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Effect of dietary neutral detergent fiber on mid-infrared predicted milk constituents of non-traditional dairy sheep breeds milked on an accelerated lambing system.

N. Kochendoerfer

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06-22-2020

Abstract:

114
Effect of dietary neutral detergent fiber on mid-infrared predicted milk constituents of non-traditional dairy sheep breeds milked on an accelerated lambing system.
N. Kochendoerfer*, M. L. Thonney, D. M. Barbano. Cornell University Ithaca, NY.

The effect of replacing dietary NFC with highly digestible NDF from soy hulls (SH) on milk constituents of Finnsheep � Dorset ewes (n = 53) was tested in short and frequent 73-d lactations. The experiment was a triply replicated Latin square (3 ewe groups each with 3 pens of 4—6 animals per pen, 3 lactations, 3 diets). The diets (L-SH, M-SH, H-SH) contained 31.7, 36.3, 40.0% aNDFom and 41.3, 37.2, 31.9% NFC, respectively. Milk was weighed at each 2X milking and ~9 weekly samples across each of the 127 lactations were collected and refrigerated until analyzed. The 1170 samples were analyzed with a Fourier transform mid-infrared spectrophotometer and validated with Mojonnier ether extract, Kjeldahl, and MUN reference chemistry. Milk yield and component concentrations were regressed on DIM to obtain average concentrations for each individual lactation. The resulting data were analyzed using a model that included Square Number, Pen and Lactation within Square Number, and Diet. True protein, fat, and lactose concentrations, with means of 5.28 � 0.05, 5.91 � 0.09, and 4.81 � 0.08, respectively, were not significantly affected by level of dietary NDF. True protein, fat, and lactose yields were highest for ewes fed the M-SH diet (P < 0.05), reflecting their overall higher milk yields. Ewes fed the M-SH diet generated the highest concentrations of de novo, mixed, and preformed fatty acids per 100 g milk (P < 0.05). Lactose predicted milk yield (r2 = 0.99) and the relationship between protein and milk yield was stronger (r2 = 0.93) than the relationship between fat and milk yield (r2 = 0.75). Mixed origin fatty acids had the strongest relationship with total fat concentration (r2 = 0.71). Percentages of fatty acids that were de novo and mixed origin had means of 38.5 � 0.27, and 26.7 � 0.19, respectively, and were not affected by diet. Preformed fatty acid concentrations were highest (P < 0.05) for the M-SH diet (35.5 � 0.16). The diet with medium soyhull inclusion supported significantly higher milk and milk component yields, as well as numerically higher milk fat concentrations.

Keywords: sheep, sheep milk, NDF.