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Effects of method of offering broiler litter and level of prairie hay intake on growth of Boer × Spanish wethers
Small Ruminant Research 55 (2004) 123–133
Effects of method of offering broiler litter and level of prairie hay intake on growth of Boer × Spanish wethers Y. Mekasha a,b , R.C. Merkel a , A.L. Goetsch a,∗ , T. Sahlu a , K. Tesfai a a
E (Kika) de la Garza American Institute for Goat Research, Langston University P.O. Box 730, Langston, OK 73050, USA b Animal Science Department, Alemaya University, Dire Dawa, Ethiopia Received 9 April 2003; received in revised form 12 December 2003; accepted 30 December 2003
Abstract Thirty-four Boer × Spanish wethers (18 ± 0.3 kg initial BW; 5 months of age) were used in a 12-week experiment (2 × 2 + 1 factorial arrangement of treatments) to determine effects of ad libitum consumption of broiler litter (B) alone or mixed with corn (60% B; BC) and of ad libitum versus restricted (R) prairie hay intake on feed intake and growth performance. Treatments were: Control: ad libitum intake of hay plus an average of 26 g per day of a mineral-based supplement; AH-B: ad libitum intake of hay and B offered separately; AH-BC: ad libitum intake of hay and BC; RH-B: restricted intake of hay (approximately 1% BW; DM basis) and ad libitum intake of B; RH-BC: restricted intake of hay and ad libitum intake of BC. Average corn DM intake (DMI) was 179 and 170 g per day for AH-BC and RH-BC, respectively, and B DMI was similar among supplement treatments (P > 0.05; 258, 271, 299 and 258 g per day for AH-B, AH-BC, RH-B and RH-BC, respectively). Hay DMI averaged 494, 442, 336, 175 and 160 g per day (S.E. = 16.7), and total DMI was 516, 700, 782, 474 and 585 g/d (S.E. = 26.2) for Control, AH-B, AH-BC, RH-B, and RH-BC, respectively. Overall ADG ranked (P < 0.05) AH-BC > AH-B and RH-BC > Control and RH-B (−6, 34, 79, 3 and 50 g), and the ratio of ADG:DMI ranked (P < 0.05) AH-BC and RH-BC > AH-B > Control and RH-B (−13, 49, 97, 5 and 85 g/kg) for Control, AH-B, AH-BC, RH-B and RH-BC, respectively. Total tract OM digestibility in period 2 ranked (P < 0.05) Control < AH-B, AH-BC and RH-B < RH-BC (34.0, 46.6, 49.8, 50.0 and 63.7% for Control, AH-B, AH-BC, RH-B and RH-BC, respectively). Ruminal fluid ammonia N concentration was lowest among treatments (P < 0.05) at 2 and 6 h after supplementation for Control (e.g., 6 h: 4.0, 19.5, 17.2, 38.2 and 25.8 mg/dl for Control, AH-B, AH-BC, RH-B and RH-BC, respectively; S.E. = 2.69). The ratio of acetate:propionate was greatest among treatments (P < 0.05) at 0, 2 and 6 h for Control (e.g., 6 h: 5.27, 4.04, 3.28, 3.64 and 3.10 for Control, AH-B, AH-BC, RH-B and RH-BC, respectively; S.E. = 0.218). In conclusion, depending on production goals and availability of high-quality feedstuffs such as cereal grains, free-choice consumption of B may be a simple and useful method of supplementing low-quality forage. © 2004 Elsevier B.V. All rights reserved. Keywords: Goats; Broiler litter; Supplementation
1. Introduction
∗ Corresponding author. Tel.: +1-405-466-3836; fax: +1-405-466-3138. E-mail address: [email protected] (A.L. Goetsch).
Broiler litter is a byproduct of the poultry industry, high in nitrogenous compounds generally thoroughly and rapidly degraded by ruminal microorganisms (Crutchfield et al., 1996). Thus, it is commonly used
0921-4488/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2003.12.009
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to supplement ruminants consuming low-nitrogen forages (Fontenot et al., 1996; Goetsch and Aiken, 2000). However, broiler litter is also usually moderate in available energy concentration, allowing use in diets of growing ruminants (El-Ashry et al., 1987; Flachowsky and Henning, 1990; Gurung and Rankins, 2001) though perhaps at levels less than for mature animals. In fact, in some instances when broiler litter has been included in cattle diets with basal forages of similar or even slightly greater OM digestibility, total intake has risen and there has been no change in digestible OM intake (Patil et al., 1993, 1995a,b; Rossi et al., 1996, 1998). Even though broiler litter is available and relatively inexpensive in many parts of the world, one factor restricting its use is method of feeding. Typically, broiler litter is mixed with a palatable cereal grain, such as corn. The odor and(or) taste of broiler litter prevent most producers from feeding it separately or alone. Nonetheless, some cattle producers with animals that are well accustomed to broiler litter do successfully feed it unmixed with other feedstuffs. Likewise, there are many reports of cattle gaining access to broiler litter while being deep-stacked and consuming the byproduct. Certainly the availability of other feedstuffs impacts such occurrences and practices. For example, with drought and low forage availability and quality, one would expect greater potential to feed broiler litter without being mixed with concentrate feedstuffs. Thus, objectives of this experiment were to determine effects of method of broiler litter feeding on feed intake, digestibility and performance by growing goats. More specifically, the study was designed to assess whether separate feeding of broiler litter compared with a mixture with corn would be effective with growing goats consuming a low-N forage and how level of forage feeding may impact effects of feeding broiler litter alone or mixed with corn.
2. Materials and methods 2.1. Animals and management The 12-week experiment was approved by the Langston University Animal Care Committee. Forty Boer × Spanish wether goats approximately 5 months of age and weaned 1 month earlier were selected.
Wethers were treated with Cydectin (Fort Dodge Animal Health, Wyeth, Madison, NJ) when moved to the housing facility. However, 2 weeks later some wethers showed evidence of tapeworm infestation and, thus, were treated with Valbazen (Pfizer Inc., New York, NY). Housing was individual in 1.1 × 1.2 m elevated pens with plastic-coated expanded metal floors. There was a 3-week period before the experiment began for adaptation to experimental conditions, including use of nipple waterers and consumption of broiler litter. During this time feed intake was restricted, with stepwise increases in the level of broiler litter in a mixture with ground corn until the contribution of broiler litter was 67% (as fed basis). Correspondingly, dietary levels of corn and hay were decreased, with hay being offered in a separate container. At the end of this period, 35 wethers (18.3 kg BW; S.E. = 1.85) that had adapted well to consumption of broiler litter were assigned to the five dietary treatments, with seven wethers per treatment. The allocation to treatments was for similar mean BW and variation in BW within treatment. 2.2. Treatments The treatment arrangement was a 2×2+1 factorial. Treatments were: Control: ad libitum intake of prairie hay with a mineral-based supplement; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter). Thus, there were two methods of feeding broiler litter, two levels of prairie hay intake and a Control. Broiler litter was obtained from a production unit where litter had not been completely harvested for more than 1 year, with packed litter removed at the end of each growing period (averaging 6 weeks in length). After transport to the research site, litter was deep-stacked for approximately 5 months. Average temperature in the second, third and fourth months was 43, 50 and 42 ◦ C near the top, middle and bottom areas of the stack, respectively. The mixture of broiler litter and corn was achieved by thorough hand-mixing. The
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amount of hay for RH-B and RH-BC treatments was based on average BW of wethers on each treatment, which was determined at 3-week intervals. When intake was ad libitum, feedstuffs were offered at approximately 120% of consumption on the preceding few days. Feeding was initially at 0900 h; however, after a few weeks hay was offered at both 0900 and 1500 h to minimize spillage. Control wethers received a mineral-based supplement (20% trace mineralized salt and 30% dicalcium phosphate, with 50% commercial dried molasses-roughage product mixture included to promote consumption) at 0.145% BW. 2.3. Measures and analyses Wethers were weighed before feeding in the morning at the beginning of the experiment and at 3-week intervals. Feedstuffs and refusals were weighed daily and sampled once weekly. Composite samples for feedstuffs and refusals (within wether) were formed for each 3-week period. In addition, feedstuffs and refusals were sampled daily during week 6, when feces was sampled. To collect most feces over the 7-day period, a wire mesh screen was placed beneath each pen. Samples obtained daily were used to form a composite sample on a fresh-weight basis for each animal. Partial DM concentration of refusal and fecal samples was determined by oven-drying at 55 ◦ C. Thereafter, all samples were ground to pass a 1 mm screen before analysis for DM (100 ◦ C), energy, ash, Kjeldahl N (AOAC, 1990), NDF, ADF (filter bag technique; ANKOM Technology Corp., Fairport, NY) and acid insoluble ash (ash in ADF residue). Acid insoluble ash was used as an internal, inert marker to determine digestibilities. On 1 day in week 8, blood was collected at 0, 2 and 6 h after the 09:00 h meal via jugular venipuncture into a tube containing potassium oxalate and sodium fluoride (Becton Dickinson, Rutherford, NJ) and centrifuged at 1500 × g. Plasma was stored at −20 ◦ C until being analyzed for non-esterified fatty acids (NEFA; Wako Pure Chemical, Richmond, VA) and for protein and urea N colorimetrically using a Technicon AutoAnalyzer II System (Technicon Instruments, Tarrytown, NY). At the same times, ruminal fluid was collected via stomach tube. Ruminal pH was determined immediately after sampling with a pH meter, followed by placement of 5 ml into a tube
