Feed intake and production performance
The mean DM intake was 13.32, 12.84 and 13.38 kg/d in CON, SO125 and SO250 groups, respectively. There was no difference (P>0.05) in DM intake of lactating buffaloes among the dietary treatments. As free vegetable oils are rapidly released in the rumen and have subsequent potential deleterious effects on the resident microbiota, fibre digestion and DM intake. Therefore, to avoid a decrease in DM intake, the
NRC (2001) had recommended that rations for dairy cows with a maximum of 6-7% ether extract (on % DM basis). In the present study, the ether extract concentrations in the ration of lactating buffaloes were below the recommended level. Hence, there was no adverse effect of sunflower oil supplementation (125 or 250 ml/h/d) on DM intake. In agreement with the present findings, no changes in DM intake were reported in dairy cows supplemented with sunflower oil at 1.5, 3.0 and 4.5% of DM (
DeSouza et al. (2019);
Lopes et al., 2020). On the contrary to the present findings,
Kairenius et al., (2018) observed that DM intake was decreased in dairy cows fed grass silage-based diet containing 500 g/d of sunflower oil.
Dietary inclusion of sunflower oil improved milk yield by 17.9 to 20.7% (P=121), 6% FCM yield by 16.4 to 22.9% (P=177) and ECM yield by 16.0 to 23.0% (P=166) in SO125 and SO250 groups, respectively as compared to the CON group (Table 2; Fig 1). There were no differences (P>0.05) in yields of milk fat, SNF, protein and lactose due to supplementation of sunflower oil. The observed improvement in milk yield in sunflower oil supplemented groups might be due to the change in ruminal fermentation pattern leading to increased propionate production in rumen. Propionate is the most important substrate for hepatic gluconeogenesis (accounting for 60-74% total substrate), which is highly associate with milk yield in cows
(Aschenbach et al., 2010). Besides of that, glucose is a precursor of lactose, an osmotic constituent of milk, which increases water secretion and consequently milk volume (
Lei and Simoes 2021). Similar to the present findings,
Dai et al., (2011) reported significant (P<0.05) increase in milk yield (26.4
vs. 25.5 kg/d) in dairy cows supplemented with 2% sunflower oil. In contrast, no effects on milk production performance due to feeding of sunflower oil in dairy cows were reported in the earlier studies
(Silva et al., 2018; DeSouza et al. (2019);
Ferlay and Chilliard 2020). The milk composition (fat, SNF, protein and lactose) were not affected (P>0.05) among the dietary groups. Similar to the present findings,
Silva et al., (2018) and
Lopes et al., (2020) reported no effect on milk composition of dairy cows fed sunflower oil. However,
DeSouza et al. (2019) reported that there was linear decrease (P<0.05) in percentages of milk fat due to sunflower oil (1.5, 3.0 and 4.5%) supplementation. Dietary supplementation of sunflower oil had no effect (P>0.05) on feed efficiency in lactating buffaloes (Table 2). No effect on feed efficiency may be attributed to similar DM intake among the treatment groups. This is in agreement with the results of
Beauchemin et al., (2009) who found that supplementation of 3.3% added fat (on DM basis) crushed sunflower seeds in lactating cows had no effect on the feed efficiency.
Milk fatty acid profile
The results of supplementation of sunflower oil on milk fatty acids of lactating Mehsana buffaloes are given in Table 3. The short chain fatty acids (C4:0 to C10:0) and medium chain fatty acids (C12:0 to C16:0) of milk did not differed among the different dietary groups. In long chain fatty acids (> C16:0) of milk fatty acid percentages of C20:0 and C24:0 were significantly decreased due feeding of sunflower oil as compared to the CON. Supplementation of sunflower oil (125 or 250 ml/h/d) did not influenced percentages of milk saturated fatty acids, unsaturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids in lactating Mehsana buffaloes. Supplementation of sunflower oil at both the dose rate did not have any detrimental effect on milk fatty acid composition in lactating buffaloes. Milk fatty acids are mainly derived from two major sources, uptake of long-chain fatty acids from peripheral circulation and
de novo synthesis of short- and medium-chain fatty acids in the mammary gland (
He and Armentano 2011). Moreover, during the onset of lactation, the energy requirements for milk production exceed nutrient intake, and animal experience a period of negative energy balance, causing the mobilisation of long-chained fatty acids from adipose tissue and incorporation into milk fat. In agreement with the present findings,
Lopes et al., (2021) found that with supplementation of sunflower oil in dairy cows significantly reduced milk fat percentages of long chain fatty acids.
Blood metabolites
The findings of supplementation of sunflower oil on blood metabolites of lactating Mehsana buffaloes are given in Table 4. The serum concentrations of glucose, total proteins, albumin, urea, creatinine, triglycerides, ALT and AST were not affected (P>0.05) by the sunflower oil supplementation in lactating buffaloes. Lack of effect on liver enzymes ALT and AST due to feeding sunflower oil in lactating buffaloes indicates that supplementation did not have any adverse effect on liver function.
The serum level of cholesterol was 129.23, 155.10 and 164.23 mg /dL in CON, SO125 and SO250 groups, respectively. There was significant (P<0.01) increase in serum cholesterol concentration due to supplementation of sunflower oil (125 and 250 ml/d) as compared to the CON group. Vegetable oil supplementation in the diet encourages the production of lipoproteins in the intestine which is the major site of
de novo cholesterol synthesis in ruminants, thus leads to elevated levels of serum cholesterol. Similarly, earlier studies also reported that supplementation of sunflower oil in diet of dairy cows increased serum cholesterol concentration (
DeSouza et al. (2019);
Lopes et al., 2020).