Effect of shading strategies on intake, digestibility, respiratory rate, feeding behaviour, and performance of feedlot-finished Nellore bulls in the semi-arid region of Brazil

Figures & data

Table 1. Chemical composition of the diet used during the experimental period.

Item^a	Diet
	Proportion, g/kg
Corn silage	428.1
Silage of rehydrated corn grain	243.1
Ground corn	248.8
Soybean meal	42.1
Protein mineral mix^b,c	37.9
	Composition, g/kg
Dry matter	590.60
Ash	48.70
Crude protein	118.90
Ether extract	4.80
Neutral detergent fibre	229.90
Acid detergent fibre	129.20
Lignin	65.90
iNDF	93.90
Total carbohydrates	748.90
Non-fibrous carbohydrates	519.00
Total digestible nutrients*	782.40
Net energy (maintenance), Mcal/day	5.60
Net energy (gain), Mcal/day	6.25

^a Nutrient on a dry basis (grams per liter) – DM – dry matter; iNDF – insoluble neutral detergent fibre. *National Research Council (NRC) (2016).

^b Composition of the Protein mineral core: Ground corn 50%, 18% urea cattle, 7% white salt, 9% Premix, 16% calcitic limestone.

^c Premix mineral levels: phosphorus (160 g/kg); magnesium (15 g/kg); sulphur (70 g/kg); sodium (0 g/kg); copper (2,340 mg/kg); manganese (1,800 mg/kg); zinc (8,660 mg/kg); iodine (173 mg/kg); cobalt (138 mg/kg); selenium (45 mg/kg); fluorine (max) (2,656 mg/kg) and sodium monensin (6,000 mg/kg).

Table 2. Composition of ingredients used in the animals' diet during the experiment.

Item	Composition, %
	Corn silage	Silage of rehydrated corn grain	Ground corn	Soybean meal	Protein mineral mix
Dry matter	34.51	67.19	88.84	90.01	92.37
Ash	4.97	0.81	1.68	6.92	45.00
Crude protein	7.22	7.78	9.72	50.08	55.09
Ether extract	3.30	3.71	3.76	2.69	1.88
Neutral detergent fibre	46.74	8.57	15.82	19.21	7.91
NDFap	44.03	7.42	14.21	11.04	7.11
Acid detergent fibre	32.21	3.18	3.84	8.63	1.92
Lignin	12.92	1.25	1.37	1.73	0.69
Total carbohydrates	80.51	84.71	84.58	41.29	42.29
Non-fibrous carbohydrates	33.77	76.14	69.92	26.82	34.96
Total digestible nutrients	64.73	84.79	81.34	73.00	68.50
Indigestible neutral detergent fibre	18.19	3.66	3.73	1.91	1.86

NDFap: neutral detergent fibre corrected for ash and protein.

Table 3. Ruminal kinetics of the dry matter of the ingredients and the experimental diet.

Item	Corn silage	Silage of rehydrated corn grain	Diet	SEM
Fraction a, %	25.74	39.22	35.68	0.41
Fraction b, %	43.08	46.27	43.16	1.83
Degradation rate c, %/h	3.35	3.34	3.34	0.14
Colonisation time, h	5.08	7.06	6.73	0.37
Potential degradability, %	68.83	85.50	78.84	1.90
Effective degradability, k = 2%	52.58	68.00	62.68	1.35
Effective degradability, k = 5%	42.93	57.65	52.97	1.00
Effective degradability, k = 8%	38.40	52.78	48.39	0.81
Undegradable fraction, %	31.16	14.50	21.15	1.90

SEM: standard error of the mean; k: passage rate digesta (AFRC 1993).

Table 4. Means (minimum–maximum) of the climatic variables during the experimental period.

Item	Sun	Shading		SEM	p Value
		Artificial	Natural
Air temperature, °C	31.0 a (18.10–48.00)	30.3 ab (18.60–46.00)	29.9 b (19.90–41.30)	0.29	.02
Relative humidity, %	40.9 b (11.40– 58.80)	50.9 a (14.30–95.00)	39.2 b (15.40–71.00)	0.71	<.01
Black globe temperature, °C	54.4 a (17.50–101.85)	42.6 b (18.80–96.09)	30.4 c (19.90–45.00)	0.85	<.01
Wind speed, m/s	2.6 b (0.0–4.50)	3.2 a (0.0–4.00)	3.0 a (0.0–4.50)	0.15	.01
Radiant thermal load, W m^–2	447.5 a (337.66– 619.08)	442.8 a (329.73–595.02)	429.2 b (348.14–536.30)	2.43	<.01
BGHI	79.5 a (63.54–100.24)	79.3 ab (64.42–95.99)	76.8 b (65.98–90.89)	0.37	<.01

Means followed by same letter in the line does not differ by Tukey’s test (p < .05).