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containing 1 ml of 25% (w/v) metaphosphoric acid for volatile fatty acid (VFA) analysis (Lu et al., 1990) and of 3 ml of fluid into a tube with 2 ml of 3 N HCl for ammonia analysis (Broderick and Kang, 1980). 2.4. Statistical analyses Data of one wether on the AH-BC treatment that developed urinary calculi in the first part of period 3 were omitted from analyses. Based on visual appearance, all feed refusals for the broiler litter-corn mixture were broiler litter, which was assumed to estimate separate intake of broiler litter and corn. Data for repeated measures (i.e., feed intake, average daily gain, gain efficiency and concentrations of constituents in ruminal fluid and blood) were first analyzed as a split-plot in time with GLM procedures of SAS (1989). When the interaction between time and treatment was significant (P < 0.05), data were analyzed separately for each 3-week period or sampling time with treatment in the model. When the interaction was not significant, data were averaged over time before analysis. For feed intake, average daily gain (ADG) and gain efficiency (ADG:DM intake), because treatment effects on average measures over the entire experiment were of interest, average values were also analyzed regardless of significance of the interaction. Initial BW was used as a covariate for analysis of feed intake, ADG and the ratio of ADG:DM intake. Means were separated by least significance difference with a protected F-test (P < 0.05). 3. Results and discussion 3.1. Feedstuff composition The chemical composition of broiler litter was fairly similar to litter used by Animut et al. (2002) and Abebe et al. (2003), characteristically high in ash, CP and Cu (Table 1). Prairie hay was quite low in CP and slightly less than expected. 3.2. Feed intake There was an interaction (P < 0.05) between 3-week period and treatment in total DM intake (DMI; Table 2). The interaction appeared due to
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Table 1 Composition of feedstuffs consumed by growing Boer × Spanish wether goats (% DM) Item
Prairie hay
Broiler litter
Corn–broiler litter mixturea
Ash (%) Crude protein (%) Neutral detergent fiber (%) Acid detergent fiber (%) Energy (MJ/kg) Mg (%) P (%) S (%) K (%) Ca (%) Fe (mg/kg) Cu (mg/kg) Zn (mg/kg)
7.0 3.6 74.5 49.9 17.6 0.21 0.07 0.08 0.29 0.35 51 5 27
20.4 29.8 39.2 19.0 15.0 0.81 2.21 0.49 3.50 2.96 638 583 531
12.2 21.2 28.4 12.7 16.3 0.56 1.53 0.33 2.28 1.93 411 339 321
a
60% broiler litter and 40% corn (DM basis).
differences in DMI between AH-B and AH-BC and between RH-B and RH-BC that varied in magnitude among periods; method of feeding broiler litter and level of hay intake influenced how intake changed with advancing time. For differences between AH-B and AH-BC, broiler litter consumption was similar between treatments in each period. Hay intake for AH-B was similar in period 1 and changed little with advancing period. For AH-BC, hay intake decreased slightly as periods progressed. Conversely, when hay intake was restricted for RH-B and RH-BC, broiler litter intake in periods 1 and 2 was similar between treatments, tending to be less in period 1 for RH-B than for RH-BC. But, broiler litter intake for these restricted hay treatments was greater (P < 0.05) for RH-B in periods 3 and 4, with a greater difference in period 4 than 3.
Table 2 Effects of method of feeding broiler litter and level of hay feeding on dry matter intake (g per day) by growing Boer × Spanish wether goats 3-week period
1
2
3
4
Mean
Treatmenta
Feedstuff
Control
AH-B
AH-BC
RH-B
RH-BC
S.E.
21 b 0a 530 c
0a 172 b 411 b
118 c 185 b 402 b
0a 197 b 186 a
156 d 244 b 182 a
5.0 26.7 9.5
Total
551 b
583 b
706 c
383 a
582 b
30.5
Corn or mineral supplement Broiler litter Hay
27 a 0a 524 c
0a 277 b 488 c
192 b 287 b 388 b
0a 278 b 177 a
176 b 268 b 164 a
12.2 25.6 21.4
Total
551 ab
766 c
867 c
455 a
610 b
36.0
Corn or mineral supplement Broiler litter Hay
29 a 0a 451 c
0a 277 bc 436 c
203 b 305 c 274 b
0a 349 c 170 a
180 b 270 b 137 a
13.9 27.9 21.8
Total
479 a
712 c
783 c
519 ab
587 b
38.3
Corn or mineral supplement Broiler litter Hay
28 a 0a 470 c
0a 306 bc 434 c
203 b 306 bc 265 b
0a 372 c 168 a
166 b 251 b 156 a
13.8 28.6 26.0
Total
499 a
740 b
773 b
540 a
572 a
39.3
Corn or mineral supplement Broiler litter Hay
26 a 0a 494 d
0a 258 b 442 c
179 b 271 b 333 b
0a 299 b 175 a
170 b 258 b 160 a
10.3 19.3 16.7
Total
520 ab
700 c
782 d
474 a
588 b
26.2
Corn or mineral Broiler litter Hay
supplementb
a, b, c: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter). b Mineral supplement for Control and corn for other treatments.
Y. Mekasha et al. / Small Ruminant Research 55 (2004) 123–133
Mean broiler litter intake was similar among AH-B, AH-BC, RH-B and RH-BC treatments (Table 2). This suggests that there was a factor(s) limiting the amount of broiler litter consumed, which might minimize potential for effective feeding alone when forage intake is restricted. In addition, Silanikove and Tiomkin (1992) suggested that diets very high in poultry litter and low in forage are toxic to beef cows through liver damage elicited by high ruminal ammonia absorption. However, it seems doubtful that this was a factor in the present experiment, since average dietary CP concentration in the digestibility period was 3.4, 10.9, 12.0, 16.8 and 13.6% for Control, AH-B, AH-BC, RH-B and RH-BC, respectively. In periods 3 and 4, broiler litter intake was greater (P < 0.05) for RH-B versus RH-BC. This implies that the low intake of nutrients caused by restricted hay intake, particularly without corn supplementation, affected factors influencing broiler litter intake. These findings, along with similar broiler litter intake between RH-B and RH-BC in periods 1 and 2, indicate that the length of time on a low nutritional plane can influence adaptation to consumption of broiler litter. Overall and in all but the first period, total DMI was greater for ad libitum versus restricted hay intake treatments as expected (P < 0.05; Table 2). Likewise, average total DMI was greater with than without corn (P < 0.05). Although, in some periods total DMI was not different between AH-B and AH-BC or between RH-B and RH-BC. Total intake was similar between Control and RH-B but was greater (P < 0.06) for RH-BC than for Control. Hence, with RH-B, consumption of broiler litter substituted for hay. Also, greater total intake for RH-BC versus Control was because of only partial rather than complete substitution of corn for hay. Broiler litter supplementation with the AH-B treatment did not increase hay intake compared with Control as might have been expected with a supplement high in CP given with a low-CP forage like this prairie hay. In fact, hay intake in periods 1 and 2 was lower for AH-B than for Control. This may reflect differences between broiler litter and other common CP supplements like soybean meal, such as in CP, non-protein N and fiber concentrations as well as other characteristics including palatability and odor.
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3.3. Digestion Total OM digestibility ranked (P < 0.05) Control and AH-B < AH-BC and RH-B < RH-BC (Table 3). Energy digestibility ranked (P < 0.05) Control < AH-B, AH-BC and RH-B < RH-BC. The ranking (P < 0.05) of digestible OM intake was Control and RH-B < AH-B and RH-BC < AH-BC. The ranking for DE intake was similar, although the difference between AH-BC and RH-BC was not significant (P > 0.05). Digestible OM intake was more in line with differences among treatments in ADG than was DE intake. The digestibilities do not clearly reflect a positive effect of broiler litter supplementation on extent of digestion of hay fiber. This is because increases in digestion of total dietary fiber would be expected with dietary addition of broiler litter and(or) corn because of their greater digestibilities than hay (Table 3). However, because OM intake was greater for AH-B, AH-BC and RH-BC than for Control, the time of digesta residence in the rumen was most likely shorter. Hence, with an extent of NDF digestion similar to or greater than that for the Control, broiler litter may have increased rate of digestion of hay fiber. As noted earlier, consumption of corn did not appear to lessen digestion of fiber (NDF and ADF) in hay (Table 3). Corn averaged 23 and 29% of average total DMI. These levels would not be expected to have appreciable negative effects on fiber digestion (Horn and McCollum, 1987). Perhaps mixing with broiler litter may limit corn intake to a level less than needed to depress digestion of hay fiber. Except for Control, total tract CP digestion was less than predicted based on estimates of true protein digestibility and metabolic fecal CP of Moore et al. (2004). This might reflect some heat damage of nitrogenous compounds in broiler litter during deep-stacking, although heating did not appear excessive. Another possibly involved factor is volatilization of N from broiler litter between the time of feeding and actual consumption. 3.4. ADG and ADG:DMI There was an interaction in ADG between 3-week period and treatment (P < 0.05; Table 3). In period 1, ADG ranked (P < 0.05) AH-BC > C, AH-B and
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Table 3 Effects of method of feeding broiler litter and level of hay feeding on digestion by growing Boer × Spanish wether goats Item
Organic matter Intake (g per day) Digestion % g per day Energy Intake (MJ per day) Digestion % MJ per day Nitrogen Intake (g per day) Digestion % g per day Neutral detergent fiber Intake (g per day) Digestion % g per day Acid detergent fiber Intake (g per day) Digestion % g per day
Treatmenta Control
AH-B
AH-BC
RH-B
RH-BC
S.E.
