Abstract
Aim of study: To examine the effects of a biphasic schedule of feeding n-3 fatty acids on dairy cows.Area of the study: Isfahan, Iran.Materials and methods: 140 lactating Holstein cows were allotted at calving into two groups of 70 animals and received one of two dietary treatments: 1) saturated fatty acids (SFA, containing 80% palmitic acid) or 2) calcium salt of fish oil (CSFO, containing 16% eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA)), with an n-6/n-3 FA ratio of approximately 7 for SFA and 5 for CSFO treatments. The dietary supplements were fed to the respective groups at 240 g/head.day from 0 to 21 days in milk, and 120 g/head.day from 22 to 150 days in milk. Milk yield was recorded biweekly and milk composition was evaluated monthly. The concentration of FA in the milk and blood was determined on d-90 of the experiment in 10 cows randomly selected from each group. Reproductive indices were recorded until d-150.Main results: The CSFO supplementation did not affect average milk yield, milk composition or milk somatic cell count (SCC); however, in some weeks it decreased milk SCC (p<0.05). Plasma concentrations of palmitic acid and n-3 FA as well as milk fat concentration of EPA and DHA increased in the CSFO-fed cows (p<0.05). Feeding the CSFO decreased open days (100 vs 119 days, p<0.05), service per conception and all service conception rates (p<0.05).Research highlights: The implementation of a two-stage feeding program of n-3 FA improved reproductive variables and reduced milk SCC in dairy cows.
Highlights
Reis et al (2012) demonstrated that feeding cows with moderate quantities of poly-unsaturated fatty acids (PUFA) improves production performance as compared to feeding saturated FA (SFA)
Chemical composition of the experimental diets showed that their neutral detergent fiber (NDF), acid detergent fiber (ADF) and non-fiber carbohydrates concentrations were within the values recommended by the NRC (2001) for high-producing cows (Table 2)
Milk production and composition did not differ between treatments, but a treatment × time interaction was noted for somatic cell count (SCC), where cows on CSFO diet showed lower SCC compared to SFA cows in the first milk sampling after calving
Summary
Reis et al (2012) demonstrated that feeding cows with moderate quantities of poly-unsaturated fatty acids (PUFA) improves production performance as compared to feeding saturated FA (SFA). McFadden (2020) explored the role of saturated and unsaturated FA as bioactive signaling molecules in modulating insulin secretion and sensitivity Progresses in this field has demonstrated that the ratio of two important subclasses of FA, namely n-6 and n-3 (or alternatively omega-FA), plays a prominent role in reproduction success, embryonic survival, service per conception (Ballard & Byrd, 2018), and open days (Dirandeh et al, 2013). A strategic feeding of both subclasses of omega FA should be explored in such a way that the benefits of n-3 FA in enhancing reproduction and health coincided with the potential of n-6 FA in cyclicity resumption (Silvestre et al, 2011) The latter strategy constructs the underlying hypothesis of the present study; the objectives of this farm-scale trial, were to investigate the impacts of feeding a combination of n-6 and n-3 FA in a biphasic feeding schedule from calving to 150 days in milk (DIM) on reproduction and performance of dairy cows
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