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ANIMAL NUTRITION |
* Department of Animal and Range Sciences, North Dakota State University, Fargo 58105; and
and
Dickinson Research Extension Center, Dickinson, ND 58601
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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0.02) with advancing season. Supplementation decreased (P = 0.05) ruminal pH, whereas ruminal ammonia and VFA concentrations were greater (P 0.02) in SUP calves. In Exp. 2, creep-fed calves had greater ADG and final BW than CON calves (P < 0.01). Calves offered HS tended (P = 0.07) to have increased gain efficiency above CON than LS calves. Field peas can be used as an ingredient in creep feed to increase calf weight gain without negatively affecting ruminal fermentation and digestion.
Key Words: Digestibility • Field Pea • Forage • Intake • Nursing Calves • Ruminal Fermentation
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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). Field pea is a legume crop that fits in well with small grain rotations. Production has increased due to adaptability to the northern Great Plains, sustainability, and the use of conventional cultivation and handling equipment (Anderson, 1998). Although grown primarily as a human food, a potential use for field peas is livestock feed (Reed et al., 2004a,b; Soto-Navarro et al., 2004). The energy content of field peas is similar to corn or other cereal grains, whereas the protein content is approximately 25% (NRC, 1984) and the starch content is 47% compared with other cereal grains (Reed et al., 2004a).
Supplemental creep feed can increase weaning weights of nursing calves (Faulkner et al., 1994; Lardy et al., 2001; Loy et al., 2002). However, creep feed must provide limiting nutrients in the calf’s diet to be effective (Loy et al., 2002), and creep feed should not negatively affect forage intake or digestion (Caton and Dhuyvetter, 1997). Increased grain intake (>0.4% of BW) may lead to decreased forage digestibility (Pordomingo et al., 1991). Loy et al. (2002) reported no differences in forage intake between unsupplemented and supplemented calves. However, Lardy et al. (2001) reported forage intake tended to be higher in unsupplemented calves compared with calves receiving supplemental undegradable intake protein.
Our objectives were to determine effects of a field pea-based creep feed and advancing season on diet composition, intake, digestion, in situ disappearance rate, ruminal fill, and ruminal fermentation characteristics in nursing beef calves grazing native range. In addition, a field study was conducted to evaluate effects of salt-limited, field pea-based creep feed on calf performance. Due to the nutrient profile of field peas, we hypothesized that a field pea-based creep feed would have limited effects on ruminal fermentation, digestibility, and intake.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Study Area.
Research was conducted at the Dickinson Research Extension Center Ranch, approximately 35 km northwest of Dickinson, North Dakota, on section 16 T 143 North R 96 West. This area is characterized by a continental climate with warm summers and cold winters. The average annual temperature is 6.0°C, with the average temperatures for July, August, September, and October being 20.0, 19.4, 12.8, and 6.1°C, respectively (NDAWN, 2003a). The growing season ranges from 99 to 142 d (Biondini and Manske, 1996). The 30-yr average precipitation is 42.2 cm, with 86% from April to October. Precipitation and temperature data were recorded using a weather station located at the Dickinson Research Extension Center Ranch operated by the North Dakota Agricultural Weather Network.
The principle vegetation of the study area is mixed-grass prairie dominated by grasses of medium height (Biondini and Manske, 1996). Major forage species include western wheatgrass (Pascopyrum smithii [Rydb.] A.Love), prairie junegrass (Koeleria pyramidata [Lam.] Beauv.), needle-and-thread (Stipa comata Trin. and Rupr.), and green needlegrass (Stipa viridula Trin.). Associated with these species are several shorter grasses and sedges, including blue grama (Bouteloua gracilis H.B.K.), threadleaf sedge (Carex filifolia Nutt.), and sun sedge (Carex heliophila Mack.). Three major range sites dominate the study area (Biondini and Manske, 1996) and include sandy, shallow, and silty (USDA SCS, 1982).
Animals and Diets.
