Literature Review ANSC 312 Grant Edwards
Getting started Critically discuss whether current grazing systems to low post grazing pasture residuals are restricting intake of dairy cows. Finding literature Library database (CAB abstracts) http://library.lincoln.ac.nz/ Google Find around 10 relevant papers and read them. Use reference list from ‘good’ papers to find more references. Decide on 2 main topics that you will cover At end of introduction, state the objectives of the review (what’s covered and what’s not covered) e.g. The purpose the review is to examine the effect of grazing residuals on DM intake and determine whether current grazing management is restricting intake.
Using table/figures Copy and paste tables/figures from the paper Create your own table using relevant data
Copy and paste
Create your own Table 1: Herbage mass (pre- and post-grazing), post-grazing height and daily herbage intake of pasture grazed by dairy cows in two grazing systems that assessed the effects of herbage allowance (Experiment 1) or grazing severity (Experiment 2). (From Mayne et al., 1987) Experiment 1 Experiment 2 Residual sward height Low Medium High s.e. mean Severe Moderate Lax Herbage mass Pre-grazing (OM/ha) 3480 3760 3730 155.3 NS 2430 2410 3940 178.9 *** Post-grazing (OM/ha) 1850 2210 2370 80.7 *** 990 1340 2590 213.9 *** Post-grazing height (mm) 42 51 59 0.9 *** 49 60 87 Daily herbage intake Period I 8.9 10.2 11.1 4.6 NS 10.22 10.85 13.02 0.505 ** Period II 6.6 9.9 10.5 2.51 NS 11.35 12.26 11.09 0.44 NS Period III 8.1 9.5 2.12 NS Overall 7.9 1.13 NS 10.8 11.5 12 0.49 NS s.e. mean = standard error of the mean NS=not significant; * = P<0.05; **=P<0.01 and ***=P<0.001
Statement Low post-grazing residuals can restrict daily dry matter intake and limit animal productivity. Example Mayne et al., (1987) found that cows grazing to high residuals (>60mm) had higher dry matter intakes (10kg OM/cow/day) than cows grazing to low residuals (<60mm; 13kg OM/cow/day) (Table 1). In a 10 day study by Lee et al., (2008) dairy cows were given the same allowance above a pre determined post-grazing height. In this case the daily dry matter intake was similar between three treatment groups (14.8 kg DM/cow/day). Mayne et al., (1987) used grazing severity and pasture allowance to achieve different post grazing residuals however Lee et al., (2008) separated these factors by having the same pasture allowance between treatment groups.
Explain Low post grazing residuals may not be the only factor contributing to restricted intakes in dairy cows. Other factors such as pasture allowance may contribute to the effects of post grazing residual on dry matter intake and animal performance.
Citing references Low post-grazing residuals can restrict daily dry matter intake and limit animal productivity. Mayne et al., (1987) found that cows grazing to high residuals (>60mm) had higher dry matter intakes (10kg OM/cow/day) than cows grazing to low residuals (<60mm; 13kg OM/cow/day) (Table 1). In a 10 day study dairy cows were given the same allowance above a pre determined post-grazing height (Lee et al., 2008) . In this case the daily dry matter intake was similar between three treatment groups (14.8 kg DM/cow/day). Mayne et al., (1987) used grazing severity and pasture allowance to achieve different post grazing residuals however Lee et al., (2008) separated these factors by having the same pasture allowance between treatment groups. Low post grazing residuals may not be the only factor contributing to restricted intakes in dairy cows. Other factors such as pasture allowance may contribute to the effects of post grazing residual on dry matter intake and animal performance.
Referencing Use the New Zealand Society of Animal Production style A study by Mayne et al., (1987) showed that.... An increase in herbage allowance corresponded to an increase in post-grazing height and an increase in dry matter intake (Mayne et al., 2003)
Referencing Brown AB, Black BC 2012. Title of paper. Name of Journal Volume: page-numbers Lee JM, Donaghy DJ, Roche JR 2008. Short communication: Effect of Postgrazing residual pasture height on milk production. Journal of Dairy Science 91: 4307-4311 Mayne CS, Newberry RD, Woodcock SCF, Wilkins RJ 1987. Effect of grazing severity on grass utilisation and milk production of rotationally grazed dairy cows. Grass and Forage Science 42: 59-72