The type of lipid supplement has crucial implications for forage particle size in calf starter diets

Table 6 Least square means for urinary purine derivatives in dairy calves fed starters containing alfalfa hay with different particle sizes (small vs. long particles) with different lipid supplements (SBO vs. PLF, both 2.5% DM basis) (n = 13 calves per treatment)

Item	Treatments¹				SEM	P-value²
	SP		LP			FPS	Lipid	FPS × Lipid	T	FPS × T	Lipid × T	FPS × Lipid × T
	SBO	PLF	SBO	PLF		FPS	Lipid	FPS × Lipid	T	FPS × T	Lipid × T	FPS × Lipid × T
Creatinine, mg/dL
d 41–44	120	118	111	114	8.5	0.13	0.85	0.65
d 66–69	138	133	139	143	12.7	0.26	0.94	0.26
Overall	129	126	124	128	11.0	0.73	0.84	0.26	0.004	0.068	0.93	0.64
Urine volume, L/d
d 41–44	1.21	1.25	1.31	1.27	0.079	0.289	0.953	0.470
d 66–69	1.71	1.78	1.71	1.64	0.146	0.304	0.891	0.229
Overall	1.45	1.52	1.51	1.47	0.106	0.945	0.951	0.167	0.001	0.13	0.88	0.65
Allantoin, mmol/d
d 41–44	7.79^ab	7.56^ab	6.24^c	8.28^a	0.694	0.289	0.021	0.004
d 66–69	13.1^b	15.8^ab	12.1^c	17.7^a	1.58	0.52	0.004	0.031
Overall	10.4^b	11.7^ab	9.2^c	13.0^a	1.70	0.99	0.007	0.003	0.009	0.27	0.008	0.69
Uric acid, mmol/d
d 41–44	0.73	0.76	0.88	0.79	0.022	0.101	0.454	0.462
d 66–69	1.16	1.19	1.25	1.18	0.082	0.622	0.608	0.385
Overall	0.95	0.94	1.06	0.98	0.079	0.110	0.373	0.256	0.007	0.43	0.96	0.79
Total PD, mmol/d
d 41–44	8.53^ab	8.28^ab	7.11^c	9.08^a	0.894	0.436	0.036	0.008
d 66–69	14.3^b	17.0^ab	13.4^c	18.9^a	1.73	0.51	0.003	0.042
Overall	11.4^b	12.6^ab	10.2^c	13.9^a	1.59	0.86	0.014	0.028	0.005	0.33	0.001	0.72
MPS, g/d³
d 41–44	45.6^ab	44.3^ab	38.0^c	48.5^a	2.64	0.43	0.036	0.008
d 66–69	76.8^b	91.2^ab	70.4^c	101^a	6.78	0.51	0.003	0.042
Overall	61.2^b	67.8^ab	54.9^c	74.8^a	5.90	0.86	0.010	0.023	0.005	0.33	0.001	0.72

¹Treatments: alfalfa hay provided as small particle size supplemented with soybean oil (SP-SBO); alfalfa hay provided as small particle size supplemented with palm fatty acids (SP-PLF); alfalfa hay provided as long particle size supplemented with soybean oil (LP-SBO); alfalfa hay provided as long particle size supplemented with palm fatty acids (LP-PLF)
²Statistical comparisons: Forage particle size (FPS) = small versus long particle sizes; Lipid = soybean oil versus palm fatty acids; FPS × Lipid = interaction between alfalfa hay particle sizes and supplemental lipid; T = time; FPS × T = forage particle size × time; Lipid × T = lipid source × time; FBS × Lipid × T = forage particle size × lipid source × time
³Microbial protein synthesis (MPS) was estimated from urinary purine derivatives (PD) excretion based on Chen and Gomes [33] as MPS (g/d) = 70 × PD (mmol/d)/(0.85 × 0.116 × 0.83 × 1,000) × 6.25
^a−cDifferent small letters indicate differences of a variable within one period (interaction FPS × Lipid; P ≤ 0.05)

ISSN: 2049-1891