The purpose of this study was to determine goat milk physicochemical parameters during the feed scarcity season. An evaluation was made for 398 milk samples from 80 multiparous goats belonging to three different production systems: (S1) mechanized milking grazing pasture and harvested residue (alfalfa) and grain supplemented; (S2) system grazing native pasture; and (S3) system grazing native pasture and grain supplemented. The general averages were: fat (FT) 4.0 ± 0.20%, protein (PR) 3.3 ± 0.05%, lactose (LC) 4.9 ± 0.09%, nonfat solids (NFS) 8.9 ± 0.13%, total solids (TS) 14.5 ± 0.20%, temperature (TM) 24.6 ± 1.06°C, and acidity (pH) 6.7 ± 0.049. Most of the physicochemical components of milk were affected (p < 0.0001) by the production system × month interaction and production system × group × month interaction. The FT content was higher (p < 0.05) in S2 (4.56 ± 0.18) than in S1 (3.64 ± 0.20) and S3 (3.50 ± 0.20). LC differed (p < 0.05) in S2 (5.07 ± 0.08) than in S1 (4.77 ± 0.09) and S3 (4.70 ± 0.09). No differences were observed for the rest of the variables (p < 0.05) among the production systems. The study unveiled a higher content of FT, LC, NFS, PR, and TS for S2 than for S1 and S3. This higher content may be explained because S2 only grazed on herbs and shrubs, in contrast to S1 and S3 which were additionally supplemented with grain concentrates.

T he aim of this study was to determine the compositional quality of local goat milk from Comarca Lagunera, Mexico. Variables measured were: fat, protein, lactose, non-fat solids and total solids. Three hundred and fifty lactating local goats were randomly taken from 6 flocks. The goats were managed extensively and fed with native vegetation, although the diet was occasionally supplemented with agricultural residues. Farms were visited monthly from February to September 2013 to be present at milking time. Milk was manually homogenized to take samples which were later examined with a MilkoScope Expert Automatic® analyzer. Data were analyzed with SAS V 9.0 software to characterize the milk component curves as a function of time. Overall means for milk components were: fat 4.13 % ± 0.66, protein 3.32 % ± 0.29, lactose 4.95 % ± 0.43, non-fat solids 7.41 % ± 0.67 and total solids 13.14 % ± 1.7. There were significant differences (P<0.01) between months for protein, lactose, non-fat solids and total solids. ResumenE l objetivo del presente trabajo fue determinar la calidad composicional de la leche de cabras locales de la Comarca Lagunera de México. Se midieron las variables: grasa, proteína, lactosa, sólidos no grasos y sólidos totales. Para el estudio se tomaron al azar 350 cabras locales lactantes de seis rebaños. Las cabras fueron manejadas en forma extensiva y alimentadas con vegetación nativa, en pocos casos la dieta se complementó con esquilmos de cultivos agrícolas. Las explotaciones se visitaron mensualmente de febrero a septiembre del 2013, para estar presente al momento de la ordeña. La leche fue homogenizada manualmente para extraer muestras que posteriormente se examinaron con el equipo MilkoScope Expert Automatic®. Los datos recopilados se analizaron con el programa SAS V 9.0 para caracterizar las curvas de componentes de la leche en función del tiempo. Las medias generales de los componentes fueron: grasa 4.13 ± 0.66 %, proteína 3.32 % ± 0.29, lactosa 4.95 % ± 0.43, sólidos no grasos 7.41 % ± 0.67 y sólidos totales 13.14 % ± 1.7. Se encontraron diferencias significativas (P<0.01) entre los meses de estudio para proteína, lactosa, sólidos no grasos y sólidos totales.