title: Hydrogenated fish fat for grazing dairy cows in summer.
abstract: Thirty-two multiparous Holando argentino cows in mid lactation were randomly assigned to two treatments: control or HFF (hydrogenated fish fat) at Rafaela, 31 degrees 11' South, during summer 1997/1998, to evaluate the effect of using HFF as a supplement under grazing conditions. Animals in both treatments grazed an alfalfa pasture, and were confined from 1000 hours to 1700 hours daily in a shaded pen where water was provided ad libitum. During each milking, animals in the control group received 3.73 kg dry matter per cow each day (DM cow(-1) day(-1)) concentrate (15% crude protein; 8.69 MJ energy for location/kg DM). Cows in the HFF group received 3.25 kg DM cow(-1) day(-1) concentrate, plus 0.200 kg DM cow(-1) day(-1) HFF. Both diets presented similar energy, protein and neutral detergent fibre contents. The trial was performed during a strong "El Niño" event, which resulted in a total rainfall of 396.3 mm (80% higher than normal). The mean temperature was 23.7 (SD 3.2) degrees C and the mean temperature humidity index was 72.9 (SD 4.96). Production data were analysed using a completely randomised design with analysis of covariance. Supplementation with HFF produced an increase in daily milk production (26.4 (SD 2.46) l/cow compared to 23.9 (SD 2.68) l/cow for the controls; P<0.05). Milk fat production was higher for HFF (P<0.05): 941 (SD 96) g cow(-1) day(-1) as compared to controls, which yielded 846 (SD 95) g cow(-1) day(-1). Milk protein yields also differed significantly (P<0.05), the respective values for HFF and controls being 795 (SD 72) g cow(-1) day(-1) and 715 (SD 83) g cow(-1) day(-1). It was concluded that hydrogenated fish fat could be a good ingredient to sustain high yields and elevated maintenance requirements in a grazing system during hot conditions.
authors.affiliation: School of Veterinary Sciences National University of Littoral, Santa Fe, Argentina.
authors.forename: M R
authors.initials: MR
authors.lastname: Gallardo
authors.forename: S E
authors.initials: SE
authors.lastname: Valtorta
authors.forename: P E
authors.initials: PE
authors.lastname: Leva
authors.forename: H C
authors.initials: HC
authors.lastname: Castro
authors.forename: J A
authors.initials: JA
authors.lastname: Maiztegui
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle; D005223:Fats / Q000378:metabolism*; D005260:Female; D005396:Fish Products; D006304:Health Status; D018882:Heat Stress Disorders; D006865:Hydrogenation; D012621:Seasons; D013696:Temperature
chemical_list: D005223:Fats