Evaluation of a method to predict negative feedstuff associative effects in meat goats consuming diets with different forage sources and levels of concentrate

Figures & data

Table 1. Predictions of decreases in basal forage intake by growing and yearling Boer goat wethers to account for effects of supplemental concentrate on intake of ME resulting from potential decreases in forage intake and digestion with the web-based goat nutrient requirement calculation system for goats of Langston University (LINC).

Supplement DM intake^a
	g/kg BW^0.75		Forage OM digestibility (%)^b
% BW	24 kg BW	47 kg BW	45	50	55	60	65
0.50	11.1	13.1	0	0	0	0	0
0.75	16.6	19.6	0	0	16	36	56
1.00	22.1	26.2	0	11	31	51	71
1.25	27.7	32.7	9	29	49	69	89
1.50	33.2	39.3	27	47	67	87	107
1.75	38.7	45.8	43	63	83	103	123
2.00	44.3	52.4	55	75	96	115	135

^aAverage BW in the experiment was 24 and 47 kg for growing and yearling wethers, respectively.

^bValues in the body of the table are decreases in basal forage intake as a percentage of supplemental concentrate intake. For example, with a level of concentrate of 1.00% BW and a value of 100%, the predicted decrease in forage intake to project change in intake of ME due to potential change in forage intake and digestion also would be 1.00% BW.

Table 2. Composition of feedstuffs consumed by growing and yearling Boer goat wethers.

	Grass hay source
Item	A	B	C	SEM	Concentrate supplement (mean ± SEM)
Ash (% DM)	8.3^a	8.6^a	10.7^b	0.32	3.2 ± 0.14
CP (% DM)	5.2^a	7.9^b	12.3^c	0.38	22.8 ± 1.83
Gross energy (MJ/kg DM)	17.7	17.3	17.5	0.16	18.3 ± 0.06
NDF (% DM)	79.1^b	70.7^a	68.9^a	0.63	10.3 ± 0.40
ADF (% DM)	54.2^c	42.8^a	45.5^b	0.56	4.1 ± 0.12
ADL (% DM)	12.6^b	8.8^a	11.8^b	0.54

Notes: Six samples of each feedstuff, with two weekly composites from daily samples formed in each period. Grass hay source means without a common superscript letters (a–c) differ (P < .05).

Table 3. P values for effects of animal age, supplement level, and forage source on intake and digestion by Boer goat wethers.

Item	Effect P value^a
	A	S	A × S	F	A × F	S × F	A × S × F
DM intake (g/kg BW^0.75)
Hay	0.157	<0.001	0.637	<0.001	0.824	0.369	0.964
Supplement	0.737	<0.001	0.590	0.202	0.933	0.962	1.000
Total	0.165	0.103	0.654	<0.001	0.837	0.373	0.967
DM (g/day)
Intake
Hay	0.001	<0.001	0.026	<0.001	0.598	0.423	0.990
Supplement	<0.001	<0.001	<0.001	0.991	0.997	1.000	1.000
Total	<0.001	0.027	0.681	<0.001	0.599	0.426	0.990
Digestion (%)	0.095	<0.001	0.053	0.002	0.256	0.118	0.674
Digestion (g/day)	<0.001	<0.001	0.126	0.001	0.448	0.647	0.995
Supplement DM intake (% total)	0.065	<0.001	0.281	<0.001	0.908	0.156	0.991
OM
Intake (g/day)	<0.001	0.009	0.729	<0.001	0.603	0.433	0.991
Digestion (%)	0.134	<0.001	0.049	0.003	0.323	0.139	0.660
Digestion (g/day)	<0.001	<0.001	0.193	<0.001	0.475	0.660	0.995
Gross energy
Intake (MJ/day)	<0.001	0.010	0.723	<0.001	0.616	0.457	0.990
Digestion (%)	0.137	<0.001	0.059	0.001	0.377	0.111	0.699
Digestion (MJ/day)	<0.001	<0.001	0.128	0.005	0.594	0.689	0.998
CP
Intake (g/day)	<0.001	<0.001	0.041	0.021	0.942	0.926	1.000
Digestion (%)	0.060	<0.001	0.234	<0.001	0.501	0.420	0.784
Digestion (g/day)	<0.001	<0.001	0.059	0.440	0.864	0.977	0.999
N balance measures (g/day)
Fecal excretion	<0.001	0.089	0.157	<0.001	0.501	0.420	0.784
Urinary excretion	<0.001	<0.001	0.440	<0.001	0.209	0.377	0.800
Balance	<0.023	0.220	0.997	<0.001	0.156	0.524	0.838
NDF
Intake (g/day)	<0.001	<0.001	0.021	<0.001	0.550	0.499	0.980
Digestion (%)	0.004	<0.001	0.001	0.325	0.483	0.049	0.875
Digestion (g/day)	<0.001	<0.001	0.001	<0.001	0.504	0.801	0.971
ADF
Intake (g/day)	<0.001	<0.001	0.010	<0.001	0.552	0.530	0.971
Digestion (%)	0.014	0.015	0.009	0.528	0.526	0.017	0.917
Digestion (g/day)	<0.001	<0.001	0.002	0.003	0.487	0.793	0.860

^aA = animal age (growing vs. yearling wethers); S = supplement level (0, 15, 30, and 45 g/kg BW^0.75; DM); F = forage source (three sources of grass hay).

