ANIM2501 Lecture Notes - Lecture 12: Livestock Grazing Comparison, Dry Matter, Ad Libitum
Pasture Quality
1. Introduction and definition
Animal production is function of:
- Pasture yield: Affected by type of pasture, climate, stocking rate and management.
- Efficiency of utilization: Affected by stocking rate and management
- Pasture quality: Energy, proteins, minerals, vitamins, absence of toxins.
- Animal factors: Breed, health, husbandry
*First three are pasture factors.
The key parameters
- Voluntary intake of dry matter
- Digestibility of dry matter
- Production closely related to intake of digestible matter
2. Measurement of pasture quality
- In vivo using animals
- In vitro using laboratory methods
- In sacco where samples are put in nylon bags and placed in the gut of cannulated (fistulated)
animals
- NRIS- Near Infrared Reflectance Spectroscopy
(A) In vitro method
- Pre-incubation of ground sample in acid pepsin
- Incubation in celulose enzyme
- DMD%= 100 x DM sample- (DM residue - DM blank) / DM sample
(B) In vivo method (animal house)
Dry matter digestibility (DMD) and voluntary intake (IV)
- Based on intake and digestion of chopped forage in metabolism pens
- Sheep normally used as smaller and more economic than cattle
- Problem is sometimes they dowan eat cause not used to that feed.
Method:
- Forages cut/dried at 70 C
- Forages chaffed to 2-5cm lengths
- Each feed fed to approx 8-10 sheep ad lib.
- Settling in period of 7-14 days, followed by measurement period of 10 days
- Feed eaten and refused measured, faeces collected daily, weighed.
find more resources at oneclass.com
find more resources at oneclass.com
0.75 is metabolizable body weight. Younger animals metabolize faster than older ones.
(B) In-vivo method (grazing animals)
- The cuticle (waxy coating) of herbage contains indigestible alkanes (saturated hydrocarbons)
- Alkane profile specific to plant species. Molecules contain different propotions of C21 to C37
atoms (finger prints). Can identify species from alkane profile.
- When animals eat, they excrete this indigestible material in faeces.
- Concentration of alkanes in faeces allows estimation of amount and composition of diets.
- Can analyse faeces using NRIS (Near Infrared Reflectance Spectroscopy)
What is NRIS?
- Enables producers to directly assess diet quality.
- The NRIS calibration equations produce predictions of pasture quality not exact quantitative
determinations.
- Mostly use faeces samples and can be used to determine:
- Dry matter digestibility (DMD)
- Dietary crude protein (CP)
- Faecal nitrogen (N) concentration
- Non-grass proportion of diet (like shrubs)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Pasture yield: affected by type of pasture, climate, stocking rate and management. Efficiency of utilization: affected by stocking rate and management. Pasture quality: energy, proteins, minerals, vitamins, absence of toxins. Production closely related to intake of digestible matter: measurement of pasture quality. In sacco where samples are put in nylon bags and placed in the gut of cannulated (fistulated) animals. Nris- near infrared reflectance spectroscopy (a) in vitro method. Dmd%= 100 x dm sample- (dm residue - dm blank) / dm sample (b) in vivo method (animal house) Dry matter digestibility (dmd) and voluntary intake (iv) Based on intake and digestion of chopped forage in metabolism pens. Sheep normally used as smaller and more economic than cattle. Problem is sometimes they dowan eat cause not used to that feed. Each feed fed to approx 8-10 sheep ad lib. Settling in period of 7-14 days, followed by measurement period of 10 days. Feed eaten and refused measured, faeces collected daily, weighed.
