Sunflower seeds are a safe, palatable and nutritive ingredient for ruminants. They are used as an energy source but they are particularly valued as a supplement for ensuring the correct fatty acids profile of meat and dairy products. This is because sunflower oil is rich in polyunsaturated fatty acids and conjugated linoleic acid, which have proven beneficial effects on human health (anticarcinogenic activity, anti-hypercholesterolemia and anti-fat deposition) (Peng et al., 2010; Basarab et al., 2007). Feeding sunflower seeds resulted in higher conjugated linoleic acid and C18:2 omega-6 content in milk and meat of cows, ewes, goats, steers and sheep (Yin FuQuan et al., 2009; Wyss et al., 2006; Ortiz et al., 1998b; Addis et al., 2009; Zhang et al., 2006). Sunflower seeds might also have beneficial effects on reproductive parameters in both females and males (Girginov et al., 2008; Adeel et al., 2009).
Sunflower seeds might also result in increasing lag time of degradation in the rumen and in a reduction of methane emissions (Beauchemin et al., 2009; He et al., 2005). Sunflower seeds improve rumen bacterial activity: they reduce the rumen protozoa (rumen bacteria predators) and thus increase total bacteria and subsequent bacterial amino acid flow (Ivan et al., 2004).
The energy value of sunflower seeds has not been widely studied. INRA-AFZ and NRC give ME values of 17.9 and 19.7 MJ/kg respectively (Sauvant et al., 2004; NRC, 2001). A much higher value of 21.50 MJ/kg DM was estimated in a trial with steers (Gibb et al., 2004).
Sunflower seeds can be fed raw (unprocessed). Cracking or rolling sunflower seeds prior to feeding had no advantage, as the large seed size results in cows chewing and breaking them down during rumination. Sunflower seeds should be mixed with other feeds to prevent over-selection due to their high palatability (NSA, 2012).
Feeding lactating cows with sunflower seeds provides energy and valuable fatty acids for milk quality enhancement. Sunflower seeds have been shown to increase milk quality by increasing unsaturated fatty acids in the milk and, particularly, polyunsaturated fatty acids (Yin FuQuan et al., 2009; Wyss et al., 2006; Ortiz et al., 1998b). Sunflower seeds had a positive effect on conjugated linoleic acid and omega-6 fatty acid milk content (He et al., 2005; Liu et al., 2008). In addition to their desirable effects on health, these fatty acids have positive effects on technological characteristics of milk and butter (butter spreadability, storage) as well as butter flavour (Kudrna et al., 2008; Silva Hernandez et al., 2007; Middaugh et al., 1988). However, because sunflower seeds are high in fat, large amounts of sunflower seeds in the diet may cause scouring and depress feed consumption, milk yield, and milk fat and protein content (Wyss et al., 2006; Schori et al., 2006; Mansoori et al., 2011b; Sarrazin et al., 2004). Recommended inclusion levels are thus moderate: 7.5-8% sunflower seeds in dairy diets resulted in satisfactory fatty acids profiles without depressing milk production (Mansoori et al., 2011b; Sarrazin et al., 2004).
Prepartum energy supplementation, regardless of energy source, may improve reproductive performance. Sunflower seeds included at 6.7% in the diet had positive effects on primiparous dairy cows as it decreased the interval from calving to first ovulation (Mendoza et al., 2008). Multiparous dairy cows fed sunflower seeds had a higher rate of first conception (Girginov et al., 2008; Banta et al., 2007). However, other reproductive performance such as feedlot performance and carcass characterisitics were not affected by the inclusion of sunflower seeds (Banta et al., 2007).
In dairy cows, roasting reduced DM intake, milk fat content and milk fat yield but did not affect milk production (Sarrazin et al., 2004). Heat-treated sunflower seeds could be included at up to 7.5% in the diet (Mansoori et al., 2011a). Formaldehyde treatment was beneficial to milk fat yield and milk production because of greater digestibility of dry matter and fatty acids but did not have a protective effect on polyunsaturated acids (Petit, 2003). Heat treatment had a negative effect on milk protein when sunflower seeds were incuded at 15% of the diet (Mansoori et al., 2010).
Whole sunflower seeds could be included at 15% of the diet for finishing steers replacing the same percentage of rolled barley. Sunflower seeds improved feed efficiency and decreased DM intake, but not the yield of lean meat. They decreased carcass global fat content while increasing muscle fat (Mir et al., 2008). Feeding sunflower seeds also had a positive effect on meat quality by increasing the levels of conjugated linoleic acid in both fat and muscle (Basarab et al., 2007). In heifers, whole sunflower seed seemed to improve growth efficiency (NSA, 2012). Sunflower seeds introduced in a barley-based diet prevented liver abscesses but caused energy loss in the feces because of decreasing stearate digestibility (Mir et al., 2008).
Lambs and meat sheep
Feeding lambs and meat sheep on sunflower seeds is a good way to improve nutritional quality of the meat without impairing dressing percentage or carcass characteristics (Almeida et al., 2011; Peng et al., 2010). In lambs, it increased the proportion of unsaturated fatty acids at the expense of saturated fatty acids (Macedo et al., 2008a; Peng et al., 2010). In meat ewes, sunflower seeds increased the levels of polyunsaturated fatty acids and conjugated linoleic acids (Peng et al., 2010). The inclusion of sunflower seeds at 20% of the diet did not change qualitative and morphometric characteristics of lamb carcasses (Macedo et al., 2008b).
Including sunflower seeds in lamb diets may help reducing protein supplementation: sunflower seeds added to a low protein diet yielded the same average daily gain as a high protein ration. They also increased the digestibility of high concentrate rations. Their effect on feed intake resulted in an improved feed conversion ratio (Ivan et al., 2004).
Sunflower seeds can be introduced in ewes diets at 6-10% (Peng et al., 2010; Zhang et al., 2007). Ewes supplemented on sunflower seeds had similar DM intakes and nutrient utilization as ewes fed the control diet (Zhang et al., 2007). Digestibility of DM and fatty acids was higher, particularly for oleic acid (C18:1), resulting in higher levels of long chain fatty acids in both milk and meat (Addis et al., 2009; Zhang et al., 2007; Peng et al., 2010). Supplementation with sunflower seeds had no effect on milk yield and decreased milk total solids, milk protein and milk fat contents (Zhang et al., 2006). However, the levels of unsaturated fatty acids (C18:3) and conjugated linoleic acids were greater in milk and cheese (+ 63% and + 140%, respectively) for ewes fed sunflower seeds than for ewes fed control (Addis et al., 2009; Zhang et al., 2006). The cheese composition in C18:1t11 and C18:2c9t11 fatty acids was similar for ewes fed sunflower meal and for grazing animals during the period of high quality pasture (Addis et al., 2009).
Sunflower seeds can be included at 6-10% in goat diets in order to alleviate weight loss during periods of feed scarcity (Warambwa et al., 1992). Sunflower seeds resulted in slightly lower milk yields but had a limited impact on milk fat and milk protein content. Feeding sunflower seeds to goats improved the content of long chain fatty acids in milk at the expense of short chain fatty acids, thus improving cheese quality (Zucali et al., 2007).