quality (127 relative feed value) hay was fed ad libitum ... fed as round bales, feed costs alone may be $1.50 ...... Va
The Professional Animal Scientist 23 (2007):366–372
Restricting Time of Access to Large Round Bales of Hay Affects Hay Waste and Cow Performance A. J. Miller,1 D. B. Faulkner, T. C. Cunningham, and J. M. Dahlquist Department of Animal Sciences, University of Illinois at Urbana-Champaign 61801
ABSTRACT Simmental cows in the third trimester of gestation were used in 2 trials to determine the effects of time-restricted access to large round bales on cow performance and hay disappearance. In trial 1, highquality (127 relative feed value) hay was fed ad libitum (no time restriction) or access-restricted to 9, 6, or 3 h/d. In trial 2, average-quality (96 relative feed value) hay was fed ad libitum or access-restricted to 9 or 6 h/d. In both trials, 72 cows were blocked by BW and assigned to 12 pens resulting in 6 cows per pen and 3 or 4 pens per treatment. Each pen had adequate bunk space for 7 cows, and time was limited by gates that prevented access to feeders. Results of trial 1 indicated cows on all treatments gained BW with a linear (P < 0.01) and quadratic (P = 0.03) treatment effect favoring increased time of access. As time of access increased, hay disappearance increased linearly (P < 0.01) and quadratically (P < 0.01), as did manure production, both linearly (P = 0.002) and quadratically (P = 0.07). Hay waste increased linearly (P = 0.009) with increasing time of access. In trial 2, BW gains were not different across treatments. Hay disappearance, manure production, and fecal output all increased linearly (P < 0.01) with increasing time
1
Corresponding author:
[email protected]
of access. In both trials, N, P, and K outputs followed the trend of manure output and increased linearly with increasing time of access. Restricting time of access to large round bales of hay reduced hay disappearance while maintaining acceptable levels of cow performance. Key words: restricted intake, forages, hay, beef cows
INTRODUCTION Costs associated with feeding the producing beef cow represent over 60% of the total costs in a cow-calf production system and are the greatest determinant of profitability for beef producers (Miller et al., 2001). Generally, the most expensive time to feed a beef cow is through the winter months when grazing is not available and supplemental feed is required. Due to ease of handling and simplicity of management, one of the most common methods of providing supplemental feed during this period is to provide unrestricted access to large round bales of hay. Unfortunately, this method also is one of the most expensive. For ad libitum hay fed as round bales, feed costs alone may be $1.50 per day or more (Loerch, 1996) depending on value of the hay. Additionally, feeding loss has been documented to be 12 to 25% with feeding long stem hay ad libitum (Belyea et al., 1985). Restricted
feeding of hay to meet the nutrient requirements of the cow would have the potential to dramatically reduce feed costs by minimizing feed waste, eliminating over consumption, and reducing manure production (Driedger and Loerch, 1999). Furthermore, performance advantages may be realized due to reductions in maintenance requirements (Sainz and Bentley, 1997) and improved digestibility (Tyrrell and Moe, 1975). The most precise method of program-feeding hay to meet nutrient requirements would be to feed processed hay in a bunk, but equipment costs would be prohibitive to all but the largest cowcalf producers. Therefore, the objective of this trial was to investigate the impacts of restricting the time of access to large round bales of hay on cow and calf performance, hay waste, and manure production.
