By Charlotte Westwood, Veterinary Nutritionist, PGG Wrightson Seeds
“Chicory or bulb turnips, which is the better feed for lactating dairy cows?” A recent dairy grazing study has delivered insights and information around feeding summer crops to cows.
To help understand the farm system fit for chicory and turnips, during summer 2020 PGG Wrightson Seeds commissioned a large dairy grazing study run on a commercial dairy farm near Huntly. Two herds were managed separately and milked into twin dairy vats. Data collected included kg of dry matter (DM) of each crop consumed per hectare (ha), cow body condition score (BCS) and milk responses by cows fed either turnips or chicory.
Picture 1.0: Puna II Chicory
Puna II chicory (16 ha) and Barkant® and Cleancrop™ bulb turnips (2.3 ha; 1.5ha as Barkant and 0.8 ha as Cleancrop turnips) were established during spring 2019. Starting early December 2019, all cows grazed chicory before being split into two study herds. From mid-January 2020, 250 cows continued grazing chicory and 150 cows transitioned to turnips. Cows remained on each crop until late February 2020 at which time turnip cows returned to chicory. All cows remained on chicory until late March when chicory was sprayed out for regrassing.
Picture 2.0: Cleancrop summer bulb turnip
The cows diet
After allowing for wastage during grazing, cows consumed 4kgDM/cow/day of either chicory or turnips. The remainder of the diet was the same for each herd and included maize silage, grass silage, palm kernel extract (PKE), pasture and waste onions and potatoes.
Milk data and body condition score
Herds were milked once daily, and daily bulk milk volume, milk protein %, milk fat %, lactose and somatic cell counts; SCC, and fat evaluation index (FEI) and milk fatty acids were measured for each herd with milk from each herd collected into separate vats. Weekly herd testing provided milk volume and milk component information for individual cows. A proportion of cows from each herd were body condition scored at the start and end of the study.
Feed supply curve differed for chicory and turnips
Turnip DM yield averaged 12.2 tDM/ha over 2.3ha, providing 150 cows with 4kgDM/cow/day of turnips (consumed) for six weeks from mid-January until late February 2020. In contrast, Puna II chicory yielded just over 7.5 tDM/ha between establishment and spray out. The unexpectedly low chicory DM yield reflected hot, dry drought conditions during summer 2020.
- Chicory is useful when a lower daily amount of summer crop is required over a longer period of time. In contrast, turnips are useful to ‘feedbank’ crop accumulated before late December, pushing feed ahead to be eaten for a shorter period of time during mid to late summer. During drought years, slow chicory regrowth may not adequately match feed demand.
- A relatively larger area of chicory than turnips is needed to support herd feed demands (DairyNZ Farmfact “Chicory Management” 1-72b; DairyNZ Farmfact “Turnips-Growing a High Yielding Crop” 1-62). Regrassing costs associated with returning relatively larger areas of chicory to pasture will increase costs associated with chicory crops. Additionally, opportunity costs of pasture foregone are greater when larger areas of chicory are removed from the grazing round.
Figure 1.0: Feed supply curve of Turnips and Chicory over the duration of the trial
Cow body condition score
Anecdotal evidence is that turnip-fed cows may lose (or not gain) body condition when consuming turnips. Findings from this grazing study did not support this observation. After six weeks on summer crops, both herds had gained an average of 0.1 BCS with little difference noted between herds. Careful transition of cows onto turnips, and ongoing feeding of maize silage and PKE to turnip-fed cows prevented loss of BCS sometimes seen in cows consuming turnips-based diets.
- Cows that consume turnips do not necessarily lose body condition.
Figure 2.0: Body Condition Score (BSC) of chicory and turnip cows at the start and end of study
Milk production and composition
Based on bulk vat data and herd test results, milksolids production was similar for cows consuming the same allocation of either chicory or turnips. This result agrees with outcomes from 1990s research reported by DRC (now DairyNZ). Twin cows fed the same amount of either turnips or chicory during both summer and autumn produced the same amount of milksolids and had similar gMS/kgDM responses to each crop type (Waugh et al, 1998).
Concentration of milk protein, milk fat and milk lactose was similar for milk from turnip and chicory-fed cows. These results differ from Waugh et al (1998) who reported a lower milk fat % for turnip-fed cows.
Neither herd ‘graded’ based on fat evaluation index (FEI) results, despite all cows consuming up to 2.5 kgDM of PKE/cow/day. Milk FEI may increase for turnip-fed cows due to medium-chain fatty acids present in turnip bulbs and/or from mild rumen acidosis when cows first transition onto turnips.
- Milksolids responses by cows are similar when cows consume the same amounts of chicory or turnips. Decisions around which crop to plant should reflect agronomic and feed budget decisions (which crop will yield the most DM to best match herd demand when pasture supply is limiting).
- While FEI was slightly higher for bulk milk from turnip-fed cows they did not reach levels at which penalties apply. These results show turnips and PKE can be successfully fed together but bulk milk FEI should be monitored.
Figure 3.0: Weekly herd test milk production (kgMS) per cow
Figure 3.1: Bulk vat (7 day rolling average) milk production (kgMS) per cow
Many thanks to Fonterra for the assistance with the collection, processing and handling of bulk milk data.
Waugh CD, Clark DA, Harris SL, Thom ER, Copeman PJA, Napper AR (1998) Chicory for milk production. Proceedings of the New Zealand Grasslands Association 60: 33-37