Abstract
Abstract The main objective of the study was to determine the effect of transition from a conventional milking system (CMS) to an automatic milking system (AMS) on survival of 6361 Polish Holstein-Friesian cows to second (SL2), third (SL3) and fourth (SL4) lactation as well culling reasons. The cows were born between 2002 and 2015 and calved between 2004 and 2018. All data for the survival analysis and culling reasons of cows in 17 herds during operation of CMS and AMS were extracted from the SYMLEK official milk recording system. Cow survival (SL2, SL3 and SL4) was analysed with multiple logistic regression using the following effects in the model: milking system (MS), first calving season (CS), age at first calving (AFC), ease of first calving (CE), birth of a dead calf at first calving (DC), milk yield (MY) for full first lactation (MY – this effect was ignored in SL2 analysis), herd (H), and MS × H interaction. In the next stage of the study, χ2 test was used to analyse culling reasons of cows (udder diseases, low fertility – infertility and reproductive disorders, locomotor diseases, low milk yield, other diseases – metabolic, digestive and respiratory diseases, accidents and chance events) in the first, second and third lactation and collectively in the first three lactations. Logistic regression analysis indicated a significant effect of MS, AFC, DC on SL2 and SL3, and of MY on SL3 and SL4. Moreover, H and MS × H interaction had a highly significant effect on SL2, SL3, and SL4. Cows used in AMS barns were characterized by significantly worse SL2 and SL3 compared to CMS (odds ratio), by 27.8% and 31.0%, respectively. It was also observed that the effect of switching from CMS to AMS on cow survival was determined by herd membership – in most herds this effect was unfavourable. A distinctly positive effect of milking automation on cow survival (SL2, SL3, SL4) was noted in only one barn (herd) – it was a new barn with a considerably expanded number of milked cows, where the lying area was covered with straw. When analysing the reasons for culling in the first three lactations collectively, it was found that after the AMS system was introduced into the herds, there were increases in the rate of culling for locomotor diseases (by 0.85 percentage points (p.p.)), low milk yield (1.36 p.p.) and other diseases (3.01 p.p.). It was also observed that the automation of milking reduced culling due to udder diseases by 0.37 p.p., low fertility by 3.24 p.p., and accidents and chance events by 1.60 p.p.
Highlights
Research findings show that longevity is playing an increasing role in breeding programmes (PFHBiPM, 2020) because it has a significant effect on the profitability of dairy cattle breeding (Pelt et al, 2015)
When considering the above parameters in terms of the milking system, it was established that cows from automatic milking system (AMS) barns first calved around 1 month earlier and their first lactation milk yield was 1821 kg higher compared to their age mates in conventional milking system (CMS) barns (Table 3)
Analysis of the reasons for culling in the first three lactations together showed that after the AMS system was introduced into the herds, the rate of culling increased for locomotor diseases, low milk yield (1.36 p.p.) and other diseases (3.01 p.p.)
Summary
Research findings show that longevity is playing an increasing role in breeding programmes (PFHBiPM, 2020) because it has a significant effect on the profitability of dairy cattle breeding (Pelt et al, 2015). The idea of functional longevity was defined by Sewalem et al (2008) as the number of days from first calving to culling, death, or censoring; adjusted for the effect of milk yield. A similar definition of productive life was provided by Vukasinovic et al (1997), one difference being that they analyse numbers of months and not days, as can be found in the research of Sewalem et al (2005). Zavadilová et al (2011) uses a similar definition of functional longevity to length of productive life; it is the mean number of days between the first calving and culling. The idea of functional survival (length of productive life) was defined by Sewalem et al (2005) as the number of days from first calving to calving, death, or culling, and the record is censored if the cow has a calving. Due to the low heritability of longevity traits, of particular importance is to pinpoint the non-genetic sources of their variation, among which it is justifiable to consider a change of milking system
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