Most dairy cows across the country are grazing grass by day; however in recent nights, frost has curtailed grass growth rates leading to increased supplementation whether it is extra concentrate in the milking parlour or introducing a partial mixed diet before evening milking. In the majority of cases cows are in a good metabolic state in regard to optimum body condition score and health status. The transition from non-lactating to lactating can be a stressful time for dairy cows and specific management must be priority here.
It is important to monitor dry matter intake of cows in all stages of lactation so cows do not suffer from negative energy balance (NEB) particularly in early lactation. High dry matter intake and an increased ratio of sugar based feed based ingredients (beet pulp) are associated with good responses to reproductive performance. In the lead up to calving, a reduced intake of between 25-40% is common, thereby it is important to offer pre-calving cows a higher energy density diet three weeks prior to calving.
The hormonal changes prior to calving affect appetite and thereby reduce feed intake shortly before calving. The decrease in feed intake combined with the initiation of lactation and production of colostrum starts a period of NEB, this period must be minimised too offset the degree of mobilisation. Approximately 33% of cows in each herd suffer a higher degree of mobilisation compared to the other 77% of cows within a herd that mobilise less and have a shorter severity of NEB and hence less body condition loss. A greater degree of NEB will supress the immune system, lead to uterine infection, mammary infections due to a lower count of white blood cells and higher somatic cell count.
Metabolically the cow responds releasing non esterified free fatty acids and ketones from the adipose tissue of which alters normal energy metabolism in the liver. These changes will affect ovarian function and will interfere with follicle development and maintenance of pregnancy.
The first three weeks following calving will provide the biggest challenge for the dairy cows, focus must be on reducing the degree of NEB. I would advise if possible to place cows approaching calving 7-10 days in a separate area and offer them a high energy dense diet. This will be important to encourage a smooth transition from non-lactating to lactating. Need to be careful that any changes in diets are done in a subtle way to avoid an oversupply of starch in the rumen.
The rumen microbes need time to adapt to the change in the diet and if the diet is not correctly balanced rumen acidosis maybe prevalent thereby also affecting reproductive performance. Infectious disease post calving can also have a significant effect on fertility for instance hypocalcaemia (milk fever), retained placenta, difficult calving etc.
In terms of diet, it is important that sufficient energy is provided but just the correct amount matched to the milk yield and breeding value of the specific cow. An imbalance of energy or too much protein will have a negative impact on reproductive performance, excessive amount of rumen degradable protein delays first ovulation or oestrus, reduced conception rate to first service. The cow will have to mobilise excessive protein thereby using up energy in disposing excessive protein.
It cows are already in NEB the problem is exacerbated with more ammonia and urea produced thereby having negative effects oocyte and embryo development. Altered pH is the biggest challenge in dairy diets following calving as acidosis is never too far away.
It is important that sufficient minerals are offered post calving together with a post calving mineral. Pay particular attention to key trace elements to include magnesium, phosphorus, sodium, iodine, selenium. Don’t forget about vitamins, it is very important to have elevated levels of vitamin E to boost immunity and vitamin A & D.
In summary dry matter intake, protein and energy requirement together with mineral balance will be crucial to the reproductive performance, whilst the key will be to balance the diet to the type of cow you have on each specific farm. In Connolly’s Red Mills we have tailored feeds to offset some of the associated problems I have mentioned and to have an overall successful breeding programme.