MATERIALS AND METHODS Trial 1 Seventy-two Simmental cows (567 ± 55 kg) in the third trimester of gestation were used to evaluate 4 treatments: ad libitum hay feeding (no time restriction) or access-restricted feeding of 3, 6, or 9 h/d. Cows were blocked by BW and assigned to 12 pens resulting in 6 cows per pen and 3 pens per treatment. All cows were removed from feed and water for 16 h prior to taking initial and final
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weights to eliminate fill differences. A common diet of ground hay was fed ad libitum for 5 d before taking final BW. Initial and final BCS on a 1 to 9 scale (Wagner et al., 1988) were taken at the same time as BW. Cow BCS was determined by the same experienced evaluator at each time. The trial was conducted from September 13 to December 9 (87 d). Climatological data indicated that the average dry bulb temperature during this trial was 11.6°C (52.9°F) compared with a 121-yr average of 9.7°C (49.4°F; NCDC, 1999). Precipitation measurements indicated a total of 15.5 cm of water equivalent during this trial compared with a 121-yr average of 19.8 cm (NCDC, 1999). Pens were 11.0 × 10.7 m concrete lots each with a 7 × 7 m open-front shed. Each pen was equipped with a 3.7 m fence-line round bale feeder allowing 0.6 m per cow and a 7.3 m feed bunk allowing 1.2 m per cow. Time of access was limited by gates that prevented access to hay feeders. Hay fed consisted of 17.6% CP, 45% NDF, 35.2% ADF, and had a relative feed value of 127. Hay was stored inside. All bales were weighed when fed to measure hay disappearance, and random core samples were taken and composited for DM and nutrient analysis. Feed refusal estimates were taken by cleaning the feeders and weighing all feed refused whenever spoiled hay accumulated in the feeders. Samples of feed refusals were collected for DM analysis. Hay DM fed minus DM refused was used to calculate hay disappearance. Pens were cleaned at the beginning of the trial and every 28 d during the trial. Manure output was weighed and sampled when pens were cleaned. Manure samples were analyzed for DM, N, P, and K concentrations. Diet digestibility estimates were made by feeding Cr2O3 at the rate of 10 g/d per head with 0.9 kg/d per head of cracked corn as a carrier for 10 d. This was fed as a supplement to the hay during the trial. On d 10, fecal samples were collected and composited by pen at 8, 16, and 24 h
postfeeding. Samples were analyzed for chromium content (Williams et al., 1962) to determine differences in diet digestibility.
Trial 2 Seventy-two Simmental cows (588 ± 91 kg) in the third trimester of gestation were used to evaluate 3 feeding time restrictions: ad libitum feeding (no time restriction) or access-restricted feeding of 6 or 9 h/d. Cows were blocked by BW and assigned to 12 pens resulting in 6 cows per pen and 4 replications. Initial and final BW of cows were taken 16 h after removal from feed and water to eliminate fill differences. A common diet of ground hay was fed ad libitum for 5 d prior to taking final BW. Initial and final BCS on a 1 to 9 scale (Wagner et al., 1988) were taken at the same time animals were weighed. Cow BCS was determined each time by the same experienced evaluator. This trial was conducted from September 12 to December 12 (89 d). Climatological data indicated that the average dry-bulb temperature during this trial was 9.0°C (48.2°F) compared with a 121-yr average of 9.7°C (49.4°F; NCDC, 2000). Precipitation measurements indicated a total of 20.8 cm of water equivalent during this trial compared with a 121-yr average of 19.8 cm (NCDC, 2000). Large round bales of hay were purchased from one source at 2 times. Core samples of individual bales were composited and analyzed to provide initial DM and nutrient content information. Individual bales were weighed and sampled as fed and composited to calculate DM and nutrient composition as fed. Hay feeders were cleaned whenever spoiled hay accumulated in the feeders throughout the trial, and feed refusals were sampled and analyzed for DM content. Cows were allowed access to bales in 3.7-m fence-line hay feeders located in each pen, thus allowing 0.6 m per cow of feeder space. Pens were 11.0 × 10.7 m concrete lots each with a 7 × 7 m open-front shed. Each pen also included a 7.3 m feed bunk in
which a mineral supplement was fed daily. Time of access to hay was restricted by gates that prevented access to the hay feeders following the assigned time allotment each day. Hay DM fed minus DM refused was used to calculate hay disappearance. Pens were cleaned at the beginning of the trial and every 28 d during the trial. Manure output was weighed and sampled when pens were cleaned. Manure samples were analyzed for DM, N, P, and K concentration. Diet digestibility estimates were made by feeding Cr2O3 at the rate of 10 g/d per head with 0.9 kg/d per head of cracked corn as a carrier for 10 d. This was fed as a supplement to the hay during the trial. On d 10, fecal samples were collected and composited by pen at 8, 16, and 24 h postfeeding. Samples were analyzed for chromium content (Williams et al., 1962) to determine differences in diet digestibility. All experimental procedures were approved by the Laboratory Animal Care Advisory Committee of the University of Illinois.
