Nutritional evaluation and productivity of supplemented sheep grazing in semiarid rangeland of northeastern Brazil

Mathematical models to predict the lamb weight at birth and at weaning reared in the tropical warm-climate pasture

Our objective was to evaluate the productive parameters of ewes and their lambs in relation to ewe age and to develop models for predicting lamb weight at birth and weaning in a tropical warm-climate pasture. Individual data were collected from 273 ewes and 273 lambs, between 2013 and 2021. During this period all animals were kept on pastures of Brachiaria brizantha cv. Marandu All lambs in the experiments were supplemented in creep-feeding. A descriptive statistical analysis was performed using the PROC SUMMARY procedure in SAS (SAS University Edition, SAS Institute Inc. Cary, CA, USA). Pearson correlation coefficients between variables were estimated using the PROC CORR procedure in SAS (SAS University Edition, SAS Institute Inc. Cary, CA, USA). Model adjustments and variable selection were performed using PROC REG in SAS (SAS University Edition, SAS Institute Inc. Cary, CA, USA). The STEPWISE option and Mallow's C(p) were used to select the variables included in the equations. Outliers were identified by evaluating the studentized residuals based on the predicted values from the equations. Residual analysis was predicted by regression minus observed values and those that fell outside the range of -2.5 to 2.5 were removed. Several statistics were used to assess the predictability of the equations, including the coefficients of determination (r2) and mean standard error (RMSE). The average ewe age at lambing was 3.4 ± 1.7 years, with an average weight of 56.9 ± 8,9 kg and average body condition score (BCS) of 2,4 ± 0.8 points. The average ewe age at weaning was 51.1 ± 7.9, with average BCS of 1.8 ± 0.8 points. The average lamb at birthing was 3.9 ± 0.9 kg. The average lamb at weaning was 21.0 ± 4.9, with daily gain of 0.2 ± 0.1 kg/day and total gain of 17.1 ± 4.7 kg birth to weaning. The lamb produced by ewe at lambing was 5.3 ± 1.7 kg/ewe. The lamb weaned by ewe at weaning was 28.7 ± 10.8 kg/ewe. The ratios of lamb produced per ewe at birth and at weaning were 0.1 ± 0.03 and 0.6 ± 0.2, respectively. The lamb's birth weight showed a positive linear relationship with the age of the ewe, increasing by 115 g per year of age. The regression equations adjusted for ewe age had maximum points ranging from 4.2 to 5.2, occurring at average age of 4,7 years. The other characteristics showed a quadratic tendency. The results suggest the culling of ewes at five years of age to generate lambs with ideal weight at birth and at weaning raised in warm tropical pastures.

Effect of concentrate supplement to ewes on nutritive value of ingested Caatinga native forage nutritive value as affected by season

The objective of this study was to identify by microhistological technique the reference chemical components for use as indicators of the nutritive value of Caatinga plants forage grazed by sheep throughout the year. A flock of twenty mixed-race meat ewes, multiparous, in production, with an average 34.84 ± 1.75 kg live weight and 36 months of age was assigned to supplement treatment of 0, 200, 350, and 500 g concentrate/head/day for 3 years. The experiment was designed as a randomized complete design with repeated measures over time. Supplementation with concentrate did not influence chemical composition of selected forage. In contrast, season heavily influenced diet chemical composition. Canopy stratum, season, and plant botanical family of selected species affected forage chemical composition selected by ewes. The ewes selected forage with greater nutritive value during the rainy season. Based on principal component analysis of the nutritive value of the primary forage species selected, ewes preferentially grazed plants contained greater neutral detergent fiber, acid detergent fiber, crude protein (CP), C fraction of nitrogenous compounds, and carbohydrate fractions A + B1 and C compared to the average native Caatinga herbage. Rangeland botanical composition and ewe diet varied during the year, affecting forage nutrients on offer, with the best diet selected during the rainy season because of the presence of dicotyledonous herbaceous species rich in CP as well as soluble carbohydrates and nitrogenous compounds. Concentrate supplement strategies for ewes on rangelands, such as Caatinga, should be determined by herbaceous species nutritive value during the rainy season and deep-rooted perennial dicotyledons during the dry season. These include the need to monitor ewe selection of forage species and their nutritive value, which is effectively accomplished with fecal microhistological techniques.