Nutritive merits of whole Nutrasaff safflower seed when fed to Holstein dairy cows during midlactation

Abstract

A lactation study was conducted to assess productive performance of dairy cows fed varying levels of whole Nutrasaff safflower seed (NSS), a new variety of safflower seed, and identify its impact on milk fat content and milk fatty acid (FA) composition. Fifteen Holstein dairy cows in midlactation (118 ± 38.5 days in milk) were assigned randomly to three balanced 5 × 5 Latin squares according to previous milk yield. Each period lasted 21 d with 14 d of treatment adaptation and 7 d of data collection. The cows were fed diets containing approximately 560 g/kg dry matter (DM) forage and 440 g/kg DM concentrate mixture. Within square, cows were randomly assigned to one of five dietary treatments being: whole linted-cottonseed without NSS (CS), 10 g/kg DM NSS (NSS10), 20 g/kg DM NSS, 30 g/kg DM NSS and 40 g/kg DM NSS. The NSS was added to the diets by replacing whole linted-cottonseed in the CS diet. Intake of DM, N and fiber decreased by the NSS10 diet compared to the CS diet. Increasing level of NSS inclusion linearly decreased N intake, but it linearly increased fiber intake. Digestibilities of DM and organic matter (OM) increased in the NSS10 diet compared to the CS diet, whereas they linearly decreased with increasing dietary level of NSS. Milk yield averaged 33.7 kg/d, and was similar among dietary treatments. Milk fat content linearly decreased with increasing NSS inclusion, while milk true protein and lactose contents did not differ among dietary treatments. Milk fat content was affected when NSS was included at 40 g/kg DM, with an 11% reduction. Efficiency of use of feed N to milk N increased, but milk urea N decreased by feeding the NSS10 diet compared to the CS diet, implying that NSS supplementation improved dietary N use for milk production. However, the N utilization efficiency tended to decrease ( P=0.08) with increasing NSS inclusion level, and milk urea N was not affected by level of NSS inclusion. Cis-9, trans-11 conjugated linoleic acid (CLA), and trans-10 18:1 FA linearly increased with increasing NSS inclusion level. This study demonstrates that supplementing NSS in dairy diets can be a promising means of fat supplementation to lactating dairy cows without negative impacts on lactational performance at up to 30 g/kg DM. The increased cis-9, trans-11 CLA concentration due to addition of NSS can enhance milk quality because of its potentially beneficial health effects. However, the beneficial effect of NSS was counterbalanced by an unfavorable increase of trans-10 18:1 FA.