Statistical Analysis Effects of dietary treatment on cow performance, manure production and fecal output, hay waste, and manure nutrient output were analyzed using the GLM procedure (SAS Institute, Cary, NC) for a completely randomized design with pen as the experimental unit. Linear and quadratic contrasts were used for analyzing time allotments. Contrast coefficients were developed for unequal treatment spacing using SAS for orthogonal polynomial contrasts.
RESULTS AND DISCUSSION Trial 1 Composition of the hay fed in this trial is listed in Table 1. Due to the limited amount of information available on DM consumption as a function of time, high-quality alfalfa hay was used in the initial trial to guard
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Table 1. Hay analyses for Exp. 1 and 2 (DM basis)1 Item
Exp. 1
Exp. 2
CP, % ADF, % NDF, % TDN, % NEl, Mcal/kg NEq, Mcal/kg NEm, Mcal/kg Relative feed value Ca, % P, % Mg, % K, % S, %
17.6 35.2 45.0 62.3 1.3 0.8 1.4 127 1.1 0.3 0.2 2.2 0.2
15.4 38.3 57.1 61.2 1.2 0.8 1.3 96 0.9 0.3 0.2 1.5 0.2
1
Cattle in both trials were fed 0.11 kg/d per head trace mineralized salt with composition (%): NaCl, 20 to 24; Ca, 14.5 to 16.5; P, > 8; Mg, > 1.1; S, > 0.71; K, > 2.24; Fe, > 0.25; Zn, > 0.25; Mn, > 0.25; Cu, > 0.03; Co, > 0.003; I, > 0.004; Se, > 0.0026, and vitamin A, > 529,100; vitamin D3, > 88,183; vitamin E, > 441 IU/kg.
against excessive BW loss by the most time-restricted cows. Results of cow performance are presented in Table 2. Cows on all treatments gained BW during the trial with a linear (P < 0.01) and quadratic (P = 0.03) treatment effect favoring increased time of access. Given the stage of gestation of the cows (third trimester), it is estimated that fetal growth contributed a significant portion of this BW gain. Daily intake, calculated by sub-
tracting hay waste from hay disappearance as listed in Table 3, ranged from 4.5 kg DM/d per head for the cows allowed 3 h of access to 8.1 kg DM/d per head for cows allowed ad libitum access. Given this range in apparent intakes, it was expected that longer access would enhance performance; however, it is important to note that cows restricted to 3 h of access maintained body condition and exhibited sufficient BW gain to support fetal growth. Cows began the trial at an average BCS of 5.5 (SD 0.2) on a 1 to 9 scale and concluded the trial with an average BCS of a 6.0 (SD 0.3) with a range from 5 to 8 for individual cows, thus further indicating that cows maintained or gained body condition across all treatments during the trial. Results of hay disappearance and manure production are listed in Table 3. As time of access increased, hay disappearance increased linearly (P < 0.01) and quadratically (P < 0.01). Hay disappearance was calculated as the amount of hay that was placed in the feeders minus that refused. Hay that appeared to be spoiled and was not being consumed by the cows was removed from the feeders and weighed for a measure of hay refusal. Given hay quality and inside storage method, hay refusals were negligible and comparable across treatments in both trials: this, combined with the difficulty in accurately predicting what cows would no longer consume, resulted in hay disappearance from the feeder reported as a measure of intake and waste as opposed to
Table 2. Effect of restricting time of access to hay on cow performance (Exp. 1) Treatments Item Initial BW, kg Final BW kg BW change, kg Initial BCS Final BCS BCS change
P-value
3h
6h
9h
Ad libitum
SE
Linear
Quadratic
570 624 54 5.7 5.8 0.1
563 636 73 5.4 5.8 0.5
565 652 87 5.4 6.1 0.7
571 665 94 5.4 6.2 0.8
10.9 15.2 6.8 0.1 0.1 0.1
0.81 0.10 0.006 0.32 0.04 0.01
0.64 0.45 0.03 0.05 0.36 0.03