Eight Angus xHereford nursing steer calves (145 ± 27 kg initial BW) were fitted with ruminal cannulas. Surgical and animal handling procedures were conducted using protocols approved by North Dakota State University Institutional Animal Care and Use Committee. Surgeries were conducted on June 10, 2002, and calves were allowed 28 d to recover before initiation of the study. Calves were allotted randomly to one of two treatment groups: 1) control (CON; unsupplemented); or 2) field pea-based supplemental creep (SUP; 19.1% CP, DM basis; Table 1) fed at 0.45% of BW daily (DM basis).
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Sampling Periods. Calf responses to treatment and seasonal effects were measured during four experimental periods, each 24 d in length. Experimental periods were July 8 to July 31 (JUL), August 5 to August 30 (AUG), September 9 to October 2 (SEP), and October 11 to November 3 (OCT).
All calves were gathered into a holding pen for ruminal evacuations at dawn on d 1 of each experimental period. Digesta was placed in plastic bags lining 133-L plastic containers. After evacuation, calves were returned to the pasture with their dams and allowed to graze for 60 to 90 min. Calves were gathered and in situ masticate samples collected, subsampled, and frozen (–10°C). Evacuated contents were returned to the animals following sampling.
Cows and calves were brought into the holding pen and individually weighed on d 7 of each experimental period, 3 h before sunset (sunset ranged from 2130 in July to 1700 in October). Weights of SUP calves were used to calculate the amount of individual supplement provided each day. On d 7 and 8, estimates of milk consumption using a 12-h weigh-suckle-weigh procedure (Boggs et al., 1980) were collected. Briefly, calves were separated from their dams for 3 h, returned to their dams and allowed to nurse until satisfied, and then separated for 12 h. Following separation, calves were weighed, allowed to nurse until satisfied, and weighed again. Milk consumption was expressed on a 24-h basis for reporting purposes.
Creep feed supplementation began on 15 July. All calves were gathered daily at 0730, and supplemented calves were offered field pea-based creep at 0.45% of BW (DM basis) at 0800. If creep was not consumed after 1 h, it was placed in the rumen via the cannula. On d 14 to 21 of each experimental period, fecal collections were performed using fecal collection harnesses and canvas bags with plastic liners. Fecal bags were removed and samples collected at 0800 and 1700, with a 10% subsample collected, composited, and frozen (–10°C) for later analysis.
In situ masticate samples collected on d 1 by ruminal evacuation techniques were composited across all calves within experimental period for in situ fermentation. Samples were placed in a cooler, transported to the laboratory, lyophilized (Virtis Genesis 25LL; The Virtis Co., Inc., Gardiner, NY), and ground in a Wiley mill (2-mm screen; Arthur H. Thomas, Philadelphia, PA). Five-gram samples were sealed with an impulse sealer (AIE-200, American Int. Electric, Whittier, CA) in Dacron bags (10 x20 cm, 50 x15 µm pore size; Ankom, Fairport, NY). On d 14 to 18, composited forage in situ bags were ruminally incubated within nylon lingerie washing bags (30.5 x25.4 cm) for 96, 48, 36, 24, 16, 12, 8, 4, 2, and 0 h in all calves. On d 22 to 24, creep feed (2 mm grind; 5 g on an as-fed basis) in situ bags were incubated for 48, 36, 24, 16, 12, 8, 4, 2, and 0 h. At time point 0 for each incubation, all lingerie bags were removed from the rumen and placed in a 20-L plastic container of tap water. Rinsing procedures followed those described by Mathis et al. (2001), with the following modifications made due to the distance bags had to be transported to the top-loading washing machine. Bags were transported to ranch headquarters, where individual in situ bags were removed from lingerie bags and rinsed with tap water. These bags were placed into another 20-L plastic container of tap water, where they were mixed and transferred to a 20-L plastic container of clean water. This process of rinsing was repeated four times. Individual bags were placed back in clean lingerie bags. Following this rinsing process, bags were rinsed in a top-loading washing machine (model VVSR1070B0WW3, Hotpoint, Louisville, KY) according to Mathis et al. (2001). The machine was filled with 45 L of cold water. Bags were agitated for 1 min, drained, and spun for 2 min. This procedure was repeated five times, rather than the 10 times recommended by Mathis et al. (2001) because they had already been subjected to previous hand washing. After washing, individual in situ bags were allowed to drip dry. The following day, bags were arranged on metal trays and placed in a 55°C forced-air oven for 48 h. Following drying, bags were sorted by animal, placed in plastic bags, and transported to the laboratory for weights and chemical analyses.
