Lisa Whitfield
Reproduction
Massey Dairy No. 1 boasts impressive reproduction statistics, with a three-week submission rate of 95% and a six-week in-calf rate of more than 80% most seasons.
The whole herd is mated using AI, with the top cows receiving straws from LIC bulls with desirable once-a-day genetic traits such as udder support, milking speed, front teat placement and capacity.
The remainder of the herd are mated to Wagyu, Angus or short-gestation Hereford semen. Using a no-bull approach for mating the milking herd is seen as a way to improve biosecurity on the farm.
With a high six-week in-calf rate, the number of cows on heat each day over the tail-end of the mating season can be very low, so two home-bred bulls have been reared each season for use as teasers.
Heifer rearing
Excellent young stock rearing has been a priority for the farm. From the day they are born, calves are given every opportunity to thrive. All day colostrum is tested for quality using a brix refractometer, and the highest quality colostrum is prioritised for the youngest calves.
Young stock are weighed monthly. Regular, quiet handling contributes to their good nature, making them easy to handle when they come into the milking herd.
Early season weighing is used to assist with weaning decisions. All calves, regardless of breed are reared to at least 100kg before they are weaned off milk. Calf meal is fed to help them transition to a grass diet, and is fed if required to fill deficits over their first summer. Calves follow the cows around the farm, with mid-round pasture covers no longer than 2400kg drymatter (DM) offered.
Heifers consistently exceed their target growth rates, reaching an average of 73% of their mature cow liveweight by their first mating, and 100% of their mature cow liveweight by 21-22 months old.
Drenching has historically been done at the monthly weighing. Last season, between December and May, calves were selectively drenched using a triple-combination oral based on average daily gain. Any calves which fell below expected growth rates in the month between weighing were drenched, and any calf which had a particularly low growth rate was examined to identify if other health issues required attention. This approach led to an 85% reduction in the amount of drench used over the first six months post-weaning, with no detrimental effects on growth rates seen.
Maiden heifers have traditionally been mated to homebred Jersey bulls and over the last few years, have achieved pregnancy rates of between 95 and 100%. The heifers were synchronised for the first time last season, with 56% conceiving to AI using a new synchrony program, and an overall pregnancy rate of 95%. The process generated an additional 19 replacement heifer calves. Heifer synchrony is seen as a way to improve the rate of genetic gain in the herd, as well as to reduce the number of bobby calves.
Bone growth
Ongoing research with the young stock from the farm is being undertaken to collect data which will provide useful information on the growth characteristics of the bones of normal New Zealand dairy calves, particularly of the humerus. Spontaneous humeral fractures are a significant cause of mortality in two and three-year-old dairy animals in NZ. The predisposing and causative factors leading to situations where humeral fractures occur are poorly understood.
Massey Dairy No. 1 young stock are contributing a wealth of data to understand what is normal for bone growth. The humerus is a difficult bone to measure in the live animal due to its location close to the body, so finding practical ways to assess its’ mass is another goal of this project.
A farmer survey on spontaneous humeral fractures is open and we invite any farmers to participate to contribute information on their experiences with this condition. See link to the survey is below.
Maintaining pregnancy
Last season we undertook early pregnancy diagnosis for the milking herd. Pregnancy diagnosis was undertaken weekly, when cows were between days 27 to 35 post-mating with no return to oestrus. All cows were subsequently scanned six weeks following the end of the 9.5 week mating period.
Based on scanning results, 84% of the herd became pregnant within six weeks of the start of mating. However, by the final herd scan in February, the six-week in-calf rate had dropped to 80%. Early loss of pregnancy is a well-known occurrence in dairy cattle, with reported rates for New Zealand cows at 9.1% (Cuttance and Mason, 2015). Pregnancy loss at this stage is not usually noted because few people have their cows scanned so early.
Early pregnancy loss is one of many presentations of phantom cows – they become pregnant or assumed to be pregnant because they don’t return to heat during the mating period, however, they end up not being pregnant at the herd scan. Over the next few seasons we hope to collect more of this data, and to expand the project to involve more farms, to quantify this effect and see whether there are any differences apparent under the once-a-day milking system compared to a twice-a-day system.
Reference:
Cuttance EL, Mason WA (2015) Risk factors for and reproductive outcomes of phantom cows on New Zealand dairy farms. New Zealand Veterinary Journal 63 (5), Pp 276-283.
QR code and link to the survey on spontaneous humeral fractures in heifers: https://massey.au1.qualtrics.com/jfe/form/SV_eOKv5T2ffyqnsz3
- Lisa Whitfield is the former senior lecturer in production animal health and senior veterinarian in farm services at Massey University.