Table 4. Effects of animal age, supplement level, and forage source on intake and digestion by Boer goat wethers.

		Animal type^1			Forage source^2				Supplement level^3
Item^4	A, F^5	Grow	Year	SEM	A	B	C	SEM	0	15	30	45	SEM
DM intake (g/kg BW^0.75)
Forage		34.9	30.8	1.96	29.7^a	42.9^b	25.9^a	3.92	48.5^c	41.8^c	25.9^b	15.2^a	2.77
Supplement		21.6	21.7	0.20	21.9	21.5	21.6	0.20	0.0^a	14.8^b	23.8^c	43.1^d	0.29
Total		56.5	52.5	1.95	51.6^a	64.4^b	47.6^a	2.18	48.5	56.6	54.7	58.3	2.76
DM
Intake (g/day)
Hay					402^a	592^b	355^a	30.6
	Grow								458^c	449^c	345^abc	199^a	59.1
	Year								810^e	730^d	383^bc	221^ab
Supplement					312	312	312	5.8
	Grow								0^a	158^b	323^d	483^e	16.3
	Year								0^a	257^c	530^e	745^f
Total		604^a	919^b	30.6	714^a	904^b	667^a	31.1	634^a	797^b	791^b	824^b	43.2
Digestion (%)		69.7	66.6	1.26	70.6^b	63.6^a	70.2^b	1.44	54.8^a	69.0^b	74.8^c	74.1^bc	1.78
Digestion (g/day)		421^a	613^b	17.6	510^a	573^b	469^a	19.4	342^a	540^b	589^b	598^b	24.9
Supplement DM intake (% total)		37.5	41.5	1.42	40.2^b	33.8^a	44.6^c	1.56	0.0^a	28.7^b	54.6^c	74.8^d	2.01
OM
Intake (g/day)		564^a	861^b	28.0	669^a	842^b	626^a	28.6	578^a	740^b	746^b	787^b	39.6
Digestion (%)					72.0^b	66.0^a	72.0^b	1.34
	Grow								57.4^a	69.7^b	76.2^bcd	81.8^d	2.27
	Year								55.6^a	71.6^bc	76.9^cd	70.9^bc
Digestion (g/day)		404^a	594^b	16.3	489^a	556^b	452^a	18.0	323^a	513^b	569^bc	590^c	23.1
Energy
Intake (MJ/day)		10.7^a	16.3^b	0.52	12.7^a	15.9^b	11.9^a	0.54	11.0^a	14.0^b	14.1^b	14.9^b	0.74
Digestion (%)		68.5	65.5	1.35	69.3^b	62.4^a	69.5^b	1.51	53.3^a	67.8^b	73.9^c	73.2^bc	1.91
Digestion (MJ/day)		7.4^a	10.7^b	0.30	8.9^a	9.9^b	8.3^a	0.34	5.8^a	9.3^b	10.4^bc	10.7^c	0.43
CP
Intake (g/day)					103^a	117^b	99^a	4.5
	Grow								43^a	71^a	101^b	126^c	7.4
	Year								58^a	116^bc	151^d	187^e
Digestion (%)		72.9	66.3	2.30	74.4^b	63.8^a	70.7^b	2.06	50.9^a	73.0^b	78.2^b	76.4^b	3.26
Digestion (g/day)		65^a	90^b	3.4	80	79	73	4.1	26^a	68^b	99^c	118^d	4.8
N balance measures (g/day)
Faecal		3.3^a	6.1^b	0.45	3.6^a	6.2^b	4.2^a	0.38	3.9	4.2	4.4	6.2	0.63
Urinary		5.5^a	8.4^b	0.38	6.0^a	6.2^a	8.6^b	0.45	3.3^a	5.7^b	9.0^c	9.9^c	0.54
Balance		−1.5b	−2.8^a	0.37	−1.0^b	−1.3^b	−4.1^a	0.46	−1.7	−1.5	−2.9	−2.5	0.53
NDF
−Intake (g/day)					319^a	454^b	284^a	21.7
	Grow								321^b	334^bc	278^ab	191^a	39.4
	Year								592^d	543^cd	326^bc	234^ab
Digestion (%)	Grow								57.3^b	60.6^b	61.4^b	58.4^b	3.41
	Year								56.6^b	62.9^b	56.8^b	30.0^a
	A								56.9^cd	65.2^de	69.5^e	40.3^a	4.18
	B								54.2^bcd	55.9^cd	58.5^cde	47.2^ab
	C								59.7^cde	64.0^de	49.3^abc	43.7^ab
Digestion (g/day)					163^a	190^a	247^b	13.7
	Grow								178^b	193^b	172^ab	111^a	23.1
	Year								337^c	342^c	193^b	71^a
ADF
Intake (g/day)					188^a	271^ab	167^a	13.3
	Grow								200^c	199^c	160^abc	105^a	23.0
	Year								373^d	322^d	185^bc	124^ab
Digestion (%)	Grow								46.4^b	41.9^b	47.3^b	49.2^b	5.27
	Year								44.7^b	51.4^b	41.1^b	13.5^a
	A								45.2^cde	52.6^e	59.9^e	22.7^a	6.32
	B								42.8^bcde	45.6^cde	47.1^cde	37.7^abcd
	C								48.6^cde	52.6^de	25.5^ab	33.7^abc
Digestion (g/day)					89^a	118^b	74^a	8.3
	Grow								89^b	91^b	78^b	52^ab	13.6
	Year								169^c	168^c	86^b	189^c