Ruminal fluid samples (200 mL) were collected on d 18 to 20 using a suction strainer. Beginning on d 18, ruminal fluid was collected at 0600, 1200, and 1800. On d 19 and 20, times were advanced 2 h each day to represent every even daylight hour during the collection period. Ruminal fluid pH was read immediately following collection using a Beckman 200 series portable pH meter (Beckman Instruments, Inc., Fullerton, CA), and then the sample was acidified with 7.2 N H2SO4 at 1 mL/100 mL ruminal fluid and frozen (–10°C) for later analysis of NH3-N and VFA.
Calves were gathered before dawn and ruminally evacuated to determine ruminal DM and OM fill on d 22. All ruminal content and fluid was removed and placed in plastic liners in 133-L containers. Calves were turned out and allowed to graze 60 to 90 min. During this time, ruminal contents were weighed, a 2-kg sub-sample was taken for DM determination, and a 2-kg subsample was mixed with 1 L of formalin/saline solution (3.7% formaldehyde/0.9% NaCl; wt/vol) for isolation of bacterial cells (Zinn and Owens, 1986). Ruminal content samples were frozen (–10°C) for later analysis. Following grazing, calves were gathered and diet masticate samples were collected and frozen (–10°C) for later analysis of grazed dietary chemical components. Evacuated contents were returned to each animal following completion of diet collection.
On d 23, Co-EDTA (200 mL; Uden et al., 1980) was dosed intraruminally at 0600. Ruminal fluid samples (200 mL) were collected at the following times: 0600 (before dosing), 0800, 0900, 1100, 1400, 1700, and 2000 to measure fluid passage rate. Ruminal fluid pH was determined immediately after collection and then samples were acidified with 7.2 N H2SO4 at 1 mL/100 mL ruminal fluid and frozen (–10°C) for later analysis of Co concentration.
Laboratory Analyses. Fecal samples were thawed, mixed, and subsampled, dried in a forced-air oven (50°C; model SB-350; The Grieve Corp., Round Lake, IL) for 48 h, and ground in a Wiley mill (1-mm screen; Arthur H. Thomas). Masticate samples were freeze-dried and ground through a Wiley mill (1-mm screen).
Fecal, masticate, and creep feed samples were analyzed for DM, OM, and CP (Methods 930.15, 942.05, and 990.02, respectively; AOAC, 1997). The ADF analyses were conducted according to Goering and Van Soest (1970) and NDF according to Robertson and Van Soest (1991) using an Ankom 200 fiber analyzer (Ankom Co., Fairport, NY) as sequentials. In vitro OM digestibility (IVOMD) Tilley and Terry, 1963) was determined using composited inoculate from two ruminally cannulated steers fed a grass hay diet. Acid detergent insoluble nitrogen was analyzed using the Kjeldahl method of nitrogen determination on the ADF residue. Ruminal fluid samples were centrifuged at 20,000 xg for 20 min and analyzed for NH3-N (Broderick and Kang, 1980) and VFA (Goetsch and Galyean, 1983). Ruminal fluid with cobalt was centrifuged at 20,000 xg for 20 min, and cobalt was determined using an air-plus-acetylene flame using atomic absorption spectroscopy (model 3030B, PerkinElmer, Inc., Wellesley, MA) as described by Uden et al. (1980).
