Genetic parameters for performance, feed efficiency, and carcass traits in Senepol heifers.

Improving feed efficiency is a key breeding goal in the beef cattle industry. In this study, we estimated the genetic parameters for feed efficiency and carcass traits in Senepol cattle raised in tropical regions. Various indicators of feed efficiency [gain to feed ratio (G:F), feed conversion ratio (FCR), residual weight gain (RG), residual intake and body weight gain (RIG), and residual feed intake (RFI)] as well as growth [final BW, average daily gain (ADG), and DM intake (DMI)], and carcass [rib-eye area (REA), backfat thickness (BF), intramuscular fat score, and carcass conformation score] traits were included in the study. After data editing, records from 1 393 heifers obtained between 2009 and 2018 were used for the analyses. We fitted an animal model that included contemporary group (animals from the same farm that were evaluated in the same test season) as the fixed effect, and a linear effect of animal age at the beginning of the test as a covariate; in addition to random direct additive genetic and residual effects. The (co)variance components were estimated by Bayesian inference in uni- and bivariate analyses. Our results showed that feed efficiency indicators derived from residual variables such as RG, RIG, and RFI can be improved through genetic selection (h2 = 0.14 ± 0.06, 0.13 ± 0.06, and 0.20 ± 0.08, respectively). Variables calculated as ratios such as G:F and FCR were more influenced by environmental factors (h2 = 0.08 ± 0.05 and 0.09 ± 0.05), and were, therefore, less suitable for use in breeding programs. The traits with the greatest and impact on genetic progress in feed efficiency were ADG, REA, and BF. The traits with the greatest and least impact on growth and carcass traits were RG and RFI, respectively. Selection for feed efficiency will result in distinct overall effects on the growth and carcass traits of Senepol heifers. Direct selection for lower RFI may reduce DMI and increase carcass fatness at the finishing stage, but it might also result in reduced growth and muscle deposition. Residual BW gain is associated with the highest weight gain and zero impact on REA and BF, however, it is linked to higher feed consumption. Thus, the most suitable feed efficiency indicator was RIG, as it promoted the greatest decrease in feed intake concomitant with faster growth, with a similar impact on carcass traits when compared to the other feed efficiency indicators.

Water requirements of beef production can be reduced by genetic selection.

Growing concerns regarding sustainability in agriculture include the availability of drinking water, which is putting pressure on livestock production, especially the beef sector, for more efficient practices. Thus, genetic parameters were estimated for traits related to water intake and water use efficiency in Senepol cattle. Senepol females (n = 925) and males (n = 191) were evaluated in performance tests carried out from 2014 to 2019. Daily dry matter intake (DMI) and water intake (WI) were recorded by electronic feed and water bunks (Intergado Ltd.). Other traits assessed included average daily gain (ADG); mid-test metabolic BW (BW0.75); residual water intake based on ADG (RWIADG), estimated as the residual of the linear regression equation of WI on ADG and BW0.75; residual water intake based on DMI (RWIDMI), estimated as the residual of the linear regression equation of WI on DMI and BW0.75 (RWIDMI); water conversion ratio (= WI/ADG); gross water efficiency (GWE = ADG/WI); residual feed intake estimated as the residual of the linear regression equation of DMI on ADG and BW0.75 (RFI); feed conversion ratio (= DMI/ADG) and gross feed efficiency. Genetic (co)variances were estimated with bivariate analyses. The heritabilities for WI, RWIADG and RWIDMI were 0.38, 0.36 and 0.33, respectively. Water conversion ratio, RWIADG and RWIDMI showed positive genetic and phenotypic correlations with WI, whereas GWE was negatively correlated with WI, suggesting that traits related to water use efficiency may be useful to identify cattle with reduced WI. Water intake showed positive genetic (r = 0.79) and phenotypic (r = 0.60) correlations with DMI, suggesting the use of WI to estimate DMI in future studies. Both RWIADG and RWIDMI were genetically correlated with RFI (0.67 and 0.57, respectively) and ADG (0.49 and 0.44, respectively), showing that RWI is positively associated with feed efficiency, but has an antagonistic relationship with growth. This antagonism, however, may be managed using selection indexes. Genetic improvement of water use efficiency in Senepol cattle is possible through selection and may reduce the water requirements of beef production systems.

Short communication: Tick-borne disease is associated with changes in feeding behavior in automatically fed weaned dairy calves.

