Fertility Workshop

Published 21 November 14

Fertility and youngstock updates

Both the reproductive efficiency of dairy cattle and calf rearing techniques are on-going challenges for our industry. Here, Dr Jenny Gibbons summarises the headlines from a workshop held in September 2014 at the Royal Veterinary College (RVC), and the latest from the DairyCo Research Partnership on Health, Welfare and Nutrition led by Nottingham University.

Fertility workshop

Over fifty delegates from academia, farming, nutrition, consultancy, vet/animal health, breeding, milk recording and the farming unions took part in the one-day event on fertility held at the RVC.

Two farmers, Andrew Leggott and Chris James, described how they strive to improve and maintain good fertility on two very different dairy systems, and Professor Claire Wathes from the Royal Veterinary College presented ‘Heifer Fertility – benefits of getting it right’.  

Claire said some 15-20% of dairy production costs were associated with replacement heifer rearing. But while the evidence to support calving heifers for the first time at 24 months of age for maximising profitability on-farm was overwhelming, the average age at first calving was closer to 29 months in GB. So why do so many heifers calve down later, she asked?

“A five-year study of 17 dairy herds, conducted in the south west of England by researchers at the RVC, reported that heifers calving at 23 to 25 months produced almost 7,000kg more milk and spent 11% more of their lives in milk (45% vs 34%) over five years compared with heifers calving for the first time at over 30 months.   

“The younger-calving animals were also more likely to survive to third calving. Heifers calving at less than 23 months got to third lactation by 1,500 days of age – 4.1 years – whereas those calving at greater than 30 months only got to second lactation by that stage. This means heifers calving at the optimum of 24 months are fitting in an extra lactation compared with those calving at 30 months or greater.”  

She said heifers in the study calving for the first time at the optimum of 24 months, went on to have a consistently shorter calving interval over each of the next three lactations. “As the return on investment of rearing replacement heifers from birth to first lactation is not fully recovered until at least the end of the first lactation, it is more economical to rear heifers to calve at younger ages. These heifers will go on to have better survival rates to second and third lactation.”

Watch out for more findings from this workshop in the next issue of DairyLeader.

 

Colostrum is key

Achieving the optimum age at first calving starts with good care of young calves. A recent review of the scientific literature on optimal colostrum transfer was carried out by RVC researchers and DairyCo as part of the research partnership led by Nottingham University. It reported that correct colostrum management is the perfect combination of quality, quickness and quantity – 3Qs.

To remind you these are:

Quality
Good quality colostrum contains at least 50 grams per litre of immunoglobulin G (IgG). You can’t tell the quality of colostrum by looking at it so you need to test it using a colostrometer or refractometer. Disease-causing pathogens multiple quickly in colostrum so to ensure optimal quality, colostrum must be collected hygienically and fed promptly or stored in a fridge, freezer or pasteurised. Testing for total bacterial count is the way to work out whether your farm is at risk of feeding ‘bacterial soup’ to new born calves and comprising their immunity.

Quickly
Calves must receive their first colostrum feed as soon as possible after birth, ideally within two hours, to optimise immunity but at the latest within six hours. The efficiency of immunoglobulin absorption from colostrum declines rapidly from over 40% at birth to less than 5% by 20 hours after birth.

Quantity
Give a first feed of 3 litres or 10% of body weight; this should be followed up by another similar size feed within 12 hours of birth.

A short information film, ideal as aid memoir and for less experienced team members, on the 3Qs will be released soon.

It’s worth remembering that young animals have the ability to convert feed into growth most efficiently during the first two months of life, but growth rates will vary according to the energy and protein content of the milk and the volume and frequency with which it is supplied.

To support optimal growth rate, calves must be fed sufficient energy and protein. This depends on the total amount of milk solids fed per calf per day, as opposed to the volume of milk. To achieve growth rates of 700g per day pre-weaning, each calf should be fed 700g to 900g of milk solids in two or preferably more feedings. A calf weighing 45kg requires 7.32MJ/day for maintenance under thermoneutral conditions.

Whole milk contains about 22.59MJ of ME/kg of dry matter, which means it requires about 325g of milk solids (2.6 litres fresh milk, assuming 12.5% solids content) for maintenance alone. Most milk replacers are lower in fat content than whole milk so they have less energy (ME) per unit of dry matter (typically 16.74-19.67MJ/kg DM). This means that calves will require more milk replacer dry matter just for maintenance. Calves provided with higher volumes of milk, nearer to 15-20% of their live weight early in life, can double their nutrient intake and gain more weight – up to 1kg/day.

Heifers targeted to calve for the first time at 24 months require a growth rate of more than 750g/day to achieve optimal performance in terms of milk yield and longevity. Improved monitoring for growth at regular intervals could help ensure that all animals within a group are achieving a minimum average daily gain of 750g/day, and then have adequate body size for first breeding at 13 to 14 months and hence calve close to 24 months. Achieving these goals consistently means providing the calf with enough energy and protein, starting at birth, to exploit its early growth potential. 

The full research, summarised here, can be found in:

Cooke, J.S and Wathes, D.C. 2014: Rearing heifer calves for optimum lifelong production, Cattle Practice Vol 22, Part 1, p66-71, which can be downloaded here

Correa, MT, et al: Effect of calfhood morbidity on age at first calving in New York Holstein herds, Prev. Vet. Med., 6:253-262, 1988.

Patel, S., Gibbons, J., Wathes, D.C. 2014: Ensuring optimal colostrum transfer to new-born dairy calves, Cattle Practice. Vol 22, Part 1, p95-104, which can be downloaded here