The present study aimed to evaluate the effects of milking system (MS) and diet characteristics on milk quality and dietary totaltract apparent digestibility (ttaD) in dairy cows. Twenty-one Holstein dairy farms (ranging from 60 to 200 lactating cows) located in Northern Italy were involved in the trial. Nine farms fed to the cows a hay-based diet (HB) while 12 supplied a silagebased diet (SB). Among farms, 10 were equipped with robotic milking (RM) and 11 with a conventional milking parlours (CON). Farms were selected a priori in order to have both MS represented in both dietary type (DT). Diet and faeces were sampled 4 times in each farm every 30 days from June to September 2020. In particular, a representative sample of the total mixed ration was collected from the feed bunk, 2kg of faeces were collected from a 20% of the lactating cows and 500 mL of bulk milk representative of the previous 24 h were collected from the tank in order to assess the chemical composition. A subsample of both ration and faeces was used to evaluate the proportion of undigested NDF as marker to estimate the ttaD of nutrients (DM, NDF, ADF, ADL, cellulose, hemicellulose and ash). Fat and protein content, somatic cell count, mineral content (Ca, P, Na), milk clotting ability (a30, RCT), pH, titrable acidity, and curd yield were determined on milk samples. Data were analysed using a linear mixed model; for milk traits the MS, month of sampling, DT and interaction between MS and month of sampling were used as fixed factors while the farm nested within MS was the random effect. As regards digestibility traits, the model included the fixed effects of DT, month of sampling, interaction between DT and month of sampling and MS, while the random effect was the farm nested within DT. Results show that milk composition, mineral content, clotting ability, pH and titrable acidity were not affected by the MS, but cows milked with CON had a greater DM and ash ttaD compared to cows milked with RM (p = .015 and p = .029). Cows fed with SB diet showed a higher milk fat (p = .006), casein (p = .045), and Ca content (p = .028) compared to those fed with HB. The diet based on SB showed higher ttaD of DM compared to HB diet (p = .001). Further analyses revealed that the interaction between MS and DT was significant for ttaD of cellulose and milk Ca content. Acknowledgements Results of the present study are preliminary, as part of the project ‘Innovamilk’ funded by the AGER cooperative.

Bovine milk quality and apparent digestibility of diets as affected by diet characteristics and milking system / Simoni, Marica; De Lorenzi, Claudia; Pozza, Marta; Giaccone, Daniele; Revello Chion, Andrea; Comino, Luciano; Righi, Federico. - In: ITALIAN JOURNAL OF ANIMAL SCIENCE. - ISSN 1828-051X. - 20:1(2021), pp. O164.1-O164.236. ((Intervento presentato al convegno ASPA 24th Congress Book of Abstract tenutosi a Padova, Italy nel 21-24 Settembre 2021 [10.1080/1828051X.2021.1968170].

Bovine milk quality and apparent digestibility of diets as affected by diet characteristics and milking system

Marica Simoni;Federico Righi
2021

Abstract

The present study aimed to evaluate the effects of milking system (MS) and diet characteristics on milk quality and dietary totaltract apparent digestibility (ttaD) in dairy cows. Twenty-one Holstein dairy farms (ranging from 60 to 200 lactating cows) located in Northern Italy were involved in the trial. Nine farms fed to the cows a hay-based diet (HB) while 12 supplied a silagebased diet (SB). Among farms, 10 were equipped with robotic milking (RM) and 11 with a conventional milking parlours (CON). Farms were selected a priori in order to have both MS represented in both dietary type (DT). Diet and faeces were sampled 4 times in each farm every 30 days from June to September 2020. In particular, a representative sample of the total mixed ration was collected from the feed bunk, 2kg of faeces were collected from a 20% of the lactating cows and 500 mL of bulk milk representative of the previous 24 h were collected from the tank in order to assess the chemical composition. A subsample of both ration and faeces was used to evaluate the proportion of undigested NDF as marker to estimate the ttaD of nutrients (DM, NDF, ADF, ADL, cellulose, hemicellulose and ash). Fat and protein content, somatic cell count, mineral content (Ca, P, Na), milk clotting ability (a30, RCT), pH, titrable acidity, and curd yield were determined on milk samples. Data were analysed using a linear mixed model; for milk traits the MS, month of sampling, DT and interaction between MS and month of sampling were used as fixed factors while the farm nested within MS was the random effect. As regards digestibility traits, the model included the fixed effects of DT, month of sampling, interaction between DT and month of sampling and MS, while the random effect was the farm nested within DT. Results show that milk composition, mineral content, clotting ability, pH and titrable acidity were not affected by the MS, but cows milked with CON had a greater DM and ash ttaD compared to cows milked with RM (p = .015 and p = .029). Cows fed with SB diet showed a higher milk fat (p = .006), casein (p = .045), and Ca content (p = .028) compared to those fed with HB. The diet based on SB showed higher ttaD of DM compared to HB diet (p = .001). Further analyses revealed that the interaction between MS and DT was significant for ttaD of cellulose and milk Ca content. Acknowledgements Results of the present study are preliminary, as part of the project ‘Innovamilk’ funded by the AGER cooperative.
Bovine milk quality and apparent digestibility of diets as affected by diet characteristics and milking system / Simoni, Marica; De Lorenzi, Claudia; Pozza, Marta; Giaccone, Daniele; Revello Chion, Andrea; Comino, Luciano; Righi, Federico. - In: ITALIAN JOURNAL OF ANIMAL SCIENCE. - ISSN 1828-051X. - 20:1(2021), pp. O164.1-O164.236. ((Intervento presentato al convegno ASPA 24th Congress Book of Abstract tenutosi a Padova, Italy nel 21-24 Settembre 2021 [10.1080/1828051X.2021.1968170].
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11381/2909029
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