Tick-borne disease is a hemolytic disease complex that causes extensive losses to the dairy industry in tropical regions. Its timely diagnosis is challenging and labor intensive. Our objective was to investigate whether tick-borne disease was associated with changes in ingestive behavior of weaned dairy calves. Weaned calves (n = 35) enrolled at 108 ± 8 d of age were group housed (n = 12, 12, and 11/group) for 4 wk in the experimental pen, which had 12 electronic feed bins and 2 electronic water bins. Data were automatically collected at each feed or water bin visit via radio frequency identification ear tags. Water and total mixed ration were provided ad libitum. Calves were examined weekly for tick-borne disease detection. A disease bout was confirmed if packed cell volume was ≤25% at any exam. Diseased calves received antimicrobial and antipyretic treatment. Data were summarized by day within bin type (feed or water) as intake (kg/d; as-fed basis), frequency of visits (visits/d), and total duration of visits (min/d). Day of detection was set as d 0; a 9-d behavioral screening period for evaluation of behavioral changes was set according to d 0 (d -4 to +4). A within-calf mean was calculated for the healthy period (HP; mean of all days between 2 consecutive negative exams) for each response variable. Data were analyzed as within-calf differences between HP and each day of the behavioral screening period. Tick-borne disease was detected in 12 calves; thus, only data referent to these animals were included in the analyses. Compared with HP, daily feed intake was reduced on d -1, 0, and +1, and daily frequency and total duration of feed bin visits were reduced from d -3 to d +4. Daily feed intake was reduced by 35% on d -1 (3.5 ± 0.4 vs. 5.4 ± 0.5 kg/d for HP), and daily frequency and duration of visits were reduced by 27% (56.3 ± 7.8 vs. 76.7 ± 8.1 visits/d for HP) and 24% (27.0 ± 3.8 vs. 35.4 ± 3.9 min/d for HP) on d -3, respectively. Daily water intake on d 0 (9.1 ± 1.4 kg/d) was lower than at HP (12.9 ± 1.6 kg/d), but other drinking behaviors were not different from healthy means during the screening period. Feeding behavior, but not drinking behavior, was different from HP means before detection at weekly exams. Therefore, feeding behavior could be further explored for the development of algorithms for tick-borne disease detection.

Validation of a system for monitoring individual feeding and drinking behaviour and intake in young cattle.

The objective of this study was to validate an electronic system for monitoring individual feeding and drinking behaviour and intake developed for young cattle housed in group. A total of 35 Holstein-Gyr crossbred heifers (BW: 180±52 kg; age: 121.5±32.5 days), fitted with an ear tag containing a unique passive transponder, were distributed in three groups of 12, 12 and 11 animals per period and had free access to 12 electronic feed bins and two electronic water bins (Intergado® Ltd). The dimensions of feed and water bins, as well as the sensors position were appropriate for young cattle. The system documented the visit frequency and duration, as well as the feed and water intakes, by recording the animal's identification tag, bin number, initial and final times of visits and the difference of feed/water weight at the start and end of each bin visit. Feed bins were monitored using time-lapse video recording over 4 days and the water bins were monitored over 6 days. For each feed bin, two feeding events were monitored using manual weighings with an external scale immediately before and after the animal's visit and the difference between them was assumed as feed intake (n=24 observations). For the water bins, 60 manual weighings were made. Video and manual weighing data were regressed on the electronic feeding and drinking behaviour and intake data to evaluate the system's precision and accuracy. The system showed high specificity (98.98% and 98.56% for the feed and water bins, respectively) and sensitivity (99.25% and 98.74%, respectively) for identifying an animal's presence or absence. Duration of feed and water bin visits as well as feed and water consumption per visit estimated by the system were highly correlated and precise compared with the observed video and manual weighing data (r 2=0.917, 0.963, 0.973 and 0.986, respectively). It was concluded that Intergado® system is a useful tool for monitoring feeding and drinking behaviour as well as water and feed intakes in young cattle housed in groups.

Technical note: A facility for respiration measurements in cattle.

