Effect of maize, rumen-protected fat and whey permeate on energy utilisation and milk fat composition in lactating goats.
Articolo
Data di Pubblicazione:
2002
Citazione:
Effect of maize, rumen-protected fat and whey permeate on energy utilisation and milk fat composition in lactating goats / L. Rapetti, G.M. Crovetto, G. Galassi, A. Tamburini, A. Sandrucci, G. Succi, G. Battelli. - In: ITALIAN JOURNAL OF ANIMAL SCIENCE. - ISSN 1594-4077. - 1:1(2002 Jan 01), pp. 43-53. [10.4081/ijas.2002.43]
Abstract:
The efficiency of utilisation of diets with different proportions of energy sources (starch, fat, lactose) was studied with three
pairs of lactating Saanen goats; the animals were fed, in a Latin square design, 3 silage-based diets containing (on DM
basis) the following energy sources: 32% maize meal (diet M); 4.7% rumen-protected fat (Megalac®) and 23.5% maize
meal (diet F); 9.8% milk whey permeate powder and 22.3% maize meal (diet W). During each of the three experimental
periods, 8 days of total collection balance trials were conducted during which goats were allocated for 72 h (three 24 h
cycles) in open circuit respiration chambers to determine methane and heat production and, hence, the energy balance.
Diet F, in comparison with diets M and W, significantly increased the milk fat content (4.13 vs 3.11 and 3.14%,
P<0.001) and the 4%-FCM yield (3367 vs 2927 and 3055 g/d, P<0.01 and P<0.05, respectively), while no relevant
changes were observed for milk protein content and yield. Energy digestibility was equal in diets F and W. Megalac®
did not decrease fibre digestibility. The partition of the gross energy intake (EI) differed significantly between diets:
diet M had lower DE (72.4 vs 74.3 and 74.3%; P<0.01) and ME (62.1 vs 64.7 and 63.5%; P<0.05) in comparison
with diets F and W, respectively. Energy lost as methane was not significantly decreased by the inclusion of rumenprotected
fat in the diet, although a trend for a reduction of methanogenesis was observed. Heat production determined
by treatment F was lower in comparison with the other treatments. This difference was almost significant
(P=0.056) when expressed as a percentage of the ME. Milk energy output increased significantly (+12%, P<0.001)
by including fat in the diet, as compared with treatments M and W: 21.4 vs 19.1 and 19.0% of the EI. The net energy
content of the protected fat was 27.94 MJ NEl/kg DM (+340% vs maize meal); its kl value resulted 0.77. The
corresponding values for whey permeate were 7.76 MJ NEl/kg DM (-5% vs maize meal) and 0.50, respectively.
Summarizing, the efficiency of energy utilization in diet M was significantly lower in comparison with the other two
diets in terms of digestibility and metabolisability, while its NEl content was similar to that of diet W. On the other
hand, diet F had a significantly higher ME (P<0.01) and NEl (P<0.05) as compared to the other two diets. Diet F
greatly influenced the fatty acid composition of the milk fat with less short (-30%) and medium (-33%) chain fatty
acids and more (+18%) long chain fatty acids. In conclusion, whey permeate and even more Megalac® can be successfully
used as feed ingredients in the diet of highly productive lactating goats, but the economical convenience
of their utilisation must be evaluated based on the market values of feedstuffs.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Dairy goat ; Energy metabolism ; Rumen-protected fat ; Whey permeate
Elenco autori:
L. Rapetti, G.M. Crovetto, G. Galassi, A. Tamburini, A. Sandrucci, G. Succi, G. Battelli
Link alla scheda completa: