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
Butterfat production - dairy cows
1 Fats & oils 2
Forages
VFA
Sugar
Rumen 1 Direct – Fats and Oils 50% of butterfat is produced directly from dietary sources i.e. rumen protected fats or bodyfat breakdown. 2
C2
Indirect - Forages and sugar 50% of butterfat is produced from the end products of rumen fermentation - volatile fatty acids (VFAs). Forage is broken down to acetate (C2) and sugars are broken down to butyrate (C4).
Planning a strategy Try to plan a nutritional strategy prior to the problem of reduced butterfat developing. Assess both the quantity and the nutrient quality of grass and review the feeds available to the cows. With this information plan a solution that fits both the situation and timing of the problem. Grass nutrients to focus on to improve milk quality: Oil – is high in polyunsaturated fatty acids which can prevent
FA>C16:0
C4
FA<C16:0 Milk fat
rumen microbes breaking down fibre into butterfat pre-cursors (C2 and C4). Fibre (NDF) – lower fibre grass passes through the rumen quicker reducing the opportunity for breakdown. Low dry matter can make the situation worse. Sugar – high sugar levels are fermented rapidly in the rumen which can reduce pH (acidosis) which, in turn, can reduces fibre breakdown.
To help improve butterfat maintain a healthy rumen and high levels of fibre digestion or supply a direct source of saturated fatty acids. The table below demonstrates problems that may arise, their timing and possible solutions.
Timing
Early season
Early season
Late season
All season
All season
Issue
Insufficient fibre
Control RFC
Heat stress, causing rumen health issues
Oversupply of oil
Mineral status
Aim for
>34% NDF >100 RI*
160-180 RFC <100 AI**
Minimise impact of heat stress
<4.5% DMI
Magnesium 0.25% DMI Salt
Solution
• Soya Bean Hulls • Sugar Beet Pulp • Monitor Grazing DMI
• Levucell • RumiBuff
• Levucell • RumiBuff
• Supply C16 fat • Butterlac
• Minimise Polyunsats
* RI Rumination Index **AI Acidosis Index
For more information contact your local ForFarmers account manager or call 0845 722 5583.
• Magnesium supplement • Rock salt