Forage Particle Size
for
Dairy Cows
乳牛的芻料顆粒大小
A. F. Kertz, Ph.D., Dipl ACAN
July 2010
Advancing the Science of Animal Nutrition
Forages for Dairy Cows
乳牛的芻料
• Cows cannot digest forage fiber
乳牛不能消化芻料纖維
• But microbes in rumen have enzymes that
can
但瘤胃中的微生物有可消化纖維的酵素
• Cows “ruminate” forage particles and other
larger particles
乳牛可反芻芻料顆粒和其他較大的顆粒
Advancing the Science of Animal Nutrition
Forages for Dairy Cows
乳牛的芻料
• Rumination reduces particle size
反芻會減小顆粒大小
• Smaller particles have more surface area to increase
fermentation of forage
較小的顆粒有較多的表面積，以增加芻料的發酵
• Larger forage particles form “mat” on top of rumen
contents
在瘤胃內容物的上層，較大的芻料顆粒形成“墊層
“
Advancing the Science of Animal Nutrition
Forages for Dairy Cows
乳牛的芻料
• “mat” helps trap particles so that they are
fermented more in rumen
“墊層”有助於留住顆粒，因此顆粒在瘤胃中有
較佳的發酵
• “mat” slows flow out of rumen so digestibility is
increased
“墊層” 減慢離開瘤胃的流量，因而消化率增加
• “mat” is decreased with low forage level and
smaller forage particle size
“墊層”隨著低芻料水平和較小的芻料顆粒而減
少
Advancing the Science of Animal Nutrition
Physical Nutrition
生理營養
 Key to optimised ration digestibility is rumen function
最佳化的飼糧消化率其關鍵是瘤胃的功能
 Physical Fiber optimises rumen function through correct ration presentation
經由給予正確的飼糧，物理纖維使瘤胃有最佳的功能
Shorter fibre leads to: 較短的纖維導致：
 Dense fibre mat 緊密的纖維墊層
 Reduced rumen contractions 降低瘤胃收縮
 Reduced cud chewing 減少反芻咀嚼
 Increased passage of smaller particles
增加較小顆粒的通過
Increased concentrates leads to: 增加精料導致：
 More small particles 較多小顆粒
 Increased microbial activity 增加微生物活性
 Increased acid production 增加酸產量
 Reduced fibre digestion 減少纖維消化
 Increased health issues 增加健康問題
 Reduced feed efficiency (FCE) 降低飼料效率
Keenan TMR Mixers
Advancing the Science of Animal Nutrition
Forage Particle Size and impact upon cudding (rumination)
芻料顆粒大小以及對於反芻的衝擊
Mixed ration
混合芻料
Coarse Cut
粗碎
Medium Cut
中等
Fine Cut
粉碎
Dry matter intake Kg/day
乾物質採食量 公斤/天
22.2
22.0
22.4
Milk yield Kg/day
乳量 公斤/天
31.1
32.1
31.5
**Milk fat % 乳脂率
3.8
3.6
3.0
520
~ 8.5 hr
466
~7.5 hr
374
~ 6.25 hr
6
5.9
5.3
**Rumination (cudding)
minutes/day 反芻 分鐘/天
**Av. Rumen pH 瘤胃pH
**Lower milk fat, less rumination, and lower pH all indicate marginal acidosis
which will lead to lower intake, milk production and health problems.
較低的乳脂、較少反芻，以及較低的pH皆顯示瀕臨酸症，將導致較低的採食量、乳量和
健康的問題。
Keenan TMR Mixers
Advancing the Science of Animal Nutrition
Digestibility Varies
消化率的變異
• Average digestibility of ground corn = 80%
but variability causes range from 64 to 96 %
玉米粉的平均消化率= 80%
但變異的範圍從 64 至 96 %
• That means 20% is not digested 也就是有20% 是未消化的
• But dependent on corn color (varies), you may not see undigested
corn in the manure
但要看玉米的顏色（變動），你可能看不到糞便中未消化的玉米
• Main factors are: 主要因素為：
 accuracy in measuring digestibility 測定消化率的準確性
 particle size of corn 玉米的顆粒大小
 hybrid 雜交品種
Firkins et al. J. Anim. Sci. 79(E. Suppl.):E218–E238, 2001.
Advancing the Science of Animal Nutrition
Fatty Acid Digestibility
脂肪酸消化率
Summary of 9 Dairy Cow Studies
100
Digestability (%)
90
80
70
60
50
40
Total
C16:0
C18:0
C18:1
C18:2
C18:3
*Fat has 2.25 more energy than
protein and
carbohydrates.
Palmitic
Stearic
Oleic
Linoleic Linolenic
Advancing the Science of Animal Nutrition
Grummer and Rabelo (1999)
Alfalfa Hay—Chopped Particle Size
%
> 19 mm
18↔8 mm
< 8 mm
Alfalfa Hay Barley Silage
47
6
20
33
74
20
DDGS
0
0
100
1/3 alfalfa particles less than 8 mm—mostly leaves
which have most of protein and calcium
1/3苜蓿顆粒小於8毫米—大部分是葉子，含有很多的蛋白質和鈣
3/4 barley silage particles 18 to 8 mm—wetter and less brittle
than alfalfa hay
3/4大麥青貯料顆粒為 18 至 8 毫米— 相較於苜蓿乾草較濕
潤且較不易碎
Distillers dried grains all small particles
蒸餾乾燥穀物皆為小顆粒
Zhang et al. J. Dairy Sci. 93:3243-5253, 2010.
Advancing the Science of Animal Nutrition
Particle Size Impact
顆粒大小的影響
• Alfalfa Hay 苜蓿乾草
 Loses forage value as is chopped 當其切短即損失芻料價值
 Brittle so small stems and leaves shatter and may be lost to wind and
settling out before in TMR
易碎因此小莖和葉片會斷落，可能在開始製成TMR前隨風散失和沉底
• Wet Ensiled Forages 濕的青貯料
 Are flexible so do not shatter like alfalfa hay
柔軟的，因而不會像苜蓿乾草一般會斷落
 Provide moisture to TMR and acidity for palatability and minimizes
dryness 提供水分給TMR，且酸度能增加適口性，另外避免乾燥
Ground grains and by-products 磨碎穀物和副產物
 Most have no particle size effects 大多沒有顆粒大小的作用
Advancing the Science of Animal Nutrition
Recommendations 建議
•
•
•
•
•
•
Grind/chop forage in TMR mixer so do not lose smaller particles—especially with
alfalfa
在TMR混合器機中磨碎/切短芻料，因而不會損失較小的顆粒—特別是在苜蓿
Do NOT over chop. 6-7cm in length is desirable
不要過度切短。長度要有6-7公分
– Characteristics of TMR mixer TMR 混合機的特性
– Time and sequence of mixing 混合的時間和順序
Add water if all dry ingredients—up to 50% in Arizona study—very low humidity
需加入水，假使所有原料皆為乾的—在Arizona的研究指出加到50%—溼度很低
Particle size affects intake, digestibility, milk production and fat/protein components
顆粒大小會影響採食、消化率、乳量和乳脂/乳蛋白成分
Avoid “bare bunk disease”, have some leftovers ~2%, can feed to larger heifers
避免飼槽清空疾病，要有一些剩料約2%，剩料可餵給較大的女牛
Advancing the Science of Animal Nutrition