A respiration system consisting of 4 climate-controlled chambers and 1 set of flowmeters and analyzers was constructed and validated. Each chamber had volume of 21.10m(3) (3.68×2.56×2.24m) and was made from steel with double-glazed windows on either side enabling visual contact between animals. The chambers are independently climate-controlled and can maintain temperature and relative humidity in a range from 5 to 45°C and 30 to 80%, respectively. A flow generator and mass flowmeter continuously pull air from each chamber and a slight negative pressure inside the chamber is ensured. Air from all chambers and ambient air share a common gas analysis and data acquisition system for monitoring O2, CO2, and CH4 concentrations over the measurement period, with the cycle time set to 20min. Analyzers are regularly calibrated and the chambers have mean recoveries of 99.0 and 98.0% for CO2 and CH4, respectively. The chambers are equipped with infrared cameras and electronic feed and water bins for intake measurements, as well as sensors for monitoring animal position and heart rate. Data acquisition and analysis software is used to calculate the rate of consumption of O2 and production of CO2 and CH4. The dynamic respiration measurements are integrated with feed intake data and other sensors. The daily gas exchanges are estimated by integration to determine methane emission and heat production. We conducted a trial with 12 lactating 3/4 Holstein × 1/4 Gyr crossbred dairy cows (6 multiparous and 6 primiparous) under 2 feeding regimens (ad libitum or restricted) to validate the system. Two 22-h respiration measurements were obtained from each cow. Restricted-fed cows showed lower values for milk yield, methane emission, and heat production compared with ad libitum-fed animals. We found no difference between groups for CH4 produced per kilogram of dry matter intake. Repeatability for CH4 emission and heat production was high (0.97 and 0.92, respectively). The respiration system described herein is a useful tool for measuring the dynamic and accumulated data of heat production, methane emission, and feed intake.

Energy partitioning and methane emission by sheep fed sorghum silages at different maturation stages / Partição de energia e emissão de metano por ovinos alimentados com silagem de sorgo em diferentes estádios de maturação

Energy partitioning and methane production by sheep fed silages of three commercially available sorghum hybrids (BRS 610, BR 700 and BRS 655) harvested at three maturation stages (milk, soft dough and floury) were evaluated in open circuit respiration chambers. A complete randomized design was used in a 3 × 3 (hybrids × maturity stages) factorial arrangement, and the means were compared by the Student-Newman-Keuls (SNK) test (P<0.05). The intake of dry matter, digestible dry matter, gross energy, digestible energy and metabolizable energy were not affected by maturation stage, but were influenced by hybrid. The net energy intake was influenced by maturity and sorghum genetics. The fecal output represented the main source of energy loss, as percentage of gross energy intake (48% to 52%), followed by heat increment (10% to 19%), methane emissions (4% to 6%) and urine (1% to 2%). There were no differences (P>0.10) among the treatments for the apparent digestibility of gross energy and metabolizability (qm). An interaction (P<0.05) between sorghum hybrid and maturation stages was observed for the efficiency of metabolizable energy utilization for maintenance (km), which ranged between 0.53 and 0.78. No differences (P>0.10) among treatments occurred in the daily methane production. There is substantial genetic diversity within sorghum species, determining different nutritional values. Sorghum genetics and maturity at harvest should not be an opportunity to reduce the contribution of agriculture to methane emissions.

A partição de energia e a produção de metano por ovinos alimentados com silagens de três híbridos de sorgo comerciais (BRS 610, BR 700 e BRS 655), colhidos em três estádios de maturação (leitoso, pastoso e farináceo), foram avaliadas em câmaras respirométricas de circuito aberto. Utilizou-se delineamento inteiramente ao acaso, em arranjo fatorial 3 x 3 (híbridos x estádios de maturação), e as médias foram comparadas pelo teste Student-Newman-Keuls (SNK) (P<0,05). Os consumos de matéria seca, de matéria seca digestível, de energia bruta, de energia digestível e de energia metabolizável não foram afetados pelo estádio de maturação, mas foram influenciados pelo híbrido de sorgo. O consumo de energia líquida foi influenciado pela maturidade e pelo híbrido. As perdas de energia nas fezes representaram a principal fonte de perda energética como porcentagem do consumo de energia bruta (48% a 52%), seguida pelo incremento calórico (10% a 19%), pela emissão de metano (4% a 6%) e pela urina (1 a 2%). Não houve diferenças (P>0,10) entre os tratamentos para a digestibilidade aparente da energia bruta e para a metabolizabilidade (qm). Foi observada interação (P<0,05) entre híbrido de sorgo e estádio de maturação para eficiência de uso da energia metabolizável para mantença (Km), que variou entre 0,53 e 0,78. Não ocorreram diferenças (P>0,10) entre tratamentos na produção diária de metano. A emissão de metano em gramas por kg de matéria seca digestível e por kg de fibra em detergente neutro digestível foi inferior no estádio pastoso comparado ao estádio farináceo.

Technical note: Validation of a system for monitoring individual feeding behavior and individual feed intake in dairy cattle.

