Nitrogen balance of Saanen goats in early lactation fed diets with different protein : energy ratio
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Data di Pubblicazione:
2009
Citazione:
Nitrogen balance of Saanen goats in early lactation fed diets with different protein : energy ratio / L. Rapetti, S. Colombini, G.M. Crovetto, G. Galassi. ((Intervento presentato al convegno Joint Annual Meeting ADSA-ASAS tenutosi a Montreal, Canada nel 2009.
Abstract:
Aim of the experiment was to evaluate the protein:energy ratio (MP/NEl)
of the diet in early lactating goats on N balance. 8 Saanen goats were
used in two consecutive N balance trials at 8-14 (P1) and 28-34 (P2)
DIM. The dietary treatments were as follows: 56 (LOW) or 65 (HIGH)
g MP/Mcal NEl, estimated with INRA model (2007). The CP contents
of the diets were 15.1 (LOW) and 17.3% (HIGH) on DM. Both diets
had 1.69 Mcal of NEl on DM. The forages fed (DM basis) were corn
silage (28%) and dehydrated alfalfa hay (22%); in diet HIGH, soybean
meal and corn gluten meal partially substituted corn grain. 4 d after kidding,
goats were confined to metabolic cages. During each 6 d of trial,
individual DMI, milk production and total collection of excreta were
recorded. All data were statistically analyzed by GLM procedure (SAS,
2008) considering the diet and period effect and their interaction. DMI
was influenced only by period, not by dietary treatment (2.06 and 2.97
kg/d, in P1 and P2 respectively; P<0.001); milk yield had the same trend
increasing from 3.91 to 5.49 kg/d (P<0.001). Milk fat, crude protein
and casein contents (%) were affected (P<0.01) only by period (4.77
vs 3.55, 3.67 vs 3.47, 2.63 vs 2.46, for fat, CP and casein, in P1 and P2,
respectively). Milk urea nitrogen (MUN) was directly related to MP/
Mcal NEl ratio: on average 6.9 and 15.3 mg/dL with LOW and HIGH
diets (P<0.001). The higher SBM inclusion in diet HIGH determined
a higher CP digestibility (73.3 vs 67.8%, P<0.001); however, urinary
nitrogen excretion resulted higher for this diet (19.7 vs 12.9% of N
intake, P<0.01). N utilization for milk production (milk N, % of N intake)
was higher in diet LOW (42.8 vs 36.7, P<0.01) and lower in the second
period (41.4 vs 38.2, P<0.05) because of the higher DMI. These results
suggest that a MP/NEl ratio of about 60 (with approximately 16% CP
486 J. Anim. Sci. Vol. 87, E-Suppl. 2/J. Dairy Sci. Vol. 92, E-Suppl. 1
on DM), should be adequate to meet the requirements of high yielding
dairy goats during early lactation.
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Keywords:
goats ; N balance ; protein:energy ratio
Elenco autori:
L. Rapetti, S. Colombini, G.M. Crovetto, G. Galassi
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