488 b
673 c
786 d
390 a
566 b
30.8
44.0 a 215 a
48.1 a 324 b
55.7 b 440 c
54.6 b 215 a
67.6 c 379 b
1.88 21.4
9.2 b
12.7 c
14.6 c
7.4 a
10.6 b
0.57
34.0 a 3.5 a
46.6 b 5.8 b
49.8 b 7.3 c
50.0 b 3.8 a
63.7 c 6.7 bc
2.89 0.40
3.0 a
13.3 bc
16.7 c
12.2 b
13.3 bc
1.48
21.1 a 0.6 a
33.9 ab 4.8 b
42.5 bc 7.2 b
39.9 bc 5.7 b
52.9 c 6.8 b
5.12 0.87
396 b
484 c
431 b
250 a
265 a
16.6
48.9 a 194 a
55.6 b 268 c
52.8 ab 228 b
65.6 c 165 a
63.4 c 167 a
1.95 12.3
262 b
299 c
255 b
143 a
147 a
10.6
41.8 b 124 c
39.8 ab 101 b
35.9 a 94 b
52.9 c 76 a
50.2 c 74 a
1.88 5.6
a, b, c, d: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
RH-BC > RH-B, whereas ADG was similar among treatments in period 2. ADG in period 3 was less (P < 0.05) for Control versus AH-BC, RH-B and RH-BC and greater (P < 0.05) for AH-BC and RH-BC than for AH-B. Period 4 ADG ranked (P < 0.05) AH-BC and RH-BC > AH-B and RH-B > Control. Over the entire experiment, ADG ranked (P < 0.05) AH-BC > AH-B and RH-BC > Control and RH-B. Gain efficiency (ADG:DMI) was also affected by an interaction between 3-week period and treatment (P < 0.05; Table 4). Gain efficiency was lowest among treatments (P < 0.05) in period 1 for RH-B and less
(P < 0.05) for RH-BC versus AH-BC, whereas values were similar among treatments in period 2. Differences in period 3 were fairly similar to those in ADG, as was also the case in period 4. Gain efficiency during the entire experiment ranked (P < 0.05) AH-BC and RH-BC > AH-B > Control and RH-B. Overall, offering broiler litter free-choice and alone increased ADG by Boer cross goats when consuming hay ad libitum but not with hay intake restricted to 1% BW. This was the end-result of broiler litter DMI being less than the difference in hay DMI between RH-B and Control and the higher ash concentration in
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Table 4 Effects of method of feeding broiler litter and level of hay feeding on ADG and ADG:DM intake (DMI) by growing Boer × Spanish wether goats Item
Period
Treatmenta Control
83 b 39 3 ab 13 b
AH-BC
ADG (g per day)
1 2 3 4
−6 a
34 b
79 c
ADG:DMI (g/kg)
1 2 3 4
116 bc −71 −52 a −54 a
142 bc 48 1 ab 21 b
222 c 37 52 bc 99 c
Mean
−13 a
49 b
97 c
Mean
62 b −36 −24 a −26 a
AH-B
155 c 36 46 c 78 c
RH-B −28 a 0 27 bc 12 b 3a −113 a −35 49 bc 19 b 5a
RH-BC
S.E.
52 b 39 46 c 60 c
16.0 23.2 13.1 8.4
50 b
7.5
91 b 58 78 c 103 c
38.8 58.0 21.8 12.3
84 c
9.0
a, b, c: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
broiler litter than hay. Furthermore, OM and energy digestibilities in period 2 were less than necessary to compensate for these differences, which resulted in similar DE intake in period 2 and presumably throughout the experiment. Greater ADG for AH-B versus Control was because of the low substitution ratio (i.e., decrease in hay intake relative to the level of consumption of broiler litter) for the replacement of hay by broiler litter and greater energy digestibility for AH-B, which resulted in greater DE intake for AH-B. Hence, the primary reason for the difference in ADG between AH-B and Control was additional nutrients from broiler litter. The lower ADG:DMI ratio for AH-B versus RH-BC indicates less efficient utilization of hay than corn, encompassing differences in digestibility and possibly efficiency of metabolism. Although, similar ADG between these two treatments (P < 0.17) reflects compensation via greater hay intake by AH-B wethers. Mixing corn with broiler litter increased ADG similarly with both ad libitum and restricted hay intake. In part, this may reflect that the amount of corn consumed was less than necessary to decrease ruminal fiber digestion. Comparisons of AH-B versus AH-BC and RH-B versus RH-BC indicate that inclusion of supplemental corn did not lessen additional digestible
nutrients achieved by broiler litter supplementation. Greater ADG for RH-BC versus RH-B was in response to the substantial increase in total DMI (i.e., 114 g overall). Greater ADG for AH-BC compared with AH-B also resulted from an increase in total DMI (i.e., 82 g). But, this difference was less than when hay intake was restricted because of considerable substitution of corn for hay. 3.5. Ruminal fluid conditions The concentration of total VFA in ruminal fluid was less (P < 0.05) for Control versus RH-B, with intermediate (P > 0.05) concentrations for other treatments (Table 5). Because of potential differences in ruminal fluid volume, these concentrations do not necessarily reflect total quantities of VFA in the rumen. There were interactions between sampling time and treatment in molar percentages of propionate, butyrate and valerate and in the acetate:propionate ratio (Table 5). The molar percentage of acetate ranked (P < 0.05) AH-BC and RH-BC < RH-B < AH-B < Control. At 0 h, the molar percentage of acetate was lowest among treatments (P < 0.05) for Control; however, at 2 h the molar percentage of acetate was still lowest among treatments (P < 0.05) for Control,
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Table 5 Effects of method of feeding broiler litter and level of hay feeding on concentrations of volatile fatty acids, ammonia N and pH in ruminal fluid of growing Boer × Spanish wether goats Item
Time after feeding (h)
Treatmenta Control
AH-B
AH-BC
RH-B
RH-BC
S.E.
Volatile fatty acids Total (mol/100 mol)
Mean
41.3 a
45.6 ab
43.0 ab
50.1 b
45.8 ab
1.99
Molar percentage Acetate
Mean
78.2 d
74.4 c
68.2 a
72.0 b
67.0 a
0.59
Propionate
0 2 6
14.3 a 15.3 a 14.9 a
17.2 b 18.2 b 18.5 b
17.9 b 21.4 c 21.6 c
19.2 b 18.5 b 19.8 bc
19.0 b 22.0 c 22.0 c
0.94 0.95 1.05
Isobutyrate
Mean
0.55
0.68
0.63
0.93
Butyrate
0 2 6
5.6 a 5.5 a 5.7 a
6.1 ab 5.6 ab 5.8 a
Isovalerate
Mean
0.45
0.72
1.17
Valerate
0 2 6
0.34 a 0.34 a 0.31 a
0.34 a 0.35 a 0.31 a
Acetate: propionate
0 2 6
5.50 b 5.13 c 5.27 c
Ammonia N (mg/dl)
0 2 6
pH
Mean
0.59
0.118
10.9 c 8.7 c 10.2 c
0.44 0.36 0.77
0.80
0.93
0.218
0.60 b 0.46 b 0.48 b
0.37 a 0.49 b 0.36 a
0.59 b 0.52 b 0.44 b
0.051 0.033 0.026
4.33 a 4.09 b 4.04 b
3.98 a 3.36 a 3.28 a
3.75 a 3.96 b 3.64 ab
3.66 a 3.12 a 3.10 a
0.244 0.217 0.218
4.1 a 4.1 a 4.0 a
7.1 ab 22.3 bc 19.5 bc
6.3 ab 18.9 b 17.2 b
8.8 b 26.8 cd 25.8 c
1.40 2.12 2.69
6.64 c
6.70 c
6.52 b
6.44 a
0.238
10.8 c 8.5 c 8.2 bc
7.0 b 6.6 b 6.6 ab
15.7 c 29.7 d 38.2 d 6.68 c
a, b, c, d: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
but levels were greater (P < 0.05) for supplemented treatments with than without corn. The molar percentage of acetate was similar at 6 h, except that the level was similar (P > 0.05) among AH-BC, RH-B and RH-BC. Molar percentages of isobutyrate and isovalerate were similar among treatments (P > 0.05). At 0 and 2 h, the molar percentage of butyrate was greatest among treatments (P < 0.05) for treatments with supplemental corn. Differences were comparable at 6 h, except for a similar (P > 0.05) concentration between AH-BC and RH-B. The molar percentage of valerate was greatest among treatments for AH-BC and RH-BC at 0 and 6 h. Findings at 2 h were comparable, except for a similar level for AH-BC, RH-B
and RH-BC. The acetate:propionate ratio was greatest among treatments (P < 0.05) for Control at all times. The ratio was similar (P > 0.05) among supplemented treatments at 0 h, but at 2 h the ratio was lower (P < 0.05) for treatments with supplemental corn. Differences among supplemented treatments were comparable at 2 and 6 h, except for similar (P > 0.05) ratios among AH-BC, AH-B and RH-BC. Overall, corn supplementation had expected effects on acetate and propionate levels and their ratio (i.e., decrease), and a decreased acetate:propionate ratio with broiler litter feeding has been noted in other experiments as well (Patil et al., 1995a; Rossi et al., 1996, 1998; Wang and Goetsch, 1998).
