Effect of fat and forage sources on performance, ruminal fermentation, and blood metabolites in dairy calves

In recent years, researchers have focused to find out the best dietary composition to provide maximum performance and health for the animal. Therefore, providing suitable nutritional conditions is aimed to improve the growth performance of calves. There are reports of the use of dietary fatty acids to alter growth performance as well as the immune response in suckling calves. Using a fat source is suggested as a way to improve energy and improve calf growth performance. However, the relationship between the level of forage consumption and the type of fat source in infant calves is not well understood. Therefore, a study was designed and conducted to evaluate the effects of fat source with or without alfalfa hay forage in the starter diet on performance, nutrient digestibility, and blood and rumen parameters of Holstein dairy calves.

This experiment with 40 newborn Holstein calves with a mean age of 3 days and a mean weight of 39 ± 1.8 kg with 4 treatments and 10 replications was a factorial arrangement in a completely randomized design. Experimental treatments were included: 1) starter diet containing soybean oil supplement without alfalfa; 2) starter diet containing soybean oil supplement with 15% alfalfa; (3) starter diet containing palm oil supplement without alfalfa; 4) starter diet contained palm oil supplement along with 15% alfalfa hay. Daily starter intake and 10-d intervals body weight were recorded and the feed conversion ratio was calculated for each group. To determine blood parameters on day 36 of experiment, blood samples were taken from the jugular vein. Apparent digestibility of nutrients (organic matter, dry matter, NDF, crude protein and ether extract) was measured using acid-insoluble ash as an internal marker.

The results showed that feeding alfalfa hay along with soybean oil could negatively affect the starter consumption, average daily gain and final weight of suckling calves. Thus, the lowest starter consumption, daily gain and final weight were found when soybean oil was fed with alfalfa hay. Dry matter intake (milk + starter) and feed efficiency did not be affected by oil, alfalfa forage and their interactions. The results showed that the digestibility of organic matter in the treatment containing soybean oil with alfalfa was the lowest (P < 0.05). The highest digestibility is related to the treatment of palm oil with alfalfa and the lowest amount is found for soybean oil with alfalfa. The highest concentration of ammonia nitrogen was for calves receiving soybean oil with alfalfa and the lowest amount was related to the treatment of palm oil with alfalfa (P <0.05). The results showed that alfalfa, oil and alfalfa and oil interaction had a significant effect on short chain fatty acid concentration (P <0.05). Rumen pH, and acetate, propionate concentrations and acetate to propionate ratio and short chain fatty acids were not affected by alfalfa, oil and their interactions. Oil supplementation and the interaction could have a significant effect on blood concentrations of glucose, insulin and beta-hydroxybutyrate (P <0.05). While soybean oil, alfalfa and the interaction of oil and alfalfa did not have significant effect on other metabolites.

It can be concluded that despite the level of forage in the starter diet, soybean oil supplementation compared to the diet containing palm oil reduced performance, nutrient digestibility and also impaired ruminal fermentation. Simultaneous feeding of soybean oil and alfalfa forage had a negative effect on feed intake and performance of dairy calves, and on the other hand, when consuming forage during the pre-weaning period of calves, the use of palm oil is more advisable rather than soybean oil.