197 d (years 1 and 2, respectively).
Traditional cow-calf system weaningCalves from the TRAD treatment were weaned on Oct. 16, 2018 and Oct. 11, 2019 (year 1 and 2, respectively). After weaning, on Nov. 15, 2018 and 8, 2019 (years 1 and 2, respectively), cows in the TRAD treatment grazed corn residue fields. Corn residue fields were stocked at 1.69 and 1.43 ha/cow (years 1 and 2, respectively) and grazing days were 119 and 123 d (years 1 and 2, respectively).
Grower phaseCalves were weaned using a fence-line weaning strategy. All calves from the four replicates within treatment were comingled in a pen. Calves were fence-line weaned for three d and limit-fed grass hay at 2.0 % of BW before transport to the feedlot at ENREC (2 miles). Calves, steers and heifers, were sorted into their previous cow group on d - 6. Steers and heifers from each experimental unit were fed together in one pen.
Weaning BW measurements were collected on two consecutive days and averaged following 5 d limit-fed period. The weaning BW measurement also served as the growing initial BW.
Calves were implanted with 36 mg zeranol (Ralgro; Merck Animal Health, Madison, New Jersey) on d 1. Calves were vaccinated with Bovi-Shield Gold One Shot (Zoetis) and for Clostridial and Histophilus somnus (Ultrabac 7/Somubac; Zoetis). Calves received parasite control as well (Dectomax; Zoetis Animal Health).
Calves were maintained in their original replicate for the grower and finisher phases. All calves received a common grower diet consisting of 35.0% grass hay, 30.0% modified distillers grains plus solubles (MDGS), 30.0% dry-rolled corn and 5.0% supplement. The grower diet was formulated to provide 200 mg/calf daily of monensin (Rumensin 90; Elanco Animal Health). The ALT grower phase occurred from Jan. 29 to May 22 and Feb. 5 to June 4 (years 1 and 2, respectively. The TRAD grower phase was from Oct. 26 to Feb. 16 and Oct. 22 to Feb. 18 (years 1 and 2, respectively). The grower phase was 113 d and 120 d (years 1 and 2, respectively).
The ending BW for the grower phase was used to measure the initial BW for the finisher phase. The difference between the ending BW for the grower and initial BW for the finisher is the animal BW gain assumed for the limit-fed period (1 lb/d).
Steers were implanted on d 1 with Revalor-IS and heifers implanted with Revalor-IH (Merck Animal Health). Cattle were re-implanted on d 84 with Revalor-200 (Merck Animal Health).
The ALT finisher phase was from May 29 to Oct. 29 (first shipping date; year 1) and Dec. 10 (second shipping date; year 1) and June 10 to Nov. 10 (first shipping date; year 2) and Jan. 5 (second shipping date; year 2). The TRAD finisher phase was from Feb. 22 to July 16 (first shipping date; year 1) and Aug. 13 (second shipping date; year 1) and Feb. 25 to June 23 (first shipping date; year 2) and July 28 (second shipping date; year 2).
In year 1, the finishing diet consisted of 33.5% DRC, 33.5% HMC, 20.0% MDGS, 8.0% grass hay and 5.0% supplement (DM basis). In year 2, due to feed seasonal limitations, the finishing diet consisted of 51.0% HMC, 30.0% Sweet Bran, 15.0% corn silage and 4.0% supplement (DM basis).
Shipping dates were calculated to target 0.6 in. of back fat between the 12th and 13th rib using ultrasound. Due to fat variation within pen, calves within pen were allotted to one of two shipping dates.
In year 1, the ALT cattle were on feed for 154 and 196 d while the TRAD cattle were on feed for 145 and 173 d. In year 2, ALT cattle were on feed for 154 and 210 d and TRAD cattle were on feed for 120 and 155 d.
Hot carcass weight (HCW) was collected on day of harvest. Following a 48 h chill, longissimus muscle (LM) area, 12th rib fat thickness, and USDA marbling score were collected. Carcass-adjusted final BW was calculated from HCW using a common dressing percent of 63% to calculate ADG and F:G.
Results
Cow and Preweaning PerformanceThere were no differences (P ≥ 0.27) in conception rates, calving rates and weaning rates for ALT vs. TRAD (Table 2). However, there was an increase (P = 0.04) in the rate of twin offspring (9.42 vs. 2.90 ± 3.29 %, respectively) for ALT vs. TRAD, respectively. This response was unexpected.
