Increased concentration of water‐soluble carbohydrate in perennial ryegrass (Lolium perenne L.): milk production from late‐lactation dairy cows

Abstract

Eight multiparous Holstein±Friesian dairy cows in late lactation were used to investigate the potential of using perennial ryegrass with a high concentration of watersoluble carbohydrate (WSC) to increase the ef®ciency of milk production. After a pretreatment period on a common pasture, the cows were each given ad libitum access to one of two varieties of zero-grazed grass continuously for 3 weeks. Treatments were: high sugar (HS), an experimental perennial ryegrass variety bred to contain high concentrations of WSC; or control, a standard variety of perennial ryegrass (cv. AberElan) containing typical concentrations of WSC. The two grass varieties were matched in terms of heading date. All animals also received 4 kg day ±1 standard dairy concentrate. Grass dry matter (DM) intake was not signi®cantly different between treatments (11á6 vs. 10á7 kg DM day ±1 ; s.e.d. 0á95 for HS and control diets respectively), although DM digestibility was higher on the HS diet (0á71 vs. 0á64 g g ±1 DM; s.e.d. 0á23; P < 0á01) leading to higher digestible DM intakes for that diet. Milk yield from animals offered the HS diet was higher (15á3 vs. 12á6 kg day ±1 ; s.e.d. 0á87; P < 0á05) and, although milk constituent concentrations were unaffected by treatment, milk protein yields were signi®cantly increased on the HS diet. The partitioning of feed N was signi®cantly affected by diet, with more N from the HS diet being used for milk production (0á30 vs. 0á23 g milk N g ±1 feed N; s.e.d. 0á012; P < 0á01) and less being excreted in urine (0á25 vs. 0á35; s.e.d. 0á020; P < 0á01). In a separate experiment, using the same grasses harvested earlier in the season, the fractional rate of DM degradation, measured by in situ and gas production techniques, was higher for the HS grass than for the control. It is concluded that increased digestible DM intakes of the HS grass led to increased milk yields, whereas increased ef®ciency of utilization of the HS grass in the rumen resulted in the more ef®cient use of feed N for milk production and reduced N excretion.

The effect of dietary water soluble carbohydrate to nitrogen ratio on nitrogen partitioning and isotopic fractionation of lactating goats offered a high-nitrogen diet

“…The relatively small and non-significant dietary effect on NUE contrasted with results from cows fed a diet of around 3.2% N with elevated WSC in the diet, which showed improvement in NUE (Miller et al, 2001). In this study, the proportion of NI excreted in urine (UN/NI) was high (on average >48%; Table 3) compared with results from lactating dairy cows studies (Miller et al, 2001;Moorby et al, 2006).…”

“…Results from feeding cows on 3.2% dietary N (in the DM) showed that it was possible to decrease UN/FN by around 27% (Miller et al, 2001). Such change of N excretion was achieved either through increasing FN, as a function of increasing DMI or decreasing UN, as a function of increasing rumen microbial protein synthesis (Miller et al, 2001). Our goats were fed high dietary N (on average 4.5% of DM) and high WSC (on average 26.9% of DM), and there was no effect on UN/FN (Table 3).…”

Managing variations in dairy cow nutrient supply under grazing

“…In Wales, the potential of using perennial ryegrass with enhanced levels of water-soluble carbohydrates (WSC) was investigated in dairy cows using experimental perennial ryegrass varieties bred to contain a high concentration of WSC (Miller et al, 2001;Moorby et al, 2006). The concept is that provision of readily available energy can have a significantly positive influence on N utilisation efficiency and animal performance.…”

Testing water-soluble carbohydrate QTL effects in perennial ryegrass (Lolium perenne L.) by marker selection

“…Perennial ryegrass (Lolium perenne L.) is the most widely used species (Burgon et al 1997) and, as feed costs can make up as much as 35% of the total production cost (Nix 2009), the nutritional value of this fodder has a major impact on the eYciency and proWtability of animal production systems. It is important that ruminant feeds provide the animal with an easily fermentable source of energy to the rumen (Miller et al 2001) and carbohydrates generally provide this. However, the energy content of grass forages can sometimes be rather low for eYcient fermentation in the rumen and Miller et al (2001) showed experimentally that feeding grass cultivars containing a high water-soluble carbohydrate (WSC) content gave rise to increased milk and meat production.…”

“…It is important that ruminant feeds provide the animal with an easily fermentable source of energy to the rumen (Miller et al 2001) and carbohydrates generally provide this. However, the energy content of grass forages can sometimes be rather low for eYcient fermentation in the rumen and Miller et al (2001) showed experimentally that feeding grass cultivars containing a high water-soluble carbohydrate (WSC) content gave rise to increased milk and meat production. Furthermore, their study demonstrated that the high sugar content of these cultivars also reduced nitrogen partitioning into urine and thus can help to lower ammonia emissions to the environment.…”