Ruminal bacteria were isolated from a 2-kg sample of ruminal contents. Ruminal contents were blended (model 37BL19 CB6; Waring Products, New Hartford, CT) on high speed for 1 min, and the mixture strained through four layers of cheesecloth. Feed particles and protozoa in ruminal samples were removed via centrifugation at 1,000 xg for 10 min. Bacteria were separated from supernatant by centrifuging at 20,000 xg for 20 min. Isolated bacteria were frozen, lyophilized, and analyzed for DM, ash, N (as previously described), and purines (Zinn and Owens, 1986).
Forage intake was calculated using the total fecal output and forage in vitro OM indigestibility. Forage fecal output (DM) was converted to an OM basis using the analyzed OM of feces. Forage fecal output on an OM basis was determined by subtracting the indigestible fraction of the supplement from feces of supplemented calves using in vitro OM indigestibility of the supplement. To determine forage OM intake, forage fecal output of OM was divided by forage in vitro OM indigestibility.
Statistical Analyses. The Mixed procedure of SAS (SAS Inst., Inc., Cary, NC) was used for all statistical computations. The data was analyzed as a split-plot in time. The whole plot was experimental period which occurred in JUL, AUG, SEP, and OCT, whereas the two treatments served as the split-plot. For dietary composition, intake, digestibility, and in situ data, fixed effects in the model included treatment, period, and the period x treatment interaction. The repeated effect was period and animal within treatment, which was used to test treatment effects. Period and subsequent interactions were tested with residual error.
In situ data was evaluated using the Ørskov and McDonald (1979) model, d = a + b (1 – e–kd), where a is the soluble fraction, b is the slowly degraded fraction, d is extent and kd is the rate of degradation. The Mixed procedure of SAS also was used to analyze the ruminal fermentation data (pH, NH3-N, and VFA) using a split-split-plot analysis. The fixed effects in the statistical model included treatment, period, and period xtreatment interaction. The repeated effect was time and animal within period xtreatment was used as the error term for the split-split-plot. When no significant time xtreatment interactions were noted (P < 0.05), main effects of treatment and period were reported.
Experiment 2
Animals and Diets.
All animal care and handling procedures were conducted according to protocols approved by the North Dakota State University Institutional Animal Care and Use Committee. Eighty Angus xHereford cows with Angus, Red Angus, and Hereford-sired calves were used to evaluate the effects of salt and CP level in field pea-based creep diets on calf performance. Treatments included CON, a field pea-based creep feed containing (as-fed basis) 8% salt (LS, 19% CP), a field pea-based creep feed containing 16% salt (HS, 19% CP), and a high-protein soybean meal and field pea-based creep feed containing 16% salt (HIPRO, 35% CP; Table 2).
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Cow/calf pairs grazed replicated native pastures on section 16 T 143 North R 96 West, which were adjacent to the pastures in the metabolism study and of similar forage composition. Twelve pastures were used in yr 1 and eight pastures were used in yr 2. Four pairs grazed each 20-ha pasture for each 35-d period. After each 35-d period, cows and calves were weighed and rotated to a different pasture. All cattle had ad libitum access to water, salt, and a commercial mineral mix (American AgCo; 11% Ca, 12% P, 2.3% Mg, 2.0% K, 1.0% S, 27 mg/kg of Co, 70 mg/kg of I, 35 mg/kg of Se, 2.7 g/kg of Cu, 4.7 g/kg of Mn, 4.8 g/kg of Zn, 500 kIU/kg of vitamin A, 75 kIU/kg of vitamin D3, and 5 kIU/kg of vitamin E; as-fed basis).
Sampling Periods. In 2001, cattle were placed on trial on July 25, with calf and cow weights and BCS measured on August 29, October 3, and November 7. In 2002, the trial was initiated on July 25, and weights and BCS of cows were measured on August 29, October 3, and November 6.
