Average daily gain rates determine eye muscle area and rump fat depth of beef heifers

Figures & data

Table 1. Feeding management systems during the study period.

	Feeding management systems
Period	FS1 (n = 9)	FS2 (n = 8)	FS3 (n = 9)	FS4 (n = 16)
16 Apr 2013 to 17 July 2013
Autumn to winter	All heifers received supplement^a at 1.5% BW three times weekly and grazing for 14 days on Pennisetum americanum, for 31 days on Brachiaria decumbens, and for 47 days Avena strigosa Schreb.
18 July 2013 to 7 Nov 2013
Winter to spring	No supplement and grazing on a ryegrass pasture	0.5% cracked corn relative to BW and grazing on a ryegrass pasture	1.0% cracked corn relative to BW and grazing on a ryegrass pasture	1.5% cracked corn relative to BW and grazing on a ryegrass pasture
08 Nov 2013 to 1 Jan 2014
Spring to summer	All heifers grazed on natural pasture with 12% BW pasture allowance
02 Jan 2014 to 25 Feb 2014
Summer	All heifers grazed on Pennisetum americanum

FS1: feeding system 1; FS2: feeding system 2; FS3: feeding system 3; FS4: feeding system 4; BW: body weight.

^a supplement: consisting of 87% cracked corn, 10% soybeans and 3% mineral salt with 80 g phosphorus/kg and containing 17% crude protein and 79% total digestible nutrients.

Table 2. Diet nutrient density during the evaluation period.

		Bromatological composition
Feed	Year	DM, %	TDN, % of DM	CP, % of DM	ME, Mcal/kg of DM
Millet (Pennisetum americanum)
April	2013	25.40	60.22	10.01	2.17
January	2014	18.76	63.43	17.04	2.29
February	2014	21.65	63.35	12.96	2.29
Brachiaria decumbens
May	2013	43.72	53.67	5.13	1.94
Black oats (Avena strigosa Schreb)
June	2013	14.75	63.79	23.06	2.30
July	2013	14.76	63.78	23.34	2.30
Ryegrass (Lolium multiflorum Lam)
July	2013	15.55	60.30	22.98	2.18
August	2013	14.23	57.63	25.82	2.08
September	2013	18.30	55.53	23.78	2.00
October	2013	21.36	55.70	18.80	2.01
November	2013	32.23	44.80	17.04	1.62
^aNatural pasture
November	2013	34.30	54.10	7.50	1.95
December	2013	41.60	53.80	7.00	1.94
^bSupplement	–	75.67	79.00	17.00	3.04
^cCracked corn	–	87.91	86.22	9.05	3.35

DM: dry matter; TDN: total digestible nutrients; CP: crude protein; ME: metabolizable energy.

^a The main species that conform the natural pasture of the Brazilian pampa biome are: Paspalum notatum (25.73%), Andropogon lateralis (9.73%), Paspalum paucifolium (9.69%), Axonopus affinis (6.60%), Eryngium horridum (3.98%) and other species (44.27%).

^b Supplement consisting of 87% corn, 10% soybeans and 3% mineral salt with 80 g phosphorus/kg.

^c Corn used in FS2, FS3 and FS4, from July to November in grazing of the ryegrass pasture.

Table 3. Descriptive summary of body composition of beef heifers submitted to FS1, FS2, FS3, FS4 feeding systems with different periods at the time of ultrasound evaluation (0, 77, 140, 189, 244 and 315 days).

	Feeding management systems
Variable	FS1 (n = 9)	FS2 (n = 8)	FS3 (n = 9)	FS4 (n = 16)
	Mean	Mean	Mean	Mean	RMSE
ADG, kg/day
0 days	0.000	0.000	0.000	0.000	–
77 days	−0.079	0.169	0.009	0.153	0.13
140 days	0.619	0.734	0.789	0.832	0.13
189 days	0.939	1.084	1.022	1.037	0.13
244 days	0.464	0.598	0.568	0.658	0.13
315 days	0.242	0.133	0.208	0.173	0.13
Longissimus muscle area, cm^2
0 days	51.03	47.67	53.01	53.13	4.35
77 days	46.51	41.48	46.15	45.17	4.43
140 days	46.07	43.64	50.79	49.35	7.07
189 days	46.06	46.71	49.73	50.49	3.56
244 days	45.84	51.48	55.68	52.17	6.78
315 days	41.53	45.59	50.17	51.70	3.80
Rump fat depth, mm
77 days	4.71	3.60	4.18	4.37	1.35
140 days	3.79	3.22	4.62	4.73	1.47
189 days	3.85	3.89	5.70	5.32	1.60
244 days	3.49	3.94	5.29	5.88	0.62
315 days	2.59	4.11	3.72	4.85	1.69
Back-fat thickness, mm
0 days	4.68	3.84	4.08	4.24	1.18
77 days	3.16	2.99	3.01	3.47	1.86
140 days	2.58	2.81	3.11	3.17	1.73
189 days	3.26	4.13	4.29	4.55	0.81
244 days	2.27	3.42	3.94	4.33	1.36
315 days	1.24	2.44	1.98	3.17	1.00

FS1: feeding system 1; FS2: feeding system 2; FS3: feeding system 3; FS4: feeding system 4; RMSE: root mean square error; ADG: average daily gain.

Table 4. Mixed model estimates for ADG, age and intercept associated with body composition of 42 beef heifers.

	Longissimus muscle area			Rump fat depth			Back-fat thickness
Dependent variable	Solution^a	SEM	p value	Solution	SEM	p value	Solution	SEM	p value
ADG, kg/day	5.07370	1.902	<.01	1.099600	0.533	.04	0.146700	0.436	.73
Age, days	0.06919	0.022	<.01	0.011350	0.007	.11	0.009896	0.005	.08
Intercept	25.76170	11.377	.02	0.005183	3.567	.99	−0.274600	2.787	.92

ADG: average daily gain.

^a Solution is the estimate from the fixed effect (ADG and age) in the mixed model analysis for Longissimus muscle area, Rump fat depth and Back-fat thickness.

Figure 1. Effect of average daily gain (ADG) and age on longissimus muscle area. ULMA: longissimus muscle area.

Figure 2. The relationship between average daily gain (ADG) and rump fat depth. URFD: rump fat depth.