hay offered and refused. Refusals likely would have been greater had the hay been of lesser quality and stored outside. Additionally, with the trials conducted in the fall there was less time for weather to affect hay quality and storage losses than if the trials had been conducted in the spring. Manure production as measured by 28-d pen scraping also indicated linear (P = 0.002) and quadratic (P = 0.07) increases with increasing time of access. Fecal output exhibited linear (P < 0.01) and quadratic (P < 0.01) differences across treatments with a large increase from 3 to 6 h followed by a peak at 9 h and slight decline in total fecal output for the ad libitum access treatment. An estimate of hay waste was obtained by subtracting fecal output from collected manure production. Hay waste expressed as a percentage of hay disappearance was not statistically different across treatments and ranged from 23% for the cows with 6 h of access to 40% for the cows with ad libitum access. These figures are substantially higher than those reported by Belyea et al. (1985; 12.4 to 24.7%). In the Belyea et al. (1985) study, cattle were fed in a bunk with angled headgates similar to the feeder design of the current research, and heifers were used as opposed to mature cows. Buskirk et al. (2003) also reported lesser feed waste figures (3.5 to 14.6%) when researching different feeder designs, with greater losses for linear type feeders (similar to the present research) than round feeders. Buskirk et al. (2003) reported greater occurrences of agonistic interactions with linear type feeders, which was positively correlated with feed loss. In the current study, feed waste was calculated by subtracting fecal output from total manure collection. This method likely leads to an increase in waste figures. In both of the previously mentioned trials, cattle were fed on concrete and feed waste was measured by daily hand collection. This frequent cleaning around feeders likely contributed to decreased waste
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Table 3. Effect of restricting time of access to hay on hay disappearance and manure production (Exp. 1) Treatments
P-value
Item
3h
6h
9h
Ad libitum
SE
Linear
Quadratic
Hay disappearance,1 kg DM/d Manure production,2 kg DM/d Fecal output,3 kg DM/d Hay waste,4 kg DM/d Hay waste,5 % Intake,6 kg DM/d Digestibility, %
8.0 5.3 2.7 2.7 33.3 5.4 49.4
11.1 6.8 4.2 2.6 23.2 8.5 50.5
13.3 8.9 4.7 4.2 31.5 9.1 48.6
15.5 10.3 4.2 6.1 39.5 9.4 53.4
0.33 0.77 0.11 0.80 5.9 0.85 4.1
0.0001 0.002 0.0002 0.009 0.21 0.03 0.48
0.0001 0.07 0.0001 0.70 0.49 0.03 0.76
1
Calculated as amount offered minus refusals. Physical collection of manure from pens including hay waste. 3 Calculated from chromium concentration in feces. 4 Calculated by subtracting fecal output from manure production. 5 Calculated by dividing hay waste amount by hay disappearance. 6 Calculated as hay disappearance minus hay waste. 2
figures. In the current study, pens were scraped every 28 d and it was noted that as manure increased around feeders, there was increased trampling and mixing of feed pulled from the feeders with fecal output. When expressed in kilograms, hay waste exhibited a linear (P = 0.009) increase with increasing time of access. The amount of hay waste for the cows with ad libitum access was more than double that of cows limited to 3 or 6 h of access. Total kilograms of hay waste were similar between the 3- and 6-h treatments. It appeared that cows limited to 3 h of access were more aggressive around the feeder than those on other treatments. This behavior may explain why the total amount of waste per hour was increased for the 3-h treatment relative to the other treatments. However, total kilograms of hay waste was still less for the 3- and 6-h treatments than 9 h or ad libitum. Intakes decreased linearly (P = 0.03) and quadratically (P = 0.03) with decreasing time of access. Digestibility measurements were not impacted by time of access (linear, P = 0.48; quadratic, P = 0.76). Sainz (1995) stated that as feed intake decreases, a slower rate of passage of feed particles from the rumen might be expected, re-
