Breeding and genetics may be getting much of the blame for current poor dairy cow fertility, but changes to animal feeding diets could go a large part of the way to correcting it.
BOCM Pauls’ Wynn Morris told delegates at the British Cattle Conference, Shropshire that a typical mating period currently resulted in 40% of cows pregnant, 10% fertility failure, 40% early embryo loss and 10% late embryo loss or abortion. “It’s the 40% early embryo loss which is most worrying as this leads to cows cycling irregularly.”
However, reducing calving interval by just one month from 13 months to 12 months results in a 7% increase in milk yield over three lactations, he explained. “We’ve bred cows with a willingness to milk, leading to a situation where cows are giving ‘credit card milk’, whereby they milk off their backs for a long period early in lactation.
“This results in negative energy balance, with many cows losing more than one body condition score in the first month after calving. This means they are losing at least 42kg of bodyfat and this has to be paid back somewhere. Fertility is the cost.”
Commenting on a number of trials, Mr Morris said a study to assess egg quality had found that low starch diets led to more better quality eggs being produced. “Insulin levels in diets also have a major role to play and differentiating diets on insulin level has been found to increase pregnancy rate by 33%.
“Feeding cows solely a cycling diet which is high in insulin led to 27% of cows being in-calf at 120 days post calving, feeding solely a mating diet low in insulin led to the same pregnancy rate. The same was true when cows were fed a mating diet until the first progesterone rise followed by a cycling diet.
“However, feeding a cycling diet until the first progesterone rise followed by a mating diet led to 60% of cows being in-calf at 120 days post-calving.”
This clearly shows a two stage approach to feeding is worthwhile in terms of increasing conception, But when questioned Mr Morris admitted it would be difficult for many farms to implement this kind of regime in practice.
Revealing on-farm feeding results, Mr Morris said introducing diets designed to aid fertility had led to significant improvements in conception rates. “On one 150-cow unit the calving interval has been cut by 25 days in six months, with a yield gain of four litres in the first month. Pregnancy rates rose from 32% to 65% in the first six months too.”
However, SAC geneticist Mike Coffey questioned whether this approach could lead to further problems, as it meant it was possible to breed from cows with lower inherent fertility, thereby possibly perpetuating the current problems of infertility. In repsonse Mr Morris admitted this may be true, but added that farmers had to feed for the cows they had now. “Undoubtedly the long-term goal must be for breeding and nutrition to work hand in hand, but we have to address the issues on-farm now too.”