Statistical Analyses. The Mixed procedure of SAS was used to analyze calf and cow performance data. The model included treatment as the fixed effect and year as random effect, with experimental unit being pasture group. The variables analyzed for the calf data included initial BW, final BW, ADG, creep intake, gain above control, and gain efficiency above control. Contrasts were determined for CON vs. supplemented, LS vs. HS, and HS vs. HIPRO. The variables analyzed for the cow data included initial BW, final BW, weight change, initial BCS, final BCS, and BCS change. Contrasts were determined for CON vs. supplemented, LS vs. HS, and HS vs. HIPRO.
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Results and Discussion |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Rainfall for the months of April through October 2001 was 40.5 cm, which is 12% above the 30-yr average. The majority of rainfall occurred in June and July and was 70% above the long-term average, whereas August and October rainfall was 93% below average (NDAWN, 2003a,b). In 2002, rainfall was 35.3 cm, or 2% below the long-term average. Rainfall was above average in June, July, and August, and below average in September and October (NDAWN, 2003a,b).
Experiment 1
Grazed Diet Quality.
There were no treatment xperiod interactions detected for any components of the masticate samples (P < 0.13); therefore, main effects of treatment and period are reported in Table 3. Nutrient composition of grazed forage diet masticate samples was not different between treatments, except for CP, which was greater (P = 0.05) for SUP compared with CON. The greater level of CP may be due to salivary contamination because SUP calves may have had greater blood urea concentrations and consequently more N recycling than CON calves (Huntington and Archibeque, 1999; Lapierre and Lobley, 2001).
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). Increased CP and ADIN levels were observed in AUG, which was likely due to above normal rainfall for AUG and JUL and below normal for SEP and OCT. Loy et al. (2002) reported an increase in CP between AUG and SEP on sandhills tallgrass prairie. This increase was likely a result of the growth of cool season grasses, which made up 60% of the vegetative species in that pasture. We did not observe the increased forage quality in AUG and SEP that Loy et al. (2002) reported, which is likely due to differences in rainfall patterns.
In vitro OM digestibility also exhibited a linear response (P < 0.001), with a distinct decline in OCT that was likely due to weather conditions and snow cover. During the OCT collection period, there was approximately 15 cm of snow cover. This likely affected diet selection because animals may have been limited in available forage from which to select. In addition, forage that was available had decreased quality due to plant maturity. Our IVOMD values for grazed forage samples were similar to those of Loy et al. (2002); however, Loy et al. (2002) reported an increase in IVOMD from AUG to SEP, whereas we noted a linear decrease across season. Similarly, Kirby and Parman (1986) reported a decrease in forage CP and IVOMD from late June through mid-October for pastures at the same location using cow/calf pairs. Other researchers have reported a decrease in IVOMD across season (McCollum and Galyean, 1985; Krysl et al., 1987). Forage NDF and ADF were not different across season (67.2 ± 1.4% NDF; 40.0 ± 0.9% ADF). Other studies (Krysl et al., 1987; Olson et al., 1994) have reported an increase in the plant fiber fractions with increasing maturity and dormancy, but our results did not follow the same pattern. The studies conducted by Olson et al. (1994) and Krysl et al. (1987) used yearling cattle rather than nursing calves to evaluate forage quality and the fiber fractions, which may explain some of the differences between the studies. However, Grings et al. (1995) reported an increase in ADF with advancing season when using suckling calves to collect diets. These researchers also reported that suckling calves consumed diets lower in ADF than mature steers.
Intake.
No treatment xperiod interactions (P < 0.20) were detected for OM intake. Treatment effects were not evident for milk or forage OM intake (kg/d; Table 4; P = 0.89 and 0.33, respectively). By design SUP calves had greater (P < 0.01) creep intake (kg/d) compared with CON, and SUP calves had greater (P = 0.05) total OM intake than CON calves. Loy et al. (2002) reported no differences in milk or forage intake between supplemented and control calves, whereas Lardy et al. (2001) reported supplemented calves had lower forage intake compared with controls, with no differences in milk intake when expressed on a kg/d basis. These differences may be due to differences in the forage calves were consuming. The study conducted by Loy et al. (2002) involved native tallgrass prairie in southeastern North Dakota, with grasses being 60% cool season and 40% warm season. The study by Lardy et al. (2001) was conducted on subirrigated meadow regrowth in the sandhills of Nebraska, which comprises predominately cool-season grasses. In drylot situations where the calves were fed freshly harvested endophyte-infected tall fescue, Cremin et al. (1991), Faulkner et al. (1994), and Tarr et al. (1994) reported that forage OM intake decreased with increasing levels of supplement intake.