Note: Means within a grouping without a common superscript letters (a–e) differ (P < 0.05).

¹Animal age: Grow = growing wethers; Year = yearling wethers.

²Forage source: three sources of grass hay.

³Supplement level (0, 15, 30, and 45 g/kg BW^0.75; DM).

⁴DM, dry matter; OM, organic matter; CP, crude protein; NDF, neutral detergent fibre; ADF, acid detergent fibre.

⁵A, animal age; F, forage source.

Table 5. P values for effects of animal age, supplement level, and forage source on ruminal fluid characteristics of Boer goat wethers.

Item	Effect P value^a
	A	S	A × S	F	A × F	S × F	A × S × F
pH	0.080	<0.001	0.122	0.580	0.536	0.406	0.351
VFA
Total (mmol/l)	0.823	0.459	0.765	0.165	0.171	0.201	0.111
Molar percentage
Acetate	0.027	<0.001	0.166	0.828	0.405	0.018	0.634
Propionate	0.011	<0.001	0.022	0.271	0.158	0.003	0.134
Isobutyrate	0.220	<0.001	0.373	0.015	0.971	0.576	0.354
Butyrate	0.588	<0.001	0.463	0.908	0.131	0.272	0.015
Isovalerate	0.458	<0.001	0.484	0.173	0.747	0.321	0.543
Valerate	0.734	<0.001	0.477	0.028	0.809	0.389	0.705
Ammonia N (mg/100 ml)	0.045	0.001	0.589	0.730	0.816	0.224	0.402

^aA = animal age (growing vs. yearling wethers); S = supplement level (0, 15, 30, and 45 g/kg BW^0.75; DM); F = forage source (three sources of grass hay).

Table 6. Effects of animal age, supplement level, and forage source on ruminal fluid characteristics of Boer goat wethers.

			Animal type^1			Forage source^2				Supplement level^3
Item	A^4	F^5	Grow	Year	SEM	A	B	C	SEM	0	15	30	45	SEM
pH			6.46	6.37	0.034	6.38	6.41	6.44	0.041	6.63^c	6.52^c	6.36^b	6.13^a	0.048
VFA
Total (mmol/l)			67.1	66.1	3.03	62.4	70.3	67.1	3.17	62.4	64.4	67.8	71.8	4.24
Molar percentage
Acetate			73.2^b	70.9^a	0.66
		A								78.9^fg	76.6^efg	70.7^c	60.7^a	1.42
		B								75.4^def	74.8^de	72.6^cd	66.4^b
		C								80.1^g	74.0^cde	72.0^cd	62.5^a
Propionate	Grow									15.2^ab	15.0^ab	14.2^a	17.5^b	0.93
	Year									15.4^ab	14.3^a	16.8^ab	22.9^c
		A								15.0^abc	13.9^ab	16.4^bc	22.5^d	0.96
		B								17.2^c	15.2^abc	15.5^abc	17.3^c
		C								13.7^a	15.0^abc	14.6^abc	20.8^d
Isobutyrate			0.50	0.56	0.029	0.50^a	0.48^a	0.61^b	0.034	0.40^a	0.47^ab	0.54^b	0.71^c	0.043
Butyrate^6	Grow	A								4.50	7.78	9.82	14.22	0.865
		B								5.60	9.24	8.83	11.01
		C								4.33	8.69	10.55	14.46
	Year	A								5.23	8.10	11.66	11.50
		B								6.53	7.82	10.02	14.93
		C								4.88	8.73	10.80	11.62
Isovalerate			1.06	1.14	0.072	1.06	1.02	1.22	0.080	0.61^a	0.81^a	1.22^b	1.74^c	0.098
Valerate			0.68	0.69	0.027	0.62^a	0.68^ab	0.75^b	0.032	0.38^a	0.51^b	0.66^c	1.19^d	0.033
Ammonia N (mg/100 ml)			22.8^b	17.4^a	1.76	20.4	21.0	18.7	2.15	9.6^a	18.5^b	26.4^c	25.8^c	2.55