The objective of this study was to validate an electronic system for monitoring individual feeding behavior and feed intake (Intergado Ltd., Contagem, Minas Gerais, Brazil) in freestall-housed dairy cattle. No data have been published that validate either the behavioral measurement or the feed intake of this system. Feeding behavior data were recorded for 12 Holstein cows over 5d using an Intergado system and time-lapse video. The cows were fitted with an ear tag containing a unique passive transponder and provided free access to 12 feed bins. The system documented the visit duration and feed intake by recording the animal identification number, bin number, initial and final times, and the difference between feed weight at start and end of each feed bin visit. These data were exported to Intergado web software and reports were generated. Electronic data on animal behavior were compared with video data collected during the same evaluation period. An external scale was used to manually measure and validate the electronic system's ability to monitor dairy cow feed intake for each feed bin visit. The feed intake was manually measured for 4-h time periods and compared with the sum of the feed intake recorded by the monitoring system for each cow visit during the same time period. Video and manual weight data were regressed on the electronic feeding behavior and feeding intake data to evaluate the precision of the monitoring system. The Intergado system presented high values for specificity (99.9%) and sensitivity (99.6%) for cow detection. The visit duration and feed intake per visit collected using the electronic monitoring system were similar to the video and manual weighing data, respectively. The difference between the feed intake measured manually and the sum of the electronically recorded feed intake was less than 250g (25,635±2,428 and 25,391±2,428g estimated using manual weighing and the electronic system, respectively). In conclusion, the Intergado system is a reasonable tool to monitor feeding behavior and feed intake for freestall-housed dairy cows.

Valor nutricional de híbridos de sorgo em diferentes estádios de maturação / Nutritional value of hybrids of sorghum in different maturation stages

Avaliaram-se a composição bromatológica e a digestibilidade in vitro das plantas, folhas, colmos e panículas de três híbridos de sorgo (BRS 610, BR 700 e BRS 655) colhidos em três estádios de maturação (leitoso, pastoso e farináceo). O delineamento utilizado foi o inteiramente casualizado, em arranjo fatorial 3x3 (híbridos x estádios de maturação), sendo as médias comparadas pelo teste SNK (P<0,05). Os teores de matéria seca (MS) das plantas variaram de 25,73% a 43,96% e aumentaram com a maturidade. A concentração de proteína bruta (PB) das plantas manteve-se inalterada (P>0,05) entre as idades de corte para todos os híbridos. Os teores de fibra insolúvel em detergente neutro (FDN) e fibra insolúvel em detergente ácido (FDA) das plantas não foram influenciados pelo estádio de maturação. Os coeficientes de digestibilidade in vitro da MS (DIVMS) das plantas do BRS 610 não variaram com a maturidade, mas para o BR 700 e BRS 655 apresentaram redução entre o estádio leitoso e o farináceo. As variações observadas nas porcentagens de MS, PB, FDN, FDA e DIVMS das frações folha, colmo e panícula ocorreram de forma diferente entre os híbridos com o avanço da maturidade. Os híbridos BR 700 e BRS 655 devem ser ensilados no estádio leitoso, enquanto o BRS 610 pode ser colhido nos três estádios de maturação avaliados.

The nutritional value of the plants, leaves, stems and panicles of three hybrids of sorghum (BRS 610, BR 700 and BRS 655) at three maturation stages (milk, soft dough and flour) were evaluated. A complete randomized design was used in a factorial arrangement 3x3 (hybrids x ages of cut), and the means were compared by SNK (P<0.05). Dry matter contents of the plants varied from 25.73% to 43.96% and increased with maturity. The percentage of crude protein (CP) of the plants remained constant (P>0.05) among cuts for all the hybrids. The values of neutral detergent fiber (NDF) and acid detergent fiber (ADF) of the plants were not affected by maturation stages. The in vitro dry matter digestibility (IVDMD) of the plants of BRS 610 didn't change with maturity, but decreased between milk and floury stages for BR 700 and BRS 655. Differences in the percentages of DM, CP, NDF, ADF and IVDMD of the plant fractions (leaves, steam and panicle) occurred differently among hybrids with the advance of maturity. The hybrids BR 700 and BRS 655 should be ensiled at milk stage, while the BRS 610 can be harvested at the three maturation stages evaluated.