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) were not different (P = 0.90 and 0.56, respectively) between CON and SUP; however, total OM intake was greater (P = 0.03) for SUP than for CON calves. This is due to the additive effect of the supplement in the diet rather than a substitution effect. Loy et al. (2002) reported no differences in forage intake on a g/kg of BW basis when calves grazed native tallgrass prairie and were fed supplements consisting of soyhulls, soy-hulls and soybean meal, or xylose-treated soybean meal, feather meal, and blood meal. Lardy et al. (2001) reported tendencies for greater forage intake in unsupplemented calves compared with supplemented calves, and greater total intake by supplemented calves than by controls, and no effect of creep feed on milk intake. Cremin et al. (1991), Faulkner et al. (1994), and Tarr et al. (1994) reported substitution effects of supplementation for nursing calves, with the supplemented calves consuming more creep and less forage as a percentage of BW when calves consumed harvested forages in drylot feeding protocols. In these studies, calves were penned separately from their dams, except when allowed to nurse, which occurred twice daily. Tarr et al. (1994) reported that control and calves receiving a high level of corn-based supplement tended to have greater milk intakes than the low- and moderate-creep-intake calves. Cremin et al. (1991) and Faulkner et al. (1994) reported no treatment effects on milk intake.
Period effects were noted for forage intake. Forage intake increased linearly (kg/d; P < 0.01) with advancing season. When expressed on a grams per kilogram of BW basis, forage intake tended (P < 0.08) to increase with season. This response was due to changes in diet composition with milk making up a smaller proportion of the total diet. Milk intake (kg/d) was not altered by advancing season, but decreased linearly (P < 0.01) when expressed as grams per kilogram of BW. This response was due to the combined effect of increased calf BW and no differences in milk consumption. Lardy et al. (2001) and Loy et al. (2002) reported similar results in milk intake with advancing season.
In Situ Degradability.
Treatment xperiod interactions were not present for forage in situ rates of DM, NDF, ADF, and CP degradability (Table 5). Period effects (P 0.01) were present at all time points, with linear and quadratic responses with the greatest rate of degradability in SEP and the least in OCT for all components. The high rate of degradability in SEP was due to above average rainfall in AUG. Samples for in situ degradability were collected 3 wk before the masticate samples that were used to determine grazed forage quality; therefore, caution should be taken when trying to make a direct comparison between in situ degradabilities and grazed forage diet quality. Forage in situ samples for SEP contained 11.1% CP, but the grazed forage diet sample contained 8.1% CP. Previous research conducted near this location reported a linear decrease of NDF with advancing season for the 12- to 72-h incubation times (Johnson et al., 1998). Johnson et al. (1998) also reported a decrease in extent of CP degradation with advancing season and increased degradation at the early incubation times from 0, 4, and 8 h. The in situ DM disappearance in the Johnson et al. (1998) study was similar to the in situ NDF disappearance, and also agrees with Caton et al. (1993).
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). Johnson et al. (1998) reported decreased rate of in situ NDF and CP disappearance with advancing season on similar type forages using yearling steers. We also observed a tendency (P = 0.06) for a treatment xperiod interaction for rate of creep DM degrabability.
Ruminal Fermentation.