In the current study, during the first five days of breeding, cows remained on the limit-fed diet, then placed on fall forage oats which may contribute to twinning. Cow morbidity and replacement rates did not differ (P ≥ 0.78). Breeding BCS distributions did differ (P < 0.01) with a larger proportion of score 5.0 and fewer scores of 6.5 to 7.0 for ALT compared to TRAD cows (data not shown). Likewise, weaning BCS distributions were different (P < 0.01) with a larger proportion of scores 4.0 to 5.0 for ALT compared to TRAD cows (data not shown).
In general, the ALT cows maintained a lower BCS closer to 5.0 throughout the production system. Differences in body condition among production systems are likely due to controlling energy intake of ALT cows during the confined, limit-feeding period compared to TRAD cows on pasture. Even though ALT cows had a shift towards lower BCS from breeding to weaning compared to TRAD cows, conception rates were not different (P = 0.88) among treatments.
As designed, calf age at weaning was not different (P = 0.76) at 168 d for both treatments (Table 3). Calf birthweight, not including the removed twin calf, did not differ (P = 0.35) among TRAD and ALT treatments. Calf wean BW was 99 lbs. lighter (P < 0.01) for ALT calves compared to TRAD calves. As a result of lower weaning weights, lbs. of calf weaned per cow exposed was 108 lbs. less (P < 0.01) for ALT cows compared to TRAD cows.
In the current experiment, preweaning calf morbidity was greater (P < 0.01) for ALT calves compared to TRAD calves. Over half of the calves 58.04 %from the ALT treatment were treated at least once for morbidity compared to 16.70 % of TRAD calves. This difference may be attributed to wet pen conditions in the first year of the study.
Post-weaning performanceDue to differences in weaning BW in the cow-calf phase, initial BW for the grower phase was 96 lbs. lighter (P < 0.01) for ALT calves compared to TRAD calves. Ending BW was 53 lbs. lighter (P < 0.01) for ALT calves compared to TRAD calves, illustrating that ALT calves compensated with greater ADG (P < 0.01) compared to TRAD calves. There was no difference (P = 0.17) for DMI among treatments. Thus, ALT calves had improved (P < 0.01) F:G compared to TRAD calves. Morbidity treatments (i.e. coccidiosis, diphtheria, ear infection, foot rot, lameness, pinkeye, prolapse, were greater (P < 0.01) for TRAD compared to ALT calves.
Due to differences in ending BW in the grower phase, initial BW for the finisher phase was lower (P < 0.01) for ALT calves compared to TRAD calves. Days on feed were 168 and 141 for ALT and TRAD treatments, respectively, in order to harvest cattle at a targeted 12th rib back fat thickness of 0.6 in. Carcass-adjusted final BW did not differ (P = 0.15) among treatments. Dry matter intake did not differ (P = 0.33) between production system, although ADG was lower (P = 0.02) for ALT calves compared to TRAD calves. Lower ADG and no difference in DMI lead to dramatically poorer (P = 0.01) F:G for ALT calves compared to TRAD calves.
Hot-carcass weight did not differ (P = 0.20) between ALT and TRAD treatments. In the current experiment, cattle were harvested based on predicted 12th rib fat thickness, not age. Longissimus muscle area was greater (P = 0.04) for ALT compared to TRAD calves. The ALT treatment had less (P = 0.05) 12th rib back fat compared to the TRAD calves but were 0.59 vs. 0.65 in., respectively. Due to the large numerical improvement in growth performance for TRAD calves in year 2, predicted 12th rib back fat thickness was underestimated. Marbling score did not differ (P = 0.73) among treatments.
Performance differences shifted from growing to finishing, with ALT calves having greater ADG and better F:G than TRAD in the 117-d growing program, but lower ADG and poorer F:G in the finishing phase. It is worth noting that cattle were not fed at the same time of year, with weather stresses during finishing more challenging for ALT cattle.
ConclusionsThis experiment evaluated performance of a cow-calf production system utilizing confinement, cover crop and corn residue compared to a traditional, pasture-based cow-calf production system. It provides evidence that reproduction is not impacted negatively in a partially-confined cow-calf system. The project also illustrates potential challenges with partially-confined systems including calf health and reduced weaning weight.
In this study, the impacts of the production system cannot be separated from spring versus late summer calving. Nevertheless, while calves born into a partially-confined system may require additional days on feed, the carcass characteristics are similar compared to a traditional system.
Erickson is a professor, Drewnoski is an associate professor and MacDonald is a professor, all in the Department of Animal Science at the University of Nebraska-Lincoln. Carlson, is a former UNL graduate student, and current beef Extension specialist at North Dakota State University.