Note: Means within a grouping without a common superscript letters (a–g) differ (P < .05).

¹Animal age: Grow = growing wethers; Year = yearling wethers.

²Forage source: three sources of grass hay.

³Supplement level (0, 15, 30, and 45 g/kg BW^0.75; DM).

⁴A = animal age.

⁵F = forage source.

⁶Significant animal age × forage source × supplement level interaction, although superscripts on interaction means are omitted because of the large number.

Figure 1. Effects of animal type on time spent eating throughout the day and the hourly pattern of time idle.

Figure 2. Effects of level of supplemental concentrate and forage source on time spent ruminating throughout the day. Panel A = A forage source, Panel B = B forage source, and Panel C = C forage source.

Table 7. P values for effects of animal age, supplement level, and forage source on feeding behaviour and position.

	Feeding behaviour
Source of variation^a	Eating	Ruminating	Idle	Standing and lying
A	0.042	0.015	0.015	0.798
S	0.053	0.040	0.028	0.436
A × S	0.773	0.930	0.955	0.969
Period	0.278	0.066	0.521	0.022
F	0.231	0.181	0.135	0.823
A × F	0.959	0.914	0.987	0.239
S × F	0.824	0.813	0.953	0.559
A × S × F	0.959	0.330	0.812	0.837
H	<0.001	<0.001	<0.001	<0.001
A × H	0.005	0.099	0.781	0.328
S × H	0.069	0.494	0.690	0.019
A × S × H	0.931	0.464	0.745	0.880
F × H	0.090	0.956	0.888	0.460
A × F × H	0.926	0.829	0.965	0.466
S × F × H	0.154	0.046	0.061	0.016
A × S × F × H	0.965	0.748	0.989	0.928

^aA = animal age (growing vs. yearling wethers); S = supplement level (0, 15, 30, and 45 g/kg BW^0.75; DM basis); F = forage source (three sources of grass hay); H = hour.

Table 8. Effects of animal age, supplement level, and forage source on feeding behaviour and position of Boer goat wethers.

Item	Animal age^1			Forage source^2				Supplement level^3
	Grow	Year	SEM	A	B	C	SEM	0	15	30	45	SEM
Feeding behaviour (% of day)
Eating	19.1^b	15.3^a	1.22	17.5	18.2	15.9	1.17	19.8	19.9	14.7	14.3	1.74
Ruminating	28.4^b	23.4^a	1.30	25.8	27.8	24.2	1.41	30.1^b	27.5^ab	23.0^a	23.1^a	1.83
Idle	52.6^a	61.4^b	2.29	56.8	54.2	60.0	2.29	50.4^a	52.5^a	62.3^b	62.7^b	3.24
Position (% of day)
Standing	48.5	47.9	3.41	46.8	48.8	48.9	3.11	55.2	44.4	46.6	46.5	4.83
Lying	51.5	52.1	3.41	53.2	51.2	51.1	3.11	44.8	55.6	53.4	53.5	4.83

Note: Means within a grouping without a common superscript letters (a and b) differ (P < .05).

¹Grow = growing wethers; Year = yearling wethers.

²Forage source: three sources of grass hay.

³Supplement level (0, 15, 30, and 45 g/kg BW^0.75; DM).

Table 9. Actual and predicted ME intake (kJ/kg BW^0.75) for Boer goat wethers.

Source of variation	Treatment	Actual		Predicted
		Mean	SEM	Mean	SEM
Animal age × supplement level (g/kg BW^0.75)	Growing – 15	530	32.3	563	3.6
	Growing – 30	634		631
	Growing – 45	709		619
	Yearling – 15	547		575
	Yearling – 30	541		684
	Yearling – 45	555		697
Animal age	Growing	624	18.7	604	2.1
	Yearling	548		652
Supplement level (g/kg BW^0.75)	15	539	22.9	569	2.5
	30	587		657
	45	632		658
Forage source	A	595	19.7	590	1.8
	B	632		739
	C	531		555