Feeding less protein could boost fertility

Rather than pushing fresh cows to peak yields quickly, dairy farmers should consider feeding less protein and allowing yields to increase in a steady pattern.

By doing so, cows are less likely to experience negative energy balance and consequently have less fertility issues, according to dairy research scientist Ryan Law of the Agri-Food and Biosciences Institute.

“Rather than reducing the energy gap post-calving by feeding high concentrate feed levels, dietary concentrate and protein levels could be reduced to ease milk production and delay peak lactation until intake potential is higher,” he said.

In a study, three different feed protein levels were fed in early lactation to determine the effect on intakes and yields.

“When crude protein levels were reduced from 17.5% to 14.5%, milk yields dropped by 3.5 litres a day, but intakes remained the same at an average 18.5kg for cows and heifers,” he explained.

However when protein was dropped to 11.5% from 17.5%, intakes decreased by 2kg a cow a day and yields reduced by 10 litres a cow a day.

“Compared to the 17.5% feed, the 14.5% protein ration improved conception rates in the first 100 days of the breeding programme and also improved negative energy balance.”

In a further study, Dr Law compared two methods of protein feeding. All cows received a basal TMR of 15% crude protein and 35% concentrate (about 7 kg), but in line with average farm practice, one group (Flat Rate Feeding or FRF) also received additional concentrate feeding through out of parlour feeders as soon as they calved. This was built up to 7kg a day, bringing total crude protein levels up to 18%.

The second group (Slow Start-Up or SSU) just received the basal diet until 28 days post-calving when they also started to receive additional concentrates. By day 42, both groups were on the same diet.

“Dry matter intakes were similar for the first four weeks post-calving and then intakes for cows in the SSU group actually increased over the FRF group,” explained Dr Law.

“In fact in weeks 1-20 post calving SSU cows had significantly higher forage intakes (10.4 kg DM a day) compared to the FRF group (9.0 kg DM a day).”

And as a result of eating more TMR, the SSU cows’ concentrate intakes were also higher after week seven.

Adopting such a strategy did not significantly impact milk yields or quality in the first 20 weeks post-calving, with only a 1kg a day reduction in yields.

“You may lose 140 litres in the first 20 weeks, but it is a small sacrifice to pay in terms of improved longevity, health and negative energy balance,” he said.

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