The University of Minnesota has initiated a crossbreeding study including more than 10 000 dairy cows over an eight-year period.Between April and September 2008 Prof Les and junior scientist Amy Hazel enrolled 10 dairies in the new study to compare pure to crossbreeds in a rotational three-breed system of Holstein, Montbeliarde, and Swedish breeds.
The aim is to compare the profitability of crossbred dairy cattle with that of pure Holsteins, which currently comprise more than 90% of the dairy cows in the USs. Oonly pure will be initially enrolled in the project as foundation cattle, and 4 185 heifers and cows have been committed to the study across the 10 dairies. Around 40% of the foundation of pure Hholsteins will continue to be bred to Holstein AIai bulls, in successive generations across the years of the study, while 30% will be mated to Montbeliarde and 30% to Sswedish Red bulls.
the 10 dairies, which range in size from 250 to 1 620 cows, are among the best in Minnesota for production and reproductive management. However, collectively, they’re near the Minnesota average for stillbirth rate, death rate, and turnover rate, huge factors in the profitability of dairying.the dairy owners believe their performance for calving difficulty, stillbirth, health disorders, and the death and survival of cows needs substantial improvement to boost profitability.Many achieve superior production and reproduction, but at considerable expense in labour and other inputs. Crossbreeding should reduce labour requirements and health disorders in individual cows.
A follow-up study
this research is a follow-up to a field study conducted by Prof Hhansen and Brad Hheins, also from the University of Minnesota, with six Californian dairies, which compared pure Hholsteins with crossbred with Normande, Montbeliarde, and Sscandinavian Rred cattle. Tthe Californian study ignored data for health traits, which will be emphasised in the new Minnesota study.
In the Californian study, survival from calving to first observation of milk recording was compared for crossbreeds versus pure Holsteins that calved for the first time in six California dairies.Cows calved for the first time from June 2002 to January 2005, and continue to be gauged for production, fertility, and other traits.
A seventh dairy participated in the whole-herd buy-out programme, although heifers were retained to continue dairying. Cows from that dairy were removed from the analyses of survival.The percentage of 416 pure Hholstein and 1 075 crossbred cows that died or were culled in the six dairies during first lactation are shown in Table 2. Death rate, culling rate, and total removal rates reflect the actual percentage of cows that left the six dairies before first observation for milk recording and up to the 305th day of lactation. The difference between crossbreds and pure Holsteins was statistically significant in all cases.
Cow deaths
Only 10 of 1 075 crossbred cows (0,9%), but 15 of 416 pure Holsteins (3,6%) died prior to first observation for milk recording. Furthermore, 18 of 1 075 crossbred cows (1,7%), compared to 22 of 416 pure Holstein cows (5,3%) died during the first 305 days of first lactation.
Total removals
More crossbreds remained in these dairies than pure Holsteins did, with only 2,6% of crossbreds removed (died or culled) before first observation for milk recording compared to 8,7% of pure Holsteins – in other words, pure Holsteins were three times more likely than crossbreds to die or be culled in this period.Also, only 7,4% of the crossbred cows, versus 15,9% of the pure Holsteins, were removed by the 305th day of first lactation.
Industry interpretation
With replacement heifers valued at more than US 000 (R22 500) in the US in recent years, the 6,1% difference (8,7% pure Holsteins minus 2,6% crossbreds) in first-calf heifers lost after calving, but before first observation for milk recording, has huge financial implications for the profitability of dairying. – Robyn Joubert |fw