Treatment xperiod interactions were not present (P < 0.30) for any ruminal fermentation parameters measured; therefore, main effect means of treatment and period are reported in Table 6. Ruminal pH was lower (P < 0.05) in SUP calves compared with CON calves and decreased linearly (P < 0.01) with advancing season. Decreased ruminal pH level for the SUP calves is likely explained by increased starch level in the diet. Cremin et al. (1991), Faulkner et al. (1994), and Tarr et al. (1994) reported similar results with supplemental corn or corn gluten meal-based creep feeds (Cremin et al., 1991), corn or soyhulls (Faulkner et al., 1994), and corn and corn cobs (Tarr et al., 1994). The decrease in the ruminal pH reported in these studies is likely due to dietary additions of fermentable starch, which could potentially decrease forage digestibility (Caton and Dhuyvetter, 1997). In our study, ruminal pH was decreased with addition of supplement; however, forage digestibility was not affected. Reed et al. (2004a) reported similar results with a decreased ruminal pH with increasing levels of field peas in beef steers fed forage-based diets, however forage digestion was not decreased with the inclusion of field peas. Reed et al. (2004a) attributed those results to lower starch and higher degraded intake protein levels than traditional cereal grains, such as corn.
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and Tarr et al. (1994) reported decreased ruminal NH3-N concentrations with the addition of a corn- or soyhull-based supplement to the diet. Satter and Slyter (1974) reported that an NH3-N concentration below 3.57 mM could potentially decrease forage digestion. In our study, CON had ruminal NH3-N concentrations below 3.5 mM; however, our results indicate the lower ruminal NH3-N levels did not negatively influence forage digestion in CON compared with supplemented calves. A quadratic response (P < 0.01) in ruminal NH3-N was present with advancing season, with a greater ruminal NH3-N concentration in AUG, which was likely due to the increased CP in the forage the calves were grazing during that period, along with the increase in supplement intake (kg/d).
Total VFA concentration was greater (P < 0.02) for SUP than for CON. Supplemented calves had decreased (P < 0.01) acetate, increased (P < 0.02) butyrate, and increased (P < 0.03) valerate compared with CON. The increase in total VFA is likely due to the fermentation of the supplemental feed. Decreased acetate proportions can be explained by a decrease of forage as a proportion of total intake in supplemented calves; however, increases in propionate proportions in response to supplementation were not observed. Butyrate and valerate increased (P < 0.03) in response to supplementation. Cremin et al. (1991) reported a similar decrease in acetate and increase in butyrate when supplemental corn or corn gluten meal was offered. A decrease in molar proportion of acetate was also reported by Faulkner et al. (1994) and Tarr et al. (1994), but they reported an increase in propionate proportions, which was not evident in our study. This may be due to the differences in level of supplement offered in the studies conducted by Tarr et al. (1994) and Faulkner et al. (1994) compared with ours. Supplemented calves also had a tendency for lower (P = 0.06) acetate:propionate ratio compared with CON, which is supported by the results of other research (Cremin et al., 1991; Faulkner et al., 1994; Tarr et al., 1994). Total VFA concentration decreased linearly (P < 0.01) and acetate proportion increased linearly (P = 0.05) with advancing season. The decrease in total VFA concentration was likely a result of less fermentable carbohydrate being consumed by the calves in OCT as well as an increase in ruminal volume. Increasing acetate proportions in response to advancing season is likely due to increased forage consumption as well as decreased forage IVOMD in OCT compared with JUL.
No treatment xperiod interactions were present for fluid dilution rate (P = 0.88) or ruminal volume expressed either in L (P = 0.58) or L/kg of BW (P = 0.72; Table 7). Neither fluid dilution rate (P = 0.67) nor ruminal volume expressed either in liters (P = 0.45) or liters per kilogram of BW (P = 0.59) differed between treatment groups. Period effects were not present for fluid dilution rate, but ruminal volume increased linearly (P < 0.01) with advancing season, which was due to growth of calves and increased ruminal capacity. Previous research (Faulkner et al., 1994; Tarr et al., 1994) reported an increase in fluid dilution rate and a decrease in ruminal volume with increased levels of creep feed; however, our study only evaluated one level of creep feed intake, so that comparison could not be made.
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Calf Performance.