sulting in longer residence times that should increase the extent of digestion of the feed. However, Varga and Prigge (1982) compared all forage diets fed at 60 and 90% of ad libitum and found no digestibility differences between treatments; however, particulate passage rate also was not different across these 2 treatments and there was no ad libitum treatment for comparison. Intake and output of N, P, and K in Trial 1 are given in Table 4. Disappearance of all 3 nutrients increased linearly (P < 0.01) and quadratically (P < 0.01) with increasing time of access. These results agree with trends seen in increasing DM disappearance. Manure composition data indicates a linear increase in concentration of N with increasing time of access (P = 0.06); combined with increasing manure production with increasing time, this resulted in linear (P < 0.01) and quadratic (P = 0.02) increases in N output. Calculations indicate that the percentage of N that was fed that was recovered in the manure ranged from 45.6 to 59%. It is likely that these percentages increased somewhat with increasing time of access because of the increasing amounts of hay in the manure. It is recognized that these figures would not account
for pen run-off and volatilization as pens were cleaned on a monthly basis. Reductions in fecal N excretion may be partially explained by reductions in metabolic fecal N (Swanson, 1977), which has been related to DMI, DM digestibility (Hutchinson and Morris, 1936), and fecal DM excretion (Hironaka et al. 1970). Phosphorus data indicates that manure composition did not vary with increasing time of access (linear, P = 0.30; quadratic, P = 0.83), and thus total P output increased with increasing manure output (linear, P < 0.01). Morse et al. (1992) demonstrated that reductions in P intake reduced P excretion to a similar degree as the reduction in intake. Driedger and Loerch (1999) reported a trend toward increased P digestion and reduced excretion with limit-fed corn diets compared with forage ad libitum, but because P intakes differed, the observed differences may have been due to diet or intake. Potassium data indicates similar trends to that seen with P. Disappearance increased with increasing access (linear, P < 0.01; quadratic, P < 0.01). Manure composition was not different across treatments (linear, P = 0.26; quadratic, P = 0.88). Total K output increased linearly (P < 0.01) with increasing access.
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Table 4. Effect of restricting time of access to hay on nutrient output (Exp. 1) Treatments Item Nitrogen Disappearance,1 kg/d Manure composition, % N N output,2 kg/d % N recovered3 Phosphorus Disappearance,1 kg/d Manure composition, % P P output,2 kg/d % P recovered3 Potassium Disappearance,1 kg/d Manure composition, % K K output,2 kg/d % K recovered3
P-value
3h
6h
9h
Ad libitum
SE
Linear
Quadratic
0.226 1.95 0.103 45.6
0.312 2.05 0.136 43.5
0.374 2.34 0.205 54.9
0.436 2.49 0.256 59.0
0.009 0.18 0.02 3.90
0.0001 0.06 0.0001 0.02
0.0001 0.38 0.02 0.43
0.031 0.53 0.028 90.7
0.039 0.54 0.036 91.7
0.045 0.56 0.049 109.1
0.051 0.60 0.062 121.8
0.0009 0.05 0.005 9.68
0.0001 0.30 0.0008 0.04
0.0001 0.83 0.10 0.54
0.177 3.15 0.166 93.9
0.243 3.40 0.225 92.5
0.292 3.20 0.279 95.8
0.339 3.74 0.382 112.8
0.007 0.34 0.02 7.50
0.0001 0.26 0.0001 0.07
0.0001 0.88 0.10 0.68
1
Disappearance calculated from hay analysis, average pen hay disappearance, and mineral supplementation. Calculated from composition and pen manure output. 3 Calculated as a percent of disappearance. 2
Trial 2 Composition of hay fed in Trial 2 is listed in Table 1. This trial utilized lesser quality hay than the first trial, and the 3-h time of access treatment was removed. It was estimated that the 3-h treatment would not allow for adequate intake levels to support acceptable cow performance if lesser quality hay was used. Cow performance is listed in Table 5. Weight gains in this trial ranged from 64 to 76 kg/cow and were not different across treatments (linear, P = 0.12; quadratic, P = 0.36). Body condi-