Qualidade da silagem de híbridos de sorgo em diferentes estádios de maturação / Silage quality of sorghum hybrids in different maturation stages

Avaliou-se a qualidade das silagens de três híbridos de sorgo, BRS 610, BR 700 e BRS 655, colhidos em três estádios de maturação da planta, grãos leitoso, pastoso e farináceo. O delineamento utilizado foi o inteiramente ao acaso, em esquema fatorial 3x3 (híbridos x estádios de maturação), com quatro repetições. Os teores de matéria seca apresentaram variação de 22,9% a 41,3%. O BR 700 apresentou maior porcentagem de matéria seca que os demais híbridos em todas as idades de corte. Os teores de proteína bruta e as frações fibrosas, fibra em detergente neutro e fibra em detergente ácido, apresentaram comportamento diferente entre estádios de maturação e entre híbridos. Os valores de lignina não foram alterados com o avanço da idade de corte. Os coeficientes de digestibilidade in vitro da matéria seca das silagens variaram de 50,7% a 55,6% e comportaram-se de forma diferente com a maturidade para cada hibrido. De acordo com os valores de pH, de nitrogênio amoniacal e de ácidos orgânicos encontrados, as silagens dos três híbridos são classificadas como de boa qualidade em todos os períodos de colheita.

The quality of silages of three sorghum hybrids BRS 610, BR 700 and BRS 655 harvested at three maturation stages, milk, soft dough and floury grains, was evaluated. A complete randomized design was used in a 3x3 factorial arrangement (hybrids x maturation stages), with four repetitions. Dry matter values varied from 22.9% to 41.3%. BR 700 had a higher percentage of dry matter than the other hybrids in all ages. The content of crude protein and fibrous fractions, neutral detergent fiber and acid detergent fiber presented different behavior between the maturation stages and between hybrids. The lignin values were not modified with the advancement of the cut age. The in vitro digestibility of silages varied from 50.7% to 55.6% and presented different behavior among each hybrid maturity. According to the pH, ammonia nitrogen, organic acids and dry matter values, the silages of the three hybrids were classified as good fermentation quality at all harvest periods.

Consumo e digestibilidade aparente de silagens de sorgo em diferentes estádios de maturação / Intake and apparent digestibility of sorghum silages at different maturation stages

Avaliaram-se o consumo e a digestibilidade aparente, em ovinos, das silagens dos híbridos de sorgo BRS 610, BR 700 e BRS 655 colhidos em três estádios de maturação dos grãos: leitoso, pastoso e farináceo. Os valores de consumo da matéria seca, em gramas por quilograma de unidade de tamanho metabólico (CMS-UTM), variaram de 45,90g/UTM/dia a 59,99g/UTM/dia e não diferiram com o avanço do estádio de maturação para todos os híbridos (P>0,05). No estádio pastoso, o BRS 655 apresentou menor CMS-UTM em relação aos demais híbridos (P<0,05), que foram semelhantes entre si (P>0,05). Foi observado menor consumo de proteína digestível para os híbridos com tanino, BR 700 e BRS 655, em relação ao BRS 610 (P<0,05) nos estádios pastoso e farináceo. Todos os tratamentos apresentaram balanço de nitrogênio levemente positivo, com valores entre 0,02g/UTM/dia e 0,20g/UTM/dia. Não houve diferenças nos valores de digestibilidade da fibra entre os híbridos com tanino, BR 700 e BRS 655, e sem tanino, BRS 610. Recomenda-se a utilização da silagem do híbrido BRS 610, colhida no estádio pastoso. Os híbridos BRS 655 e BR 700 devem ser colhidos no estádio leitoso.

The intake and apparent digestibility of the silages of the sorghum hybrids BRS 610, BR 700 and BRS 655 harvested at three maturation stages of milk, soft dough and floury grains by sheep were evaluated. The dry matter intake, in grams per metabolic weight (DMI-MW), ranged from 45.90 to 59.99g/MW/day and didn't change with maturity (P>0.05) for all the hybrids. At the soft dough stage, BRS 655 presented lower DMI-MW (P<0.05) than the other hybrids, which were similar (P>0.05). The hybrids with tannin (BR 700 and BRS 655) had lower intakes of digestible protein than the BRS 610 at the soft dough and floury stages (P<0.05). All the treatments showed slight positive nitrogen balance which varied from 0.02g/MW/d to 0.20g/MW/d. No differences were observed in fiber digestibility among hybrids with tannins (BR 700 e BRS 655) and without tannins (BRS 610). The use of BRS 610 is recommended and should be ensilaged at soft dough stage. The hybrids BR 655 and BR 700 should be harvested at milk stage.