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Table 6 Effects of method of feeding broiler litter and level of hay feeding on concentrations of non-esterified fatty acids (NEFA), protein, glucose and urea N in plasma of growing Boer × Spanish wether goats Item
Time after feeding (h)
Treatmenta Control
AH-B
AH-BC
RH-B
RH-BC
S.E. 12.67 5.48 8.26
NEFA (eq./dl)
0 2 6
79.5 72.6 bc 84.1
53.2 59.9 ab 61.2
102.3 76.5 c 84.8
63.7 55.3 a 47.9
80.7 65.6 abc 67.5
Protein (g/dl) Glucose (mg/dl)
Mean Mean
7.42 12.9 a
7.68 36.4 bc
7.69 29.9 b
7.63 39.9 c
7.56 33.9 bc
0.157 3.13
Urea N (mg/dl)
0 2 6
4.3 a 4.8 a 4.3 a
16.6 b 23.3 b 32.0 c
15.1 b 21.8 b 27.9 b
29.4 c 33.2 c 39.2 d
18.2 b 22.6 b 30.5 bc
1.48 1.40 1.30
a, b, c, d: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
The concentration of ammonia N in ruminal fluid at all times was lowest among treatments (P < 0.05) for Control (Table 5). These levels for Control suggest possible limitations of ruminal fiber digestion and(or) microbial growth (Miller, 1973; Satter and Slyter, 1974). However, because supplementation with broiler litter alone did not appear to increase the extent of ruminal digestion of fiber in hay, fiber digestion may not have been limited by ruminal availability of nitrogenous compounds. At 0 h, the concentration was greatest among treatments (P < 0.05) for RH-B in accordance with the highest dietary CP concentration. At each time, corn supplementation either decreased or tended to decrease ruminal ammonia N concentration, which is as expected because of increases in ruminally fermentable energy. Ruminal pH ranked (P < 0.05) RH-BC < AH-BC < Control, AH-B and RH-B. 3.6. Plasma constituents Plasma concentrations of NEFA and urea N were affected by interactions (P < 0.05) between sampling time and treatment (Table 6). The NEFA concentration was similar among treatments (P > 0.05) at 0 and 6 h. Treatment differences at 2 h were not in agreement with differences in intake of digestible OM or DE. NEFA concentration was not correlated (P > 0.05) with period 2 ADG. Therefore, these NEFA concen-
trations do not seem affected only by likely fat mobilization by Control goats compared with positive ADG for three of the other treatments. Plasma protein concentration was similar among treatments (P > 0.05). Plasma urea N concentration was lowest among treatments (P < 0.05) for Control at all times of sampling, in agreement with ruminal concentrations of ammonia N (Nikoliæ et al., 1980). Also in accordance with ruminal ammonia N concentration, at 0 h urea N concentration was greatest among supplemented treatments (P < 0.05) for RH-B, and similar differences (P < 0.05) were noted at 2 h. Likewise, corn supplementation decreased (P < 0.05) urea N concentration at 2 and 6 h (i.e., AH-BC versus AH-B and RH-BC versus RH-B). Thus, urea N concentration appeared to be affected by factors influencing ruminal ammonia N concentration, such as consumption broiler litter with CP rapidly and thoroughly degraded in the rumen, as well as corn supplementation that increased microbial uptake of ammonia through the increase in ruminally fermentable energy.
4. Summary and conclusions In summary, neither method of feeding broiler litter nor level of hay intake influenced overall broiler litter intake, suggesting presence of factor(s) limiting
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broiler litter consumption. When offered alone, broiler litter did not appear to increase the extent of digestion of fiber of this low-quality, low-CP forage, although impact on rate of digestion is possible. Broiler litter feeding enhanced ADG when hay was offered free-choice presumably because of additional nutrients from broiler litter. Mixing broiler litter with corn may be a means of restricting corn intake to a level less than necessary to adversely affect ruminal fiber digestion. The broiler litter-corn mixture had less effect on intake of hay relative to the amount of supplemental feedstuffs consumed than did broiler litter when fed without corn. In conclusion, offering broiler litter alone free-choice increased ADG by Boer cross goats when consuming hay ad libitum but not with hay intake restricted to 1% BW. The lower ADG:DMI ratio for AH-B versus RH-BC indicates less efficient utilization of hay than corn, although similar ADG reflects compensation via greater hay intake. Mixing corn with broiler litter increased ADG similarly with both ad libitum and restricted hay intake.
Acknowledgements This research was supported by the Institutional Development Partnership Program of the United Negro College Fund/United States Agency for International Development and the resulting partnership between Langston University, Langston, OK, and Alemaya University, Dire Dawa, Ethiopia. Appreciation is expressed to farm and laboratory personnel of the E (Kika) de la Garza American Institute for Goat Research for their assistance. Also, appreciation is extended to Larry Morrison for providing broiler litter. References Abebe, G., Merkel, R.C., Animut, G., Sahlu, T., Goetsch, A.L., 2003. Effects of ammoniation of wheat straw and supplementation with soybean meal or broiler litter on feed intake and digestion in yearling Spanish wether goats. Small Rumin Res. 51, 37–46. Animut, G., Merkel, R.C., Abebe, G., Sahlu, T., Goetsch, A.L., 2002. Effects of level of broiler litter in diets containing wheat straw on performance of Alpine doelings. Small Rumin Res. 44, 125–134. AOAC, 1990. Official Methods of Analysis, 14th ed. Association of Official Analytical Chemists, Washington, DC.
Broderick, G.A., Kang, J.H., 1980. Automated simultaneous determination of ammonia and total amino acids in rumen fluid and in vitro media. J. Dairy Sci. 63, 64–75. Crutchfield, D.J., Goetsch, A.L., Johnson, Z.B., 1996. Chemical constituents in different particle size fractions of deep-stacked broiler litter. Biores. Technol. 57, 99–104. El-Ashry, M.A., Khattab, H.M., El-Serafy, A., Soliman, H., Elmoula, S.M., 1987. Nutritive value of poultry wastes for sheep. Biol. Wastes 19, 287–298. Flachowsky, G., Henning, A., 1990. Composition and degestibility of untreated and chemically treated animal excreta for ruminants. A review. Biol. Wastes 31, 17–36. Fontenot, J.P., Ayangbile, G.A., Allen, V.G., 1996. Potential for recycling animal wastes by feeding to reduce environmental contamination. In: Kornegay, E.T. (Ed.), Nutrient Management of Food Animals to Enhance and Protect the Environment. CRC Press, Boca Raton, FL, pp. 199–218. Goetsch, A.L., Aiken, G.E., 2000. Broiler litter in ruminant dietsimplications for use as a low-cost byproduct feedstuff for goats. In: Merkel, R.C., Abebe, G., Goetsch, A.L. (Eds.), The Opportunities and Challenges of Enhancing Goat Production in East Africa. Langston University, Langston, OK, pp. 58–69. Gurung, N.K., Rankins Jr., D.L., 2001. Use of soybean hulls in broiler litter-based diets fed to beef cattle. J. Appl. Anim. Res. 19, 193–201. Horn, G.W., McCollum III, F.T., 1987. Energy supplementation of grazing ruminants. In: Judkins, M.B. (Ed.), Grazing Livestock Nutrition Conference. University of Wyoming, Laramie, pp. 125–136. Lu, C.D., Potchoiba, M.J., Sahlu, T., Fernandez, J.M., 1990. Performance of dairy goats fed isonitrogenous diets containing soybean meal or hydrolyzed feather meal during early lactation. Small Rumin Res. 3, 425–434. Miller, E.L., 1973. Evaluation of foods as source of nitrogen and amino acids. Proc. Nutr. Soc. 32, 79–84. Moore, J.E., Goetsch, A.L., Luo, J., Owens, F.N., Galyean, M.L., Johnson, Z.B., Sahlu, T., Ferrell, C.L., 2004. Prediction of fecal crude protein excretion of goats. Small Rumin Res., in press. Nikoliæ, J.A., Pavlièeviæ, A., Zeremski, D., Negovanoviæ, D., 1980. Adaptation to diets containing significant amounts of non-protein nitrogen. In: Ruckebusch, Y., Thivend, P. (Eds.), Digestive Physiology and Metabolism in Ruminants. AVI Publishing Co. Inc., pp. 603–620. Patil, A.R., Goetsch, A.L., Galloway Sr., D.L., Forster, L.A., 1993. Intake and digestion by Holstein steer calves consuming grass hay supplemented with broiler litter. Anim. Feed Sci. Technol. 44, 251–263. Patil, A.R., Goetsch, A.L., Kouakou, B., Galloway Sr., D.L., Forster Jr., L.A., Park, K.K., 1995a. Effects of corn versus corn plus wheat in forage-based diets containing broiler litter on feed intake, ruminal digesta characteristics and digestion in cattle. Anim. Feed Sci. Technol. 55, 87–103. Patil, A.R., Goetsch, A.L., Kouakou, B., Park, K.K., Galloway Sr., D.L., Johnson, Z.B., 1995b. Nutritive value of deep-stacked and composted broiler litters for growing cattle. Prof. Anim. Sci. 11, 100–105.
