Effects of Inclusion of Schizochytrium spp. and Forage-to-Concentrate Ratios on Goats' Milk Quality and Oxidative Status

Abstract

Although the dietary inclusion level of polyunsaturated fatty acids (PUFA) and the forage: concentrate (F:C) ratio affect milk quality, their interaction has not been broadly studied. To address such gaps and limitations a two-phase trial using twenty-two dairy goats was carried out. During the first phase, both groups (20 HF n = 11; high forage and 20 HG n = 11; high grain) were supplemented with 20 g Schizochytrium spp./goat/day. The 20 HF group consumed a diet with F:C ratio 60:40 and the 20 HG-diet consisted of F:C = 40:60. In the second phase, the supplementation level of Schizochytrium spp. was increased to 40 g/day/goat while the F:C ratio between the two groups were remained identical (40 HF n = 11; high forage and 40 HG n = 11; high grain). Neither the Schizochytrium spp. supplementation levels (20 vs. 40) nor the F:C ratio (60:40 vs. 40:60) affected milk performance. The high microalgae level (40 g) in combination with high grain diet (40 HG) modified the proportions of docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and conjugated linoleic acid (CLA) and the ω3/ω6 ratio in milk, to a beneficial manner according to human health recommendation guidelines. However, the highest inclusion level of Schizochytrium spp. (40 g) and foremost in combination with the high grain diets (40 HG) induced an oxidative response as observed by the increased protein carbonyls (CP) and malondialdehyde (MDA) levels in milk and blood plasma indicating severe limitations for a long-term, on-farm application. In conclusion, the supplementation with 20 g Schizochytrium spp. and high forage diet (60:40) appears to be an ideal formula to enrich dairy products with essential biomolecules for human health without adversely affect milk oxidative stability.

Keywords: DHA; MDA; TAC; antioxidant; fatty acid; forage; grains; microalgae; rumen; starch.

Figure 1

Mean milk performance of goats fed diets with 20 g Schizochytrium spp. and two different forage to concentrate ratios (20 HF; red line and 20 HG; blue line) throughout the experimental period. Error bars represent the standard error of the means (SEM). 20 HF: 20 g Schizochytrium spp. and high forage diet (60:40); 20 HG: 20 g Schizochytrium spp. and high grain diet (40:60).

Figure 2

Mean milk performance of goats fed diets with 40 g Schizochytrium spp. and two different forage to concentrate ratios (40 HF; red line and 40 HG; blue line) throughout the experimental period. Error bars represent the standard error of the means (SEM). 40 HF: 40 g Schizochytrium spp. and high forage diet (60:40); 40 HG: 40 g Schizochytrium spp. and high grain diet (40:60).

Figure 3

Discriminant plots separating (A) the four dietary treatments (20 HF; blue, 20 HG; green, 40 HF; red, and 40 HG; pink) according to pooled data of two sampling time (21st and 42nd experimental day) on the blood plasma fatty acid profile and (B) the four dietary treatments (20 HF; blue, 20 HG; green, 40 HF; red, and 40 HG; pink) according to pooled data of two sampling time (21st and 42nd experimental day) on the milk fatty acid profile. 20 HF: 20 g Schizochytrium spp. and high forage diet (60:40); 20 HG: 20 g Schizochytrium spp. and high grain diet (40:60); 40 HF: 40 g Schizochytrium spp. and high forage diet (60:40); 40 HG: 40 g Schizochytrium spp. and high grain diet (40:60).

Figure 4

Pearson correlation of milk fatty acids of goats in four dietary treatments.

Figure 5

Discriminant plots separating (A) the four dietary treatments (20 HF; blue, 20 HG; green, 40 HF; red, and 40 HG; pink) according to pooled data of two sampling time (21st and 42nd experimental day) on the blood plasma oxidative status and (B) the four dietary treatments (20 HF; blue, 20 HG; green, 40 HF; red, and 40 HG; pink) according to pooled data of two sampling time (21st and 42nd experimental day) on the milk oxidative status. 20 HF: 20 g Schizochytrium spp. and high forage diet (60:40); 20 HG: 20 g Schizochytrium spp. and high grain diet (40:60); 40 HF: 40 g. Schizochytrium spp. and high forage diet (60:40); 40 HG: 40 g Schizochytrium spp. and high grain diet (40:60).