Do Sweat the Small Stuff

Words by Dr Rob Derrick

For mental wellbeing we are often advised not to sweat the small stuff, but sometimes it pays to review the finer details.

By September most dairy farmers who rely on supplementary feeds will have some straights, blends or compound feed on forward contracts, or have silage ready for use or be hoping to make more soon. Unless working to very tight budgets, the amount actually fed will be being tweaked according to need, depending how well cows came through the winter and how well pastures are growing. Bulk feeds aside, given the tight markets I think it is worth taking a little time to consider the small stuff across all production systems.

Calcium

Advice around calcium supplementation in New Zealand has tended to be confined to colostrum mobs and when feeding very low calcium feeds like fodder beet and maize silage. Grasses are a poorer source of calcium than clovers. Grains and straights including palm kernel expeller and distillers’ dark grains are low in calcium. Cows will mobilise calcium in early lactation, but bone levels need to be replenished at some point or cows will subsequently be at more risk for milk fever. If feeding lowcalcium supplements – not just maize silage - to support milk production, limestone flour is an economical way to avoid relying too heavily on a high clover content in pastures.

Ionophores

Rumen modifiers improve the efficiency of feed use and help protect cows from bloat and ketosis. In-feed options are more economical than trough treatments or boluses, so if mixer wagons, blends or compound feeds are being used the economics are much more compelling. Monensin has been listed as an inhibitor substance with regards to methane by ACVM - even if it doesn’t become a registered methane inhibitor it’s good to know it is making a difference.

Magnesium

The ideal magnesium level for a herd of cows at any time is difficult to calculate, because the level of magnesium in the pasture and other soluble minerals like potassium which affect uptake is so variable. ‘Magnesium staggers’ are a clear sign of deficiency, but at a subclinical level under or over-supply can be difficult to spot. Attention to detail and avoiding excesses while covering needs is going to be more important as sustainability becomes more critical. When using multiple magnesium sources, knowing the elemental magnesium level in each source – which can vary with supplier – can help avoid surprises.

Mycotoxin binders

Not all moulds create mycotoxins, but after such a wet season in the North Island it’s not surprising higher levels of zearalenone and deoxynivalenol are being reported in maize silage. These mycotoxins may lead to challenges with reproduction and weight gain; others are indicated by ‘jumpy’ behaviour. Screening tests have improved enormously in recent years, so the chance of identifying and quantifying the presence of key mycotoxins in suspect feeds provides a more reliable way to select an appropriate toxin binder.

Rumen buffers

Although not a label claim, ionophores are associated with reducing the risk of acidosis, so fit really well with feeding supplements rich in fermentable carbohydrates. Wet acidic silage carries a high acid load and if finely chopped may not support the rumination required to buffer the rumen, so if fed alongside starch feeding a rumen buffer like AcidBuff is worth considering.

Rumen-protected fats

Rumen-protected fats can be used to increase the energy density of a diet. They can be used from the start of lactation to support higher levels milk production, but can especially help just before and through mating. Pasture species often want to become reproductive just as the mating season for dairy cows gets underway, with an increase in fibre levels and decrease in energy – which is bad timing because we want cows to be gaining weight through mating. Some types of fatty acids have a special role in conception rates over and above an effect through helping offset a weight loss. Mega-Max is a relatively new type of calcium soap without the soapy taste which contains a fatty acid profile which supports both weight gain and fertility – giving users a two-way bet on a win.

Sodium 

Cattle evolved on feeds that are low in sodium, so have developed efficient absorption processes and are avid consumers of salt. Maize silage is especially low in sodium and should normally be fed with salt. Salt aids palatability of feeds. Dry matter intake and milk yield has been found to increase at sodium concentrations well above those needed to meet dietary requirements, so aiming to just prevent a deficiency feels like setting the bar too low.

Trace minerals

Trace minerals are not normally associated with catastrophic downer cow issues associated with calcium and magnesium, but are important catalysts that make a host of bodily functions work better. Monitoring the trace element status of animals is recommended especially prior to mating, or if poor animal performance can’t be explained by more obvious reasons.

Iodine supplementation is always a topical issue pre-mating, with some products delivering well in excess of meeting expected requirements The US Food and Drug Administration have increased the maximum limit for iodine supplementation from EDDI (ethylenediamine dihydriodide) from 10mg/day to 50mg/day for milking cows, because the reduced consumption of iodised salt putting some groups with high iodine requirement (such as pregnant and nursing women) at risk of being iodine deficient. Supplementing cows with higher levels of iodine over mating than is required to prevent a deficiency could be beneficial, for both the cows and consumers of the milk products.

Vitamins

Ruminants can produce Vitamin A – which is important for low light vision and reproduction - from β-carotene in green forages. Stored forages have lower β-carotene levels than fresh forages and most grains and by-products are practically void in β-carotene..

The production of vitamin D3 - which is critical for regulating bone calcium levels - from sunlight should be adequate in grazing livestock but is less reliable the further the date is from the summer solstice and when cloud cover limits sunlight hours.

Fresh pasture is also a good source of Vitamin E – an important anti-oxidant which works with selenium - but levels are decreased by wilting and ensiling. Vitamin E levels are normally correlated to the fat content of feeds.

Your local NRM Nutrition Specialist will be happy to discuss the finer details of your dairy cow diet this spring.

RECOMMENDED TEST TYPE BY TRACE ELEMENT.

Primary or Secondary test options, (secondary/ less optimum test option is shown in brackets).