Y. Mekasha et al. / Small Ruminant Research 55 (2004) 123–133 Rossi, J.E., Goetsch, A.L., Galloway Sr., D.L., 1998. Intake and digestion by Holstein steers consuming different particle size fractions of broiler litter. Anim. Feed Sci. Technol. 71, 145–156. Rossi, J.E., Goetsch, A.L., Patil, A.R., Kouakou, B., Park, K.K., Wang, Z.S., Galloway, D.L., Johnson, Z.B., 1996. Effects of forage level in broiler litter-based diets on feed intake, digestibility and particulate passage rate in Holstein steers at different live weights. Anim. Feed Sci. Technol. 62, 163–177. SAS, 1989. SAS User’s Guide, vol. 2, version 6, fourth ed. SAS Inst. Inc., Cary, NC.
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Satter, L.D., Slyter, L.L., 1974. Effect of ammonia concentration on rumen microbial protein production in vitro. Br. J. Nutr. 32, 199–208. Silanikove, N., Tiomkin, D., 1992. Toxicity induced by poultry litter consumption: effect on measurements reflecting liver function in beef cows. Anim. Prod. 54, 203–209. Wang, Z.S., Goetsch, A.L., 1998. Intake and digestion by Holstein steers consuming diets based on litter harvested after different numbers of broiler growing periods or with molasses addition before deep-stacking. J. Anim. Sci. 76, 880–887.
Effects of method of offering broiler litter and level of prairie hay intake on growth of Boer × Spanish wethers Y. Mekasha a,b , R.C. Merkel a , A.L. Goetsch a,∗ , T. Sahlu a , K. Tesfai a a
E (Kika) de la Garza American Institute for Goat Research, Langston University P.O. Box 730, Langston, OK 73050, USA b Animal Science Department, Alemaya University, Dire Dawa, Ethiopia Received 9 April 2003; received in revised form 12 December 2003; accepted 30 December 2003
Abstract Thirty-four Boer × Spanish wethers (18 ± 0.3 kg initial BW; 5 months of age) were used in a 12-week experiment (2 × 2 + 1 factorial arrangement of treatments) to determine effects of ad libitum consumption of broiler litter (B) alone or mixed with corn (60% B; BC) and of ad libitum versus restricted (R) prairie hay intake on feed intake and growth performance. Treatments were: Control: ad libitum intake of hay plus an average of 26 g per day of a mineral-based supplement; AH-B: ad libitum intake of hay and B offered separately; AH-BC: ad libitum intake of hay and BC; RH-B: restricted intake of hay (approximately 1% BW; DM basis) and ad libitum intake of B; RH-BC: restricted intake of hay and ad libitum intake of BC. Average corn DM intake (DMI) was 179 and 170 g per day for AH-BC and RH-BC, respectively, and B DMI was similar among supplement treatments (P > 0.05; 258, 271, 299 and 258 g per day for AH-B, AH-BC, RH-B and RH-BC, respectively). Hay DMI averaged 494, 442, 336, 175 and 160 g per day (S.E. = 16.7), and total DMI was 516, 700, 782, 474 and 585 g/d (S.E. = 26.2) for Control, AH-B, AH-BC, RH-B, and RH-BC, respectively. Overall ADG ranked (P < 0.05) AH-BC > AH-B and RH-BC > Control and RH-B (−6, 34, 79, 3 and 50 g), and the ratio of ADG:DMI ranked (P < 0.05) AH-BC and RH-BC > AH-B > Control and RH-B (−13, 49, 97, 5 and 85 g/kg) for Control, AH-B, AH-BC, RH-B and RH-BC, respectively. Total tract OM digestibility in period 2 ranked (P < 0.05) Control < AH-B, AH-BC and RH-B < RH-BC (34.0, 46.6, 49.8, 50.0 and 63.7% for Control, AH-B, AH-BC, RH-B and RH-BC, respectively). Ruminal fluid ammonia N concentration was lowest among treatments (P < 0.05) at 2 and 6 h after supplementation for Control (e.g., 6 h: 4.0, 19.5, 17.2, 38.2 and 25.8 mg/dl for Control, AH-B, AH-BC, RH-B and RH-BC, respectively; S.E. = 2.69). The ratio of acetate:propionate was greatest among treatments (P < 0.05) at 0, 2 and 6 h for Control (e.g., 6 h: 5.27, 4.04, 3.28, 3.64 and 3.10 for Control, AH-B, AH-BC, RH-B and RH-BC, respectively; S.E. = 0.218). In conclusion, depending on production goals and availability of high-quality feedstuffs such as cereal grains, free-choice consumption of B may be a simple and useful method of supplementing low-quality forage. © 2004 Elsevier B.V. All rights reserved. Keywords: Goats; Broiler litter; Supplementation
1. Introduction
∗ Corresponding author. Tel.: +1-405-466-3836; fax: +1-405-466-3138. E-mail address: [email protected] (A.L. Goetsch).
Broiler litter is a byproduct of the poultry industry, high in nitrogenous compounds generally thoroughly and rapidly degraded by ruminal microorganisms (Crutchfield et al., 1996). Thus, it is commonly used
0921-4488/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2003.12.009
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to supplement ruminants consuming low-nitrogen forages (Fontenot et al., 1996; Goetsch and Aiken, 2000). However, broiler litter is also usually moderate in available energy concentration, allowing use in diets of growing ruminants (El-Ashry et al., 1987; Flachowsky and Henning, 1990; Gurung and Rankins, 2001) though perhaps at levels less than for mature animals. In fact, in some instances when broiler litter has been included in cattle diets with basal forages of similar or even slightly greater OM digestibility, total intake has risen and there has been no change in digestible OM intake (Patil et al., 1993, 1995a,b; Rossi et al., 1996, 1998). Even though broiler litter is available and relatively inexpensive in many parts of the world, one factor restricting its use is method of feeding. Typically, broiler litter is mixed with a palatable cereal grain, such as corn. The odor and(or) taste of broiler litter prevent most producers from feeding it separately or alone. Nonetheless, some cattle producers with animals that are well accustomed to broiler litter do successfully feed it unmixed with other feedstuffs. Likewise, there are many reports of cattle gaining access to broiler litter while being deep-stacked and consuming the byproduct. Certainly the availability of other feedstuffs impacts such occurrences and practices. For example, with drought and low forage availability and quality, one would expect greater potential to feed broiler litter without being mixed with concentrate feedstuffs. Thus, objectives of this experiment were to determine effects of method of broiler litter feeding on feed intake, digestibility and performance by growing goats. More specifically, the study was designed to assess whether separate feeding of broiler litter compared with a mixture with corn would be effective with growing goats consuming a low-N forage and how level of forage feeding may impact effects of feeding broiler litter alone or mixed with corn.
2. Materials and methods 2.1. Animals and management The 12-week experiment was approved by the Langston University Animal Care Committee. Forty Boer × Spanish wether goats approximately 5 months of age and weaned 1 month earlier were selected.