tion score data agrees with BW gain results. Cows began the trial with an average of 5.7 (SD 0.3) on a 1 to 9 scale and concluded with a 6.3 (SD 0.3). At the conclusion of the trial, BCS ranged from 4 to 8.5, indicating that all cows maintained an acceptable body condition. Hay disappearance increased linearly (P < 0.01) with increasing time of access. Unlike Trial 1 there was not a quadratic trend for a rapid increase in disappearance up to the 9-h treatment followed by a gradual leveling off to the 24 h treatment (Table 6). Manure production also increased lin-
Table 5. Effect of restricting time of access to hay on cow performance (Exp. 2) Treatments Item Initial BW, kg Final BW, kg BW change, kg Initial BCS Final BCS BCS change
P-value
6h
9h
Ad libitum
SE
Linear
Quadratic
598 661 64 5.7 6.1 0.4
599 670 72 5.9 6.5 0.6
570 646 76 5.5 6.2 0.7
17.3 17.9 4.5 0.2 0.1 0.1
0.22 0.42 0.12 0.22 0.82 0.10
0.80 0.63 0.36 0.26 0.08 0.32
early (P < 0.01) with increasing time of access, as did fecal output (P = 0.01). Subtracting fecal output from manure production resulted in the measurement of hay waste. Hay waste expressed as either kilograms of DM or as a percent of disappearance did not display a linear difference but did exhibit a quadratic trend (P = 0.06) with more waste at the 6- and 24-h times than at the 9-h time. Hay waste figures in this trial were generally less than figures seen in Trial 1, but similar to those in previous research (Belyea et al., 1985; Buskirk et al., 2003). Belyea et al. (1985) reported feeding losses of 12.4% when feeding round bales that were stored inside, which agrees with the range (8.5 to 16.4%) seen in this study. Buskirk et al. (2003) reported losses ranging from 3.5 to 14.6% depending on feeder type. Intake increased with increasing time of access (P = 0.03), as in Trial 1. The increase in intake was characterized by a quadratic trend (P = 0.11) toward a rapid increase to 9 h with the increase tailing off to ad libitum. Digestibility data indicates a 5.7% in-
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Table 6. Effect of restricting time of access to hay on hay disappearance and manure production (Exp. 2) Treatments Item
6h
9h
P-value
Ad libitum
SE
12.9 7.7 5.6 2.1 16.4 10.8 48.0
0.31 0.31 0.29 0.30 2.6 0.43 2.8
Hay disappearance,1 kg DM/d 10.7 11.2 Manure production,2 kg DM/d 5.8 6.0 Fecal output,3 kg DM/d 4.1 5.1 1.7 0.9 Hay waste,4 kg DM/d Hay waste,5 % 16.1 8.5 8.9 10.2 Intake,6 kg DM/d Digestibility, % 53.7 50.4
Linear Quadratic 0.0005 0.001 0.01 0.10 0.38 0.03 0.24
0.73 0.71 0.10 0.06 0.06 0.11 0.55
1
Calculated as amount offered minus refusals. Physical collection of manure from pens including hay waste. 3 Calculated from chromium concentration in feces. 4 Calculated by subtracting fecal output from manure production. 5 Calculated by dividing hay waste amount by hay disappearance. 6 Calculated as hay disappearance minus hay waste. 2
crease in digestibility for the 6-h treatment compared with the cows with ad libitum access, although this increase did not prove to be statistically different (linear, P = 0.24; quadratic, P = 0.55). This agrees with the lack of difference in digestibility seen in Trial 1. Previous research (Varga and Prigge, 1982) also found no digestibility differences when all forage diets were fed at differing intakes. Analysis of nutrient content of manure is presented in Table 7. Nitrogen disappearance increased linearly (P < 0.01) with increasing time of access. This would be expected as hay disappearance also increased. Percent N in the manure did not vary across treatments, and thus due to the increase in manure output with increased time of access, N output also increased linearly with increasing access (P < 0.01). The percentage of N fed that was recovered in the manure ranged from 40.6 to 45.4% and was not different across treatments (linear, P = 0.11; quadratic, P = 0.83). Nitrogen disappearance, manure composition, N output, and the percent N recovered were all similar but slightly less than the corresponding times of access in Trial 1. This would be expected due to the larger protein content of the hay in Trial 1.
