Milk yield and quality influence calf preweaning growth and ultimately the sale value of the calf at weaning. This study was conducted to evaluate the relationships of milk production and quality of beef cows to calf preweaning ADG in beef cows sired by Bonsmara, Brangus, Charolais, Gelbvieh, Hereford, and Romosinuano and from Brangus dams to determine whether the relationships were homogeneous across cow breed group. Approximately 50 cows/yr were milked monthly for 6 mo in each of the 7 yr of this study. Milk traits were included in models as linear and quadratic covariates along with interactions of the covariates with sire breed. Tests for curvilinearity and homogeneity of regression coefficients indicated the relationship of calf preweaning ADG to milk yield and quality was quadratic and homogeneous across Charolais and Gelbvieh; linear and homogeneous across Bonsmara, Brangus, and Romosinuano; and linear and different from other sire breeds in Herefords (P < 0.05). Exceptions to this were in the regression of calf preweaning ADG on the natural logarithm of somatic cell count (SCC) and milk urea nitrogen (MUN). The relationship of calf preweaning ADG to SCC was quadratic in Brangus (P < 0.05) and linear in Gelbvieh (P < 0.05) with little evidence (P > 0.05) of a relationship in Bonsmara, Charolais, Hereford, or Romosinuano. There was little evidence (P > 0.05) of a relationship of calf preweaning ADG to MUN in any of the sire breed groups. Results from this study confirmed the importance of the influence of milk yield and quality on calf preweaning growth but indicated this influence can depend on the breed composition of the cow. Furthermore, results suggest that breed origin or adaptation may have influenced the relationships of calf preweaning ADG to cow milk yield and quality.

The objective of the study was to compare fatty acid composition of longissimus dorsi (LD) and kidney fat (KF) in Holstein steers (HS), Simmental steers (SS) and Chinese LongDong Yellow Cattle steers (CLD). All steers received the same nutrition and management but in different locations. Cattle were harvested at approximately 550 kg and fatty acid composition of longissimus dorsi and kidney fat was analyzed in samples taken after 3 days of aging. There was evidence (P < 0.05) that C18:3n6 was greater in KF than LD in CLD cattle but not in HS or SS cattle. Percentage C18:1n9, C18:2n6, C18:3n3, and n6 fatty acids were greater in LD than KF for all breeds (P < 0.05), but the difference between fat sources for n6 in CLD cattle was smaller than the other two breeds. The LD had greater percentage of polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFA), and a greater ratio of n6:n3 PUFAs compared to the KF in each breed (P < 0.05). The △(9)-desaturase catalytic activity index was greater in LD than in KF in each breed group (P < 0.05). Percentage cis-9, trans-11 CLA was greater in KF than LD in HS (P < 0.05) but not SS or CLD cattle. These results indicate fatty acid percentages generally differed between longissimus dorsi fat and kidney fat. Further, there was some indication that some of these differences between fatty acid deposition sites were not consistent across breed group.

Sheep production systems in northwest China depend mostly on natural grasslands. Seasonal growth and maturity fluctuations can cause periodical restrictions in food quality and quantity. These fluctuations, in turn, result in variability in fat deposition and fatty acid profiles in different fat depots. Consequently, the study objective was to compare fat deposition, intramuscular fat (IMF) percentage and fatty acid profiles of the longissimus dorsi (LD), kidney fat (KF), tail fat (TF), and subcutaneous fat (SF) in lambs under ME restrictions similar to seasonal changes observed in the natural grasslands of northwest China. Nineteen male Dorper × Small Tailed Han lambs were assigned to 2 treatments, a control (CON) fed at 1.0 MJ / W × d and restricted (RES) by restricting ME sequentially every 30 d (0.56 MJ / W × d, 0.84 / W × d, 1.0 MJ / W × d, 0.84 MJ / W × d, 0.56 MJ / W × d, 0.28 MJ / W × d). All lambs were harvested at the end of the 180 d experimental period. Compared to CON fed lambs, restricting ME resulted in lesser IMF, fat deposition indexes ( < 0.05) except testicular and heart fat and greater ( < 0.05) SFA in LD, KF, and TF depots. The RES fed lambs had greater ( < 0.05) -3 PUFA, eicosatrienoic acid (C20:3n3), eicosapentaenoic acid (C20:5n3, EPA), and trans-linolelaidic acid (C18:2n6t) in LD muscle. The conjugated linoleic acids (CLA) content was greater in the SF depots of the CON fed lambs compared to the RES fed lambs. Fatty acid ratios (unsaturated fatty acid; USFA:SFA, MUFA:SFA, PUFA:SFA), and percentage USFA in RES fed lambs were lesser in muscle and adipose tissue compared to CON fed lambs ( < 0.05), except SF depots. In RES fed lambs, EFA were less ( < 0.05) in LD and KF depots and the ratios of functional fatty acids were lesser in LD and some adipose tissues ( < 0.05), including lesser n-6:n-3 in KF and SF ( < 0.05) depots, lesser USFA, SFA, MUFA, SFA in LD, KF, and TF ( < 0.05) depots, and lesser PUFA and SFA in LD and TF ( < 0.05) depots. Results from this research demonstrate that sequential energy restriction, as might be experience during seasonal forage quality and quantity changes in natural grasslands, result in lesser intramuscular fat with associated lesser quality, as well as, changes in fatty acid composition in different fat depots, which has implications for both meat quality and animal physiological functions.

Fatty acid (FA) composition of longissimus dorsi intramuscular fat in Black Yak and Chinese Yellow Cattle were evaluated in 44 Black Yak and 41 Chinese Yellow Cattle of both genders. Interactions of species with gender were observed for total saturated fatty acid (SFA), unsaturated fatty acid (UFA), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), palmitic acid, stearic acid, oleic acid, linolenic acid, arachidonic acid, EPA, and DHA concentrations, as well as PUFA/SFA ratio in the longissimus dorsi (p<0.05). The SFA percentage was greater in yellow cattle than yak in both genders but the species difference in heifers was greater than in steers (p<0.05). Yak had greater UFA, MUFA and PUFA percentages than yellow cattle in both steers and heifers (p<0.05) but the difference between yak and yellow cattle heifers was greater than yak and yellow cattle steers. The percentages of inolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid; and PUFA/SFA were greater in yak than yellow cattle in both steers and heifers (p<0.05). In addition, the ratio of n-6/n-3 PUFA in yak was lesser than in yellow cattle (p<0.05). These results indicated that FA composition generally differed between yak and yellow cattle but the differences were not the same in heifers as compared to steers. Results also suggested that species differences in FA composition tended to favor Black Yak over Chinese Yellow Cattle, indicating that the longissimus dorsi of Black Yak may have a higher nutritive value than that of Chinese Yellow Cattle and potential for development as a desirable natural product.

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