Wethers were treated with Cydectin (Fort Dodge Animal Health, Wyeth, Madison, NJ) when moved to the housing facility. However, 2 weeks later some wethers showed evidence of tapeworm infestation and, thus, were treated with Valbazen (Pfizer Inc., New York, NY). Housing was individual in 1.1 × 1.2 m elevated pens with plastic-coated expanded metal floors. There was a 3-week period before the experiment began for adaptation to experimental conditions, including use of nipple waterers and consumption of broiler litter. During this time feed intake was restricted, with stepwise increases in the level of broiler litter in a mixture with ground corn until the contribution of broiler litter was 67% (as fed basis). Correspondingly, dietary levels of corn and hay were decreased, with hay being offered in a separate container. At the end of this period, 35 wethers (18.3 kg BW; S.E. = 1.85) that had adapted well to consumption of broiler litter were assigned to the five dietary treatments, with seven wethers per treatment. The allocation to treatments was for similar mean BW and variation in BW within treatment. 2.2. Treatments The treatment arrangement was a 2×2+1 factorial. Treatments were: Control: ad libitum intake of prairie hay with a mineral-based supplement; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter). Thus, there were two methods of feeding broiler litter, two levels of prairie hay intake and a Control. Broiler litter was obtained from a production unit where litter had not been completely harvested for more than 1 year, with packed litter removed at the end of each growing period (averaging 6 weeks in length). After transport to the research site, litter was deep-stacked for approximately 5 months. Average temperature in the second, third and fourth months was 43, 50 and 42 ◦ C near the top, middle and bottom areas of the stack, respectively. The mixture of broiler litter and corn was achieved by thorough hand-mixing. The
Y. Mekasha et al. / Small Ruminant Research 55 (2004) 123–133
amount of hay for RH-B and RH-BC treatments was based on average BW of wethers on each treatment, which was determined at 3-week intervals. When intake was ad libitum, feedstuffs were offered at approximately 120% of consumption on the preceding few days. Feeding was initially at 0900 h; however, after a few weeks hay was offered at both 0900 and 1500 h to minimize spillage. Control wethers received a mineral-based supplement (20% trace mineralized salt and 30% dicalcium phosphate, with 50% commercial dried molasses-roughage product mixture included to promote consumption) at 0.145% BW. 2.3. Measures and analyses Wethers were weighed before feeding in the morning at the beginning of the experiment and at 3-week intervals. Feedstuffs and refusals were weighed daily and sampled once weekly. Composite samples for feedstuffs and refusals (within wether) were formed for each 3-week period. In addition, feedstuffs and refusals were sampled daily during week 6, when feces was sampled. To collect most feces over the 7-day period, a wire mesh screen was placed beneath each pen. Samples obtained daily were used to form a composite sample on a fresh-weight basis for each animal. Partial DM concentration of refusal and fecal samples was determined by oven-drying at 55 ◦ C. Thereafter, all samples were ground to pass a 1 mm screen before analysis for DM (100 ◦ C), energy, ash, Kjeldahl N (AOAC, 1990), NDF, ADF (filter bag technique; ANKOM Technology Corp., Fairport, NY) and acid insoluble ash (ash in ADF residue). Acid insoluble ash was used as an internal, inert marker to determine digestibilities. On 1 day in week 8, blood was collected at 0, 2 and 6 h after the 09:00 h meal via jugular venipuncture into a tube containing potassium oxalate and sodium fluoride (Becton Dickinson, Rutherford, NJ) and centrifuged at 1500 × g. Plasma was stored at −20 ◦ C until being analyzed for non-esterified fatty acids (NEFA; Wako Pure Chemical, Richmond, VA) and for protein and urea N colorimetrically using a Technicon AutoAnalyzer II System (Technicon Instruments, Tarrytown, NY). At the same times, ruminal fluid was collected via stomach tube. Ruminal pH was determined immediately after sampling with a pH meter, followed by placement of 5 ml into a tube
125
containing 1 ml of 25% (w/v) metaphosphoric acid for volatile fatty acid (VFA) analysis (Lu et al., 1990) and of 3 ml of fluid into a tube with 2 ml of 3 N HCl for ammonia analysis (Broderick and Kang, 1980). 2.4. Statistical analyses Data of one wether on the AH-BC treatment that developed urinary calculi in the first part of period 3 were omitted from analyses. Based on visual appearance, all feed refusals for the broiler litter-corn mixture were broiler litter, which was assumed to estimate separate intake of broiler litter and corn. Data for repeated measures (i.e., feed intake, average daily gain, gain efficiency and concentrations of constituents in ruminal fluid and blood) were first analyzed as a split-plot in time with GLM procedures of SAS (1989). When the interaction between time and treatment was significant (P < 0.05), data were analyzed separately for each 3-week period or sampling time with treatment in the model. When the interaction was not significant, data were averaged over time before analysis. For feed intake, average daily gain (ADG) and gain efficiency (ADG:DM intake), because treatment effects on average measures over the entire experiment were of interest, average values were also analyzed regardless of significance of the interaction. Initial BW was used as a covariate for analysis of feed intake, ADG and the ratio of ADG:DM intake. Means were separated by least significance difference with a protected F-test (P < 0.05). 3. Results and discussion 3.1. Feedstuff composition The chemical composition of broiler litter was fairly similar to litter used by Animut et al. (2002) and Abebe et al. (2003), characteristically high in ash, CP and Cu (Table 1). Prairie hay was quite low in CP and slightly less than expected. 3.2. Feed intake There was an interaction (P < 0.05) between 3-week period and treatment in total DM intake (DMI; Table 2). The interaction appeared due to
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Table 1 Composition of feedstuffs consumed by growing Boer × Spanish wether goats (% DM) Item
Prairie hay
Broiler litter
Corn–broiler litter mixturea
Ash (%) Crude protein (%) Neutral detergent fiber (%) Acid detergent fiber (%) Energy (MJ/kg) Mg (%) P (%) S (%) K (%) Ca (%) Fe (mg/kg) Cu (mg/kg) Zn (mg/kg)
7.0 3.6 74.5 49.9 17.6 0.21 0.07 0.08 0.29 0.35 51 5 27
20.4 29.8 39.2 19.0 15.0 0.81 2.21 0.49 3.50 2.96 638 583 531
12.2 21.2 28.4 12.7 16.3 0.56 1.53 0.33 2.28 1.93 411 339 321
a
60% broiler litter and 40% corn (DM basis).
differences in DMI between AH-B and AH-BC and between RH-B and RH-BC that varied in magnitude among periods; method of feeding broiler litter and level of hay intake influenced how intake changed with advancing time. For differences between AH-B and AH-BC, broiler litter consumption was similar between treatments in each period. Hay intake for AH-B was similar in period 1 and changed little with advancing period. For AH-BC, hay intake decreased slightly as periods progressed. Conversely, when hay intake was restricted for RH-B and RH-BC, broiler litter intake in periods 1 and 2 was similar between treatments, tending to be less in period 1 for RH-B than for RH-BC. But, broiler litter intake for these restricted hay treatments was greater (P < 0.05) for RH-B in periods 3 and 4, with a greater difference in period 4 than 3.
Table 2 Effects of method of feeding broiler litter and level of hay feeding on dry matter intake (g per day) by growing Boer × Spanish wether goats 3-week period
1
2
3
4
Mean
Treatmenta
Feedstuff
Control
AH-B
AH-BC
RH-B
RH-BC
S.E.
21 b 0a 530 c
0a 172 b 411 b
118 c 185 b 402 b
0a 197 b 186 a
156 d 244 b 182 a
5.0 26.7 9.5
Total
551 b
583 b
706 c
383 a
582 b
30.5
Corn or mineral supplement Broiler litter Hay
27 a 0a 524 c
0a 277 b 488 c
192 b 287 b 388 b
0a 278 b 177 a
176 b 268 b 164 a
12.2 25.6 21.4
Total
551 ab
766 c
867 c
455 a
610 b
36.0
Corn or mineral supplement Broiler litter Hay
29 a 0a 451 c
0a 277 bc 436 c
203 b 305 c 274 b
0a 349 c 170 a
180 b 270 b 137 a
13.9 27.9 21.8
Total
479 a
712 c
783 c
519 ab
587 b
38.3
Corn or mineral supplement Broiler litter Hay
28 a 0a 470 c
0a 306 bc 434 c
203 b 306 bc 265 b
0a 372 c 168 a
166 b 251 b 156 a
13.8 28.6 26.0
Total
499 a
740 b
773 b
540 a
572 a
39.3
Corn or mineral supplement Broiler litter Hay
26 a 0a 494 d
0a 258 b 442 c
179 b 271 b 333 b
0a 299 b 175 a
170 b 258 b 160 a
10.3 19.3 16.7
Total
520 ab
700 c
782 d
474 a
588 b
26.2
Corn or mineral Broiler litter Hay
supplementb
a, b, c: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter). b Mineral supplement for Control and corn for other treatments.
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Mean broiler litter intake was similar among AH-B, AH-BC, RH-B and RH-BC treatments (Table 2). This suggests that there was a factor(s) limiting the amount of broiler litter consumed, which might minimize potential for effective feeding alone when forage intake is restricted. In addition, Silanikove and Tiomkin (1992) suggested that diets very high in poultry litter and low in forage are toxic to beef cows through liver damage elicited by high ruminal ammonia absorption. However, it seems doubtful that this was a factor in the present experiment, since average dietary CP concentration in the digestibility period was 3.4, 10.9, 12.0, 16.8 and 13.6% for Control, AH-B, AH-BC, RH-B and RH-BC, respectively. In periods 3 and 4, broiler litter intake was greater (P < 0.05) for RH-B versus RH-BC. This implies that the low intake of nutrients caused by restricted hay intake, particularly without corn supplementation, affected factors influencing broiler litter intake. These findings, along with similar broiler litter intake between RH-B and RH-BC in periods 1 and 2, indicate that the length of time on a low nutritional plane can influence adaptation to consumption of broiler litter. Overall and in all but the first period, total DMI was greater for ad libitum versus restricted hay intake treatments as expected (P < 0.05; Table 2). Likewise, average total DMI was greater with than without corn (P < 0.05). Although, in some periods total DMI was not different between AH-B and AH-BC or between RH-B and RH-BC. Total intake was similar between Control and RH-B but was greater (P < 0.06) for RH-BC than for Control. Hence, with RH-B, consumption of broiler litter substituted for hay. Also, greater total intake for RH-BC versus Control was because of only partial rather than complete substitution of corn for hay. Broiler litter supplementation with the AH-B treatment did not increase hay intake compared with Control as might have been expected with a supplement high in CP given with a low-CP forage like this prairie hay. In fact, hay intake in periods 1 and 2 was lower for AH-B than for Control. This may reflect differences between broiler litter and other common CP supplements like soybean meal, such as in CP, non-protein N and fiber concentrations as well as other characteristics including palatability and odor.
