title: Productive and Economic Responses in Grazing Dairy Cows to Grain Supplementation on Family Farms in the South of Brazil.
abstract: Pasture-based dairy production has been a major source of income for most family farms in the south of Brazil. Increasing milk prices have spurred an increase in grain supplementation, which has been poorly implemented, resulting in low levels of efficiency. To evaluate the consequences of supplementation on milk production and composition, grazing behavior and economic return, the widely used grain management system (CC-commercial concentrate, containing 21% CP, offered at 1 kg per 3.7 L of milk) was compared with an energy supplement (GC-ground corn, with 9.5% CP, offered at 0.4% of live weight). Ten Holstein cows were paired into two groups, and subjected to the two treatments in a crossover design. The cows remained in the same grazing group, and the grain supplement was offered individually at milking time and consumed completely. Each experimental period lasted 14 days, with 10 days for diet adaptation and four days for data collection; individual milk production and samples were collected to determine levels of fat, protein, lactose, carotenoids, vitamin A and N-urea. Grazing behavior was observed (scans every 5 min) in the first 4 h after the morning milking, and chemical composition of hand plucked samples of forage were measured. The cost of the supplement and profitability per treatment were calculated. Cows supplemented with GC consumed herbage with higher crude protein (CP: 16.23 vs. 14.62%; p < 0.05), had higher biting rate (44.21 vs. 39.54 bites/min; p < 0.03) and grazing time (22.20 vs. 20.55 scans; p < 0.05) than when receiving CC. There were no differences in milk composition between treatments (p > 0.05). However, higher concentrations of β-carotene and total carotenoids were detected in the milk of cows at 70-164 days of lactation, compared to <70 days of lactation (p < 0.05). Milk production was higher (13.19 vs. 11.59 kg/day; p < 0.05) when cows consumed CC, but resulted in lower profitability compared to GC (US$ 4.39 vs. US$ 4.83/cow per day). Our results show that higher productivity does not necessarily improve profitability. Cows receiving supplement with lower levels of protein were able to adjust their grazing behavior to meet their protein needs and this level of diet modification did not alter milk composition.
authors.affiliation: Lab of Applied Ethology and Animal Welfare (LETA), Departament of Zootechny and Rural Development, Federal University of Santa Catarina, Rod. Admar Gonzaga, 1346, Florianopolis, SC 88034-000, Brazil. pinheiro.machado@ufsc.br.
authors.forename: Luiz Carlos Pinheiro Machado
authors.initials: LC
authors.lastname: Filho
authors.affiliation: Lab of Applied Ethology and Animal Welfare (LETA), Departament of Zootechny and Rural Development, Federal University of Santa Catarina, Rod. Admar Gonzaga, 1346, Florianopolis, SC 88034-000, Brazil. davila27@gmail.com.
authors.forename: Leandro Martins
authors.initials: LM
authors.lastname: D'Ávila
authors.affiliation: Lab of Applied Ethology and Animal Welfare (LETA), Departament of Zootechny and Rural Development, Federal University of Santa Catarina, Rod. Admar Gonzaga, 1346, Florianopolis, SC 88034-000, Brazil. daniele.kazama@ufsc.br.
authors.forename: Daniele Cristina
authors.initials: DC
authors.lastname: da Silva Kazama
authors.affiliation: Lab of Animal Biochemistry, Department of Zootechny and Rural Development, Federal University of Santa Catarina, Rod. Admar Gonzaga, 1346, Florianópolis, SC 88034-000, Brazil. lauana@zootecnista.com.br.
authors.forename: Lauana Luiza
authors.initials: LL
authors.lastname: Bento
authors.affiliation: Lab of Animal Biochemistry, Department of Zootechny and Rural Development, Federal University of Santa Catarina, Rod. Admar Gonzaga, 1346, Florianópolis, SC 88034-000, Brazil. shirley.kuhnen@ufsc.br.
authors.forename: Shirley
authors.initials: S
authors.lastname: Kuhnen
keywords: Voisin’s Rational Grazing; grazing behavior; livestock sustainability; milk composition