As with N, P disappearance increased linearly (P < 0.01) with increasing time of access. The percent of P in the manure did not vary across treatments and thus total P out-
put followed the same trend as manure production and increased linearly (P < 0.01) with increasing time of access. This agrees with the results seen in Trial 1. The P composition of the manure was similar to the values seen in Trial 1. This would be expected as the P levels in the forage source for each trial were similar. The percentage of P recovered ranged from 76.2 to 87.6% but was not statistically different across treatments (linear, P = 0.11; quadratic, P = 0.58). Potassium data indicates similar trends to those seen for N and P. Disappearance increased linearly (P < 0.01) with increasing access. Manure composition did not vary across treatments. The percentage of K in the manure was lower in Trial 2 than Trial 1; however, K levels in the hay were approximately 50% higher in Trial 1. Total K output tended to increase linearly with increasing access (P = 0.08), and the percentage of K fed that was recovered was not different across treatments.
Table 7. Effect of restricting time of access to hay on nutrient output (Exp. 2) Treatments Item
6h
9h
Ad libitum
Nitrogen Disappearance,1 kg/d 0.262 0.275 0.316 Manure composition, % N 1.85 1.91 1.87 N output,2 kg/d 0.107 0.115 0.143 % N recovered3 40.6 42.0 45.4 Phosphorus Disappearance,1 kg/d 0.036 0.037 0.041 Manure composition, % P 0.47 0.50 0.47 0.027 0.030 0.036 P output,2 kg/d % P recovered3 76.2 81.3 87.6 Potassium Disappearance,1 kg/d 0.163 0.170 0.196 Manure composition, % K 1.86 2.07 1.86 K output,2 kg/d 0.109 0.125 0.142 % K recovered3 67.1 73.4 72.7 1
P-value SE
Linear Quadratic
0.008 0.09 0.004 1.9
0.0005 0.95 0.0002 0.11
0.73 0.63 0.72 0.83
0.001 0.03 0.001 4.3
0.0005 0.72 0.001 0.11
0.73 0.45 0.462 0.58
0.005 0.13 0.011 6.6
0.0005 0.64 0.08 0.69
0.73 0.26 0.52 0.55
Disappearance calculated from hay analysis, average pen hay disappearance, and mineral supplementation. 2 Calculated from composition and pen manure output. 3 Calculated as a percent of disappearance.
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Economics Undoubtedly the most significant potential benefit of program-fed cow diets is reduced feed costs. Loerch (1996) reported that the cost to feed a cow round baled hay ad libitum was nearly double that of limit-feeding corn and that the breakeven price for hay would be about $44/metric ton when corn is priced at $71.50/ metric ton. Assuming the hay used in Trial 1 had a fair market value of $88/metric ton, the reductions in hay usage between cows allowed ad libitum access and those limited to 3 h/d would have been worth $0.66/cow per day (Table 8). This equates to savings of $1,980 for a 25-cow herd that feeds hay 4 mo/yr. These savings do not include additional reductions in labor and machinery cost associated with feeding hay and manure removal. Miller et al. (2001) reported that whereas feed costs were the largest driver of profitability in a commercial cow-calf operation, deprecation and operating costs were the second and third largest determinants and were both significantly correlated to feed costs. This indicates that not only are the costs of feed itself significant, but costs associated with physically feeding the cows (fuel, repairs, equipment depreciation, etc.) also significantly impacted profitability. Reductions in the amount of hay that is fed and manure that is removed will reduce these expenses.
Miller et al.
IMPLICATIONS Results of this study indicate that limiting the time that cows have access to a large round bale of hay to as little as 3 h/d will result in acceptable cow performance depending on hay quality. Limiting time of access will also reduce hay use by limiting intake and decreasing hay waste, thereby reducing feed costs for the cow-calf producer. Further benefits of this program include decreased manure production and total nutrient output. Reductions in hay fed and manure produced will also provide the additional benefits of less equipment and labor costs for the producer.
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