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3.3. Digestion Total OM digestibility ranked (P < 0.05) Control and AH-B < AH-BC and RH-B < RH-BC (Table 3). Energy digestibility ranked (P < 0.05) Control < AH-B, AH-BC and RH-B < RH-BC. The ranking (P < 0.05) of digestible OM intake was Control and RH-B < AH-B and RH-BC < AH-BC. The ranking for DE intake was similar, although the difference between AH-BC and RH-BC was not significant (P > 0.05). Digestible OM intake was more in line with differences among treatments in ADG than was DE intake. The digestibilities do not clearly reflect a positive effect of broiler litter supplementation on extent of digestion of hay fiber. This is because increases in digestion of total dietary fiber would be expected with dietary addition of broiler litter and(or) corn because of their greater digestibilities than hay (Table 3). However, because OM intake was greater for AH-B, AH-BC and RH-BC than for Control, the time of digesta residence in the rumen was most likely shorter. Hence, with an extent of NDF digestion similar to or greater than that for the Control, broiler litter may have increased rate of digestion of hay fiber. As noted earlier, consumption of corn did not appear to lessen digestion of fiber (NDF and ADF) in hay (Table 3). Corn averaged 23 and 29% of average total DMI. These levels would not be expected to have appreciable negative effects on fiber digestion (Horn and McCollum, 1987). Perhaps mixing with broiler litter may limit corn intake to a level less than needed to depress digestion of hay fiber. Except for Control, total tract CP digestion was less than predicted based on estimates of true protein digestibility and metabolic fecal CP of Moore et al. (2004). This might reflect some heat damage of nitrogenous compounds in broiler litter during deep-stacking, although heating did not appear excessive. Another possibly involved factor is volatilization of N from broiler litter between the time of feeding and actual consumption. 3.4. ADG and ADG:DMI There was an interaction in ADG between 3-week period and treatment (P < 0.05; Table 3). In period 1, ADG ranked (P < 0.05) AH-BC > C, AH-B and
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Table 3 Effects of method of feeding broiler litter and level of hay feeding on digestion by growing Boer × Spanish wether goats Item
Organic matter Intake (g per day) Digestion % g per day Energy Intake (MJ per day) Digestion % MJ per day Nitrogen Intake (g per day) Digestion % g per day Neutral detergent fiber Intake (g per day) Digestion % g per day Acid detergent fiber Intake (g per day) Digestion % g per day
Treatmenta Control
AH-B
AH-BC
RH-B
RH-BC
S.E.
488 b
673 c
786 d
390 a
566 b
30.8
44.0 a 215 a
48.1 a 324 b
55.7 b 440 c
54.6 b 215 a
67.6 c 379 b
1.88 21.4
9.2 b
12.7 c
14.6 c
7.4 a
10.6 b
0.57
34.0 a 3.5 a
46.6 b 5.8 b
49.8 b 7.3 c
50.0 b 3.8 a
63.7 c 6.7 bc
2.89 0.40
3.0 a
13.3 bc
16.7 c
12.2 b
13.3 bc
1.48
21.1 a 0.6 a
33.9 ab 4.8 b
42.5 bc 7.2 b
39.9 bc 5.7 b
52.9 c 6.8 b
5.12 0.87
396 b
484 c
431 b
250 a
265 a
16.6
48.9 a 194 a
55.6 b 268 c
52.8 ab 228 b
65.6 c 165 a
63.4 c 167 a
1.95 12.3
262 b
299 c
255 b
143 a
147 a
10.6
41.8 b 124 c
39.8 ab 101 b
35.9 a 94 b
52.9 c 76 a
50.2 c 74 a
1.88 5.6
a, b, c, d: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
RH-BC > RH-B, whereas ADG was similar among treatments in period 2. ADG in period 3 was less (P < 0.05) for Control versus AH-BC, RH-B and RH-BC and greater (P < 0.05) for AH-BC and RH-BC than for AH-B. Period 4 ADG ranked (P < 0.05) AH-BC and RH-BC > AH-B and RH-B > Control. Over the entire experiment, ADG ranked (P < 0.05) AH-BC > AH-B and RH-BC > Control and RH-B. Gain efficiency (ADG:DMI) was also affected by an interaction between 3-week period and treatment (P < 0.05; Table 4). Gain efficiency was lowest among treatments (P < 0.05) in period 1 for RH-B and less
(P < 0.05) for RH-BC versus AH-BC, whereas values were similar among treatments in period 2. Differences in period 3 were fairly similar to those in ADG, as was also the case in period 4. Gain efficiency during the entire experiment ranked (P < 0.05) AH-BC and RH-BC > AH-B > Control and RH-B. Overall, offering broiler litter free-choice and alone increased ADG by Boer cross goats when consuming hay ad libitum but not with hay intake restricted to 1% BW. This was the end-result of broiler litter DMI being less than the difference in hay DMI between RH-B and Control and the higher ash concentration in
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Table 4 Effects of method of feeding broiler litter and level of hay feeding on ADG and ADG:DM intake (DMI) by growing Boer × Spanish wether goats Item
Period
Treatmenta Control
83 b 39 3 ab 13 b
AH-BC
ADG (g per day)
1 2 3 4
−6 a
34 b
79 c
ADG:DMI (g/kg)
1 2 3 4
116 bc −71 −52 a −54 a
142 bc 48 1 ab 21 b
222 c 37 52 bc 99 c
Mean
−13 a
49 b
97 c
Mean
62 b −36 −24 a −26 a
AH-B
155 c 36 46 c 78 c
RH-B −28 a 0 27 bc 12 b 3a −113 a −35 49 bc 19 b 5a
RH-BC
S.E.
52 b 39 46 c 60 c
16.0 23.2 13.1 8.4
50 b
7.5
91 b 58 78 c 103 c
38.8 58.0 21.8 12.3
84 c
9.0
a, b, c: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
broiler litter than hay. Furthermore, OM and energy digestibilities in period 2 were less than necessary to compensate for these differences, which resulted in similar DE intake in period 2 and presumably throughout the experiment. Greater ADG for AH-B versus Control was because of the low substitution ratio (i.e., decrease in hay intake relative to the level of consumption of broiler litter) for the replacement of hay by broiler litter and greater energy digestibility for AH-B, which resulted in greater DE intake for AH-B. Hence, the primary reason for the difference in ADG between AH-B and Control was additional nutrients from broiler litter. The lower ADG:DMI ratio for AH-B versus RH-BC indicates less efficient utilization of hay than corn, encompassing differences in digestibility and possibly efficiency of metabolism. Although, similar ADG between these two treatments (P < 0.17) reflects compensation via greater hay intake by AH-B wethers. Mixing corn with broiler litter increased ADG similarly with both ad libitum and restricted hay intake. In part, this may reflect that the amount of corn consumed was less than necessary to decrease ruminal fiber digestion. Comparisons of AH-B versus AH-BC and RH-B versus RH-BC indicate that inclusion of supplemental corn did not lessen additional digestible
nutrients achieved by broiler litter supplementation. Greater ADG for RH-BC versus RH-B was in response to the substantial increase in total DMI (i.e., 114 g overall). Greater ADG for AH-BC compared with AH-B also resulted from an increase in total DMI (i.e., 82 g). But, this difference was less than when hay intake was restricted because of considerable substitution of corn for hay. 3.5. Ruminal fluid conditions The concentration of total VFA in ruminal fluid was less (P < 0.05) for Control versus RH-B, with intermediate (P > 0.05) concentrations for other treatments (Table 5). Because of potential differences in ruminal fluid volume, these concentrations do not necessarily reflect total quantities of VFA in the rumen. There were interactions between sampling time and treatment in molar percentages of propionate, butyrate and valerate and in the acetate:propionate ratio (Table 5). The molar percentage of acetate ranked (P < 0.05) AH-BC and RH-BC < RH-B < AH-B < Control. At 0 h, the molar percentage of acetate was lowest among treatments (P < 0.05) for Control; however, at 2 h the molar percentage of acetate was still lowest among treatments (P < 0.05) for Control,
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Table 5 Effects of method of feeding broiler litter and level of hay feeding on concentrations of volatile fatty acids, ammonia N and pH in ruminal fluid of growing Boer × Spanish wether goats Item
Time after feeding (h)
Treatmenta Control
AH-B
AH-BC
RH-B
RH-BC
S.E.
