ABSTRACT
The aim of this study was to evaluate the effect of high- or low-concentrate ratio in the present of sunflower oil (SFO) in all tested diets on rumen fermentation, nutrient utilization, and fatty acid profile in milk fat of lactating goat's. Eighteen Zaribi goats (averaged 43 kg ± 1Kg body weight) were divided into three similar groups (6 goats each) for use in the feeding trial, which lasted 90 days. A randomized complete block designs was applied. Experimental rations comprised iso-nitrogenous and iso caloric based on concentrate feed mixture (CFM) and berseem hay in three roughage to concentrate ratios as follow: 50:50(T1), 55:45(T2) and60:40(T3). The three rations were supplemented with 30 g SFO /kg of DM intake
The results showed that dry matter intake (P < 0.05) decreased with increasing the ratio of roughage by 26.9% and 41.0 % for T2 and T3 compared with T1, respectively. There were no significant differences among groups in DM digestibility, while OM and EE digestibility (P < 0.05) were higher in T1 ration (high concentrate) than both T2 and T3 rations (lower concentrate). All nutrients digestibility significantly (P < 0.05) increased with T1 (high concentrate and low roughage) than T3 (low concentrate and high roughage), while, no significant difference between T1 and T2 rations. On the other hand, TDN values did not affected by concentrate to roughage ratios. While, DCP decreased in T2 and T3 by increasing roughage ratio. High-roughage diet (T2 and T3) resulted in a lower rumen pH and higher total rumen VFA concentration, whereas, high concentrate diet increased rumen pH and decreased rumen VFA concentration. High-concentrate diet increased rumen ammonia-N (P < 0.05) and molar proportion of acetate to propionate. There were no significant differences in milk yield, as 4% fat corrected milk, among animals fed the tested rations supplemented with sunflower oil (SFO) as source of unsaturated fatty acids. The high roughage diets (T2 and T3) resulted in increase in linoleic (c18:2) and linolenic acid (c18:3) concentration by 69 and 45%, respectively compared with control (T1). Also, kids of T1 group had significant (P < 0.05) higher birth weight than other groups, while, there were no significant difference in daily gain among kids of the three groups.
In conclusion, high concentrate diet could have better milk yield and protein percentage, while have less fat % and yield, compare to high roughage diet. Suckling kids could benefit more gain with dams fed high concentrate diet. Low roughage diet also develop better fat profile in milk. However, more studies are needed to identify the best economic combination for feeding dairy goats.