BGHI: Black globe temperature and humidity index; SEM: standard error of the mean; p: probability.

Figure 1. Respiratory rate (± standard error of the mean for each treatment) in Nellore cattle finished in feedlot on different shading strategies in the pen and times throughout the day (interaction between assessment strategies and times: p = .18).

Figure 2. Respiratory rate (± standard error of the mean for each treatment) of Nellore cattle finished in feedlot on different shading strategies in the pen and times throughout the day (interaction between assessment strategies and times: p = .18).

Table 5. Intake and digestibility of nutrients in Nellore cattle finished in feedlot on different shading strategies in the pen.

Item^a	Sun	Shading		SEM^b	p Value^c
		Artificial	Natural
Intake, kg/day
Dry matter	7.39 b	7.77ab	8.67 a	0.34	.03
Crude protein	0.87 b	0.90 b	1.06 a	0.04	<.01
Ether extract	0.49 b	0.62 a	0.70 a	0.02	<.01
Neutral detergent fibre	1.65 b	1.85 ab	1.96 a	0.07	.02
Non-fibrous carbohydrates	3.71 b	4.19 ab	4.45 a	0.18	.02
Total digestible nutrients	5.63 b	6.07 ab	6.81 a	0.26	.01
iNDF	0.68 b	0.72 ab	0.83 a	0.03	.01
Intake, % BW
Dry matter	2.51 b	2.64 ab	2.95 a	0.11	.04
Crude protein	0.29 b	0.30 b	0.36 a	0.01	.01
Ether extract	0.17 b	0.21 a	0.24 a	0.00	.00
Neutral detergent fibre	0.56 b	0.63 ab	0.67 a	0.02	.02
Non-fibrous carbohydrates	1.26 b	1.42 ab	1.51 a	0.06	.02
Total digestible nutrients	1.92 b	2.06 ab	2.31 a	0.09	.01
iNDF	0.23 b	0.24 ab	0.28 a	0.01	<.01
Digestibility, g/kg
Dry matter	554.4 c	573.0 b	614.6 a	59.0	<.01
Crude protein	425.5 c	510.9 a	443.9 b	11.0	<.01
Ether extract	882.7 a	849.2 b	810.6 c	4.0	<.01
Neutral detergent fibre	574.2 a	532.1 b	477.1 c	59.0	<.01
Non-fibrous carbohydrates	750.9 b	794.0 a	789.3 a	17.0	<.01
Total digestible nutrients	480.3 b	542.1 a	516.5 b	10.0	<.01

^aMeans followed by same letter in the line does not differ by Tukey test (p < .05). BW: body weight.

^bSEM: standard error of the mean.

^cp: probability.

Table 6. Ingestive behaviour of Nellore cattle finished in feedlot on different pen shading strategies.

Item^a	Sun	Shading		SEM^b	Period (days)				SEM	p Value^c
		Artificial	Natural		1	8	15	22		Shading	Period	Shading × per
Feeding
hours/day	2.11 ab	2.66 a	2.00 b	0.16	2.05 a	2.06 a	2.24 a	2.68 a	0.19	0.02	0.08	0.37
min/kg DM	13.97 ab	18.85 a	13.67 b	1.27	19.43	16.41	15.06	15.10	1.47	0.02	0.13	0.42
min/kg NDFap	67.68 b	88.86 a	60.29 b	5.55	84.69	71.63	65.77	67.01	6.41	<0.01	0.15	0.43
Rumination
hours/day	4.39 b	5.05 b	6.56 a	0.22	5.86 a	5.58 ab	5.13 ab	4.77 b	0.25	<0.01	0.02	<0.01
min/kg DM	35.08 b	35.68 b	45.53 a	2.13	43.03 a	40.77 a	36.54 a	34.72 a	2.46	<0.01	0.08	<0.01
min/kg NDFap	139.90 b	168.15 b	200.78 a	9.16	186.11 a	176.22 a	162.38 a	153.72 a	10.57	<0.01	0.15	<0.01
Resting
hours/day	17.48 a	16.22 b	15.42 b	0.26	15.37 b	16.17 ab	16.8 a	17.16 a	0.30	0.00	0.00	<0.01
Chewing
number/bolus	57.79 a	51.99 b	55.68 ab	1.22	53.06 a	53.88 a	57.23 a	56.44 a	1.41	0.01	0.13	<0.01
Total, hours/day	6.51 b	7.71 a	8.57 a	0.26	8.54 a	7.82 ab	7.2 a	6.83 b	0.30	<0.01	<0.01	<0.01
seconds/bolus	53.91 a	49.51 b	54.49 a	1.02	52.06 a	52.57 a	53.61 a	52.33 a	1.18	<0.01	0.81	<0.01