Volatile fatty acids Total (mol/100 mol)
Mean
41.3 a
45.6 ab
43.0 ab
50.1 b
45.8 ab
1.99
Molar percentage Acetate
Mean
78.2 d
74.4 c
68.2 a
72.0 b
67.0 a
0.59
Propionate
0 2 6
14.3 a 15.3 a 14.9 a
17.2 b 18.2 b 18.5 b
17.9 b 21.4 c 21.6 c
19.2 b 18.5 b 19.8 bc
19.0 b 22.0 c 22.0 c
0.94 0.95 1.05
Isobutyrate
Mean
0.55
0.68
0.63
0.93
Butyrate
0 2 6
5.6 a 5.5 a 5.7 a
6.1 ab 5.6 ab 5.8 a
Isovalerate
Mean
0.45
0.72
1.17
Valerate
0 2 6
0.34 a 0.34 a 0.31 a
0.34 a 0.35 a 0.31 a
Acetate: propionate
0 2 6
5.50 b 5.13 c 5.27 c
Ammonia N (mg/dl)
0 2 6
pH
Mean
0.59
0.118
10.9 c 8.7 c 10.2 c
0.44 0.36 0.77
0.80
0.93
0.218
0.60 b 0.46 b 0.48 b
0.37 a 0.49 b 0.36 a
0.59 b 0.52 b 0.44 b
0.051 0.033 0.026
4.33 a 4.09 b 4.04 b
3.98 a 3.36 a 3.28 a
3.75 a 3.96 b 3.64 ab
3.66 a 3.12 a 3.10 a
0.244 0.217 0.218
4.1 a 4.1 a 4.0 a
7.1 ab 22.3 bc 19.5 bc
6.3 ab 18.9 b 17.2 b
8.8 b 26.8 cd 25.8 c
1.40 2.12 2.69
6.64 c
6.70 c
6.52 b
6.44 a
0.238
10.8 c 8.5 c 8.2 bc
7.0 b 6.6 b 6.6 ab
15.7 c 29.7 d 38.2 d 6.68 c
a, b, c, d: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
but levels were greater (P < 0.05) for supplemented treatments with than without corn. The molar percentage of acetate was similar at 6 h, except that the level was similar (P > 0.05) among AH-BC, RH-B and RH-BC. Molar percentages of isobutyrate and isovalerate were similar among treatments (P > 0.05). At 0 and 2 h, the molar percentage of butyrate was greatest among treatments (P < 0.05) for treatments with supplemental corn. Differences were comparable at 6 h, except for a similar (P > 0.05) concentration between AH-BC and RH-B. The molar percentage of valerate was greatest among treatments for AH-BC and RH-BC at 0 and 6 h. Findings at 2 h were comparable, except for a similar level for AH-BC, RH-B
and RH-BC. The acetate:propionate ratio was greatest among treatments (P < 0.05) for Control at all times. The ratio was similar (P > 0.05) among supplemented treatments at 0 h, but at 2 h the ratio was lower (P < 0.05) for treatments with supplemental corn. Differences among supplemented treatments were comparable at 2 and 6 h, except for similar (P > 0.05) ratios among AH-BC, AH-B and RH-BC. Overall, corn supplementation had expected effects on acetate and propionate levels and their ratio (i.e., decrease), and a decreased acetate:propionate ratio with broiler litter feeding has been noted in other experiments as well (Patil et al., 1995a; Rossi et al., 1996, 1998; Wang and Goetsch, 1998).
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Table 6 Effects of method of feeding broiler litter and level of hay feeding on concentrations of non-esterified fatty acids (NEFA), protein, glucose and urea N in plasma of growing Boer × Spanish wether goats Item
Time after feeding (h)
Treatmenta Control
AH-B
AH-BC
RH-B
RH-BC
S.E. 12.67 5.48 8.26
NEFA (eq./dl)
0 2 6
79.5 72.6 bc 84.1
53.2 59.9 ab 61.2
102.3 76.5 c 84.8
63.7 55.3 a 47.9
80.7 65.6 abc 67.5
Protein (g/dl) Glucose (mg/dl)
Mean Mean
7.42 12.9 a
7.68 36.4 bc
7.69 29.9 b
7.63 39.9 c
7.56 33.9 bc
0.157 3.13
Urea N (mg/dl)
0 2 6
4.3 a 4.8 a 4.3 a
16.6 b 23.3 b 32.0 c
15.1 b 21.8 b 27.9 b
29.4 c 33.2 c 39.2 d
18.2 b 22.6 b 30.5 bc
1.48 1.40 1.30
a, b, c, d: means in a row without a common letter differ (P < 0.05). a Control: ad libitum intake of prairie hay; AH-B: ad libitum intake of prairie hay and broiler litter offered separately; AH-BC: ad libitum intake of prairie hay and a corn–broiler litter mixture (60% broiler litter); RH-B: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of broiler litter; RH-BC: restricted intake of prairie hay (approximately 1% BW; DM basis) and ad libitum intake of a corn–broiler litter mixture (60% broiler litter).
The concentration of ammonia N in ruminal fluid at all times was lowest among treatments (P < 0.05) for Control (Table 5). These levels for Control suggest possible limitations of ruminal fiber digestion and(or) microbial growth (Miller, 1973; Satter and Slyter, 1974). However, because supplementation with broiler litter alone did not appear to increase the extent of ruminal digestion of fiber in hay, fiber digestion may not have been limited by ruminal availability of nitrogenous compounds. At 0 h, the concentration was greatest among treatments (P < 0.05) for RH-B in accordance with the highest dietary CP concentration. At each time, corn supplementation either decreased or tended to decrease ruminal ammonia N concentration, which is as expected because of increases in ruminally fermentable energy. Ruminal pH ranked (P < 0.05) RH-BC < AH-BC < Control, AH-B and RH-B. 3.6. Plasma constituents Plasma concentrations of NEFA and urea N were affected by interactions (P < 0.05) between sampling time and treatment (Table 6). The NEFA concentration was similar among treatments (P > 0.05) at 0 and 6 h. Treatment differences at 2 h were not in agreement with differences in intake of digestible OM or DE. NEFA concentration was not correlated (P > 0.05) with period 2 ADG. Therefore, these NEFA concen-
trations do not seem affected only by likely fat mobilization by Control goats compared with positive ADG for three of the other treatments. Plasma protein concentration was similar among treatments (P > 0.05). Plasma urea N concentration was lowest among treatments (P < 0.05) for Control at all times of sampling, in agreement with ruminal concentrations of ammonia N (Nikoliæ et al., 1980). Also in accordance with ruminal ammonia N concentration, at 0 h urea N concentration was greatest among supplemented treatments (P < 0.05) for RH-B, and similar differences (P < 0.05) were noted at 2 h. Likewise, corn supplementation decreased (P < 0.05) urea N concentration at 2 and 6 h (i.e., AH-BC versus AH-B and RH-BC versus RH-B). Thus, urea N concentration appeared to be affected by factors influencing ruminal ammonia N concentration, such as consumption broiler litter with CP rapidly and thoroughly degraded in the rumen, as well as corn supplementation that increased microbial uptake of ammonia through the increase in ruminally fermentable energy.
4. Summary and conclusions In summary, neither method of feeding broiler litter nor level of hay intake influenced overall broiler litter intake, suggesting presence of factor(s) limiting
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broiler litter consumption. When offered alone, broiler litter did not appear to increase the extent of digestion of fiber of this low-quality, low-CP forage, although impact on rate of digestion is possible. Broiler litter feeding enhanced ADG when hay was offered free-choice presumably because of additional nutrients from broiler litter. Mixing broiler litter with corn may be a means of restricting corn intake to a level less than necessary to adversely affect ruminal fiber digestion. The broiler litter-corn mixture had less effect on intake of hay relative to the amount of supplemental feedstuffs consumed than did broiler litter when fed without corn. In conclusion, offering broiler litter alone free-choice increased ADG by Boer cross goats when consuming hay ad libitum but not with hay intake restricted to 1% BW. The lower ADG:DMI ratio for AH-B versus RH-BC indicates less efficient utilization of hay than corn, although similar ADG reflects compensation via greater hay intake. Mixing corn with broiler litter increased ADG similarly with both ad libitum and restricted hay intake.
Acknowledgements This research was supported by the Institutional Development Partnership Program of the United Negro College Fund/United States Agency for International Development and the resulting partnership between Langston University, Langston, OK, and Alemaya University, Dire Dawa, Ethiopia. Appreciation is expressed to farm and laboratory personnel of the E (Kika) de la Garza American Institute for Goat Research for their assistance. Also, appreciation is extended to Larry Morrison for providing broiler litter. References Abebe, G., Merkel, R.C., Animut, G., Sahlu, T., Goetsch, A.L., 2003. Effects of ammoniation of wheat straw and supplementation with soybean meal or broiler litter on feed intake and digestion in yearling Spanish wether goats. Small Rumin Res. 51, 37–46. Animut, G., Merkel, R.C., Abebe, G., Sahlu, T., Goetsch, A.L., 2002. Effects of level of broiler litter in diets containing wheat straw on performance of Alpine doelings. Small Rumin Res. 44, 125–134. AOAC, 1990. Official Methods of Analysis, 14th ed. Association of Official Analytical Chemists, Washington, DC.
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Satter, L.D., Slyter, L.L., 1974. Effect of ammonia concentration on rumen microbial protein production in vitro. Br. J. Nutr. 32, 199–208. Silanikove, N., Tiomkin, D., 1992. Toxicity induced by poultry litter consumption: effect on measurements reflecting liver function in beef cows. Anim. Prod. 54, 203–209. Wang, Z.S., Goetsch, A.L., 1998. Intake and digestion by Holstein steers consuming diets based on litter harvested after different numbers of broiler growing periods or with molasses addition before deep-stacking. J. Anim. Sci. 76, 880–887.