By Anne Hardie

The West Coast six-week in-calf rate was behind the national trend last season and though the weather played havoc, there were also other factors at play including a higher percentage of older cows.

LIC senior reproduction adviser, Jair Mandriaza, told a SMASH field day near Hokitika that a higher proportion of older cows aged nine or more in the herd meant the better the younger cows had to be.

Figures showed 8% of the West Coast cows in the survey of 140 farms totalling almost 67,000 cows were cows aged nine years or older.

Compared with two-year-olds that had a six-week in-calf rate of 68%, three-year-olds 65.5% and four to eight-year-olds of 65.6%, the older cows only reached 51.4%. The trend was similar for three-week submission and conception rate.

Age had a particularly dramatic effect on their ability to get in calf at all, with 31.3% of those older cows empty after mating. That compared with 14.1% of two-year-olds empty, 15.8% of three-year-olds and 17% of four to eight-year-olds.

Jair says the 14.1% of empty two-year-olds is an industry problem. Farmers are very good at getting heifers to good weights by 15 months, but those animals need to continue growing and heifers that struggle can end up empty the following year through no fault of their own.

Anecdotal evidence from farmers altering the milking management with younger cows, such as once-a-day-milking, was helping improve in-calf rates.

His key message for reducing overall empty rates was improving the six-week in-calf rate because figures clearly showed the highest percentage of empty cows resulted from those not getting in calf by six weeks.

Early calvers, particularly those that calved in the first three weeks, were more likely to be cycling early and have good conception rates that meant they were in calf by six weeks, whereas the cows calving nine weeks or more after the beginning of calving had significantly less success at getting in calf.

Within the group of cows calving between six and nine weeks after the beginning of calving, 26.8% did not get back in calf.

On the West Coast, just 61% of cows within herds calved within the first three weeks of the calving period last year and Jair says that is below the target of 67%.

“Early calving cows have better reproductive performance. The key is to try to address calving pattern and have a good cohort of younger cows coming into the herd and calving early. The later the cows calve, the lower their in-calf rate. That is quite a difficult group to get in calf.”

Within a herd, breeding worth (BW) was also having an impact on reproduction. In the top quartile, 68.5% were achieving the six-week in-calf rate and ending up with an empty rate of 13.1%, while 60.6% of the bottom quartile were in calf at six weeks and 19.8% did not get in calf that season. A similar pattern was clear for production worth, lactation worth and fertility breeding value.

“It is a common misunderstanding that high-producing cows are hard to get in calf but if you use lactation worth and production worth as a proxy for milk production, our data shows that isn’t the case. The highest-producing cows are no worse at getting in-calf than the lowest producers.”

Even within an age group, he says the higher performing animals with higher BWs are getting in calf more successfully than those lower-performing animals.

Another crucial factor for influencing in-calf results is heat detection and he says herd size doesn’t alter results but increasing the number of staff can make it more challenging as each person’s ability to detect heats can be varied.

He has looked at reproductive results using technology such as collars and says the six-week in-calf rate has the same distribution of results as those farmers not using technology.

“Wearable technology offers farmers more information about their cows but improving a herd’s reproductive performance comes down to what decisions are made off the back of that data.”