^aMeans followed by same letter in the line does not differ by Tukey test (p < .05). DM – dry matter; NDFap: neutral detergent fibre corrected for ash and protein.

^bSEM: standard error of the mean.

^cp: probability.

Table 7. Ingestive behaviour of Nellore cattle finished in feedlot on different shading strategies in the pen.

Item^a	Sun	Shading		SEM^b	Period (days)				SEM	p Value^c
		Artificial	Natural		1	8	15	22		Shading	Period	Shading x Per
Number of periods (n/day)
Feeding	4.45 b	7.1 a	6.65 a	0.40	6.80 a	5.00 b	6.00 ab	6.46 ab	0.46	<0.01	0.05	<0.01
Rumination	8.35 c	11.95 b	17.3 a	0.56	12.13 a	12.06 a	13.06 a	12.86 a	0.65	<0.01	0.62	<0.01
Idle	18.75 b	23.05 a	23.4 a	0.65	22.53 ab	20.66 bc	24.2 a	19.53 c	0.75	<0.01	0.00	<0.01
Duration of periods (min)
Feeding	29.21 a	25.45 ab	18.73 b	2.26	24.94 ab	31.00 a	22.87 ab	19.04 b	2.61	0.01	0.02	0.03
Rumination	32.63 a	26.66 b	23.76 b	1.21	30.04 ab	32.59 a	25.00 bc	23.10 c	1.40	<0.01	<0.01	<0.01
Idle	60.81 a	43.77 b	40.65 b	3.10	41.32 b	48.7 ab	44.54 b	59.09 a	3.58	<0.01	0.01	<0.01
Feed efficiency
g DM/h	4278.7 a	3576.5 a	4778.1 a	368.7	3288.3 b	4268.2 ab	4297.8 ab	4990.0 a	425.7	0.08	0.06	0.24
g NDFap/h	1073.1 a	758.9 b	1083.7 a	86.9	754.6 b	978.8 ab	987.2 ab	1167.1 a	100.4	0.02	0.05	0.22
Rumination efficiency
Bolus/day	300.1 c	374.7 b	439.6 a	18.1	416.1 a	379.7 ab	356.2 ab	333.8 b	20.9	<0.01	0.05	<0.01
g DM/h	2131.7 a	1741.5 b	1422.6 b	100.9	1492.3 b	1613.2 ab	2042.7 a	1912.7 ab	116.5	<0.01	0.01	<0.01
g NDFap/h	534.6 a	369.5 b	322.6 b	24.3	339.6 c	366.9 bc	482.3 a	446.9 ab	28.1	<0.01	<0.01	<0.01

^aMeans followed by same letter in the line does not differ by Tukey’s test (p < .05). DM: dry matter; NDFap: neutral detergent fibre corrected for ash and protein.

^bSEM: standard error of the mean.

^cP: probability.

Table 8. Productive performance and efficiency of Nellore cattle finished in feedlot on different shading strategies in the pen.

Item	Sun	Shading^a		SEM^b	p Value^c
		Artificial	Natural
Initial body weight, kg	293.72	294.70	292.33	1.85	.64
Final body weight, kg	436.06 b	439.42 ab	451.30 a	4.16	.05
Average daily gain, kg/day	1.41 b	1.43 b	1.55 a	0.03	.02
Feed efficiency, gain/kg DM	0.190	0.183	0.179	<0.01	.21
Hot carcase weight, kg	246.21 b	250.86 ab	254.02 a	2.78	.09
Hot carcase yield, %	56.63	57.11	56.31	0.48	.42
Carcase transfer, %	70.35	70.34	68.34	1.39	.63

^aMeans followed by same letter in the line does not differ by Tukey’s test (p < .05). DM: dry matter.

^bSEM: standard error of the mean.

^cP: probability.

National Research Council (NRC). 2016. Nutrient requirements of beef cattle. 8th ed. Washington (DC).: National Academies Press.

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