Effect of Spring Grazing Date and Stocking Rate on Sward Characteristics and Dairy Cow Production During Midlactation

Abstract

The objective of this study was to investigate the effect of initial spring grazing date and subsequent stocking rate on sward characteristics, grazing behavior, milk yield, and dry matter intake of spring-calving dairy cows during the main grazing season. Sixty-four spring-calving Holstein-Friesian dairy cows (58 +/- 9 d in milk) were balanced and randomly assigned to 1 of 4 grazing treatments (n = 16) between April 12, and July 3, 2004. Two swards, an early-grazed (E) sward and a late-grazed (L) sward had 2 stocking rates, high and medium, imposed across them. Cows grazing the E swards were stocked at 4.5 cows/ha (E4.5) and 5.5 cows/ha (E5.5), whereas cows grazing the L sward were stocked at 5.5 cows/ha (L5.5) and 6.4 cows/ha (L6.4). Sward characteristics, grazing behavior, and grass dry matter intake (GDMI) were investigated during the second (R2) and fourth grazing rotations (R4). Total dry matter yield was greater on L swards in R2. In R2, the E swards had a greater proportion of leaf as well as a lesser stem and dead dry matter yield. During R2, organic matter digestibility and crude protein content were greater on the E sward than the L sward. Pre-and postgrazing heights were greater for the L swards in R2 and R4. In R4, there was a larger leaf allowance on the E swards. Grazing time was greater and ruminating time lesser for animals grazing the E sward in R2. During R4, intake per bite was greater for the E5.5 and E4.5 treatments. Milk and solids-corrected milk yields as well as GDMI were greater for animals grazing the E sward in both R2 and R4. The results of the present study suggest that early grazing initially had a positive effect on sward quality and structure, which resulted in improved grazing behavior characteristics, increased GDMI, and increased milk production. During R4, sward quality and structure were similar between swards; thus, differences in grazing behavior were due to divergent daily herbage allowances. These results suggest that sward structure and quality as well as daily herbage allowance are important factors that influence animal performance and grazing behavior.

Effect of perennial ryegrass (Lolium perenne L.) cultivars on the milk yield of grazing dairy cows

“…Higher levels of herbage utilisation have previously been associated with improved sward nutritive value (O'Donovan et al, 2004;Kennedy et al, 2007). However, in these studies, improved chemical composition and increased herbage utilisation were confounded with pre-grazing HM.…”

Pasture characteristics of Italian ryegrass and milk production under different management strategies

“…The extended tillers and sheaths heights were lower for LLI than for HLI swards in the first and second cycles, but did not differ in the third one. Pastures with larger proportion of leaf blades in the first grazing cycle tend to maintain this characteristic and to have better digestibility in the second grazing cycle (Kennedy et al, 2007;Curran et al, 2010), whereas the quality of forage shows a greater decrease in the next grazing cycle for pastures with larger proportion of stems and dead material close to soil surface (O'Donovan et al, 2004). In terms of post-grazing height, Curran et al (2010) found that forage quality is enhanced at subsequent grazing cycles due to lower post-grazing heights and less dead material from residual pasture left from the previous cycle.…”

“…2012 Some management strategies have been studied, mainly those involving perennial ryegrass pastures in temperate climate regions, in order to achieve an optimal herbage ingestions per cow and per hectare (Delaby & Peyraud, 2009). Among these, are the hasting date of first grazing (O'Donovan et al, 2004;Kennedy et al, 2006Kennedy et al, , 2007 and the increased defoliating frequencies with reduced intervals between grazing cycles and increasing number of cycles (McEvoy et al, 2009;Curran et al, 2010;Roca-Fernandez et al, 2011). In both cases, milk yield can increase up to 2.0 kg per cow and more than 1,300 kg ha -1 .…”

A Novel Approach to Grass–Legume Management

“…However, growing this grass as an adjacent monoculture in the same paddock has been suggested as a viable alternative, which has prompted several studies of their interactions between system components (Kennedy et al, 2007).…”