FEEDING
FOCUS May 2018 • Issue 31
Managing butterfat levels at grass Butterfat level in milk can see an annual decrease in spring and early summer as cows are turned out onto lush, fresh grass. With constituent levels playing an important role in many milk contracts, supporting butterfat production nutritionally makes good sense financially.
Fresh grass in spring is nutritionally different to both fresh grass later in the season and grass silage. The high oils and sugars in spring grass, combined with a low fibre content, affect butterfat production in cows with grass in their diet. However, this years’ early seasons grass analysis is giving a different profile with higher fibre (NDF), lower sugar and very high oil levels which will be an unpredictable mix for butterfat.
Table 1. Forage quality changes across grass and silage Grass Silage 2017 Av
Early Season Fresh Grass (Mar-Jun)
Late Season Fresh Grass (Jul-Oct)
Dry Matter (%)
31.2
18.0
18.0
Protein (%DM)
14.4
24.0
21.0
ME (MJ/Kg DM)
10.8
12.2
11.2
Sugar (%DM)
6.9
8.5
6.0
NDF (%DM)
48.4
39.0
45.0
Oil (%DM)
2.5
4.5
4.5
MELK (‘/Kg DM)
976
910
925
TDP (g/Kg)
57
110
100
RFC (g/Kg)
177
180
130
MELK - More Energy for the Lactating Cow - True energy available to the cow for milk production. TDP - True Digestible Protein - The combination of microbial protein and protein that isn’t degraded in the rumen. This is used by the cow for maintenance and production. RFC - Rapidly Fermentable Carbohydrate - Starch, sugar, fibre, fermented in the rumen (< 2 hrs), plus silage fermentation products (lactic acid).
Milk Quality Challenge - butterfat 4.20 4.15
3.40
Nutritional solution
4.10
3.35
4.05 4.00
3.30
3.95 3.90
3.25
3.85 3.80
3.20
3.75 3.70
Apr
May
Jun
Jul
Aug
Sep
Butterfat (%)
Oct
Nov
Dec
Protein (%)
Jan
Feb
Mar
3.15