Initial calf BW were similar between treatment groups; however, supplemented calves had heavier (P < 0.01) final BW than CON calves (Table 8). In addition, calves that received supplement had greater (P < 0.01) ADG than CON calves. Numerous studies have indicated similar results when comparing unsupplemented calves to calves receiving unlimited supplement (Stricker et al., 1979; Prichard et al., 1989; Faulkner et al., 1994). Increased growth has also been reported for calves receiving limited supplement compared with those receiving no supplement (Lardy et al., 2001).
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). The practice of using salt to limit creep feed intake is not new; however, we know of no data detailing the use of salt to limit intake of field pea-based supplements. In our study, using salt as a limiter proved to be an effective way to control intake of calves with free access to creep feeders. Schauer et al. (2004) reported use of 16% salt to limit intake in self-fed supplements for yearling steers. This practice was effective in limiting intake and resulted in increased weight gains compared with other chemical limiters. Previous research reported varying levels of salt inclusion to limit supplement intake. Totusek et al. (1971) and Rush et al. (1972) reported that salt levels between 20 and 29.5% were effective in limiting protein supplement intake to approximately 1.25 kg of DM/d for steers grazing Oklahoma winter range. Riggs et al. (1953) evaluated salt level and intake of cows consuming dry winter range and reported that the inclusion of 25% salt in free-choice cottonseed meal limited intake to 2.0 kg/d.
Cow Performance.
There was a tendency (P = 0.06) for greater weight gain by the cows nursing CON calves (Table 8). Cremin (1989) reported an increase in weight gain of dams of calves that received unlimited creep compared with those that received limited levels of creep. Body condition score change was not different (P = 0.12) between CON vs. SUP; however, there was a treatment difference (P = 0.04) between HS and HIPRO. Our BCS results do not agree with those of Prichard et al. (1989), who reported an increase in cow BCS when calves were creep-fed. Two studies conducted on tall fescue–ladino clover pastures reported no differences in cow gain when creep feeding calves. Morrow et al. (1988) used fall-born calves, whereas Stricker et al. (1979) reported similar results when using spring-born calves.
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Implications |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Footnotes |
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3 Current address: Dept. of Anim. and Range Sci., New Mexico State Univ., Las Cruces.
2 Correspondence: 177 Hultz Hall (phone: 701-231-7660; fax: 701-231-7590; e-mail: glardy{at}ndsuext.nodak.edu).
Received for publication April 26, 2004. Accepted for publication September 10, 2004.
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Literature Cited |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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  S. F. Liao, E. S. Vanzant, J. A. Boling, and J. C. Matthews Identification and expression pattern of cationic amino acid transporter-1 mRNA in small intestinal epithelia of Angus steers at four production stages J Anim Sci, March 1, 2008; 86(3): 620 - 631. [Abstract] [Full Text] [PDF]
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T. C. Gilbery, G. P. Lardy, S. A. Soto-Navarro, M. L. Bauer, and V. L. Anderson Effect of field peas, chickpeas, and lentils on rumen fermentation, digestion, microbial protein synthesis, and feedlot performance in receiving diets for beef cattle J Anim Sci, November 1, 2007; 85(11): 3045 - 3053. [Abstract] [Full Text] [PDF]
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J. J. Reed, G. P. Lardy, M. L. Bauer, M. Gibson, and J. S. Caton Effects of season and inclusion of corn distillers dried grains with solubles in creep feed on intake, microbial protein synthesis and efficiency, ruminal fermentation, digestion, and performance of nursing calves grazing native range in southeastern North Dakota J Anim Sci, August 1, 2006; 84(8): 2200 - 2212. [Abstract] [Full Text] [PDF]
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J. J. Reed, A. L. Gelvin, G. P. Lardy, M. L. Bauer, and J. S. Caton Effect of creep feed supplementation and season on intake, microbial protein synthesis and efficiency, ruminal fermentation, digestion, and performance in nursing calves grazing native range in southeastern North Dakota J Anim Sci, February 1, 2006; 84(2): 411 - 423. [Abstract] [Full Text] [PDF]
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